Researchers point to
Prozac cancer link |
By Ben Hirschler, European Pharmaceuticals
LONDON (Reuters) - Prozac and related antidepressants
could in theory pose a cancer threat by blocking the
body's innate ability to kill tumour cells, scientists
But Professor John Gordon of the University of
Birmingham, who led the research, said on Tuesday
patients should keep taking their drugs since there was
no evidence of any link in practice.
Working in the test-tube, Gordon and others found
that the brain's mood-regulating chemical serotonin
caused some cancer cells to self-destruct.
Eli Lilly's Prozac, Glaxo SmithKline's Paxil and
Lundbeck's Celexa all "substantially blocked" this
The finding reopens controversy about the widespread
use of the class of antidepressants called selective
serotonin reuptake inhibitors (SSRIs) that first went on
sale in the 1980s.
Millions of people with depression and anxiety have
been prescribed the drugs, which have emerged as one of
the biggest sellers for the international pharmaceutical
industry. They work by stopping serotonin getting into
Gordon's discovery that serotonin plays a role in
killing a type of cancer called Burkitt's lymphoma was
published in the online edition of the medical journal
"We've shown that, in the test-tube, the SSRIs stop
the action of the serotonin on the cancer cells. But
it's nigh on impossible to extrapolate to what's
happening in the body," Gordon told Reuters.
"We must stress the effects shown for SSRIs on cancer
cells is indirect and should cause no concern whatsoever
to the many millions of people throughout the world who
are prescribed this class of antidepressants."
A spokesman for the Department of Health said the
research was at a very early stage and no increased risk
of cancer had been detected.
Rather than being alarmed, Gordon is in fact excited
that a new class of anti-cancer drugs may one day be
developed that exploit serotonin's ability to kill
"Because we know the mechanism, we are now in a
position to develop drug analogues of serotonin that
will do the same job but have better pharmacological
properties," Gordon said.
His work also provides an intriguing insight into the
way that "positive thinking" associated with serotonin
levels may play a key part in effective cancer care.
The mechanism by which serotonin can get inside
cancer cells and tell them to commit suicide -- a
process known as apoptosis -- suggests there is a clear
"dialogue" between the brain and the immune system, he
Prozac was the first SSRI to reach the market in 1987
but it has since been overtaken by Paxil, also known as
Seroxat, which racked up sales last year of 1.86 billion
Drug company officials said they did not believe
their pills caused any increase in cancer and questioned
whether the high doses used in Gordon's experiments may
have affected the results.
"These data are from an in vitro (test tube) study
and as such they cannot be extrapolated to a clinical
setting with any degree of certainty," said Martin
Sutton, a spokesman for GSK.