Sperm may hold key to cancer

The evolutionary path that separated humans from chimps 5 million years ago may have made human sperm survive better but paradoxically may have made humans prone to cancer.

The evolutionary path that separated humans from chimps 5 million years ago may have made human sperm survive better but paradoxically may have made humans prone to cancer.

A comparison of chimpanzee genes to human genes shows a concentration of genes unique to people in areas associated with sperm production and cancer, and suggests the changes that make humans unique also make us uniquely prone to cancer.

"If we are right about this, it may help explain the high prevalence of cancer," said Rasmus Nielsen of the University of Copenhagen in Denmark, who led the study while at Cornell University in New York.

Nielsen and colleagues were studying the chimpanzee genome, the collection of all DNA, for clues about what make chimps and humans different. They used genetic sequences published by Maryland-based Celera Corp.

For the report, published in the journal Public Library of Science Biology, Nielsen's team at Cornell studied the 13,731 genetic sequences that are the most different between humans and chimps.

They knew that genes having to do with smell, making sperm and fighting bacteria and viruses were likely to be different.

"While we expected to find genes involved in olfaction, spermatogenesis, and immune defence among the 50 annotated genes... we were surprised to find a very large proportion of cancer-related genes, especially genes involved in tumour suppression, apoptosis, and cell cycle control sequences," they wrote.