Bacillus thuringiensis Parasporins and Their Use in Controlling Cancer Cells

Abstract

Parasporins are Cry proteins produced by Bacillus thuringiensis (Bt) strains during sporulation processes and notable for targeting the cancer cells with their unique cytotoxicity mechanism without exerting haemolytic effect on normal cells. Parasporins are specifically produced by Bt strains with non-insecticidal effect. Although the studies on parasporins go back to the 1970s, comprehensive scan about the cytotoxicity of parasporins was performed by Mizuki and colleagues. Considering that these proteins exhibit selective toxicities on human cancer cell lines but not on normal cells, detailed studies about the mode of action of anti-cancer effect was investigated in several countries. Specificity and abundance of parasporin producing Bt species in nature brought them into an important position in terms of developing anti-cancer agents. Parasporins are classified into six groups by the committee of parasporin classification and nomenclature as parasporin-1 (PS1), PS2, PS3, PS4, PS5, and PS6 by taking the amino acid homology into account. Activated parasporins display cytotoxicity at varying degrees in different cancer cell lines. There are numerous studies about promoting the use of Bt parasporins as anti-cancer agent in human, but in depth studies should be carried out about their usability in model organisms. Researches should also be deepened especially in vivo due to production of different types of parasporins with different mechanism of action by different Bt strains. Clarification of the molecular mechanisms of toxicity for every candidate parasporin on cancer cell lines may ease the development of anti-cancer agents. Thus, the present study was conducted to provide a review about the cytotoxic impacts of Bt parasporins on human cancer cell lines.