(CANCER RESEARCH 47, 4529-4537, September 1, 1987]
Perspectivesin CancerResearch
Biological and Therapeutic Potential of Membrane Lipid Modification in Tumors1
Arthur A. Spector2 and C. Patrick Burns
Departments of Biochemistry ¡A.A. S.] and Internal Medicine [A.A.S..C.P.
B.J, University of Iowa, Iowa City, Iowa 52242
Abstract
The membrane fatty acid composition of cancer cells can be modified
either in culture or during growth in animals without disrupting basic
membrane or cellular integrity. Only fatty acids are affected; no changes
occur in membrane cholesterol, phospholipid, or protein content. There
are changes in membrane physical properties and certain cellular func
tions, including carrier-mediated transport, receptor binding, ion chan
nels, and eicosanoid production. Fatty acid modification also can enhance
the sensitivity of the cells to hyperthermia and Adriamycin. This tech
nique provides a new approach to understanding the membrane properties
of neoplastic cells. Membrane fatty acid modification also may be of
potential value as a therapeutic approach designed to augment the
cytotoxicity of other antineoplastic therapies.
Introduction
Biological membranes are composed of a lipid bilayer that
contains a central core of fatty acyl chains. This hydrophobic
core acts as a barrier, preventing the unregulated movement of
ions and metabolic products across the membrane. The fatty
acyl chains also interact with the proteins that penetrate into
the membrane, including enzymes, receptors, and transporters.
Many different kinds of fatty acyl chains normally make up the
lipid bilayer. Most of them have an even number of carbon
atoms, between 16 and 22. About 35 to 40% are saturated; the
remainder are unsaturated and contain between 1 and 6 double
bonds. Any change in the composition of the fatty acyl chains
can alter the structure of the lipid core and thereby has the
potential to affect its normal barrier function, as well as the
responsiveness of the integral proteins with which the core
interacts. Certain properties of the cell may change as a conse
quence.
ßythe early 1970s, it became evident that neoplastic cells
might be ideal targets for membrane fatty acid modification.
Tumors obtain a substantial amount of fatty acid preformed
from the host (1, 2). This is supplied primarily from the
circulating free fatty acid (3, 4) and to a lesser extent by the
triacylglycerols contained in plasma lipoproteins (5, 6). Al
though tumors can synthesize fatty acid from glucose (7),
synthesis is reduced when an adequate supply of circulating
fatty acid is available (8). Therefore, the mixture of fatty acids
provided by the host, after only minor structural modification,
is incorporated into all of the complex lipids formed by the
neoplastic cells, including the phospholipids needed for mem
brane synthesis and the formation of important regulatory
metabolites such as eicosanoids and diacylglycerol. If the com
position of the circulating fatty acid mixture can be changed
sufficiently, the phospholipids formed will have a somewhat
different fatty acid composition and possibly altered physical
and functional properties. It is possible that the characteristics
of the neoplastic cell may change sufficiently to alter its growth
Received 3/19/87; revised 6/1/87; accepted 6/3/87.
1Studies by the authors cited in this article were supported by research Grants
CA31526, DK28516, and HL14230 from the NIH.
2To whom requests for reprints should be addressed, at Department of
Biochemistry, 4-550 BSB, University of Iowa, Iowa City, IA 52242.
pattern or increase its sensitivity to certain forms of therapy.
This is the rationale for the studies carried out over the last
decade to assess the biological and therapeutic potential of
membrane fatty acid modification in neoplastic cells.
Membrane Polyunsaturated Fatty Acids
Most efforts to manipulate the fatty acid composition of cells
have focused on polyunsaturates. As opposed to saturated and
monounsaturated fatty acids, the polyunsaturates normally
present in animals cannot be synthesized de novo and therefore
are ultimately derived from the environment. Animals obtain
them from the diet; cells obtain them from the plasma and
extracellular fluid. There are two main classes of polyunsatu
rates, the n-6 or plant polyunsaturate class and the n-3 or fish
oil class. This point is illustrated in Fig. 1, which shows the
relationship of the various acids in each series, their metabolic
conversions, and the structures of the main components. The
n-6 polyunsaturates, also known as the u>-6 class, often are
referred to as essential fatty acids because serious illness results
if they become deficient. Terrestrial plants synthesize the first
member of this series, linoleic acid (18:2n-6)3, and they are
present in the diet primarily in this form. Arachidonic acid
(20:4n-6), another member of this series, is the main substrate
for prostaglandin and leukotriene synthesis in mammalian tis
sues.
The n-3 polyunsaturates, also known as the o>-3class, are
contained in the diet primarily in fish oils. Cold water vegeta
tion synthesizes the first member of this series, linolenic acid
(18:3n-3), and the fish that feed on these organisms convert the
18:3 to the two most abundant components of this class, eicosapentaenoic acid (20:5n-3) and docosahexaenoic acid (22:6n3). Although these fatty acids, especially 22:6, accumulate in
relatively large amounts in certain excitable membranes, their
functional role is presently uncertain, and there is a question as
to whether they are necessary for optimum health. As indicated
in Fig. 1, mammalian cells can interconvert the fatty acids
within each series, but they cannot convert one class into the
other.
Fatty Acid Modifications
Tumor Growth in Animals. Substantial differences in the
phospholipid fatty acid composition can be produced in Ehrlich
ascites carcinoma cells by changing the type of fat fed to the
tumor-bearing mice (9). The diets that have been tested for this
purpose contained either sunflower seed oil, which has about
70% linoleic acid, or coconut oil, which has 93% saturated fatty
acid and only 1 to 2% linoleic acid. These diets contained 16%
fat by weight, amounting to 30% of the total caloric intake.
While the plasma membrane fatty acid composition of the
Ehrlich cells was modified, no changes occurred in the mem3 The fatty acids are signified as number of carbon atoms:number of double
bonds, followed by the class. Thus, linoleic acid contains 18-carbon atoms and
two double bonds and is of the n-6 polyunsaturated fatty acid class. The notations
n-3 and n-6 signify the number of carbon atoms from the methyl terminus where
the first double bond is located.
4529
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
n-6
co°" ~
=,_
LINOLEIC
18:2
|
coo-
OCXX/
ARACHIDONIC
/\
PG,
LT,
n-3
18:3
18:4
*
20 : 3
I
20 : 4
I
5-DESATURASE
20:4
W\=A
LINOLENIC
|
_
20:5
|
|
22 : 4
22: 5
|
/=vwvcoo-
18i3
Ì,
6-DESATURASE
4-DESATURASE
LIPID MODIFICATION
_
coo-
CA^ASSA
|
22 : 5
22 :6
_.,__,
Fig. 1. The two main classes of polyunsaturated fatty acids present in mam
malian tissues. The fatty acids in each class are designated as number of carbon
;it<>ms: mimIKTof double bonds. By elongation, desaturation, and retroconversion,
it is possible to interconvert the members within each class. It is not possible,
however, to convert a member of one class into the other. Thus, IS: In 6 is a
different fatty acid than the 18:3 of the n-3 class. The structures of 18:2 and 20:4
of the n (i class, and 18:3, 20:5, and 22:6 of the n-3 class are shown. PG¡,dienoic
prostaglandins; ¿7°«,
tetraenoic lipoxygenase products.
|[
Saturated
I
P
Plasma
16:O
Membrane
Polyunsoturoted
18:O
Fatty
18:1
18:2
2O:4
Acids
Fig. 2. Differences in plasma membrane fatty acid composition of LI210
leukemic lymphoblasts resulting from dietary lipid modification. The cells were
grown i.p. for 7 days in mice fed a synthetic diet containing 16% coconut oil
(saturated) or 16% sunflower oil (polyunsaturated). Left, distribution of fatty
acids among the saturation classes. S, saturated; M, monounsaturated; /'. poly
unsaturated. Right, values for the most prevalent individual fatty acids.
brane phospholipid or cholesterol content (10). Therefore, what
occurs is a substitution of fatty acyl chains without any disrup
tion in the usual lipid bilayer structure. The fatty acid compo
sition of the nuclear membrane also was modified (11). Frac
tionation of the nuclear and plasma membrane phospholipids
indicated that all of the phospholipid classes were affected (11,
12). Similar kinds of fatty acid compositional changes occurred
in each phospholipid class and except in the case of sphingomyelin, the changes were fairly substantial.
This dietary approach is also effective in modifying the
plasma membrane fatty acid composition of LI210 leukemic
lymphoblasts (13). As in the case of the Ehrlich cell, what
occurs is a substitution of phospholipid fatty acyl chains without
any overall disturbance in the architecture of the membrane
lipid bilayer. Fig. 2 illustrates the magnitude of the changes
that can be produced in the plasma membrane fatty acid com
position of the LI210 cell. No appreciable change occurred in
the saturated fatty acid content of the plasma membrane, which
IN TUMORS
accounts for about 40% of the membrane fatty acids. However,
there was a 53% reduction in monounsaturated fatty acids and
a 77% increase in polyunsaturated fatty acids when the LI210
cells were grown in the mice fed the sunflower oil diet. Among
the individual fatty acids, the main differences occur in oleic
acid (18:1) and 18:2.
Solid tumors also can be modified in this way. For example,
large differences in the fatty acid composition of a transplanted
mammary adenocarcinoma result from feeding the tumor-bear
ing mice diets containing corn oil as opposed to hydrogenated
cottonseed oil (14). The phospholipid fatty acid composition of
hepatoma 7288CTC was modified in the rat by changes in
dietary fat content (15). Modifications in the murine HSDMi
fibrosarcoma also have been produced in this way (16). The
membranes of the solid tumors are affected; for example, the
fatty acid compositions of microsomes prepared from the mu
rine CA755 mammary adenocarcinoma and a rat mammary
tumor induced by ,/V-methyl-./V-nitrosourea are altered in re
sponse to changes in the type of dietary fat (17, 18).
The modifications in phospholipid fatty acid composition
produced by diet are fairly stable. At the time of removal from
the host, the phospholipids of LI210 cells obtained from mice
fed the sunflower oil diet contained 47% polyunsaturated fatty
acids, as opposed to 31 % when coconut oil was fed. When these
cells were subsequently maintained in culture in a standard
medium containing 20% fetal bovine serum for up to 96 h, the
polyunsaturated fatty acid content of the phospholipids changed
by only 2% in each case (19).
The fatty acid compositional changes are not limited to
membranes when the modifications are produced in vivo by the
dietary approach. Differences in fatty acid composition also
occur in the cellular neutral lipid fraction (9), which is com
posed primarily of triacylglycerol contained in the cytoplasm
in the form of lipid inclusions.
Cell Culture. While the dietary studies in animals established
that membrane fatty acid compositional changes in tumors can
be produced in vivo, the method does not permit a precise
evaluation of specific fatty acid substitutions. To examine this
question, tumor cells grown in culture have been modified with
individual fatty acids as indicated in Table 1 (20-32). Many
different types of fatty acid have been incorporated, including
plant polyunsaturates, fish oil polyunsaturates, unsaturates hav
ing double bonds in the fra/w-configuration, and fatty acids
cellC6
Table 1 Fatty acid modification of tumor cells in culture
tested"18:2, acids
Tumor
glioblastoma
carcinomaEL-4
Ehrlich
ascites
T-lymphoma
tumorFriend
FM3A
mammary
erythroleukemia
HeLa
Hepatoma 7777
leukemiaL5178Y
LI 210
leukemia
neuroblastomaNG108-15
Ml
neuroblastoma x
glioma
PC- 12 pheochromocytoma
Y-79 retinoblastomaFatty
18:3n-3*
14:0,
18:2,18:2t,c
15:0, 18:1,
0^-14:0*
17:0, 18:It, 18:2, 18:2t, 19:0
18:3n-3,20:2, 20:3n-3,
20:5n-3
18:1, 18:2
18:2, 20:4
18:1, 18:2
18:1, 18:2, 18:3n-3, 20:4,
20:5n-3, 22:4, 22:6n-3
18:3n-3, 20:2, 20:3n-3,
20:5n-3
18:2, 18:3n-3, 20:4,
22:6n-318:1,
18:2,20:416:0,
2223
2425
26
27
2824
29303132
18:0, 18:1, 18:2,20:4
18:1, 18:2, 18:3n-3, 20:4
20:5n-3, 22:6n-3Ref.20,21
" Fatty acids were added individually to the culture medium.
* Denotes polyunsaturate of the fish oil series.
' Double bonds in the rra/u-configuration.
* 12-Methylmyristic acid.
4530
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
LIPID MODIFICATION
having an odd number of carbon atoms or a branched hydro
carbon chain. Fatty acid substitutions occur in the plasma
membrane (22) and microsomes of these cells (33, 34). All of
the phospholipid classes are involved (22, 34). The extent of
enrichment with a particular fatty acid depends on the amount
of the supplemental fatty acid added to the culture medium
(32). Although not tested extensively, there is no indication
thus far of any change in the cholesterol or phospholipid
content of the membrane, or in the phospholipid head group
composition as a result of fatty acid replacements in culture
(32).
In addition to allowing for more varied fatty acid substitu
tions, the cell culture approach also can produce more extensive
enrichments than the dietary modification procedure. For ex
ample, when LI210 leukemic lymphoblasts are enriched with
22:6, the polyunsaturated fatty acid content of the phospholipids increases almost 3-fold, and there is a corresponding 58%
reduction in monounsaturates. These differences are due pri
marily to an extremely large increase in 22:6 itself and a 46%
decrease in 18:1. Although changes of this magnitude may not
be strictly applicable to tumors in vivo, they provide useful
models for investigating possible functional perturbations as
sociated with specific fatty acid substitutions.
As in the case of the dietary method, the fatty acid composi
tional changes produced in culture are not confined only to
membranes. The neutral lipid fraction, which again is composed
almost entirely of triacylglycerol, also is modified (25, 27).
When the cells are exposed to relatively high concentrations of
a supplemental fatty acid, the amount of triacylglycerol in
creases (27), so that there is a change in both the content and
fatty acid composition of the cytoplasmic lipid inclusions.
While these neutral lipid changes are a complicating factor,
they probably are not the primary cause of the perturbations in
certain membrane-related processes, described in subsequent
sections, that occur as a result of modifications in cellular fatty
acid composition.
Membrane Fluidity
Electron spin resonance studies with Ehrlich ascites carci
noma and LI210 leukemia cells show that these kinds of fatty
acid modifications are sufficient to affect the physical properties
of the plasma membrane. Small differences in the packing
density of the membrane lipids, as indicated by changes of as
much as 0.06 unit in the electron spin resonance order param
eter, occur when the cells are modified either by the dietary
procedure (13, 35) or in culture (22, 36). Plasma membranes
enriched in polyunsaturated fatty acids have the lowest order
parameters, indicating greater fluidity; this is not due to local
ization of the spin probe in cytoplasmic lipid accumulations
(37). The development of a membrane fluidity change is con
sistent with the fact that the fatty acid compositional modifi
cations are not accompanied by any compensatory changes in
membrane cholesterol content or phospholipid head group
composition.
Another electron spin resonance parameter that is perturbed
is the temperature dependence of the rotational correlation
time of the spin probe. Two distinct discontinuities normally
are observed in plasma membrane preparations, one at 31.5°C
and the other at about 22°C.These discontinuities are consid
ered to be a measure of phase transitions in the membrane lipid
bilayer. The 31.5°Ctransition is not appreciably affected by the
fatty acid compositional modifications thus far produced. By
contrast, changes of more than 5°Chave been noted in the
lower transition, which can range from 19 to 26°C(13, 22, 35).
IN TUMORS
As the polyunsaturation of the plasma membrane increases, the
temperature of this transition decreases (22). This also is an
indication that polyunsaturated fatty acid enrichment causes an
increase in plasma membrane fluidity. Actually, the interpre
tation is more complicated. The two transitions suggest that
the spin probe is contained in at least two different membrane
microe nvirónmeats, e.g., in the inner and outer leaflets of the
lipid bilayer or in coexisting liquid and crystalline domains
within the bilayer (38, 39). Apparently, the fatty acid compo
sitional modifications perturb the structural organization of the
more fluid microenvironment but have little or no effect on the
more solid domain of the plasma membrane.
To determine whether these fatty acid replacement effects
might be localized to only certain depths within the lipid bilayer,
the L1210 plasma membrane preparations were tested with
stearic acid probes containing the spin group either 5 or 12
carbon atoms distant from the carboxyl end. Under all condi
tions, the lipid bilayer was found to be more ordered in the
region closer to the polar head groups. However, fatty acid
substitutions produced the same kinds of perturbations with
both spin probes, indicating that changes in the electron spin
resonance parameters occur at both the superficial and deeper
regions of the lipid bilayer (13).
The electron spin resonance changes resulting from fatty acid
replacements in the 1 1210 and Ehrlich ascites cell plasma
membranes are similar to effects seen in other systems (40). By
contrast, no plasma membrane fluidity effects were observed
when EL-4 T-lymphoma cells were enriched with polyunsatu
rated fatty acids (23) or when Friend erythroleukemia cells were
enriched with linoleic acid (41). In the Friend cell, however, the
fluidity measurements were made in microsomes rather than
purified plasma membranes. It is possible that the crude microsomal fraction, which is composed largely of endoplasmic reticulum, may be less structurally organized than the plasma mem
brane and therefore not perturbed by these types of fatty acid
substitutions.
In summary, small changes in fluidity occur in certain plasma
membrane microenvironments when the fatty acid composition
of at least some tumor cells is modified. This may be responsible
for several of the functional perturbations that result from these
modifications.
Effects on Membrane Proteins
Transport Proteins. Transporters are integral membrane pro
teins that span the lipid bilayer. It is reasonable to assume that
changes in membrane fatty acid composition sufficient to per
turb the physical properties of certain regions of the lipid bilayer
may affect the function of integral proteins that happen to be
located in these regions. Such effects might have important
consequences for neoplastic cells, possibly influencing the up
take of nutrients or chemotherapeutic agents.
The effects of fatty acid modification on the transport of
nutrients and chemotherapeutic agents in tumor cells are sum
marized in Table 2. Positive effects on carrier-mediated trans
port have been observed in a number of cases, and enrichment
with polyunsaturated fatty acids lowers the K¿,
for several highaffinity transport systems (12, 13, 33, 34). However, the re
sponse is not uniform; in other cases, polyunsaturated fatty
acid enrichment causes an increase in K,'„
(32, 42). In these
cases, the Vâ„¢,for high-affinity transport also is increased (32,
42), whereas no ¥„„
changes occur for any of the other trans
port systems (12, 13, 33, 34). There are also a number of
transport systems with kinetic properties that at 37°Care
unaffected by changes in fatty acid composition (43, 44). How-
4531
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
LIPID MODIFICATION
Table 2 Effect of fatty acid modification on transport in tumor cells
IN TUMORS
chain content. Another possibility is that the heterogeneous
of increased
response is due to structural differences in the various kinds of
Drug/CompoundAdriamycinMethotrexateMclphalana-Aminoisobulyrate•y-AminobulyrateCholineGlutamateGlycineLeucinePhenylalanineSerineTaurineCellL1210"L1210L1210Ehrlich*Y79<
polyunsaturationLarger
transporters, with only some structures responding to changes
in the surrounding fatty acyl chains.
Only in the case of Adriamycin has the change in uptake
been shown to affect the amount of the compound actually
present in the neoplastic cell (28). Most of the other kinetic
affinityNoneDecreased
carrier
changes that have been observed are small and possibly may
have little influence on the capacity of the cell to accumulate
carrier affinity/in
the compound. Therefore, more work is needed to assess how
numberDecreased
creased carrier
carrier affinity/in
many of these types of transport changes actually have any
numberNoneLower
creased carrier
functional significance.
Ion Channels. Enrichment of NG108-15 neuroblastoma x
temperatureNoneIncreased
transition
glioma cells in culture with 18:2, 18:3n-3, or 20:4 lowers the
affinityDecreased
carrier
rate and amplitude of the sodium action potential due to a
carrier affinity/in
creased carrier numberRef.281344123434333442323443343442
reduction in the number of sodium channels (31). Saturated
•
l 12 in murine ascites lymphoblastic leukemia.
and frans-unsaturated fatty acids have the opposite effect,
* Ehrlich murine ascites carcinoma.
whereas
18:1 does not produce any change. The polyunsaturates
c Y79 human retinoblastoma.
"' MI murine neuroblastoma.
have no effect on resting membrane potential, calcium action
potential, or membrane capacitance. Therefore, as noted for
the transporters, the effect of increased polyunsaturation is
ever, ¡ntwo of these cases where no kinetic changes are observed
at 37°C,the phenylalanine and melphalan uptake systems, the selective and thus far appears limited to only one of the proteins
transporters still must be influenced by the membrane fatty acid that influences membrane excitability.
Receptor Binding. Like transporters, receptors contain a
modifications because the temperature-dependent
transitions
membrane-spanning
domain that is in contact with the fatty
of the transport rates are affected (43, 44).
To complicate matters further, different responses for the acyl chains of the lipid bilayer. In addition, receptors often
undergo association reactions that involve lateral mobility
uptake of a single compound have been reported in two different
within the plane of the membrane (46). Therefore, changes in
neoplastic cells. For example, polyunsaturated fatty acid en
membrane fatty acid composition may possibly influence their
richment decreases glutamate uptake in Ml neuroblastoma
binding or signal transduction properties.
cells but has no effect on glutamate uptake in Y79 retinoblas
Effects on binding have been demonstrated in neoplastic cells
toma cells (34, 42). Even in a single neoplastic cell, the Y79
for several receptors. The binding of drugs to the opiate receptor
retinoblastoma, only some of the transport systems are sensi
is reduced when neuroblastoma x glioma cells are grown in a
tive, and even the systems that are responsive are not all affected
medium supplemented with unsaturated fatty acids (47). Like
in the same way (32-34).
wise, the binding affinity of the insulin receptor is reduced and
Where positive responses occur, the effect does not appear
the number of accessible binding sites increases when the
to be specific for a single type of polyunsaturated fatty acid.
plasma membrane of Friend erythroleukemia or Ehrlich ascites
Similar effects have been obtained in many of these cases with
n-3 and n-6 polyunsaturates (32-34). The response is clearly to cells is enriched in polyunsaturates (25, 48). This is attributed
to the increase in membrane fluidity that results from polyun
polyunsaturation, however, because no effects were observed
saturated
fatty acid enrichment, which facilitates the insulinwith 18:1 enrichment in any of these cases. Adriamycin uptake
mediated dissociation of the receptor from an aggregated to a
was also increased as a result of enrichment with polyunsatur
ates; studies with six different fatty acids indicate that the monomolecular form (49).
The depolarization-dependent
exocytosis of norepinephrine
magnitude of the increase directly correlates with number of
from
PC
12
pheochromocytoma
cells
also is reduced when the
double bonds that they contain (28).
cells are enriched with unsaturated fatty acids (50). This occurs
No effect of fatty acid modification has as yet been observed
on the efflux of any compound from a neoplastic cell. The when exocytosis is triggered by carbamylcholine binding to the
compounds thus far tested are Adriamycin (28), glycine (45), nicotinic cholinergic receptor, as well as when the sodium
channels are activated with veratridine. None of the steps in
and phenylalanine (43).
the secretion process are affected by fatty acid modification,
In summary, the effects of fatty acid modification on trans
suggesting that the decrease is due to changes in carbamylcho
port in neoplastic cells are diverse and complex. Why only some
line binding or in coupling of the nicotinic cholinergic receptors
systems are affected and how these positive effects are brought
to ion channel activation.
about are not known. With respect to mechanism, one possi
These results suggest that membrane fatty acid modifications
bility is that the structural changes in the surrounding lipid
can perturb some receptor-mediated processes. Because of the
matrix affect the conformation of the transporter, thereby al
tering the accessibility of its binding site, the tightness of importance of growth factors and their receptors in tumor
development (51), this should be a particularly worthwhile area
binding of the ligand, the size of the transmembrane channel,
or the extent of electrochemical interactions. Alternatively, the for further study.
mobility of the transporter in the lipid bilayer may be affected.
Effects on Growth
In either case, it is clear that only certain transporters are
sensitive to lipid modulation, and even those that respond are
Certain fatty acids in high concentrations can lower the
growth rate without killing cells, and there are even reports
not all affected in the same way. This may be due to differences
that some fatty acids may exert selective toxicity against neo
in the lipid domain surrounding each type of transporter, with
different lipid microenvironments being influenced to varying
plastic cells (52). However, we find no evidence that the growth
extents by a change in membrane polyunsaturated fatty acyl of the LI 210 leukemia is affected when the fatty acid compoaccumulationIncreased
affinityLower
carrier
temperatureIncreased
transition
affinityNoneNoneIncreased
carrier
4532
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE LIPID MODIFICATION IN TUMORS
SURVIVAL (%)
100
sition is modified. There was no difference in the number of
tumor cells present in the peritoneal cavity of the mice fed
different diets, or in the incorporation of [3H]thymidine into
these cells during subsequent culture (53). Negative results also
were obtained when the L1210 cells were extensively enriched
with 22:6 in culture; the cloning efficiency in soft agar and
doubling time were unchanged as compared with unsupplemented cells (54). Dietary studies in animals with fibrosarcomas
(16) and mammary tumors (55, 56) also indicate that changes
in fatty acid composition do not affect tumor growth. By
contrast, a growth-promoting effect of polyunsaturated fat has
been reported in several adenocarcinomas (14, 57, 58). Fur
thermore, n-3 polyunsaturates have been observed to decrease
the growth of a mammary carcinoma (59). Additional studies
are needed to resolve these apparent differences.
Diets rich in polyunsaturated fats also are reported to affect
chemical carcinogenesis (60-64). However, chemical carcinogenesis is a complex, multistep process, and it is likely that the
effect occurs at an early stage, such as promotion, and not on
the growth rate of the established tumor (65-67).
Although the available evidence is not conclusive, our inter
pretation is that in most cases, fatty acid modification of
established tumors is unlikely to influence the rate of growth.
Therefore, any therapeutic benefit that may possibly result from
this approach is likely to be indirect, such as through increasing
the sensitivity of the neoplastic cells to other treatment modal
ities, rather than from a direct action on tumor growth.
Effects on Therapeutic Modalities
Chemotherapy. Adriamycin was selected to test the possibility
that fatty acid modification might make the neoplastic cell
more sensitive to chemotherapy because membranes appear to
be a target for its action (68). P388 leukemia cells that are
sensitive to Adriamycin have a different phospholipid compo
sition and membrane fluidity than resistant sublines (69, 70).
Likewise, in a series of Sarcoma 180 sublines, a correlation
exists between membrane fluidity and resistance to Adriamycin
(71). In addition, Adriamycin reportedly decreases membrane
fluidity in a dose-dependent manner (72).
In agreement with this idea, we find that enrichment of LI 210
cells with polyunsaturated fatty acids in culture considerably
increases their sensitivity to Adriamycin (28, 54). The effect of
22:6 enrichment on Adriamycin cytotoxicity is illustrated in
Fig. 3. A significant reduction in the surviving cell fraction, as
determined by a clonogenic assay, occurred at all times of
exposure to the drug longer than 1 h; at 5 h, there was a 10fold decrease. No reduction resulted from 18:1 enrichment,
indicating that this is an effect of polyunsaturation and not
exposure to fatty acids per se. Greater sensitivity occurred at all
Adriamycin concentrations between 0.1 and 0.6 ¿¿M,
and sen
sitivity increased as the cellular enrichment with 22:6 increased
(54). Studies with different polyunsaturated fatty acids indicate
that the extent of the increase in sensitivity to Adriamycin
depends on the increase in average number of double bonds per
phospholipid fatty acyl chain (28).
Adriamycin accumulation increased by 30% in the cells en
riched with polyunsaturates (28), probably explaining the en
hanced sensitivity to the drug. There was no change in the rate
of efflux of Adriamycin. Furthermore, lipid partitioning studies
indicate that there is no change in the binding of Adriamycin
to the polyunsaturated fatty acid-enriched membranes. There
fore, the larger accumulation probably is due to a greater rate
of influx.
Enrichment with 22:6 did not confer Adriamycin sensitivity
18 1
Supplemented
10
226
Supplemented
1
2345
TIME (hours)
Fig. 3. Effect of phospholipid fatty acid modification on Adriamycin sensitiv
ity. LI210 cells were grown for 2 days in medium supplemented with either
22:6n-3 or 18:1 at a concentration of 32 u\i, washed, and exposed to 0.4 »\i
Adriamycin for the times shown on the abscissa. The percentage of surviving cells
was determined using a soft agar clonogenic assay. Points, means of at least 4
separate experiments; han. SE. The /'„value was 65 ±4 min for cells grown in
22:6n-3-supplemented medium and 106 ±10 for cells grown in unsupplemented
medium (P < 0.005). Reprinted from article by M. M. Guffy el al. (54).
on a resistant murine leukemia-lymphoma, P388/ADR. This
may be due to the inability of fatty acid modification to affect
Adriamycin efflux, since it is known that resistance in P388/
ADR is caused by a more active extrusion of the drug (73).
These findings suggest that polyunsaturated fatty acid enrich
ment might be useful in increasing the fractional cell kill
produced by Adriamycin in tumors that are inherently sensitive
to this drug. This most probably occurs by enhanced cellular
accumulation of drug. However, one other possibility must be
considered. The metabolism of Adriamycin and other anthracyclines yields activated oxygen species (74). These can lead to
degradation of unsaturated fatty acids incorporated into phos
pholipid micelles (75). Thus, polyunsaturated fatty acid enrich
ment may sensitize the cell to the cytotoxicity of Adriamycin
in this manner. Regardless of its mechanism, this approach
should be extended to different kinds of neoplastic cells, as well
as to in vivo tumor models, because of its potential therapeutic
importance.
Hyperthermia. Thermal radiation can reduce the growth of
tumors, both in culture and in vivo (76), and there is evidence
that membranes are an important target of heat cytotoxicity
(77). For example, membrane-perturbing agents such as local
anesthetics and amphotericin B potentiate the effect of hyperthermia (78-80). In addition, changes in membrane lipid com
position affect the heat sensitivity of prokaryotic cells (81).
There are conflicting reports as to whether cholesterol, a major
membrane lipid constituent, plays a role in this response (82,
83). On the other hand, the fact that poikilotherms adapt
protectively to changes in environmental temperature by alter
ing their membrane fatty acid composition (84) suggests that
this lipid component may be involved in the cellular response
to heating.
To examine this possibility, the heat cytotoxicity of LI210
leukemic lymphoblasts enriched in culture with various fatty
acids was compared (36). Following enrichment, the cells were
transferred to a standard medium, heated, and then tested for
cytotoxicity by a clonogenic assay. Cells enriched in 22:6 were
more heat sensitive. The effect was greatest at 42°C,but it also
was evident at 41°C.The degree of cytotoxicity enhancement
was dependent on the degree of enrichment with 22:6 (36). Cell
survival was significantly different at 42°Cat all heating times
after 30 min; the DOvalues (min of heat treatment required to
reduce cell survival by 63% on the exponential part of the
4533
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
LIPID MODIFICATION
survival curve) were 27.5 ±1.5 (SE) min for control cells, 18.7
±0.4 min for 22:6 supplementation, and 46.2 ±1.6 for 18:1
supplementation (P < 0.001). When enriched with 18:1, the
cells contained fewer polyunsaturates and average number of
double bonds per phospholipid fatty acyl chain than control
cells, probably accounting for their apparent resistance to hyperthermia.
A mammary carcinoma grown in the mouse leg also is more
sensitive to local hyperthermia when the diet fed the host is
rich in polyunsaturated fat (17, 56). Therefore, the response is
not limited to ascites cells in culture. It also is not limited to
neoplastic cells; the heat sensitivity of mouse fibroblasts is
greater when the cells are enriched in polyunsaturated fatty
acids (83). As opposed to heat cytotoxicity, thermotolerance is
not caused or affected by changes in membrane fatty acid
unsaturation (85-87).
In summary, changes in membrane fatty acid composition
can influence the sensitivity of neoplastic cells to thermal radia
tion. The molecular mechanism responsible for this is unknown,
and more information about the process could lead to new
concepts about tissue responses to injury. This, together with
the possibility of eventual therapeutic application, makes the
relationship between membrane fatty acid composition and heat
cytotoxicity an attractive area for additional study.
Radiation. Membranes have been suggested as targets for
radiation-induced cytotoxicity (88). This is based primarily on
data obtained with prokaryotes, indicating that under certain
conditions of temperature and aeration, radiosensitivity can be
influenced by the physical state and biochemical properties of
the membrane lipids (89-91). We find negative results, how
ever, with neoplastic mammalian cells. No difference in cell
survival occurred when human Y79 retinoblastoma cells exten
sively enriched in culture with 22:6 were treated with X-rays
(92). A similar negative result was obtained with LI210 cells
modified in vivo by the dietary approach. While more extensive
studies might uncover conditions in which additive or synergistic responses between changes in membrane fatty acid compo
sition and sensitivity to ionizing radiation might occur, these
negative findings suggest that this is not a promising area for
further pursuit.
Immune Cytotoxicity. There are conflicting data as to whether
membrane fatty acid modification can make a neoplastic cell
more susceptible to immune injury. No effect on cytolysis
mediated either by antibody and complement or by effector
cells was observed in EL-4 T-lymphoma cells, even though the
physical state of the plasma membrane was altered (93). By
contrast, fatty acid compositional changes make guinea pig
hepatoma cells more susceptible to humoral immune cytotox
icity (94). Likewise, fatty acid enrichment of hepatoma 7777
cells increases complement-mediated cytolysis and susceptibil
ity to natural killer cells (27, 95). The greater sensitivity is
thought to be mediated by an increase in either membrane
fluidity or the tendency of the cell lipids to undergo peroxidation (27). Immune-mediated cytotoxicity is a potentially im
portant therapeutic application of membrane lipid modifica
tion. Therefore, the differences in the responses of the Tlymphoma and hepatoma cells must be resolved in order to
determine whether this approach is worth pursuing.
Eicosanoid Production
Eicosanoid production is another area where fatty acid mod
ification might have an influence on the properties and function
of neoplasms. Arachidonic acid is the substrate for most of the
IN TUMORS
prostaglandins and lipoxygenase products formed by animal
tissues. The arachidonic acid is stored intracellularly in mem
brane phospholipids and released when the cell is activated by
appropriate stimuli. Changes in membrane phospholipid fatty
acid composition can alter the amount of arachidonic acid
contained in these storage pools or cause the incorporation of
structurally similar analogues like 20:5n-3 into these pools (96).
This can affect the amount of prostaglandins formed by a
number of nonmalignant cells (96). Similarly, the output of
prostaglandins E2 and F2„
by MC5-5 methylcholanthrene-transformed fibroblasts, the HSDMi fibrosarcoma, and the J-lll
monocytic leukemia is reduced when the cells are exposed in
culture to 20:5 (97). Although cellular fatty acid composition
was not measured in this study, it is likely that exposure in
culture to 20:5 modified the fatty acid composition and reduced
the arachidonic acid content of membrane phospholipid sub
strate storage pools in these neoplastic cells.
Eicosanoids can influence the carcinogenic process in many
different ways. They can stimulate tumor growth (98), act as
tumor promoters (99), inhibit tumor growth (100, 101), or
influence tumor migration and the metastatic potential (102,
103). The eicosanoids that influence the tumor may be produced
either by the neoplastic cells themselves (104) or by host tissues
(105). Therefore, the relationship between fatty acid modifica
tion and eicosanoid production is likely to be complicated and
vary for different tumors. Fairly detailed studies will be needed
to sort out these possibilities. A related aspect that deserves
further study is whether the tumor-promoting actions of the n6 polyunsaturates (14, 57, 61, 62) and the apparent protection
against this afforded by the fish oil polyunsaturates (59,67) are
due primarily to effects on the capacity of the host tissues to
produce eicosanoids.
Future Directions
Membranes are a plausible target for antineoplastic therapy,
a possibility that has been generally overlooked. The present
findings provide a rationale for directing such an approach
specifically to membrane fatty acyl groups. The membrane fatty
acid composition in a neoplastic cell is not stringently regulated,
and fairly substantial modifications can be produced, even in
vivo. Fig. 4 is a conjectural model of what occurs within the
membrane when the fatty acid composition is modified. Some
of the saturated and monounsaturated fatty acyl groups are
Unmodified Membr;
•xxvRßßygaßnß
(/(/(M/o
(/(/(/
Polyunsaturated Membrane I
I
/-\ /~\ j~\ f.
rt x-v (O^^^Oi
OOQVQO
Fig. 4. Schematic diagram for a model of membrane fatty acid alteration. The
type of fatty acid chain is designated by the shape of the line. Straight lines,
saturated chains; single bend, monounsaturated chains; two bends, polyunsatu
rated chains. When the membrane contains more polyunsaturated fatty acyl
chains, the conformation and functional properties of certain enzymes, receptors,
and transport carriers or channels are modified. /.. representative enzyme such as
phospholipase; L, ligand; R, receptor, D, drug; C, transport carrier or channel.
4534
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
LIPID MODIFICATION
replaced by polyunsaturated groups without disrupting the basic
architecture of the membrane. The resulting structural changes
within the hydrophobic core of the lipid bilayer may influence
the conformation and properties of some of the transporters,
ion channels, receptors, and enzymes contained within the
membrane, thereby modulating their function or affecting their
localization within specific lipid domains. This modulation, in
turn, may influence the response of the neoplastic cell to certain
stimuli or perturbations.
Many fundamental questions regarding the relationship of
membrane fatty acid composition to cellular properties and
function remain unanswered. For example, since binding to
certain receptors is affected, is signal transduction also affected?
Are the fatty acid compositional changes in the inositol phospholipids sufficient to affect the operation of the phosphatidylinositol cycle? Is the effectiveness of the n-3 polyunsaturates
due simply to the greater number of double bonds, as suggested
by the available data (28), or is there a unique effect due to the
unsaturated bond in proximity to the methyl terminus of the
fatty acyl chain? Like certain carrier-mediated transport proc
esses, is passive diffusion through the membrane also affected?
The application of sophisticated biophysical and biochemical
techniques to the fatty acid modification model should provide
novel approaches to these and other fundamental questions in
cell biology.
Extension of this approach to other membrane lipid components, such as cholesterol or phospholipid head groups, un
doubtedly will increase our basic understanding of tumor biology. From a practical standpoint, however, it will be difficult
to bring about such changes /// vivo. For example, changes in
the plasma cholesterol concentration may alter the amount of
cholesteryl ester stored within cells, but they appear to have
little or no effect on membrane cholesterol content (106). The
main advantage of focusing on fatty acid replacements is the
potential for clinical application. Although the dietary modifications that have been used thus far are extreme and cannot be
achieved with ordinary foods, liquid formulas containing saturated or polyunsaturated fat have been taken by humans for
long periods without adverse effects (107). Dietary supplements, such as fish oil capsules, also have been administered
successfully to humans (108). For specialized needs, i.v. solu
tions containing stable polyunsaturated triacylglycerol emul
sions can be prepared. This makes it possible to consider future
clinical application without first having to develop new tech
nologies.
Since fatty acid replacements do not appear to consistently
influence tumor growth, any usefulness that this approach
ultimately may have in antineoplastic therapy almost certainly
will be indirect, as a potential adjunct to chemotherapy or
hyperthermia, not something that is likely to be effective by
itself. Furthermore, many tissues of the host, including plasma
membranes, are affected when fatty acid modification is at
tempted in vivo (109). Therefore, fatty acid replacements that
augment therapeutic effectiveness also are likely to increase
toxicity. Different tissues are modified to varying extents (109),
however, and by considering proliferarne kinetics, it may be
possible to develop protocols that lead to relatively greater
enrichment of the neoplastic cells with a particular type of fatty
acid. Such selectivity probably will be needed in order to ultimately derive any real therapeutic benefit from this approach.
References
1. Medes, G.. and Weinhouse. S. Metabolism of neoplastic tissue. XIII.
Substrate competition in fatty acid oxidation in ascites tumor cells. Cancer
Res., 18: 352-359. 1958.
IN TUMORS
2 Spector, A. A. Fatty acid metabolism in tumors. Prog. Biochem. Pharmacol., 10:42-75, 1975.
3 Spector, A. A. The importance of free fatty acid in tumor nutrition. Cancer
Res., 27: 1580-1586. 1967.
4 Mermier. P., and Baker, N. Flux of free fatty acids among host tissues,
ascites fluid, and Ehrlich ascites carcinoma cells. .1. Lipid Res., 75: 339351, 1974.
and Spector, A. A. Utilization of ascites plasma very
5 Brenneman, D. !•;..
low density lipoprotein triglycéridesby Ehrlich cells. J. Lipid Res., 15:309316, 1974.
6 Lyon, I.. Kannan. R.. Ookhtens. M., and Baker, N. Turnover and transport
of plasma very-low-density lipoprotein triglycéridesin mice bearing Ehrlich
ascites carcinoma. Cancer Res., 42:132-138, 1982.
7 Kannan, R., Lyon, I., and Baker, N. Dietary control of lipogenesis in vivo
in host tissues and tumors of mice bearing Ehrlich ascites carcinoma. Cancer
Res.. ¿0:4606-4611, 1980.
McGee. R., and Spector, A. A. Fatty acid biosynthesis in Ehrlich cells. The
mechanism of short term control by exogenous free fatty acids. J. Biol.
Chem., 250: 5419-5425, 1975.
' Liepkalns, V. A., and Spector, A. A. Alteration of the fatty acid composition
of Ehrlich ascites tumor cell lipids. Biochem. Biophys. Res. Commun., 63:
1043-1047. 1975.
10 Awad. A. H . and Spector, A. A. Modification of the fatty acid composition
of Ehrlich ascites tumor cell plasma membranes. Biochim. Biophys. Acta,
«6:723-731, 1976.
11. Awad, A. B., and Spector, A. A. Modification of the Ehrlich ascites tumor
cell nuclear lipids. Biochim. Biophys. Acta, 450: 239-251, 1976.
12. Kaduce, T. L., Awad. A. B.. Fontenelle. L. J., and Spector, A. A. Effect of
fatty acid saturation on a-aminoisobutyric acid transport in Ehrlich ascites
cells. J. Biol. Chem., 252:6624-6630, 1977.
13. Bums. C. P., Luttenegger. D. G., Dudley, D. T., Buettner, G. R., and
Spector, A. A. Effect of modification of plasma membrane fatty acid
composition on fluidity and methotrexate transport in LI210 murine leu
kemia cells. Cancer Res., 39:1726-1732, 1979.
14 Rao, G. A., and Abraham, S. Enhanced growth rate of transplanted mam
mary adenocarcinoma induced in C3H mice by dietary linoleate. J. Nati.
Cancer Inst., 56:431-432, 1976.
is Wood, R. Hepatoma, host liver, and normal rat liver phospholipids as
affected by diet. Lipids 10: 736-745. 1975.
16. Tashjian, A. H., Voelkel, E. F., Robinson. D. R., and Levine, L. Dietary
menhaden oil lowers plasma prostaglandins and calcium in mice bearing
the prostaglandin-producing IISDM, fibrosarcoma. J. Clin. Invest., 74:
2042-2048,1984.
17. Elegbede, J. A., Elson, C. E., Qureshi, A., Dennis, W. H., and Yatvin, M.
B. Increasing the thermosensitivity of a mammary tumor (CA755) through
dietary modification. Eur. J. Cancer Clin. Oncol., 22:607-615, 1986.
18 Jurkowski, J. J., and Cave, W. T.. Jr. Dietary effects of menhaden oil on
the growth and membrane lipid composition of rat mammary tumors. J.
Nati. Cancer Inst., 74: 1145-1150, 1985.
19 Burns, C. P., Luttenegger, D. G.. and Dudley. D. T. Fatty acid alteration
of L12IO murine leukemia cells. Growth rate and stability of lipid changes
in culture. J. Nati. Cancer Inst., 65: 987-991, 1980.
20. Robert, J., Rebel, G., and Mandel, P. Essential fatty acid metabolism in
cultured astroblasts. Biochimie (Paris), 59:417-423, 1977.
21. Montaudon. D., Vrignaud, P., Londos-Gagliardi, D., and Robert, J. Fluo
rescence anisotropy of cell membranes of doxorubicin-sensitive and -resist
ant rodent tumoral cells. Cancer Res., 46: 5602-5605, 1986.
22 King, M. E., and Spector. A. A. Effect of specific fatty acid enrichments on
membrane physical properties detected with a spin label probe. J. Biol.
Chem., 255:6493-6501, 1978.
23 Poon. R.. Richards. J. M., and Clark. W. R. The relationship between
plasma membrane lipid composition and physical-chemical properties. II.
Effect of phospholipid fatty acid modulation on plasma membrane physical
properties and enzymatic activities. Biochim. Biophys. Acta, 649: 58-66,
1981.
24 Maeda. M., Doi, <).. and Akamatsu, Y. Metabolic conversion of polyunsat
urated fatty acids in mammalian cultured cells. Biochim. Biophys. Acta,
530:153-164. 1978.
25 Ginsberg. B. H., Brown, T. J.. Simon, I., and Spector, A. A. Effect of the
membrane lipid environment on the properties of insulin receptors. Diabe
tes, 30:773-780, 1981.
26. Gerschenson, L. E., Mead. J. F.. Harary, I., and Haggerty, D. G., Jr. Studies
on the effects of essential fatty acids on growth rate, fatty acid composition,
oxidative phosphorylation and respiratory control of HeLa cells in culture.
Biochim. Biophys. Acta, ¡31:42-49, 1967.
Yoo,
T.-J., Chiù.H.. Spector. A. A., Whitaker. R. S., Denning, G. M., and
27.
Lee, N. F. Effect of fatty acid modifications of cultured hepatoma cells on
susceptibility to complement-mediated cytolysis. Cancer Res., 40: 10841090, 1980.
28 Burns.
C. P., and North, J. A. Adriamycin transport and sensitivity in fatty
acid modified Iraki-mil- cells. Biochim. Biophys. Acta, HHH:10-17, 1986.
29. Robert, J., Rebel. G.. and Mandel, P. Utilization of polyunsaturated fatty
acid supplements by cultured neuroblastoma cells. J. Neurochem., 30:543548. 1978.
30. McGee, R.. Jr. Membrane fatty acid modification of the neuroblastoma x
glioma hybrid, NG108-15. Biochim. Biophys. Acta, 66* 314-328, 1981.
31, Love, J. A.. Saum. W. R.. and McGee, R.. Jr. The effects of exposure to
exogenous fatty acids and membrane fatty acid modification on the electrical
4535
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
LIPID MODIFICATION
properties of NG108-1S cells. Cell. Mol. Neurobiol., 5: 333-352, 1985.
32. Yorek, M. A., l h man, B. T., and Spector, A. A. Glycine uptake by cultured
human Y79 retinoblastoma cells. Effect of changes in phospholipid fatty
acid unsaturation. J. Neurochem., 40: 70-78, 1983.
33. Hyman, B. T., and Spector, A. A. Choline uptake in cultured human Y79
retinoblastoma cells: effect of polyunsaturated fatty acid compositional
modifications. J. Neurochem., 38:650-656, 1982.
34. Yorek, M. A., Strom, D. K., and Spector, A. A. Effect of membrane
polyunsaturation on carrier-mediated transport in cultured retinoblastoma
cells. Alterations in taurine uptake. J. Neurochem., 42: 254-261, 1984.
35. King, M. E., Stavens, B. W., and Spector, A. A. Diet-induced changes in
plasma membrane fatty acid composition affect physical properties detected
with a spin-label probe. Biochemistry, 16: 5280-5285, 1977.
36. Guffy, M. M., Rosenberger, J. A., Simon, I., and Burns, C. P. Effect of
cellular fatty acid alteration on hyperthermic sensitivity in cultured LI 210
murine leukemia cells. Cancer Res., 42:3625-3630, 1982.
37. Simon. I., Burns, C. P., and Spector, A. A. Electron spin resonance studies
on intact cells and isolated lipid droplets from fatty acid-modified 1,1210
murine leukemia. Cancer Res., 42: 2715-2721, 1982.
38. Klausner, R. D., Kleinfeld, A. M., Hoover, R. L., and Karnovsky, M. J.
Lipid domains in membranes. Evidence derived from structural perturba
tions induced by free fatty acids and lifetime heterogeneity analysis. J. Biol.
Chem., 255: 1286-1295, 1980.
39. Melchior. D. L. Lipid domains in fluid membranes: a quick-freeze differ
ential scanning calorimetry study. Science (Wash. DC), 234: 1577-1580,
1986.
40. Stubbs, C. !>.. and Smith, A. D. The modification of mammalian polyun
saturated fatty acid composition in relation to membrane fluidity and
function. Him liiin Biophys. Acta, 779: 89-137, 1984.
41. Simon, I., Mathur, S. N., Lokesh, B., and Spector, A. A. Electron-spin
resonance studies of lipid-modified microsomes from Friend erythroleukemia cells. Hindi ¡in.Biophys. Acta, 804: 245-252, 1984.
42. Balear. V. J., Borg, J., Robert, J., and Mandel, P. Uptake of i «Intaniate
and taurine in neuroblastoma cells with altered fatty acid composition of
membrane phospholipids. J. Neurochem., 34: 1678-1681, 1980.
43. Im, H. B., Deutchler, J. T., and Spector, A. A. Effects of membrane fatty
acid composition on sodium-independent phenylalanine transport in
Ehrlich cells. Lipids, 14: 1003-1008, 1979.
44. Burns, C. P., and Dudley, D. T. Temperature dependence and effect of
membrane lipid alteration on melphalan transport in 1.1210 murine leuke
mia cells. Biochem. Pharmacol., 5/: 2116-2119, 1982.
45. Yorek, M. A., and Spector, A. A. Glycine release from Y79 retinoblastoma
cells. J. Neurochem., 41: 809-815, 1983.
46. Biswas, R.. Basu, M., Sen-Majumdar, A., and Das, M. Intrapeptide auto
phosphorylation of the epidermal growth factor receptor. Regulation of
kinase catalytic function by receptor dimerization. Biochemistry, 24: 37953802, 1985.
47. Ho, W. K. K.. and Cox, B. M. Reduction of opioid binding in neuroblastoma
x glioma cells grown in medium containing unsaturated fatty acids.
Biochim. Biophys. Acta, 6««:
211-217, 1982.
48. Ginsberg, B. II., .labour. J., and Spector, A. A. Effect of alterations in
membrane lipid unsaturation on the properties of the insulin receptor of
Ehrlich ascites cells. Biochim. Biophys. Acta, 690: 157-164, 1982.
49. Gould, R. J., Ginsberg, B. H., and Spector, A. A. Lipid effects on the
binding properties of a reconstituted insulin receptor. J. Biol. Chem., 257:
477-484, 1982.
50. Williams, T. P., and McGee, R., Jr. The effects of membrane fatty acid
modification of clonal pheochromocytoma cells on depolarization-dependent exocytosis. J. Biol. Chem., 257: 3491-3500, 1982.
51. Goustin, A. S., Leof, E. B., Shipley, G. D., and Moses, H. L. Growth factors
and cancer. Cancer Res., 46: 1015-1029, 1986.
52. Begin, M. E., Das, U. N., Ells, G., and Horrobin, D. F. Selective killing of
human cancer cells by polyunsaturated fatty acids. Prostaglandins Leukotrienes Med., 19: 177-186, 1985.
53. Burns, C. P., Luttenegger, D. G., and Spector, A. A. Effect of dietary fat
saturation on survival of mice with 1,1210 leukemia. J. Nati. Cancer lust.,
«7:513-515,1978.
54. Guffy, M. M., North, J. A., and Burns, C. P. Effect of cellular fatty acid
alteration on Adriamycin sensitivity in cultured LI210 murine leukemia
cells. Cancer Res., 44: 1863-1866, 1984.
55. Ip, M. M., and Ip, C. Lack of effect of dietary fat on the growth and
estrogen sensitivity of the MT-W9B transplantable mammary tumor. Nutr.
Cancer, 3: 27-34, 1981.
56. Yatvin, M. B., Abuirmeileh, N. M., Vorpahl, J. W., and Elson, C. E.
Biological optimization of hyperthermia: mollificai ion of tumor membrane
lipids. Eur. J. Cancer Clin. Oncol., 19:657-663, 1983.
57. Hillyard, L. A., and Abraham, S. Effect of dietary polyunsaturated fatty
acids on growth of mammary adenocarcinomas in mice and rats. Cancer
Res., 39: 4430-4437, 1979.
58. Hopkins, G. J., and West, C. E. Effect of dietary polyunsaturated fat on the
growth of a transplantable adenocarcinoma in C3HATB mice. J. Nati.
Cancer Inst., 58: 753-756, 1977.
59. Karmali, R. A.. Marsh, J., and Fuchs, C. Effect of u-3 fatty acids on growth
of a rat mammary tumor. J. Nati. Cancer Inst., 73:457-561, 1984.
60. Carroll, K. K. Biological effects of fish oils in relation to chronic diseases.
Lipids, 21: 731-732, 1986.
61. Braden, L. M., and Carroll, K. K. Dietary polyunsaturated fat in relation to
mammary carcinogenesis in rats. Lipids, 21: 285-288, 1986.
IN TUMORS
62. Ip, C., Carter, C. A., and Ip, M. M. Requirement of essential fatty acid for
mammary tumorigenesis in the rat. Cancer Res., 45: 1997-2001, 1985.
63. Welsch, C. W., and Aylswoith, C. F. Enhancement of murine mammary
tumorigenesis by feeding high levels of dietary fat: a hormonal mechanism.
J. Nati. Cancer Inst., 70: 215-221, 1983.
64. Roebuck, B. D. Effects of high levels of dietary fats on the growth of
azaserine-induced foci in the rat pancreas. Lipids, 21: 281 -284, 1986.
65. Ip, C. Ability of dietary fat to overcome the resistance of mature female rats
to 7,12-dimethylbenz(a)anthracene-induced
mammary tumorigenesis. Can
cer Res., 40: 2785-2789, 1980.
66. Ayslworth, C. F., Jone, C., Trosko, J. E., Meites, J., and Welsch, C. W.
Promotion of 7,12-dimethylbenz[ajanthracene-induced
mammary tumori
genesis by high dietary fat in the rat: possible role of intercellular commu
nication. J. Nati. Cancer Inst., 72:637-645, 1984.
67. O'Connor, T. P., Roebuck, B. D., Peterson, F., and Campbell, T. C. Effect
of dietary intake of fish oil and fish protein on the development of i
azaserine-induced preneoplastic lesions in the rat pancreas. J. Nati. Cancer
Inst., 75:959-962, 1985.
68. Tritton, T. R., and Hickman, J. A. Cell surface membranes as a chemotherapeutic target. In: F. M. Muggia (ed.), Experimental and Clinical Progress
in Cancer Chemotherapy, pp. 81-131. The Hague: Man inns Nijhoff Pub
lishers, 1985.
69. Ramu, A., Glaubiger, D., Magrath, I. T., and Joshi, A. Plasma membrane
lipid structural order in doxorubicin-sensitive and -resistant P388 cells.
Cancer Res., 43: 5533-5537, 1983.
70. Ramu, A., Glaubiger, D., and Weintraub, H. Differences in lipid composi
tion of doxorubicin-sensitive and -resistant P388 cells. Cancer Treat. Rep.,
68:637-641, 1984.
71. Siegfried, J. A., Kennedy, K. A., Sartorelli, A. C., and Tritton, T. R. The
role of membranes in the mechanism of action of the antineoplastic agent
Adriamycin. Spin-labeling studies with chronically hypoxic and drug-resist
ant tumor cells. J. Biol. Chem., 25«:339-343, 1983.
72. Murphree, S. A., Tritton, T. R., Smith. P. L., and Sartorelli, A. C. Adriamycin-induced changes in the surface membrane of Sarcoma 180 ascites
cells. Biochim. Biophys. Acta, 649: 317-324, 1981.
73. Inaba, M., Kobayashi, H., Saturai. Y., and Johnson, R. K. Active efflux of
daunorubicin and Adriamycin in sensitive and resistant sublines of P388
leukemia. Cancer Res., 39: 2200-2203, 1979.
74. Bachur, N. R., Gordon, S. L., Gee, M. V., and Kon, H. NADPH cytochrome
P-450 reductase activation of quinone anticancer agents to free radicals.
Proc. Nati. Acad. Sci. USA, 76:954-957, 1979.
75. Sugioka, K., Nakano, H., Noguchi, T., Tsuchiya, J., and Nakano, M.
Decomposition of unsaturated phospholipid by iron-ADP-Adriamycin co
ordination complex. Biochem. Biophys. Res. Commun., 100: 1251-1258,
1981.
76. Hahn, G. M. Hyperthermia and Cancer, New York: Plenum Publishing
Corp., 1982.
77. Lepock, J. R. Involvement of membranes in cellular responses to hyper
thermia. Radiât.Res., 92:433-438, 1982.
78. Yau, T. M. Procaine-mediated modification of membranes and of the
response to X-irradiation and hyperthermia in mammalian cells. Radiât.
Res., «0:523-541, 1979.
Hahn,
G. M., Li, G. C., and Shin, E. Interaction of amphotericin B and 43*
79.
hyperthermia. Cancer Res., 37: 761-764, 1977.
80. Yatvin, M. B., Clifton, K. H., and Dennis, W. H. Hyperthermia and local
anesthetics: potential ion of survival of tumor-bearing mice. Science (Wash.
DC), 205: 195-196, 1979.
81. Yatvin, M. B. The influence of membrane lipid composition and procaine
on hyperthermic death of cells. Int. J. Radiât.Biol., 32: 513-522, 1977.
82. Cress, A. E., Culver, P. S., Moon, T. E., and Gerner, E. W. Correlation
between amounts of cellular membrane components and sensitivity to
hyperthermia in a variety of mammalian cell lines in culture. Cancer Res.,
«.•1716-1721,1982.
83. Konings, A. W. T., and Ruifrok, A. C. C. Role of membrane lipids and
membrane fluidity in thermosensitivity and thermotolerance of mammalian
cells. Radiât.Res., /02: 86-98, 1985.
84. Hazel, J. R., and Prosser, C. L. Molecular mechanisms of temperature
compensation in poikilotherms. Physiol. Rev., 54:620-677, 1974.
85. Gonzalez-Mendez, R., Minton, K. W., and Hahn, G. M. Lack of correlation
between membrane lipid composition and thermotolerance in Chinese ham
ster ovary cells. Biochim. Biophys. Acta, 692: 168-170, 1982.
86. Anderson, R. L., and Parker, R. Analysis of membrane lipid composition
of mammalian cells during the development of thermotolerance. Int. J.
Radiât.Biol., 42: 57-69, 1982.
87. Burns, C. P., Lambert, B. J., Haugstad, B. N., and Guffy, M. M. Influence
of rate of heating on thermosensitivity of L1210 leukemia: membrane lipids
and M, 70,000 heat shock protein. Cancer Res., 46: 1882-1887, 1986.
88. Burrel, A. D., Feldschreiber, P., and Dean, C. J. DNA-membrane associa
tion and the repair of double breaks in X-irradiated Micrococcus radiodurans. Biochim. Biophys. Acta, 247: 38-53, 1971.
89. Yatvin, M. B., Gipp, J. J., and Dennis, W. H. Influence of unsaturated fatty
acids, membrane fluidity and oxygénationon the survival of an /•.'.
coli fatty
acid auxotroph following -, irradiation. Int. J. Radiât.Biol., .'5: 539-548,
1979.
90. Suzuki, S., and Akamatsu, Y. Increase of radiation damage to potassiumion permeability in I. coli cells with decrease in membrane fluidity. Int. J.
Radiât.Biol., 57:475-482, 1980.
91. Edwards, J. C., Chapman, D., and Cramp, W. A. Radiation studies of
4536
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
MEMBRANE
92.
93.
94.
95.
96.
97.
98.
99.
100.
101.
LIPID MODIFICATION
Acholeplasma laidlawii: the role of membrane composition. Int. J. Radiât.
Biol., «.-405-412, 1983.
Burns, C. P., and Spector, A. A. Membrane fatty acid modification in tumor
cells: a potential therapeutic adjunct. Lipids, 22: 178-184, 1987.
Mandel, G., and Clark, W. Functional properties of V.l.-4 tumor cells with
lipid-altered membranes. J. Immunol., 120: 1637-1643, 1978.
Schlager, S. I., and Ohanian, S. H. Tumor cell lipid composition and
sensitivity to humoral immune killing. II. Influence of plasma membrane
and intracellular lipid and fatty acid content. J. Immunol., ¡25:508-517,
1980.
Yoo, T.-J., Kuo, C. Y., Spector, A. A., Denning, G. M., Floyd, R.,
Whiteaker, S., Kim, H., Kim, J., Abbas, M., and Budd, T. W. Effect of
fatty acid modification of cultured hepatoma cells on susceptibility to
natural killer cells. Cancer Res., 42: 3596-3600, 1982.
Spector, A. A., and Yorek, M. A. Membrane lipid composition and cellular
function. J. Lipid Res., 26:1015-1035, 1985.
Levine, L., and Worth, N. Eicosapentaenoic acid: its effects on arachidonic
acid metabolism by cells in culture. J. Allergy Clin. Immunol., 74: 430436, 1984.
Yoneda, T., Kitamurn. M., Ogawa, T., Aya, S., and Sakuda, M. Control of
VX2 carcinoma cell growth in culture by calcium, calmodulin and prostaglandins. Cancer Res., 45: 398-405, 1985.
Levine, L. Arachidonic acid transformation and tumor production. Adv.
Cancer Res., 35:49-79, 1981.
Simmet, T., and Julie, B. M. Inhibition of B-16 melanoma growth in vitro
by prostaglandin D2. Prostaglandins, 25: 47-54, 1983.
Santoro, M. G., Crisari, A., Benedetto, A., and Amici, C. Modulation of
the growth of a human erythroleukemia cell line (K562) by prostaglandins:
IN TUMORS
antiproliferative action of prostaglandin A. Cancer Res., 46: 6073-6077,
1986.
102. Young, M. R., Newby, M., and Meunier, J. Relationships between mor
phology, dissemination, migration, and prostaglandin E2 secretion by cloned
variants of Lewis lung carcinoma. Cancer Res., 45: 3918-3923, 1985.
103. Fulton, A. M., and Heppner, G. H. Relationships of prostaglandin E and
natural killer sensitivity to metastatic potential in murine mammary adenocarcinomas. Cancer Res., 45: 4779-4784, 1985.
104. ('timbrando. C., Broggini, M., Castagnoli, M. N., Doni-Ili. M. G., Noseda,
105.
106.
107.
108.
109.
A., Visintainer, M.. Garattini, S., and Fanelli, R. Prostaglandin and thromboxane synthesis by Lewis lung carcinoma during growth. Cancer Res., 45:
3605-3608, 1985.
Young, M. R., and Newby, M. Enhancement of Lewis lung carcinoma cell
migration by prostaglandin E2 produced by macrophages. Cancer Res., 46:
160-164, 1986.
Rothblat, G. H., Arbogast, L. Y., and Ray, E. K. Stimulation of esterified
cholesterol accumulation in tissue culture cells exposed to high density
lipoproteins enriched in free cholesterol. J. Lipid Res., 19: 350-358, 1978.
Grundy, S. M., and Ahrens, E. H., Jr. The effects of unsaturated dietary
fats on absorption, excretion, synthesis, and distribution of cholesterol in
man. J. Clin. Invest., 49: 1135-1152, 1970.
Lee, T. H., Hoover, R. L., Williams, J. D., Sperling, R. I., Ravalese, J., Ill,
Spur, B. W., Robinson, D. R., Corey, E. J., Lewis, R. A., and Austin, K. F.
Effect of dietary enrichment with eicosapentaenoic and docosahexaenoic
acids on in vitro neutrophil and monocyte leukotriene generation and
neutrophil function. N. Engl. J. Med., 312: 1217-1224, 1985.
Burns, C. P., Rosenberger, J. A., and Luttenegger, D. G. Selectivity in
modification of the fatty acid composition of normal mouse tissues and
membranes in vivo. Ann. Nutr. Metab., 27: 268-277, 1983.
4537
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.
Biological and Therapeutic Potential of Membrane Lipid
Modification in Tumors
Arthur A. Spector and C. Patrick Burns
Cancer Res 1987;47:4529-4537.
Updated version
E-mail alerts
Reprints and
Subscriptions
Permissions
Access the most recent version of this article at:
http://cancerres.aacrjournals.org/content/47/17/4529
Sign up to receive free email-alerts related to this article or journal.
To order reprints of this article or to subscribe to the journal, contact the AACR Publications
Department at [email protected].
To request permission to re-use all or part of this article, contact the AACR Publications
Department at [email protected].
Downloaded from cancerres.aacrjournals.org on June 15, 2017. © 1987 American Association for Cancer Research.