Researchers Examine Alcohol, Cancer Link
Alcohol
could produce effects consistent with inhibiting a repair process that
keeps normal body cells from being transformed into cancer cells, according
to research released.
"Epidemiological
studies have shown that drinking alcohol is associated with an increased
risk of tumors in the esophagus, mouth, larynx and liver," David B. Couch,
associate professor of pharmacology at the University of Mississippi and
lead author of the study, told United Press International.
"In the model
system used, alcohol exposure could produce effects consistent with inhibition
of the base excision repair pathway or one of the repair pathways of deoxyribonucleic
acid -- there are several repair pathways -- base excision is just one
of them."
The study is
found in the March issue of Alcoholism: Clinical & Experimental Research.
Blood cells
of alcoholics have a greater incidence of genetic damage but it has not
been clear if alcohol itself is the cause, Couch said.
Couch, along
with Richard A. Deitrich of University of Colorado Health Science Center
in Denver, tested the survival capabilities of ovary A10 cells from Chinese
hamsters by exposing them to alcohol, genotoxicants -- substances that
can damage DNA through mutation or cancer -- and non-DNA reactive cytotoxic
agents. A10 cells were chosen because they have been engineered to express
alcohol dehydrogenase, which is known to convert alcohol to acetaldehyde
or AcHo, the first product of alcohol metabolism.
Normally when
people drink, alcohol is converted to AcHO in the liver, which is then
rapidly metabolized to acetate, which is then further metabolized by tissues
outside of the liver.
"The major
finding of this study is that alcohol causes an increase in the mutagenicity
of agents that damage DNA," said Deitrich. "This is as a result of the
metabolism of alcohol to acetaldehyde. In fact, it is clear that acetaldehyde
is the major culprit in the effects noted here."
The presumption
is acetaldehyde itself causes the damage, but it could be other aldehydes
as well. For example, it may interfere with the normal cellular mechanisms
designed to inactivate endogenous aldehydes produced in normal cellular
function or those produced as a result of alcohol's production of oxidative
damage, Deitrich said.
"The concept
of acetaldehyde being a mutagen is not a novel concept and the engineered
cells produced a lot of acetaldehyde and these cells do not have the ability
to inactivate the acetaldehyde unlike cells in the body," Boris Tabakoff,
chairman of the department of pharmacology, University of Colorado School
of Medicine in Denver, told UPI. "It would be more interesting to see if
this happened under normal conditions in how we live and not in engineered
cells to see if it has broader implications."
"An interesting
next step in the research might be to add cigarette smoke, which also contains
acetaldehyde to the alcohol," he added.
Couch acknowledged
the study did not uncover new ground but sets up further research on DNA
repair pathways and on the dose of acetaldehyde that causes damage.
"We speculate
that alcohol in a limited dose does not impact on DNA repair and that it
has a beneficial impact on lipids in the body, hence the studies on the
beneficial effects of alcohol on the body," Qingyi Wei, a molecular epidemiologist,
at the MD Anderson Cancer Center at the University of Texas in Houston,
told UPI.
"Alcohol has
been known to inhibit folate absorption and folate helps repair tissues
from mutations -- that's why folate is needed both before and in the first
weeks of pregnancy to reduce the risk of birth defects."
Folate is a
B vitamin found in a variety of foods and added to many vitamin and mineral
supplements as folic acid.
Tabakoff said
there is a line between the beneficial effects of alcohol and the damaging
effects of alcohol on human health and he advised people to take no more
than two drinks a day.
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