Washington: A low-cost diabetes drug seems to beat the growth of breast cancer, especially by preventing a number of natural and man-made chemicals that promote it.

James Trosko from Michigan State University and a team from South Korea's Seoul National University have thrown up evidence to show that use of metformin for Type-2 diabetes reduces risk of cancers.

"People with Type-2 diabetes are known to be at high risk for several diabetes-associated cancers such as breast, liver and pancreatic cancers," said Trosko, paediatrics professor at Michigan's College of Human Medicine.

"While metformin has been shown in population studies to reduce the risk of these cancers, there was no evidence of how it worked," the journal Public Library of Science quotded him as saying.

Trosko and colleagues, using culture dishes, grew miniature human breast tumours or mammospheres that activated a certain stem cell gene, according to a Michigan University statement.

Then the mammospheres were exposed to natural estrogen - a known growth factor and potential breast tumour promoter - and man-made chemicals that are known to promote tumours or disrupt the endocrine system.

The team found that estrogen and the chemicals caused the mammospheres to increase in numbers and size. However, with metformin added, the numbers and size of the mammospheres were dramatically reduced.

While each of the chemicals enhanced growth by different means, metformin seemed to be able to inhibit their stimulated growth in all cases.

(Agencies)