The two-gene situation, called homozygosity, is common in humans and earlier studies have identified extended homozygote lines, Dr Charis Eng and colleagues at the Cleveland Clinic Foundation reported.

And since genes that cause susceptibility to cancer are also numerous, it raises the likelihood that the presence of these genes and the two genes in the same area of a chromosome could 'somehow contribute to cancer predisposition', said the report published this week in the Journal of the American Medical Association.

The researchers looked at 385 people with breast, prostate, and head and neck cancers and compared them to a control group.

Genetic makeup and environmental or lifestyle factors play a role in cancer, which essentially comes from damage to the body's DNA that causes cells to grow abnormally.

If the study's results are replicated, then this predisposition to cancer 'could be taken into account in future cancer risk assessments and management', the study concluded. -- REUTERS