(CANCER RESEARCH 48, 899-906, February 15, 1988]
Bromine-80m-labeled Estrogens: Auger Electron-emitting, Estrogen Receptordirected Ligands with Potential for Therapy of Estrogen
Receptor-positive Cancers1
Eugene R. DeSombre,2 Ronnie C. Mease,3 Alun Hughes, Paul V. Harper, Onofre T. DeJesus,4 and
Arnold M. Friedman5
Ben May Institute fE. R. D., A. H.J and Department of Radiology ¡P.V. H., O. T. D., A. M. F.], The University of Chicago, Chicago, Illinois 60637; and Argonne
National Laboratory [R. C. M., O. T. D., A. M. F.J, Argonne, Illinois 60439
ABSTRACT
To assess their possible use for estrogen receptor (ER)-directed radio
therapy of estrogen receptor-containing cancers, two estrogens were
synthesized with the Auger electron-emitting nuclide bromine-80m and
administered to immature female rats. Both the triphenylethylene-based
estrogen, |80mBr]-2-bromo-l,l-bis(4-hydroxyphenyl)phenylethylene (BrBHPE) and the steroidal estrogen |80mBr|17a-bromovinylestradiol,
showed substantial diethylstilbestrol-inhibitable localization only in the
estrogen target tissues, the uterus, pituitary, ovaries, and vagina and,
except for the liver and intestines, generally lower concentrations in all
other tissues at both 0.5 and 2 h. The |80mBr|Br-BHPE (specific activity,
8700 Ci/mmol), was shown to bind specifically to the low salt extractable
ER of the rat uterus. Comparing ¡.p.,i.V., and s.c. administration of
|H""'Br|BlII*Kthe i.p. route was found to be particularly advantageous to
effect maximum, DES-inhibitable concentrations of radiobromine in the
ER-rich target organs in the peritoneal cavity. When the tissue distribu
tion of the C"""Br|Br-BIIPK was compared with that of sodium bromide80m, it was apparent that no substantial amounts of radiobromine were
released from the bromoestrogen prior to its target tissue localization.
The substantial concentration of these bromine-80m-labeled estrogens in
ER-rich tissues, combined with previously reported evidence for the
effective radiotoxicity of Auger electron-emitting nuclides within cell
nuclei suggest a good potential for such ligands for therapy of ER positive
cancers.
INTRODUCTION
Endocrine-based treatment for breast and endometrial can
cers has been an important therapeutic approach for some time
(1, 2). When it became apparent that fewer than half of the
patients responded to endocrine therapy, methods were sought
to identify the "hormone-dependent" cancers. With the recog
nition that the presence of ER6 in breast cancers is an important
discriminant in differentiating patients who are good candidates
for endocrine therapy from those who are unlikely to respond
to such treatments (3, 4), it became possible to direct such
therapy to individuals most likely to benefit (5). However,
reports from many institutions have clearly shown that while
few breast cancer patients whose tumors lack ER respond to
endocrine therapy, only about half of those with ER-positive
lesions receive objective benefit (6). Likewise, while only about
a quarter of endometrial cancers respond to endocrine therapy
(7), a significantly greater proportion are found to contain ER.
In the case of ovarian carcinomas, where few patients have been
reported to obtain remission to endocrine therapy (7), up to
half of the primary lesions are found to have ER (7, 8).
Assay of PgR, in the cancers, in addition to ER, has improved
the accuracy of identifying the "hormone-responsive" cancers
since in both breast (9) and endometrial (10) cancers it has been
found that patients with ER-positive cancers lacking PgR are
less likely to benefit from endocrine therapies than those whose
lesions also contain PgR. Nonetheless, even though these recep
tor assays help identify the "hormone-responsive" cancers, at
best only about one-fourth of all patients receive objective
benefit from current endocrine therapies while as many as twothirds have ER-positive cancers. Accordingly, it would be most
useful to have new therapies based entirely on the presence of
ER in the cancer, independent of whether the cancer is actually
"hormone dependent."
We have suggested such an approach, using estrogen recep
tor-directed radiotherapy based on incorporating the Auger
electron-emitting nuclide bromine-80m into a ligand which
retains high affinity for the estrogen receptor (11). The metastable bromine-80m has a half life of about 4.42 h and emits
an average of 7-10 low energy Auger and Coster-Kronig elec
trons.7 We have recently reported that a bromine derivative of
triphenylethylene, Br-BHPE, is estrogenic and competes effec
tively with estradici (about one-third as well as unlabeled E2)
for binding to the estrogen receptor8 (12). This report describes
our initial findings on the in vivo distribution of bromine-SOm
labeled Br-BHPE and, for comparison,.similar studies with the
steroidal bromo-estrogen, 17a-[80mBr]bromovinyl estradiol, in
the immature female rat.
Received 6/26/87; revised 10/26/87; accepted 11/12/87.
The costs of publication of this article were defrayed in part by the payment
of page charges. This article must therefore be hereby marked advertisement in
accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
1Supported by the National Institutes of Health (CA27476, HD1SS13), De
partment of Energy contract W-31-109-ENG-38 and the Julius J. Reingold
Fellowship Fund.
2 To whom requests for reprints should be addressed, at The Ben May Institute,
The University of Chicago, 5841 South Maryland Avenue, Chicago, IL 60637.
3 Present address: Medical Division, Brookhaven National Laboratory, Asso
ciated Universities, Inc., Upton, NY 11973.
4 Present address: Department of Medical Physics, University of Wisconsin
Medical Center, 1300 University Avenue, Madison, WI 53706.
' Deceased, to whose memory this manuscript is dedicated.
'The abbreviations used are: ER, estrogen receptor; Br-BHPE, 2-bromo-l,l,bis(4-hydroxyphenyl)-2-phenylethylene; Br-VE2, 17a-bromovinylestradiol; 16aBrE2, 16a-bromoestradiol-170; 16a-BrME2, 16a-bromo-I I$-methoxyestradiol17ft 17a-BrVME2, 17a-bromovinyl-l l/3-methoxyestradiol-17/3; DES, diethylstilbestrol; E2, 17/3-estradiol; PgR, progestin receptor; HPLC, high-performance
liquid chromatography; lUdR, S'-iodo-2'-deoxyuridine; BrUdR, 5'-bromo-2'deoxyuridine; TK,„E,10 mM Tris, 10 row KCI, 1 mM EDTA (pH 7.4) buffer;
DCC, dextran-coated charcoal; d.p.m., disintegrations per minute.
MATERIALS
AND METHODS
Materials. Unless otherwise mentioned chemicals were reagent grade
or better. Selenium-80 was purchased from Isotek, Miamisburg, OH.
Immature female rats, 22 days old, were obtained from SASCO, Mad
ison, WI. Acetonitrile, HPLC grade and Norit-A were from Fisher.
Dextran T40 was obtained from Pharmacia, DES from Sigma. Isotonic
saline, bacteriostatic injectant was USP, and the absolute ethanol was
from Midwest Solvents of Pékin,IL.
Production of Bromine-Hum. Bromine-80m was prepared by irradiat
ing a 0.15-mm layer of >99% enriched selenium-80 on a cooled
aluminum target at a 10°grazing angle with a 20 n.\ collimated 15
MeV proton beam using a CS-15 cyclotron at the University of Chicago
7G. F. Powell, O. T. DeJesus, P. V. Harper, and A. M. Friedman, manuscript
in preparation.
" E. R. DeSombre, R. C. Mease, J. Sanghavi, T. Singh, R. H. Seevers, and A.
Hughes. Estrogen receptor binding affinity and uterotrophic activity of triphenylhaloethylenes, manuscript in preparation.
899
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"Br-LABELED ESTROGENS
with an end of bombardment yield of 1-2 mCi per /iA-h. After dissolving
the Se target in 15 ml of 85% phosphoric acid and 10 ml of 30%
hydrogen peroxide the radiobromine (a mixture of bromine-80 and
bromine-80m) was removed by steam distillation. The distillate was
adjusted to >pH 8, evaporated to dryness, and reacted directly with the
precursor. Further details on the production of bromine-80m will be
reported elsewhere.
Synthesis of |80mBr|Br-BHPE. The """Br (no carrier added) solution
was evaporated to dryness in a 0.5 dram Kimble screw cap vial by
warming in a nitrogen stream. After dissolving the bromide in 25 n\
water, 100 ^1 of a 4.8 mM ethanolic solution of l,l-bis(4-hydroxyphenyl)-2-phenyl-2-tri-n-butylstannylethylene
(11) and 100 ¿dof a 2:1
mixture of 30% hydrogen peroxide:glacial acetic acid were added. The
vial was sealed, shaken, and allowed to stand at room temperature for
10 min. The reaction mixture was then injected onto a Ranin 0.46 \
25 cm, 5 j/m, C|8 reversed-phase HPLC column with 40% acetonitrile/
water as eluent. The [80mBr]Br-BHPE eluted at 33 min as 60% of the
and the determination of the specific activity of the |80mBr]Br-BHPE,
we calculated that the actual concentration used for the ["'""BrjBrBHPE incubations above was 9.1 nM. Considering that the affinity of
Br-BHPE for the receptor is about one-third of that of estradici,8 it is
likely that saturating conditions were employed for these assays and
therefore the specific activity calculated should be correct.
SOmBr-labeledEstrogens in Vivo. The 80mBr-labeledBr-BHPE and BrVE2 were diluted in isotonic saline containing 10% ethanol, with or
without DES, and 200 pi injected in each rat. Assay of the delivered
injectants gave the following concentrations: 12.4 pCi/200 pi, Br-BHPE
alone; 14.3 pCi/200 A for Br-BHPE with l pg DES; 17.7 pCi/200 pi
for BrVE2 alone and 19.8 pCi/200 ni for BrVE2 with l pg DES. It
appeared that the presence of DES reduced the losses of radioactive
estrogen on expulsion of the injected material from the syringes since
both injectants for each radioactive estrogen were made by similar
dilutions of a stock solution. For the first set of experiments we were
unable to determine the specific activity of the [80mBr]bromo-estrogens
total eluted radioactivity, and was concentrated by rotary centrifugation
under vacuum.
Synthesis of |80mBr|BrVE2. The 80mBr~(no carrier added) solution
by sedimentation analysis. Specific activities, obtained from the ratio
of the radioactivity to the mass determined from the IV tracing of the
was evaporated in a 0.5 dram Kimble screw cap vial to dryness by HPLC elution, for both of the purified radiobromine labeled estrogens
were approximately 4000 Ci/mmol. Inorganic bromine-80m, as sodium
warming in a stream of nitrogen. To this residue was then added 30 pi
water, 100 ¿ilof a 3.0 x 10~2 M ethanolic solution of 17t»-E-tri-ii- bromide in saline, was assayed at 111 //( ï/200¡A.
The injectants were
administered i.p. to 22-day-old female Sprague-Dawley rats and at onebutylstamiyU invii-stradini [prepared from a tetrahydropyran-ether pro
half and 2 h, three animals for each group were sacrificed by decapita
tected precursor, stanylated as for the triphenylethylene (11) and
deprotected9] and 100 M'of a 2/1 (v/v) 30% hydrogen peroxide-glacial
tion. The various tissues were removed, dissected free of extraneous
tissue, gently blotted on filter paper, and rapidly weighed. For the
acetic acid solution. The vial was sealed, shaken, and allowed to stand
studies comparing the route of administration, the [80mBr]Br-BHPE for
10 min at room temperature. The contents of the vial were injected
onto the radio-HPLC (0.46 x 25 cm, 5 ^m, Cig reversed-phase column,
s.c. and i.v. injections were made up the same way in isotonic saline,
10% ethanol, and 200 /<!were administered to each animal. For i.p.
mobile phase 60% water, 40% acetonitrile, flow rate 1.1 ml/min) and
1.1 ml fractions were collected. The 17a-E-bromovinylestradiol was
injections two concentrations were prepared, both for administration
eluted at 12.5 min containing 53% of the total radioactivity eluted from
in 1.0 ml of isotonic saline, 2% ethanol. In each case the injectants
the column. The product was concentrated at 40-45°Cunder a stream
prepared to include DES contained 1.0 tig of DES in the volume to be
of nitrogen and reconstituted in 1/1 (v/v) ethanol/water.
injected. The amounts of injected radioactivity, determined from assays
Sedimentation Analysis of |80mBr|Br-BHPE. For sedimentation analy
of aliquots of the actual injected volumes delivered from the syringes,
sis, 75 n\ of TK10E containing (60 MCi)of [80mBr]Br-BHPE were added
were: high i.p. dose [80mBr]Br-BHPE alone (1.0 ml) 61 pCi, with DES
69 pCi; low i.p. dose [80mBr]Br-BHPEalone (1.0 ml) 9.2 pCi, with DES
to 75 ¡tiof TKioE, to which was added 600 p\ of rat uterine cytosol
prepared by a 30 min 208,000 x g, 2'C centrifugation of a 1+4
16.1 pCi; S.C.and i.v. doses (0.2 ml): [80mBr]Br-BHPE alone (0.2 ml)
homogenate of immature rat uteri in I Klnl . In parallel, 25 ß\
eil l k,,¡I 7.3 pCi, with DES 14.5 pCi. For all experiments the tissue samples
containing 20 pCi of [80mBr]Br-BHPE were added to 25 M!of 10 ¿IM
and 200 ti\ portions of blood were counted in a gamma-counter set to
DES in TKioE buffer, followed by 200 pi of the same rat uterine cytosol.
record the high energy emission (i.e., 200-1000 keV) of the daughter
After mixing and incubation for l h in shaved ice these mixtures were
80Br isotope (tv, - 17 min), at equilibrium with the 80mBrparent by the
added to charcoal pellets from an equivalent volume of 1% Norite,
time of counting. Quantifying on this higher energy emission substan
0.5% dextran T40 in TK,0E buffer (DCC), the charcoal pellets resustially reduced tissue quenching which can be a problem with the
pended with a vortex mixer, incubated 10 min in ice and centrifuged at
relatively low energy y emission of the 80mBr.d.p.m. were obtained by
low speed in the cold. The supernatant solutions were removed and
comparison of the counting efficiency for the 600-KeV peak of a sample
stored in ice. Two hundred ¿dportions of the DCC supernatant incu
of 80Br to a Cesium 137 standard, and because of the short half-life of
bated in the absence of DES were added to 50 ti\ (2.5 pg) of the
80mBr,all tissue and injectant radioactivity were decay corrected to the
monoclonal antiestrogen receptor antibody H222 (13) in TKioE or 50
time of injection (time zero). The results were calculated as means and
id of TKioE, and the tubes were incubated for another hour in the cold
standard deviations for the percentage of the dose present in each tissue
prior to sedimentation analysis on high salt, 10-30% sucrose gradients
divided by the tissue wet weight in grams, or as tissue to blood ratios
in 10 mM Tris, 400 mM KC1, 1 mM EDTA (pH 8.4) buffer. Low salt
gradients, i.e., 10-30% sucrose gradients in TK,0E buffer, were used to
(dpm per mg wet weight in the tissue divided by the dpm/pl of blood
analyze the amount of specific binding of [80mBr]Br-BHPE by layering
of the same animal), thereby allowing direct comparisons of the some
200-pl portions of the charcoal-treated supernatants incubated with
what different amounts of radioactivity injected, as well as individual
radiolabeled Br-BHPE in the presence or absence of DES, described
animal differences.
above, centrifugation for 14 h at 208,000 x g, 2'C, fractionation of the
Because of the size of the counting chamber of the gamma counter,
portions (generally 100-200 mg) of the larger tissues were assayed
gradients and assay of the fractions for radioactivity. For determination
of the effective specific activity of [80mBr]Br-BHPE the results of these
[liver, intestine, brain (cerebrum), muscle (femur)J. The entire uterus,
low salt gradient assays were compared with a similar saturation assay
vagina, pair of ovaries, pair of adrenals, and hemi diaphragm were
for the estrogen receptor of the same rat uterine cytosol with [3H]taken. Fat was taken from the periphery of the inguinal mammary fat
estradiol. For that purpose 25 pi of 100 nM 6,7-['H]estradiol (specific
pads to avoid most of the mammary epithelium. Blood (200 pi) was
activity, 41 Ci/mmol; Amersham) was added to either 25 n\ of TK|0E
taken directly for assay. Because of the small size of the pituitary and
buffer or 25 pi 10 MMDES in TK,0E and 200 pi of the rat uterine
the rapid dehydration on excision, the entire tissue was placed directly
cytosol extract added to each and mixed. After incubation for l h in
into the assay tube without attempting to obtain a wet weight. The
ice these mixtures were each added to the pellets of equal volumes of
calculations all assumed a wet weight of 1 mg for this tissue.
DCC, as above, mixed, incubated in ice for 10 min, centrifuged, and
decanted. Two hundred pi of these DCC-treated extracts were analyzed
RESULTS
at the same time on similar low salt gradients. Following this analysis
' R. C. Mease, E. R. DeSombre, O. T. DeJesus, P. V. Harper, and A. M.
Friedman, manuscript in preparation.
The specific incorporation
of [80t"Br]Br-BHPE by various
tissues of the immature rat (% dose per gram wet weight of
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2017. © 1988 American Association for Cancer Research.
•Br-LABELEDESTROGENS
tissue) is shown in Fig. 1. It can be seen that DES significantly
inhibited uptake of [80mBr]Br-BHPE in the usual estrogen target
tissues: the uterus, pituitary, vagina, and ovaries. No such DESinhibitable uptake was seen in the other tissues assayed: fat,
liver, adrenal, intestine, leg muscle, diaphragm, or brain. This
pattern of "0mBruptake was the same at both 0.5 and 2 h, with
the radioactivity generally lower at 2 h. The very substantial
specific uptake (difference without and with DES) by the uterus
at both times is evident in Fig. 1. Although the intestinal
concentration was more than 10% dose/g at 0.5 h, there was
no significant difference when the radiolabeled estrogen was
administered alone or along with DES. Similar results, ex
pressed as the tissue to blood radioactivity ratio, are shown in
Fig. 2. This manner of presentation minimizes variations
among animals and differences in the amount of labeled estro
gen each animal actually received, but, as can be seen, showed
essentially the same pattern of specific uptake by estrogen target
tissues. It is clear that substantial tissue-to-blood ratios are seen
for most of the target tissues, but most obvious is the ratio of
20 for the uterus at 0.5 h.
Similar studies with [80mBr]Br-VE2 are shown in Figs. 3 and
4. With this radiobromine-labeled estrogen we also found sig
nificant, DES-inhibitable uptake by the classical estrogen target
tissues, uterus, pituitary, vagina, and ovary. Although a rela
tively high 0.5-h uptake was seen for the liver (Fig. 3), with a
higher percentage of dose/g in the absence than in the presence
of DES, it is evident from the very large standard deviations
that neither this difference nor that of the ovary at 0.5 h in the
presence and absence of DES are statistically significant. How
ever at 2 h specific uptake was seen in the ovaries but not the
liver. When expressed as tissue-to-blood ratios, Fig. 4, it is clear
that there was no DES-inhibitable difference in this ratio for
the liver at either time point.
Although the percentage of dose/g of the bromotriphenylethylene localized in the uterus at 0.5 h (Fig. 1) was nearly
B
0.5 Hr
2 Hr
Fig. 2. Tissue-to-blood ratios of radioactivity after ¡.p.administration of
[•°"'Br|Br-BHPE.
Using the experimental protocol, described in Fig. 1 and the
experimental section, the d.p.m. (corrected to time 0) per mg wet weight of each
assayed tissue in each animal was divided by the d.p.m. per /.I of blood (also
corrected to time 0) for each animal and the mean value for each group plotted
along with the SD of the mean. O. results from animals also given I «ig
DES; *,
statistical significances as for Fig. 1.
I
25Ut
20
15-
10
I
2 Hr
0.5 Hr
Fig. 3. Specific uptake of 17a-[*°™Br]bromovinylestradiol
administered i.p.
alone (D) or in the presence of l pg DES (ffl).See legend to Fig. I and experimental
section for details; *, statistical significance (see Fig. 1).
0.5 Hr
Fig. 1. Specific uptake of [*°™Br)Br-BHPE
in tissues of the immature female
rat. The [""BrlBr-BHPE was administered i.p. alone (D) or with l »ig
DES (^).
At the time indicated tissues were excised, weighed, and assayed for radioactivity
as described in the experimental section. Results, mean percentage of dose/g wet
weight of tissue; error bars, SD of the mean. Tissue codes, uterus (/"/): pituitary
(fit); vagina (V); ovary (O); fat (/'); liver (/.); adrenal (I); intestine (/): leg muscle
(A/); hem ¡diaphragm(/)); brain (Br); blood (/?/). Statistical significance of concen
trations in each tissue comparing the tissue from animals without and with
concomitant DES administration: *, P < 0.05; ", P < 0.02; "", P < 0.002.
double that seen with the steroidal estrogen (Fig. 3), the local
ization expressed as tissue/blood ratios was very similar (Figs.
2 and 4). Part of this difference may be due to the fact that
rcanalysis of the injected bromoestrogens showed that the
[80mBr]Br-BHPE, but not the Br-VE2, contained some free
bromide, apparently formed during the evaporation of the elution solvent of the HPLC purification. Although there were
only low tissue-to-blood ratios in target or nontarget tissues
after administration of [80mBr]sodium bromide, Fig. 5, the ratios
did not change a great deal over the first 2 h.
Thus, the patterns, showing specific uptake by estrogen target
tissues for both the nonsteroidal and steroidal bromine-contain-
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2017. © 1988 American Association for Cancer Research.
•"•Br-LABELED
ESTROGENS
activity of the labeled estrogen by sedimentation analysis (Fig.
6). A comparison of the DES-inhibitable binding of [3H]estradiol for a rat uterine "cytosolic" ER with that for [80mBr]BrBHPE indicated that the [80l"Br]Br-BHPE had a specific activity
30
of about 8700 Ci/mmol, about 200 times the specific activity
of the [3H]E2. We were also able to confirm that the [80mBr]Br-
Ut
T T
BHPE actually bound to the estrogen receptor, seen by the
downfield shift of the salt dissociated, 4S, form of the receptor
complex incubated with monoclonal antibody to ER (Fig. 7).
When the uterine uptake of this [80mBr]Br-BHPE was com
Ut
201
pared following the three routes of administration it was evident
that there was a substantially higher uptake by the uterus
following i.p. administration than by the other two routes at
l
Pit
10
net DPM
net DPM
OH
Pit
JL
m
%
me
i
IO
0.5 Hr
Fraction Number
Fig. 6. Sedimentation analysis of the binding of |""'"lìrll!rHIIl'I lo low salt
extractable estrogen receptor from immature rat uterus. Saturating concentrations
of [3H)E2 (41 Ci/mmol) and |M"Br]Br-BHPE, alone (
) or in the presence of
1 Amolar DES (
), were incubated with the IK containing extract, excess
unbound estrogen removed with DCC, and the labeled extracts analyzed as
described in the experimental section. The d.p.m. were corrected for decay to
time 0. Bot, bottom of the gradient.
2 Hr
Fig. 4. Tissue-to-blood ratios of radioactivity after i.p. administration of \7a[•°™Br]bromovinylestradiol.
See Fig. 2, legend, and experimental section for
details. D. results from animals also treated with 1 jig DES; *. statistical signifi
cance (see Fig. 1).
DPM
300,000-1
5 ,
3Ì
Fig. 5. Tissue-to-blood ratios of radioactivity after i.p. administration
["""Brlsodium bromide. See Fig. 2, legend, for description.
of
200,000
ing estrogens, were significantly different than the pattern seen
when inorganic radiobromide was injected, Fig. 5. This clearly
indicated that the radiobromine was not rapidly eliminated
from the estrogens before the estrogens can be specifically taken
up by the target tissues.
We explored i.p. administration of the bromine-80m-labeled
estrogens as the first approach because of our interest in the
applicability of the therapy to the i.p. métastasesoften accom
panying the spread of ovarian cancer. We were struck, however,
by the disproportionate specific localization of Br-BHPE in the
uterus and especially ovary, compared with the pituitary. It
seemed likely that this could be due to direct access of the
radiolabeled estrogen to these tissues while the pituitary would
not have access to such a high initial concentration of com
pound. Therefore, we compared the distribution of [80mBr]BrBHPE which was administered i.v. (tail vein), s.c. (back), and
i.p. at the same two time points. With improved production of
80mBrfor these studies, providing more significant amounts of
80mBrto work with, we were able to directly assay the specific
Cytosol
+
H222
100,000
Bot
IO
Fraction
20
30
Number
Fig. 7. Interaction of ["""BrlBr-BHPE bound to rat uterine low salt extract
with monoclonal antibody to the estrogen receptor. DCC-treatcd ¡"""BrlBr-BHPE
containing rat uterine cytosol described in Fig. 6 was incubated with buffer or 10
(it!/ml monoclonal anti-ER antibody H222 (13) and analyzed by sedimentation
analysis on high salt sucrose density gradients as described in the experimental
section. Bot, bottom of the gradient.
902
Downloaded from cancerres.aacrjournals.org on June 16, 2017. © 1988 American Association for Cancer Research.
"Br-LABELED ESTROGENS
both times (Fig. 8). In each case, nonetheless, most of the
uptake was DES-inhibitable. Both the low and the high dose of
[80mBr]Br-BHPE administered i.p. showed a high level of spe
cific uptake in the uterus; by 2 h very little uterine binding was
seen in rats which received DES. The preferential uterine
uptake via the i.p. route was especially evident when the data
was presented as tissue-to-blood ratios (Fig. 9). Under these
conditions the uterus-to-blood ratios on i.p. administration
were 30 to 70 while the ratios after s.c. or i.v. administration
30-25-ECO5_
20ratsT[~^~|I1
o>
a01S
15-O•a
(Dc"*
5-
7^7052
'""' j | ;; ;
Time
(hr)-rJL05
2RouteDose(ng)¿¿Ci_L0
5-r2IP
2SubO
I.V.031
IP26
_ _•
;
0.5
0.3173
03961
92immature
73
Fig. 8. Comparison of uterine concentration of radioactivity after administra
tion of ["""BrJBr-BHPE to immature female rats by three different routes.
("°™Br]Br-BHPE
(specific activity, 8700 Ci/mmol) was administered at the doses
shown alone or along with 1 mi DES (Dl. i.p., s.c. in the back, or i.v. (tail vein)
and the uteri assayed by the procedure indicated in Fig. 1. Statistical significance,
comparing the results without and with DES; high dose i.p.: 0.5 h (P = 0.1); 2 h
(/>< 0.01); low dose i.p.: 0.5 h (/>< O.OOI);2 h (/><O.OI); s.c.: 0.5 h (P< 0.01);
2 h (P < 0.01); i.v.: 0.5 h (P < 0.001); 2 h (P = 0.1).
70-60-50-
oraKT3
were less than 10 at both time points. It was also of considerable
interest for eventual therapeutic use, that an almost propor
tional increase in the uterus-to-blood ratio was seen with the
higher dose of compound, which is still a minute dose because
of the high specific activity.
The tissue-to-blood ratios for all tissues, comparing i.p., s.c.,
and i.v. routes, as well as the actual blood values for each group
are shown in Table 1. The blood levels were higher, especially
at early time points, following s.c. and i.v. administration
compared with i.p. As expected, there was a more distinct
decrease in radioactivity in blood between 0.5 and 2 h for i.V.,
compared with s.c., administration of the bromoestrogen. The
most striking differences seen, however, related to the elevated
tissue-to-blood ratios for the peritoneal target tissues (i.e.,
uterus, vagina, and ovary) following i.p. administration of the
Br-BHPE. They remained very pronounced at 2 h for these
tissues in animals administered the radiolabeled Br-BHPE
alone, while in those animals administered Br-BHPE along
with DES, by 2 h there was no significant difference related to
route of administration. One of the other important, significant
differences related to route of administration was the relative
localization of the labeled estrogen in the pituitary. Following
i.p. injection the uterus-to-pituitary ratio (i.e., uterus/blood to
pituitary/blood ratio) varied from 3.6 to 5.9 for the two doses
at the two time points, while after s.c. or i.v. administration
this ratio was about 0.35 for both time points. A similar pattern
was seen for the relative tissue-to-blood ratios for ovary com
pared to pituitary. While after s.c. or i.v. administration the
ovary-to-blood ratio was only about 3; after i.p. administration
consistently higher ratios of 12 to 17 were seen. That this
ovarian uptake was receptor dependent was seen by the sub
stantially lower ratios when DES was administered. The kidney
and adrenal levels of radioactivity appear to be generally higher
after i.p. administration but the differences generally were not
statistically significant. Neither were the differences in uptake
by these tissues in animals receiving the [80mBr]Br-BHPE alone
compared with those also given DES. It would appear that the
i.p. route is particularly advantageous to provide preferential
localization of radiolabeled estrogens in ER-rich tissues in the
peritoneal cavity while minimizing the localization in the pitui
tary.
rats0.5
DISCUSSION
The results indicate that bromine-80m-labeled l,l-bis(4-hydroxyphenyl)-2-bromo-2-phenylethylene
is a good candidate for
further study as an estrogen-receptor-directed
therapeutic
30-•Vi20-10-Time
agent, because it showed very good target tissue-specific, DESinhibitable uptake by ER-rich tissues. Its concentration in other
tissues was not DES inhibitable and was generally lower. There
was a distinct advantage to i.p. administration for maximum
localization of this radiolabeled estrogen in the uterus, vagina,
and ovary, where the compound apparently had greater direct
access to the tissue prior to its metabolism. While localization
of this compound in these estrogen target tissues, following s.c.
or i.v. administration, was still appreciable, there was a clear
(hr)
2 0.5 2
2IP2 0.5
advantage to the i.p. route. The concentration of 17a-[80mBr]RouteI*IJL0.5
I.V.0.39 Sub 0
IPDose(ng)
bromovinyl
estradici, while also significant and DES-inhibita
26/J.CÌ
0.3192 0.31
ble in the ER-rich tissues, nonetheless was consistently lower
61immature
73
73
than that seen for the bromotriphenylethylene.
This would
Fig. 9. Comparison of uterine tissue-to-blood radioactivity ratios after admin
istration of ["""BrlBr-BHPE, by three different routes. Details given in Figs. 2
suggest that at least for treatment purposes the nonsteroidal
and 8. Statistical significance comparing the results in the absence and presence
bromoestrogen may have an advantage over the steroidal Brof DES; high dose IP: 0.5 h (/><O.OI); 2 h(/><0.05); low dose i.p.: 0.5 h(/><
VE2. When compared as tissue-to-blood ratios, the bromovinyl
0.01); 2 h (P < 0.001); s.c.: 0.5 h (P < 0.02); 2 h (P < 0.01); i.v.: 0.5 h (NS); 2 h
(P < 0.05).
estradiol seemed superior, so that for imaging use this steroidal
903
40-o0mÕ
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•Br-LABELEDESTROGENS
Table 1 Tissue-to-blood ratios for [™mBr¡BHPE
High dose i.p.
0.5 h
Low dose i.p.
2h
0.5 h
+DES"
+DES°
+DES°
+DES°
Alone
Alone
Alone
Alone
5.0*15.3
±
±3.13.7
20.916.7
±
0.982.8
±
6.712.5
±
0.33.5
±
7.613.5
±
UterusOvaryVaginaKidneyAdrenalPituitaryBrainFatMuscleLiverIntestineBlood
1.11.7
±
±3.43.5
2.22.2
±
±8.16.1
1.12.5
±
1.83.8
±
0.052.3
±
±0.896.5
±0.401.8
0.601.7
+
0.322.2
±
0.932.1
±
2.91.9
±
0.801.7
±
0.362.32.55.50.521.41.04.15.90.110.51.10.020.460.100.070.650.70
±
0.421.9
±
1.51.±
0.083.4
±
±0.382.3
±0.892.4+
±0.161.1
±0.012.5
±0.303.0
9
±0.433.4
1.113.6
+0.353.3
0.73.0
+
0.487.7
±
0.575.0
±
1.22.3
±
4.33.9
±
0.850.53
±
0.920.65
±
±2.70.63
1.10.30
±
2.60.50
±
3.90.30
±
1.90.23
±
0.020.80
+
0.031.2
±
0.231.4
±
0.560.74
±
0.101.3
±
0.201.3
±
41.1±0.1
0.430.74
+
0.120.60
+
0.440.80
+
0.350.55
+
0.340.44
±
±0.350.94
1.00.36
±
0.102.5
+
56.0±0.1
0.273.6
±
±0.102.3
0.064.3
±
0.071.9
±
0.051.5
±
2.018.8
+
0.322.8
+
0.474.9
±
2.510.5
±
1.09.8
±
0.89.4
±
±0.163.7
7.20.27
+
5.20.43
+
0.520.46
±
1.20.40
±
±9.10.42
1.50.42
±
3.00.40
±
(%/g)'33.6
+ 0.216.0
+ 0.1049.0
+ 0.193.9
+ 0.1432.7
+ 0.122.2
±0.106.6
±0.0668.3
±0.23
Tissue
0.5 h
2h
0.5 h
2h
0.14*1.3
+
1.02.9
0.591.8
+
2.73.1
+
±0.341.0
UterusOvaryVaginaKidney-AdrenalPituitaryBrainFatMuscleLiverIntestineBlood
±0.51.4
0.92.3
±
0.392.0
±
0.330.90
+
0.171.3
+
0.581.6
+
1.04.0
+
0.254.0
±
0.922.1
±
±0.911.3
0.331.7
±
0.251.5
+
+0.52.1
0.281.8
±
0.071.9
±
±0.251.8
1.51.6
±
±0.261.9
±0.191.5
0.641.6
+
0.211.1
+
0.190.65
+
0.401.8
+
0.551.2
+
±0.362.1
1.01.7
±
±0.210.64
+0.1824.4
0.154.9
+
0.5818.3
+
±0.2510.2
±0.359.1
±0.316.4
±0.535.0
0.496.0
±
2.40.40
+
4.80.74
+
3.00.36
+
1.00.30
±
4.20.50
±
±6.10.73
1.30.86
±
±8.50.33
0.210.80
+
0.071.1
+
0.310.99
+
0.021.0
±
0.261.1
±
0.080.74
±
0.281.5
±
0.050.71
±
0.050.74
±
0.140.60
±
0.520.42
±
±0.420.65
±0.270.87
±0.290.90
0.600.67
±
±0.110.51
0.242.9
+
0.061.8
+
0.213.1
+
0.271.5
+
0.062.1
±
0.601.7
±
0.383.6
±
±0.093.0
0.2012.5
+
0.301.5
+
1.12.8
±
±0.622.2
±0.302.4
2.42.2
±
±0.802.4
1.12.45
±
1.21.3
+
0.281.1
±
18.50.61
±
0.540.73
±
0.070.94
±
0.960.86
±
±0.210.50
0.770.46
±
(%/g)fAlone2.3 ±0.10+DES"1.1 ±0.27Alone8.0+ +0.10+DES°2.1 ±0.33Alone3.6 + 0.19+DES°2.0 ±0.24Alone6.6 ±0.24+DES"2.4 ±0.12
°1 Mgof DES/animal.
* Mean + SD. d.p.m./mg tissue divided by <l.p.m. uI blood for each animal.
' To allow comparisons, actual percentage of dose/g for bloods is given.
bromoestrogen may have an advantage. This difference, as
expected, related to the concentration of radiolabel remaining
in the blood as a function of time after administration, and the
radiobromine concentration consistently remained higher after
the triphenylethylene. Whether this increased blood level of
radioactivity was actually due to higher levels of unchanged
radiolabeled estrogen or merely circulating metabolites will
have to be determined in subsequent studies. If the former were
true, however, it would help explain the apparent longer reten
tion or higher levels of radioactivity in target tissues at the
latter time point following administration of the triphenylbromoethylene. Although, as seen in Fig. 6, there did appear to be
some non-DES inhibitable binding of the Br-BHPE to a non
specific, 4S component present in rat uterine cytosol, it com
prised a small proportion of the total binding and thus appeared
to be less problematic than the high level of nonspecific binding
which has been reported for 17a-[77Br]bromoethynylestradiol
greater for compounds near the DNA than those located in the
cytoplasm and even greater when compared to the nuclide
outside the cell (17). With the Auger electron-emitting isotope
125I,the cytotoxicity of the isotope incorporated in DNA (from
[l25I]IUdR) was about 300 times greater than the same dose
localized at the membrane (['"IJconcanavalin A) (17). Our
preliminary results (18) with bromine-80m confirmed the im
portance of nuclear localization of the Auger emitter for effec
tive radiotoxicity in that exposure of cells to similar concentra
tions 80mBr-labeled NaBr (which does not enter the cell) or
bromoantipyrine (which distributes generally throughout the
cell) showed little effect at concentrations in which [80mBr]BrUdR incorporated in DNA was radiotoxic. This difference
may in fact be larger with Auger electron emissions from
bromine-80m than with iodine-125 in that the average Auger
energy of the bromine isotope is about one-third that of iodine
and therefore would be expected to have a shorter effective
range.7
Since the decay of bromine-80m produces bromine-80 which
decays further by ßand y emission, the irradiation of organs
by the daughter nuclide is an important consideration. Chan et
al. (19) directly compared the radiotoxicity of ['"IJUdR, an
Auger electron emitter, and ['"I]UdR, a ß-yemitter, incorpo
(14).
Neither of these estrogens appeared to show significant,
DES-inhibitable localization in the liver. Because the liver has
been reported to contain low levels of estrogen receptor, this
organ would be a concern if sufficient radiotoxic estrogen
became localized in the nucleus of the liver cells. The liver is
probably the major site of metabolism of the administered
rated into DNA where chromosomal lethality would be maxi
estrogen, and the liver enzymes are largely cytoplasmic. There
mum. They reported that it required at least 10 times more
radioactivity of the /3-7-emitting '"I to effect the same damage
fore, it is not clear what proportion of the radiolabeled estrogen
as
the Auger-emitting 12SIin the DNA. And it is likely that only
which was found in the liver was present as cytoplasmic estro
gen, as contrasted with nuclear localization via the receptor
those tissues with significant ER content will have appreciable
mechanism. Clearly both biochemical (15) and immunocytonuclear content of the radioisotope. Nonetheless considering
the worst-case situation where all the administered isotope were
chemical (16) evidence strongly suggested that estrogen recep
tor is essentially entirely present in the nucleus even in the associated with the intestinal tract contents following a 50-mCi
absence of estrogen. The distinct advantage of estrogen recep
therapeutic dose in a human, the maximum dose to the intes
tor-directed therapy using Auger electrons is that the effective
tinal mucosa from the hard ßemissions (85%, 2 MeV; 15%,
1.4 MeV) of the daughter bromine-80 is calculated to be about
ness of Auger electron emission is at least an order of magnitude
904
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"Br-LABELED ESTROGENS
275 rads, certainly an acceptable level in a patient with dissem
inated malignancy. The same activity evenly distributed in the
body would give an absorbed dose of 6.5 rads. The absorbed
dose from the high energy 7 radiation (13%, 511-662 KeV) is
trivial by comparison (320 mrads). More accurate data will
depend on further studies, but these estimates indicate accept
able risks for use in cancer patients.
The actual concentration of radiolabel in both liver and
intestine obtained from assay of small portions of these tissues
are probably not accurate reflections of the dynamic handling
of the bromoestrogens by these tissues in vivo. Clearly the route
of administration has a significant impact on the time at which
the amount of drug in the liver reaches a maximum level which
is earlier for i.v. administration than i.p. or s.c. Since only a
portion of the median lobe of liver and a 1-cm piece from the
central portion of the small intestine were taken for radioassay,
the actual concentration reported herein relates very much to
the rate at which the material passed through these two organs
and the position of the radioactive bolus in the intestine relative
to the position of tissue excised for sampling. Furthermore,
preliminary data evaluating the radioactivity of the intestine by
comparing the radioactivity of the intestinal contents with the
tissue radioactivity have clearly shown that the intestinal con
tents comprise by far the greater concentration of radioactivity.
While the total radioactivity in this organ can be appreciable,
in particular because of the excretion pattern of radioactive
estrogens in rats, cellular damage from the bromine-SOm which
depends upon nuclear localization of the nuclide should be
insignificant. As indicated above, effects of the bromine-80
daughter, especially in humans where urinary excretion is more
competitive, will have to be studied.
It should be pointed out that although there are obvious
disadvantages to working with a short half-life isotope like
bromine-80m, the production and syntheses reported here are
simple and rapid. The bromine-80m was obtained by dissolving
the Se target in peroxide, phosphoric acid, and purified by
steam distillation. After neutralization and solvent evaporation
the tributyltin derivative of the estrogen could be added directly
and, following a 10-min reaction, purified by HPLC for use,
essentially from target to animal within 2 h. The substantial
advantage in the use of an isotope with a 4.4-h half-life, a
similar half-life to that of the ER itself (20), is that there is a
very good probability that the isotope will decay while still
associated with the receptor at the DNA binding site.
Other potential candidates for bromine-80m-labeled brom
oestrogens for estrogen receptor-directed therapy are 16a-BrE2
(21), 16a-BrME2 (22), and 17a-BrVME2. The two 16a-bromoestrogens have been previously synthesized in the radiobrominated form but not with bromine-80m. Following i.v. admin
istration of 16<x-[77Br]BrE2about 7% injected dose per gram
was found at l h in the uterus of the immature rat. Although
the specific activity of that radiobromine-containing
estrogen
was not assayed, it was estimated to be about 1400 Ci/mmol
(21). In a subsequent study with another preparation of the
16a-[77Br]BrE2, with an effective specific activity determined
by receptor assay to be 389 Ci/mmol (23), the percentage of
injected dose per gram uterus was found to be 8.4%/g at 1 h,
in good agreement with the earlier study, and this uterine uptake
was reduced to about 0.5%/g when coinjected with 18 ^g
unlabeled estradiol. 16«-[77Br]BrME2,prepared with an effec
tive specific activity of 770-1450 Ci/mmol by Katzenellenbogen
et al. (22) showed excellent uptake by uterus, over 12% injected
dose/g at 1 h. The improved uterus-to-blood ratio of this 11/3methoxybromoestrogen was attributed to its low binding to
nonspecific components. Such a characteristic would be ex
pected to be especially important when used for imaging, to
which purpose those studies were directed. Whether nonspecific
binding to serum is advantageous or a deterrent to potential
radiotherapeutic use has yet to be shown.
It is important to consider whether the current studies indi
cate anything about the feasibility of the suggested new thera
peutic approach using estrogen receptor-directed radiotherapy
with an 80mBr-labeled estrogen. The 15% dose per gram tissue
localization in the uterus following i.p. administration of the
high dose [80mBr]Br-BHPE presented here corresponded to
approximately 600 molecules of estrogen per cell. Even recog
nizing the uncertainties of metabolism and circulating estrogen
concentrations, the high dose administered in these studies (7
pmol) is less than 1% of the dose which began to show satura
tion of receptor uptake of the rat uterus at 2 h (24), so higher
doses would be expected to increase receptor occupancy, if that
were needed. Calculations based upon the radiotoxicity of
[80mBr]BrUdR for CHO cells (18) indicated that the mean lethal
dose of about 77 fCi/cell for the 80mBrincorporated into DNA
corresponded to about 50 molecules per cell. This is reasonably
close to the D37 value of 130 fCi/cell reported for [77Br]BrUdR
with V79 cells (25). It would therefore appear that with the
80mBr-labeledestrogen at 10% or more of its theoretical specific
activity one should be able to show radiotoxicity.
The studies reported here demonstrate the feasibility of pre
paring and studying in animals both steroidal and nonsteroidal
estrogens with the short half-life, Auger electron-emitting iso
tope bromine-80m. The DES-inhibitable, specific uptake by
estrogen target tissues of both of these bromoestrogens in
immature rats indicated their potential for the proposed estro
gen receptor-directed radiotherapy. The extent of specific up
take of the bromine-80m labeled estrogens by ER-positive
tissues related to estimates of required nuclear concentrations
of bromine-80m needed for cell killing indicated that this
approach is promising. The demonstration of specific radiotox
icity of bromine-80m-labeled estrogen in ER-positive cancers
in vivo should be possible with preparations of bromoestrogens
with only moderately higher specific activities.
ACKNOWLEDGMENTS
We gratefully acknowledge the technical assistance of R. Dizon, P.
Kuivanen, M. I orine/. S. M. Morin, J. Olson, M. Pagulis, J. Sanghavi,
and T. Singh and thank J. Darden for help in the preparation of the
manuscript.
REFERENCES
1. Muggins, ('.. and Bergenstal, D. M. Inhibition of human mammary and
prostatic cancer by adrenalectomy. Cancer Res., 12: 134-141, 1952.
2. Kelly, R. M., and Baker, W. H. Progestational agents in the treatment of
carcinoma of the endometrium. N. Engl. J. Med., 264: 216-222, 1961.
3. Jensen, E. V., Block, G. E., Smith, S., Kyser, K. A., and DeSombre, E. R.
Estrogen receptors and breast cancer response to adrenalectomy. In: T. C.
Hall (ed.). Prediction of Response in Cancer Therapy, National Cancer
Institute Monograph No. 34, pp. 55-70. Washington, DC: U.S. Government
Printing Office, 1971.
4. McGuire, W. L., Carbone, P. P., and Vollmer, E. P. (eds.), Estrogen Recep
tors in Human Breast Cancer. New York: Raven Press, 1975.
5. DeSombre, E. R., Carbone, P. P., Jensen, E. V., McGuire, W. L.. Wells, S.
A., Wittliff, J. L., and Lipsett, M. B. Special report: steroid receptors in
breast cancer. N. Engl. J. Med., 301:1011-1012, 1979.
6. DeSombre, E. R. Steroid receptors in breast cancer. In: R. W. McDivitt, H.
A. Oberman, L. Ozzello, and N. Kaufman (eds.). The Breast, pp. 149-184.
Baltimore: Williams & Wilkins, 1984.
7. DeSombre, E. R., Holt, J. A., and Herbst, A. L. Steroid receptors in breast,
uterine and ovarian malignancy and consideration of their diagnostic and
therapeutic usefulness. In. J. B. Josimovich and J. Gold (eds.). Gynecologic
Endocrinology, Ed. 4, pp. 511-528. New York: Plenum Press, 1987.
905
Downloaded from cancerres.aacrjournals.org on June 16, 2017. © 1988 American Association for Cancer Research.
•Br-LABELEDESTROGENS
8. Holt, J. A., Caputo, T. A., Kelly, K. M., Greenwald, P., and Chorost, S.
Estrogen and progestin binding in cytosols of ovarian adenocarcinomas.
Obstet. Gynecol., 53: 50-58, 1979.
9. Horwitz, K. B., McGuire, W. L., Pearson, O. H., and SegalofT, A. Predicting
response to endocrine therapy in human breast cancer: a hypothesis. Science
(Wash. DC), 189: 726-727, 1975.
10. Ehrlich, C. E., Young, P. C. M., and Cleary, R. E. Cytoplasmic progesterone
and estradici receptors in normal, hyperplastic, and carcinomatous endometria: therapeutic implications. Am. J. Obstet. Gynecol., 141: 539-546,
1981.
11. Seevers, R. H., Mease, R. C, Friedman, A. M., and DeSombre, E. R. The
synthesis of non-steroidal estrogen receptor binding compounds labeled with
•"-Br.NucÃ-.Med. Biol., 13: 483-495, 1986.
12. Hughes, A., Mease, R. C., Harper, P. V., DeJesus, O. T., Sanghavi, J., Singh,
T., and DeSombre, E. R. Triphenylethylene-based, estrogen receptor-directed
imaging and therapeutic agents for the diagnosis and treatment of estrogen
receptor positive cancers: synthesis, receptor binding, biologic activity and
distribution in immature rats (Abstract). 69th Meeting of the Endocrine
Society, p. 258, June, 1987.
13. Greene, G. L. Application of immunochemical techniques to the analysis of
estrogen receptor structure and function. In: G. Litwack (ed.), Biochemical
Actions of the Hormones, Vol. 11, pp. 207-239. New York: Academic Press,
1984.
14. Gibson, R. E., Eckelman, W. C., Francis, B., O'Brien, H. A., Mazaitis, J. K.,
Wilbur, S., and Reba, R. C. [77Br]-17a-Bromoethynylestradiol: In vivo and
in vitro characterization of an estrogen receptor radiotracer. Int. J. NucÃ-.
Med., 9:245-250, 1982.
15. Welshons, W. V., Lieberman, M. E., and Gorski, J. Nuclear localization of
unoccupied oestrogen receptors. Nature (Lond.), 307: 747-749, 1984.
16. King, W. J., and Greene, G. L. Monoclonal antibodies localize oestrogen
receptor in the nuclei of target cells. Nature (Lond.), 307: 745-747, 1984.
17. Warters, R. L.. Hofer. K. G., Harris, C. R., and Smith, J. M. Radionuclide
18.
19.
20.
21.
22.
23.
24.
25.
toxicity in cultured mammalian cells: elucidation of the primary site of
radiation damage. Curr. Top. Radiât.Res. Quart., 12: 389-407, 1977.
DeSombre, E. R., Mease, R. C., Hughes, A., DeJesus, O. T., and Harper, P.
V. New approach to therapy of hormone-dependent cancers with Auger
electron emitting, estrogen receptor-directed ligands. Proceedings of the
Meeting of the Am. Assoc. Cancer Res., 2«:218, 1987.
Chan, P. C., Lisco, E., Lisco, H., and Adelstein, S. J. The radiotoxicity of
iodine-125 in mammalian cells. II. A comparative study in cell survival and
cytogenetic responses to '"lUdR, '"lUdR, and 'HTdR. Radiât.Res., 67:
332-343, 1976.
Nardulli, A. M., and Katzenellenbogen, B. S. Dynamics of estrogen receptor
turnover in uterine cells in vitro and in uteri in vivo. Endocrinology, J19:
2038-2046, 1986.
Katzenellenbogen, J. A., Senderoff, S. G., McElvany, K. D., O'Brien, H. A.,
Jr., and Welch, M. J. 16a["Br]Bromoestradiol-170: a high specific activity,
gamma-emitting tracer with uptake in rat uterus and induced mammary
tumors. J. NucÃ-.Med., 22: 42-47, 1981.
Katzenellenbogen, J. A., McElvany, K. D., Senderoff, S. G., Carlson, K. E.,
Landvatter, S. W., Welch, M. J., and the Los Alamos Medical Radioisotope
Group. 16a["Br]Bromo-11 /3-methoxyestradiol-17/3: a gamma-emitting estro
gen imaging agent with high uptake and retention by target organs. J. NucÃ-.
Med., 23:411-419, 1982.
McElvany, K. D., Carlson, K. E., Welch, M. J., Senderoff, S. G., Katzenel
lenbogen, J. A., and the Los Alamos Medical Radioisotope Group. In vivo
comparison of 16a-[7'Br]bromoestradiol-17/iand
16a['"I]iodoestradiol-17o.
J. NucÃ-.Med., 23: 420-424, 1982.
Jensen, E. V., DeSombre, E. R., and Jungblut, P. W. Interaction of estrogens
with receptor sites in vivo and in vitro. In: L. Martini, F. Fraschini, and M.
Motta (eds.), Hormonal Steroids, pp. 492-500. Amsterdam: Excerpta Med
ica Foundation, 1967.
Kassis, A. L, Adelstein, S. J., Haydock, D., Sastry, K. S. R., McElvany, K.
D., and Welch, M. J. Lethality of Auger electrons from the decay of bromine77 in the DNA of mammalian cells. Radial. Res., 90: 362-373, 1982.
906
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Bromine-80m-labeled Estrogens: Auger Electron-emitting,
Estrogen Receptor-directed Ligands with Potential for Therapy
of Estrogen Receptor-positive Cancers
Eugene R. DeSombre, Ronnie C. Mease, Alun Hughes, et al.
Cancer Res 1988;48:899-906.
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