The Mechanisms of Fungal Immunomodulatory Protein GMI Induces Autophagy and Therapeutic Effects in Human Lung Cancer Cells

• Main Authors: I-Lun, 辛翌綸
• Other Authors: 柯俊良
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/11510991619725245522

博士 === 中山醫學大學 === 醫學研究所 === 100 === Apoptosis, necrosis, and autophagy are three major types of programmed cel death. Autophagy is a self-digestive process that degrades the cytoplasmic constituents. Immunomodulatory protein, one major bioactive component of Ganoderma, has anti-tumor activity. In this study, recombinant fungal immunomodulatory protein, GMI, was cloned from Ganoderma microsporum and purified. We demonstrated that GMI inhibits lung cancer cell proliferation by activating autophagy, but does not induce apoptotic cell death. On western blot, GMI increased LC3 conversion and decreased p53 expression in a time- and concentration-dependent manner. p53 overexpression inhibited GMI mediated autophagy. Cytoplasmic calcium chelator BAPTA-AM was used to prove that GMI promotes autophagy via calcium-mediated signaling pathway. GMI induced autophagy through inhibiting Akt/mTOR pathway. Bafilomycin-A1 and chloroquine, the lysosome inhibitors, enhanced GMI mediated autophagic cell death. We found that GMI inhibits the expression of ATP6V0A1, a subunit of V-ATPase. Using VSV-G pseudotyped lentivirus-shRNA system for ATP6V0A1 silencing, cytotoxicity and autophagosome accumulation induced by GMI were enhanced. The capabilities of GMI to suppress cell growth, telomerase activity, and colony formation were abolished in autophagy-defective cells. GMI did not stimulate apoptosis after blocking of autophagy by 3-MA or shRNA knockdown system. In xenograft studies, oral administration of GMI inhibited the tumor growth and induced autophagy significantly in nude mice that had received a subcutaneous injection of A549 cells. Furthermore, GMI increases susceptibility to cisplatin through inducing apoptosis by autophagy. This study reveals the novel anti-cancer function of GMI. GMI may be a potential chemopreventive agent against non-small cell lung cancer.