toxoplasma: a cancer risk factor or cancer enhancer?

Toxoplasma gondii can infect various warm-blooded vertebrates, including humans. almost one-third of the world s population is infected with this parasite. t. gondii has three infectious forms: tachyzoite, bradyzoite, and sporozoite. humans become infected by ingestion of the cysts in raw or undercooked meat, ingestion of oocysts through contaminated food or water, and vertically from mother to fetus. the potential link between the t. gondii infection and cancer has attracted significant attention. toxoplasmosis can be a risk factor for the development of oral and brain cancers, while inhibiting the progression of melanoma, breast cancers, and ovarian cancers. t. gondii induces or suppresses different cancers by various mechanisms. toxoplasma infection increases the expression of anti-apoptotic proteins bcl2, bfl1, bcl-xl, bcl-w, mcl-1, bad, and bax in host cells. on the other hand, t. gondii modulates several signaling pathways by transcribing key genes such as brca1, myc, and il-6, and inhibits the growth and metastasis of the breast tumors, suggesting a potential therapeutic strategy. treatment by intertumoral injection of t. gondii δgra17 tachyzoites and anti-pd-l1 therapy significantly increased the survival of mice and suppressed tumor growth in preclinical mouse models of melanoma, lewis lung carcinoma, and colon adenocarcinoma. additionally, a strain of t. gondii attacked the cd45+cd11c+ cells associated with immunosuppression in ovarian cancer and converted them into immune-stimulated cells. despite the fact that the toxoplasma impacts can serve as either a risk factor or an inhibitor of tumor progression, more study is needed to understand the actual role of t. gondii on cancers and to examine its mechanism of action in more detail. due to prevalence of this parasite in iran and its association with abortions and subsequent economic losses, further investigations are recommended.