Expression Of Novel Antimicrobial Peptide Selysin And Its Cytotoxic Activity Against HepG2

In spite of great advance in cancer therapy, there is considerable current interest in developing anticancer agents with a new mode of action because of the development of resistance by cancer cells towards current anticancer drugs. Musca domestica, belonging to insecta, diptera, cyclorrhapha, muscidae, widely spreading in China, is the biggest number muscae in our country. A very large number of antimicrobial peptides (AMPs), which are toxic to bacteria as well as cancer cells, has been isolated from Musca domestica. So understanding the molecular mechanisms in cytotoxic activity against cancer cells of AMPs are important for explore new cancer therapeutics. In this issue, we studied the functional characterization of recombinat AMPs, Selysin, initially extracted from Musca domestica, and found that it can inhibit the proliferation of cancer cells. So we analyzed its functions in cytotoxic activity to HepG2, a kind of liver cancer cell line, in order to unveil its concealed molecular mechanisms.To procure large scale of Selysin preparation, recombinant Selysin was expressed in Pichia pastoris. We could obtain large scale Selysin preparation and continue further investigation of this promising therapeutic peptide.During our experiment, we observed that Selysin have negative effect on the proliferation of HepG2 cells. The 3H-TdR incorporation of HepG2 cells exhibited that Selysin could significantly limit DNA replication at high concentration and has none effect at low concentration. These data demonstrate that Selysin in high concertration can directly target HepG2 cell membrane, leading to the cancer cells death.Meanwhile, we found that under low concentration, Selysin induced caspase-3 activation leading the apoptosis of cells, which serves as the hallmark of apoptosis. Our work shows that under the specific concentration Selysin-induced apoptosis in HepG2 cells is caspase dependent. These phenomena suggest that the suitability of cancer cell-targeting Selysin as cancer therapeutics is plausible.