BioEd Online

Deciding not to use a condom can have a host of potentially negative side effects: including, scientists now say, aggravating cancer.

Researchers have shown that semen contains a huge dose of hormones that boosts blood vessel growth, and that cancerous cells in a woman's uterus or cervix have a high level of receptors for these hormones. The combination could prove dangerous for women at high risk of getting cancer or those already with early-stage cancer, they say.

The finding lends weight to campaigns promoting condom use, particularly in African and South American countries, where cervical cancer is most common.

Henry Jabbour's team of researchers at the Medical Research Council's Human Reproductive Sciences Unit in Edinburgh, UK, together with scientists from the University of Cape Town, South Africa, took a look at prostaglandins hormones that are produced naturally in the body, including by female reproductive organs. These hormones are known to help control the immune system and regulate cell growth.

In 2004, Jabbour and his colleagues showed that levels of prostaglandin receptors are often increased in cervical and uterine cancerous tumour cells¹. "We still don't know why that happens," Jabbour admits.

Seminal fluid contains a concentration of prostaglandins that is a thousand times greater than is present around female reproductive cells. "That is a massive dose compared to normal physiological levels," says Jabbour. So the team investigated what happens when this flood of hormones hits cancerous cells.

Double protection

The team took a standard line of cancer cells and added prostaglandin receptors up to the levels seen in cervical cancers. They then added semen, and watched to see what the prostaglandin would do. As expected, it activated genes in the cancer cells that contribute to blood vessel growth, they report in Endocrinology². In a patient, this would increase tumour size. The same thing happened with cells taken from women diagnosed with uterine cancer, they report in Human Reproduction³.

"There's a positive feedback effect too," says Jabbour. "The enzymes that make prostaglandins in female reproductive cells are also upregulated, so yet more prostaglandins will be created."

However, the researchers don't know what effect it might have on testicular cancer.

Cervical cancer is most common in women who live in the developing world. It is usually triggered by the sexually transmitted human papilloma virus; so it is already advised to use a condom to lower cancer risk.

Now it seems that semen can worsen cancer too. Jabbour advises that "sexually active women who are at risk of cervical or uterine cancer should encourage their partners to wear a condom."

Jabbour adds that blocking prostaglandin receptors might be a potential approach for cervical cancer therapy. "That would tackle both possible sources of prostaglandin - those produced naturally by women and those introduced to the body by sperm."

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