A chemical produced by fat cells makes colon cancers grow faster, a
US study has suggested.
The British Journal of Surgery study could help explain why
severely overweight people appear to be at far greater risk of the
disease.
A team at the University of California, San Diego found that the
hormone leptin triggered increased growth in human colon cancer
cells.
Obese people are up to three times more likely to develop
colorectal cancer.
Other researchers have already found that some colon cancer cells
appear to be set up to respond to leptin, with "receptors" for the
chemical on their surfaces.
The more fat cells a person has, the more leptin will be in their
bloodstream.
The San Diego team wanted to find further evidence of the link by
watching what happened to human cancer cells exposed to the
hormone.
In a laboratory, they added the hormone to different varieties of
cancer cell.
Growth was stimulated in all the cell lines - and in two out of
three tested, the hormone also hampered the usual process of
programmed death that allows the body to replace normal cells, but
which often malfunctions in cancers.
Dr Kim Barrett, who led the research, said: "These results may
explain why obesity increases a person's risk of colonic
cancer.
"The fact we have shown how leptin stimulates these cells means
that drug companies may be in a better position to develop new
treatments against the disease."
Obesity increasing
In the UK it is currently estimated that one in five men and a
quarter of women are obese, with as many as 30,000 people a year
dying prematurely from obesity-related conditions, including
cancers.
Britain now has the most obese population in Europe.
A study published this week suggested that severely obese men
doubled their risk of dying from prostate cancer, and obesity is
also believed to increase the chance of developing breast
cancer.
Body Mass Index
Underweight: less than 20
Normal weight: 20-25
Overweight: 25 - 29.9
Obese: over 30
Morbidly obese: over 40
Calculate your BMI
Professor Alan Clarke said: "This research builds on previous work
suggesting that leptin, a hormone released from fat cells, may play
a role in the link between obesity and cancer.
"The researchers have shown that leptin is involved in two
molecular pathways known to play a role in bowel cancer
development."
"Although at an early stage, the findings shed light both on the
development of bowel cancer and the link between obesity and
cancer."
Leptin is stored in fat tissue