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Cyst hydatid and cancer: the myth continues

We read with interest the article entitled “Association between Echinococcus granulosus infection and cancer risk – a pilot study in Cyprus [1]. Although the results of the study were impressive we feel that there are some points that must be clarified. In our previous clinical observational study, we demonstrated that coexistence of cancer and hydatid disease was very rare and we proposed that E. granulosus may elicit a protective effect against cancer via antigenic similarities (such as Tn antigen) [2]. Tn antigen, a mucin-type O-linked glycan, is a well-established cell surface marker for tumors and its elevated levels have been correlated with cancer progression and prognosis. Tn antigen is expressed in approximately 90% of carcinomas, including 80% of breast cancer tissues. Tn antigen is a target for the development of anticancer vaccines. A Tn antigenbased vaccine is currently under evaluation in a phase I clinical trial in breast cancer patients [3]. Berriel et al. performed a proteomic analysis to detect the immune crossreactivity between E. granulosus and CT26 colon cancer cells. They identified two proteins: mortalin and creatine kinase M-type. Interestingly, CT26 mortalin displays 60% homology with E. granulosus hsp70 [4]. Mortalin (GRP75) has important roles in regulating a variety of processes that are essential for tumorigenesis at multiple cellular locations. Intra-tumoral and intra-peritoneal injections of an anti-GRP75 antibody results in tumor growth suppression [5]. Recently, Daneshpour showed that a mutual cross reaction exists between antigens of hydatid cyst and excretory secretory products of cancer cells [6]. Similarly, Sharafi demonstrated that the sera of patients with breast cancer cross reacted with a nonglycosylated 27 kDa band of the hydatid cyst wall [7]. Results of these studies emphasize the existence of common antigens between hydatid cysts and cancer. In Oikonomopoulou’s study, the authors compared the cancer risk of the patients previously treated for an E. granulosus infection with patients without an infection. In our previous study the principal result was that the patients with hydatid cyst had lower cancer incidence than patients without hydatid cyst, and we concluded that the presence of E. granulosus infection might be a prophylactic factor against cancer [2]. Therapy with E. granulosus may eliminate the protective effects of the infection.