BBC News - Prostate cancer 'may be a sexually transmitted disease'

Prostate cancer may be a sexually transmitted disease caused by a common yet often silent infection passed on during intercourse, scientists say - but experts say proof is still lacking. Although several cancers are caused by infections, Cancer Research UK says it is too early to add prostate cancer to this list.

The University of California scientists tested human prostate cells in the lab.
They found a sex infection called trichomoniasis aided cancer growth.
More research is now needed to confirm the link, they say in the journal Proceedings of the National Academy of Sciences (PNAS).

Here's the paper:-

Trichomonas vaginalis homolog of macrophage migration inhibitory factor induces prostate cell growth, invasiveness, and inflammatory responses