Infectious Agents Associated Cancers Epidemiology and Molecular Biology

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12.3.2 Trichomonas and Prostate Cancer (PCA)

Trichomonas vaginalis is an extracellular flagellated parasitic protozoan that causes

a relatively common parasitic sexually transmitted infection. The disease holds an

annual incidence of over 3 million. The majority of infections is asymptomatic in

men and thus is often undiagnosed and untreated. These untreated cases are hypoth-

esized to promote chronic persistent prostatic infection and resultant urethritis and

prostatitis [ 44 , 45 ].

T. vaginalis was previously suspected to be associated with the development of

PCA [ 46 ]. For decades, a couple of clinical studies seemed to support this correla-

tion. However, two recent studies gave negative results. A study that included 146

men with advanced prostate cancer demonstrated that T. vaginalis serostatus is not

associated with increased risk of metastatic or fatal prostate cancer (odds ratio <1)

[ 47 ]. This result does not support the increased risk of advanced or fatal prostate

cancer in men infected with T. vaginalis. In another study, Zhu et al. suggested that

the culture supernatant of T. vaginalis inhibits prostate cancer growth by disrupting

the proliferation and promotion of apoptosis [ 48 ].

Epidemiologic evidence for the association of T. vaginalis with prostate cancer

is inconsistent, and the role of T. vaginalis in PCA development remains controver-

sial. Thus, further study may help elucidate the association between PCA and T.

vaginalis infection.

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M. Feng and X. Cheng