Bowel Cancer Gene Linked To Sex Chromosome

It is known that certain cancers affect each gender differently. For instance, breast cancer is far more prevalent in women, while bowel cancer is more common in men. Now, for the first time, scientists have shown that the sex chromosomes play a role in the development of a cancer that affects both genders.

The research began by studying altered sequences of DNA to see if any increased the chances of getting bowel cancer. Eventually they found one on the x chromosome.

The X chromosome, along with the Y chromosome, is one of the two chromosomes that determine a person's gender. Two X's mean that a person is female, while one X and one Y mean the person will develop as a male.

The scientists found that the DNA sequence responsible for this is located in the lower levels of the SHROOM2 gene on the X chromosome. The SHROOM2 gene controls how some cells develop. It is known that mutations to this gene can cause cancer.

The theory put forth is simple: women have twice the chance of landing a completely functioning SHROOM2 gene. If there is a mutation, then there is still one other X chromosome which could contain a normal SHROOM2 gene, which will then mask the effects of the other. Men only have one X chromosome, and if there is a mutation on it, then it is more likely to affect the individual.

"To our knowledge, this is the first time that anyone has shown that one of the sex chromosomes is involved in the development of a cancer that can afflict both sexes. This may help explain why bowel cancer is slightly more common in men. Ultimately, it could also help us target screening to those who are more at risk of the disease," said Professor Richard Houlston from The Institute of Cancer, one of the researchers involved in the study.

This discovery now brings the total number of regions on the genome that are known to increase the risk of bowel cancer to 20.

To obtain these results, the researchers looked at single nucleotide polymorphisms (SNP's) that were more common in cancer cases than in healthy patients. Single nucleotide polymorphisms are strands of DNA that vary between individuals.