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Bacillus thuringiensis (Bt), a spore-forming gram-positive bacterium that can produce parasporal
crystalline inclusions during its sporulation phase, has been widely used for agricultural insect pests
control. Cry has unique toxic activities against certain insects, some invertebrates, protozoa, and human
cancer cells. Parasporins (PS) have been identified as Cry bacterial proteins and have been divided into six
types including PS1, PS2, PS3, PS4, PS5, and PS6. PSs have been found to distinguish and kill certain
cancer cells through different mechanism. PS1 was found to induce various cancer cells’ death by
activating their apoptotic signaling and increasing Ca2+level; PS2 acted on certain cancer cells as a
cytolysin by targeting on plasma membrane; PS3 and PS6 acted as a pore-forming toxin and lysis cancer
cell plasma membrane; PS4 induced cancer cell death in non-apoptotic way. It has been believed that the
variant mechanisms of PSs acting on cancer cells indicated that different PSs may have targeted on
different molecules and activated different signal pathway in cancer cells. PSs could be a series of natural
bacteria products with potential roles in cancer therapy.
Keywords: Bacillus, Bacillus thuringiensis,Parasporins,Cry protein, Cyt protein, cancer cell.