IN THIS ISSUE
Bran Fiber and Calcium Effect
Ongoing studies suggest that regular,
high intake of dietary fiber and calcium
inhibits development of colon cancer. In
the present study, Alberts et al. (p. 81)
suggest this supplementation may lower
the risk of colorectal neoplasia and cancer
by reducing the concentrations of fecal
bile acids.
In a randomized, double-blinded, placebo-controlled phase II study, the investigators gave low or high doses of wheat
bran fiber (2.0 or 13.5 g) cereal and calcium carbonate (250 or 1500 mg) tablets
daily to 95 patients with resected colon
adenomas. At base line and after 3 and 9
months, stool samples were collected
from 50% of participants in each of the
four study groups for measurement of
fecal bile acids.
Both high-dose supplements were associated with statistically significant reductions in fecal bile acid concentrations,
findings showed. High-dose fiber supplements reduced geometric mean total
concentrations by 73%, and high-dose
calcium lowered them by 43%. The combined supplements, however, appeared
not to have an additive effect.
In an editorial, Wargovich and Levin
(p. 67) call the findings by Alberts et al.
encouraging, and they discuss mechanisms by which fiber and calcium might
reduce colon cancer risk. The writers
wonder, however, whether participants in
this ongoing trial will continue to adhere
to the high-fiber diet and whether adherence will translate into protection from
recurrence of colonic adenomas. They
conclude that a clearer picture of the role
of diet in the etiology and prevention of
colon cancer should soon emerge from
the combined results of this and other
ongoing colon cancer prevention trials.
Beta2-Microglobulin and
Melanoma
The loss of functional beta2-microglobulin (p^m) may be an important way
for some melanoma cells to escape recognition by antitumor CD8 + T cells and,
thus, acquire immunoresistance, Restifo
et al. (p. 100) report. This mechanism,
they say, could explain why some patients experience renewed tumor growth
after an initial response to immunotherapy.
The investigators characterized 14
melanoma cell lines for p^m protein and
messenger RNA expression and for cellsurface major histocompatibility complex (MHC) class I expression, (p^m is a
structural component of MHC class I
molecules.) Thirteen lines were established from tumors from patients undergoing immunotherapy for metastatic
melanoma, and one was derived from a
tumor from a patient in a cytokine-gene
therapy study.
For five melanoma cell lines, data suggested that mutation of one or both copies
of the f^m gene was probably responsible
for the complete loss of functional p^m
and MHC class I expression.
to stimulate a host immune response, perhaps by affecting expression of major
histocompatibility complex (MHC) class
I molecules and cell-adhesion molecules.
Kimball and Fisher (p. 109) explored the
ability of levamisole to affect MHC class
I molecule expression, cell-adhesion
molecule expression, and adhesion of
leukocytes to tumor cells in four human
colon tumor cell lines (HT-29, SW-620,
HCT-15, and LoVo), A-375 human melanoma cells, and human umbilical vein
endothelial cells.
The investigators report that levamisole can up-regulate expression of MHC
class I molecules and certain cell-adhesion molecules in some cell lines, but they
found no consistent pattern among celladhesion molecule expression, cell-cell
adhesion, and levamisole concentration.
The diversity of results and lack of
congruence with similar studies suggest
that no single mechanism of action can
yet be ascribed to levamisole in treating
colon cancer, the investigators say.
Black Tea and Cancer Risk
Breast Cancer Chemoprevention
Experimental studies have suggested
that tea protects against cancer. In the
current epidemiologic study, however,
Goldbohm et al. (p. 93) report findings
that do not support the hypothesis that
black tea protects against four major cancers.
The investigation used information
from The Netherlands Cohort Study on
Diet and Cancer, in which 58 279 men
and 62 573 women aged 55-69 years
completed a diet and risk-factor questionnaire at entry. During the next 4.3 years,
200, 650,764, and 650 cases of stomach,
colorectal, lung, and breast cancers were
diagnosed, respectively. The investigators compared data on these patients with
data on 3500 subjects randomly selected
from the cohort.
Results showed that, after controlling
for confounding factors, the risk for each
of the cancers studied was similar for tea
drinkers and nondrinkers.
In a brief communication, Anzano
et al. (p. 123) report that raloxifene and
9-c/s-retinoic acid (9cRA) generated statistically significant reductions in mammary carcinogenesis in rats. 9cRA is a
chemopreventive agent. Raloxifene, an
estrogen response modifier, was investigated for chemopreventive activity because it does not promote uterine
epithelial growth, a concern with longterm use of tamoxifen, which has been
shown to increase risk of endometrial
cancer, the investigators say.
The investigators induced breast tumors by injecting nitrosomethylurea intravenously into 264 virgin female
Sprague-Dawley rats, which were randomly selected to receive raloxifene (60
or 20 mg/kg diet) and/or 9cRA (60 mg/kg
diet) or no treatment.
Rats fed high or low doses of raloxifene had statistically significant reductions in the incidence and weight of breast
tumors, compared with controls. The addition of 9cRA to the regimens significantly reduced tumor incidence and
weight even further. Also, these agents
were not toxic at the levels studied.
Levamisole and Cell Molecules
Levamisole, used successfully in adjuvant treatment of colon cancer, is thought
Journal of the National Cancer Institute, Vol. 88, No. 2, January 17, 1996
IN THIS ISSUE
65
A NEW
BROCHURE TO
INCREASE PATIENT
AWARENESS OF
THE IMPORTANCE
OF TREATING
CANCER PAIN
Patients have a right to pain
control. • Patients have a role
in communicating their pain.
• Patients should talk to their
doctors or nurses as soon as pain
begins. • Patients should not let
fears keep them in pain.
Get Relief From Cancer Pain is written at a
5th grade reading level and is available through
the National Cancer Institutes Cancer
Information Service at 1-800-4-CANCER or
the American Cancer Society at
1-800-ACS-2345.