Spirocerca lupi and dogs: the role of nematodes in carcinogenesis

Abstract

Response from Luis A. Herrera and Patricia Ostrosky-WegmanOne of the major objectives of our article 1xDo helminths play a role in carcinogenesis?. Herrera, L.A. and Ostrosky-Wegman, P. Trends Parasitol. 2001; 17: 172–175Abstract | Full Text | Full Text PDF | PubMed | Scopus (22)See all References1 was to attract the attention of scientists to the question: is chronic inflammation the only mechanism whereby parasites induce cancer? The answer seems to be no. Host–parasite relationships are rather complex, they are not limited to the development of inflammation. Parasites can interfere with cellular processes that are relevant to carcinogenesis, such as intercellular communication, signal transduction, or even secret molecules with carcinogenic potential. However, evidence supporting any alternative mechanisms is scanty, and in an attempt to stimulate research on this topic, we postulated several other possibilities by which helminths might participate in malignant transformation of host cells. Thus, we agree with Melendez and Suarez-Pellin that there are still more questions than answers on this subject. We also considered that future studies should: (1) find more epidemiological evidence for potential associations between helminthiases and cancer; this should imply the development or improvement of technologies for the detection and identification of parasites in tissue samples from patients with cancer, in particular, for the detection of past infections; and (2) use animal models in which pathological changes induced by specific parasites in humans could be reproduced and correlated with the multi-step carcinogenic process (e.g. in the mouse–Schistosoma mansoni model, the development of immature worms up to the adult stage in the murine liver is similar to the development of S. mansoni or Schistosoma haematobium in humans. In fact, this model has been used extensively to investigate the effects of schistosomiasis on hepatic carcinogen metabolism 2xRecovery of the hepatic carcinogen-metabolising capacity of schistosome-infected mice after treatment with the antischistosomal praziquantel. Sheweita, S.A. and Mostafa, M.H. Oncol. Rep. 1995; 2: 155–159PubMedSee all References, 3xRelationship between schistosomiasis and bladder cancer. Mostafa, M.H. et al. Clin. Microb. Rev. 1999; 12: 97–111PubMedSee all References.Although the Spirocerca lupi–dog model is not representative of some human helminthiasis, this model could be suitable for research into the mechanisms involved in carcinogenesis that are induced by parasites. Therefore, we strongly encourage Melendez and Suarez-Pellin to explore the interesting possibilities they described in their letter that will certainly help scientists to understand the role of helminths in human carcinogenesis.