Traditionally, the higher incidence of cancer in males was explained by the fact that men were more likely to smoke cigarettes or be exposed to hazardous chemicals in the work place, but this failed to adequately solve the discrepancy.
In fact, according to data from the National Cancer Institute, males carry on average a 20% higher risk than females of developing cancer, and this applies to children as well as adults.
Andrew Lane, co-senior author of the study, said: “Across virtually every type of cancer, occurrence rates are higher in males than in females. In some cases, the difference might be very small - just a few percent - but in certain cancers, incidence is two or three times higher in males.”
The new research, published in Nature Genetics, has offered a fuller explanation, which lies in gender genetics.
There are some genes in the human body, which have a protective tumour-suppressing function and women have been found to have an extra copy of this gene, providing a second line of defence that men do not have.
The gene in question, KDM6A, is found on the X chromosome – which women have two of rather than an X and Y like men.
During embryo formation, one of the X chromosomes in female cells shuts down and remains off-line for life. Because of this, scientists expected that men and women have an equal protection from the remaining ‘switched on’ KDM6A.
But that was not the case.
And it turns out that this is because some of the genes on the inactivated female X chromosome actually ‘escape’ the dormant state they enter during foetal development and awaken again after birth, preventing the cell from turning cancerous.
Lane said: “Under this theory, one of the reasons cancer is more common in males is that male cells would need a harmful mutation in only one copy…female cells, by contrast, would need mutations in both copies.”