Study: Prostate cancer may be linked to sexually transmitted parasite

Prostate cancer may be linked to a common sexually transmitted infection, according to a study published this week, though scientists cautioned that more research is needed to explore the apparent connection.

Scientists from UCLA examined the connection between prostate cancer and the parasite that causes trichomoniasis, the most common non-viral sexually transmitted infection. An estimated 275 million people worldwide have the parasite, including about 3.7 million in the United States, according to the Centers for Disease Control.

In their research, the scientists found that a protein secreted by the parasite trichomonas vaginalis lead to the growth of prostate cells, and also to induced inflammation, which the researchers believe causes the cells to progress to prostate cancer.

They said that while the parasite appeared to play a role in increased risk of prostate cancer, more studies needed to be done, and they added that the “sources of inflammation remain unidentified.”

A paper detailing the research was published on Monday in the Proceedings of the National Academy of Sciences.

Previous studies have shown that men who had trichomoniasis are more vulnerable to developing prostate cancer, which is the most common non-skin cancer in the U.S., affecting one in every seven American men.

Only about 30 percent of those with trichomoniasis actually have symptoms, according to the Centers for Disease Control. Those symptoms can include mild irritation to severe inflammation in the penis or vagina, as well as discomfort during urination.

Trichomoniasis is treated with a single dose of antibiotics, but because so many cases are asymptomatic, many people are unaware they have it.

Previous studies have shown that nearly 20 percent of cancer cases may be related to chronic infections due to inflammation.

And cervical cancer has been linked to a different sexually transmitted infection: the human papilloma virus (HPV).

Researchers stressed that scientists still don’t know what causes prostate cancer. While Nicola Smith from Cancer Research UK told the BBC the study suggests a possible way the parasite could encourage prostate cancer cells to grow and develop more quickly, she pointed out that the research was done in a laboratory – not on human subjects – and that previous evidence in patients failed to draw a concrete link between the two.

Smith added, "There's been a lot of research into prostate cancer risk and we're working hard to piece together the puzzle.”