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Chimp sperm may hold key to cancer


Mmm. Could my sperm really be to blame? (Image: iStockphoto)

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 and human genes shows a concentration of genes unique to humans in areas associated with sperm production and cancer.

This suggests the changes that make humans unique also make us prone to cancer, researchers write in the journal Public Library of Science Biology.

"If we are right about this, it may help explain the high prevalence of cancer," says Danish researcher Professor Rasmus Nielsen of the University of Copenhagen, who led the study while at Cornell University.

Nielsen and colleagues were studying the chimpanzee genome for clues about what make chimps and humans different.

They used genetic sequences published by Maryland-based Celera Corp, specifically the 13,731 genetic sequences that differ most 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.

"[But] 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 write.

"It is surprising to find such a large proportion of genes that may be related to tumor development and control."

Faulty systems

In cancer, cells lose their ability to self-destruct, or undergo apoptosis, when they become faulty.

Cell cycling, how cells activate, divide, and grow into two separate cells, is also disrupted in cancer.

"Eliminating cancer cells by apoptosis is one of the main processes used by the organism to fight cancer," Nielsen says.

"The connection that we saw that these genes involved in proliferation may be involved in spermatogenesis," says Cornell's Professor Andrew Clark, who worked on the study.

New species of monkey

In separate news, researchers have identified the first new species of monkey in 20 years.

Two separate teams of researchers working hundreds of kilometres apart in Tanzania identified the highland mangabey.

This medium-sized monkey is about 90 centimetres tall has a long tail, long brown fur, and a black face, hands and feet.

Adults make a distinctive, loud, low-pitched honk-bark call. They live in mountainside trees at elevations of up to 2400 metres.

Fewer than 1000 of the animals live in the highland forest, the researchers report in today's issue of the journal Science.

Hunters had described the animals but no scientist had identified them until now.

Tags: environment, health, cloning-and-dna