by ecancer reporter Janet Fricker

The latest issue of PNAS provides evidence of a link between the human-infective parasite Trichomonas vaginalis and the promotion and progression of prostate cancer.

T. vaginalis, a flagellated protozoan parasite, is the causative agent of the most common non viral sexually transmitted infection, infecting approximately 275 million people worldwide.

Several studies have positively associated T. vaginalis infection with increased incidence and severity of prostate cancer, as well as benign prostate hyperplasia.

The magnitude of the association between T. vaginalis seropositivity and overall prostate cancer risk is between 1.23 and 1.43, based on two large, nested case-control studies.

Additionally, it is known that T. vaginalis secretes a protein called T. vaginalis macrophage migration inhibitory factor (TvMIF) that is 47% similar to the proinflammatory cytokine human macrophage migration inhibitory factor (HuMIF).

Since HuMIF is reported to be elevated in prostate cancer and inflammation plays an important role in the initiation and progression of cancers, Patricia Johnson and colleagues, from the University of California, Los Angeles, set out to explore the role of TvMIF in prostate cancer.

The investigators found that:

• TvMIF has tautomerase activity that inhibits macrophage migration, and is proinflammatory.
• TvMIF binds the human CD74 MIF receptor with high affinity, comparable to that of HuMIF, which triggers activation of ERK, Akt, and Bcl-2–associated death promoter phosphorylation at a physiologically relevant concentration.
• TvMIF increases the in vitro growth and invasion of benign and prostate cancer cells.
• Sera from patients with T. vaginalis are reactive to TvMIF, especially in males.

“This study demonstrates that a specific parasite-derived protein can mimic its human homolog to increase inflammation and cell proliferation, which, in turn, may result in the promotion and progression of prostate cancer,” write the authors.

More studies on T. vaginalis and cancer, along with parasite mimics of human cytokines, they add, will aid understanding of the extent to which this chronically infective parasite affects its hosts.

Reference:

O Twu, D Dessi, A Vu, et al. Trichomonas vaginalis homolog of macrophage migration inhibitory factor induces prostate cell growth, invasiveness, and inflammatory responses. PNAS.