How tapeworms interact with cancers: a mini-review

Abstract

Cancer is one of the leading causes of death, with an estimated 19.3 million new cases and 10 million deaths worldwide in 2020 alone. Approximately 2.2 million cancer cases are attributed to infectious diseases, according to the World Health Organization (WHO). Despite the apparent involvement of some parasitic helminths (especially trematodes) in cancer induction, there are also records of the potential suppressive effects of helminth infections on cancer. Tapeworms such as Echinococcus granulosus, Taenia crassiceps, and more seem to have the potential to suppress malignant cell development, although in a few cases the evidence might be contradictory. Our review aims to summarize known epidemiological data on the cancer-helminth co-occurrence in the human population and the interactions of tapeworms with cancers, i.e., proven or hypothetical effects of tapeworms and their products on cancer cells in vivo (i.e., in experimental animals) or in vitro. The prospect of bioactive tapeworm molecules helping reduce the growth and metastasis of cancer is within the realm of future possibility, although extensive research is yet required due to certain concerns.

Keywords: Cancer; Echinococcus; Mesocestoides; Taenia; Tapeworm.

Figure 1. Anticipated mechanisms of tapeworm effects on cancer.

Although the pathways by which tapeworms suppress tumor development are unknown in many cases, several proposed mechanisms exist. The worms could directly damage cancer cells through their products or indirectly by influencing the host immune system. The latter may occur either due to the parasite exhibiting the same antigen epitopes as cancer cells or because its products affect various immune system cells, directly killing cancer cells or activating other immune cells. Of course, some not yet recognized processes/interactions might also be involved. DCs–dendritic cells, NK–natural killer cells, CD8+-CD8+ T cells, EgKI1-Kunitz-type protease inhibitor produced by E. granulosus.

Figure 2. Flowchart of how the literature was selected.