title: Lysosomal dysfunction and autophagy blockade contribute to IMB-6G-induced apoptosis in pancreatic cancer cells.
abstract: Targeting the autophagic pathway is currently regarded as an attractive strategy for cancer drug discovery. Our previous work showed that IMB-6G is a novel N-substituted sophoridinic acid derivative with potent cytotoxicity against tumor cells, yet the effect of IMB-6G on autophagy and pancreatic cancer cell death remains unknown. Here, we show that IMB-6G inhibits the growth of MiaPaCa-2 and HupT-3 pancreatic cancer cells and induces caspase-mediated apoptosis, which is correlated with an accumulation of autophagic vacuoles. IMB-6G promotes autophagosome accumulation from the early stage of treatment but blocks autophagic flux in the degradation stage, mainly through attenuation of lysosomal cathepsin activity in pancreatic cancer cells. Moreover, IMB-6G triggers lysosomal membrane permeabilization (LMP), followed by cathepsin B/CTSB and cathepsin D/CTSD release from lysosomes into the cytoplasm. Inhibition of autophagosome formation with siRNA against autophagy protein 5 (Atg5) attenuates IMB-6G-induced LMP and apoptosis. Furthermore, cathepsin inhibitors relieve IMB-6G-induced apoptosis as well. Altogether, our findings demonstrate that IMB-6G is a novel autophagy inhibitor, which induces autophagy-dependent apoptosis through autophagosomal-cathepsin axis in pancreatic cancer cells and indicate the potential value of IMB-6G as a novel antitumor drug candidate.
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Na
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Yueying
authors.initials: Y
authors.lastname: Dou
authors.affiliation: Zhejiang Provincial Key Laboratory of Geriatrics &Geriatrics Institute of Zhejiang Province, Zhejiang Hospital, Hangzhou, Zhejiang 310013, China.
authors.forename: Genxiang
authors.initials: G
authors.lastname: Mao
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Chongwen
authors.initials: C
authors.lastname: Bi
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Weiqiang
authors.initials: W
authors.lastname: Pang
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Xiaojia
authors.initials: X
authors.lastname: Liu
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Danqing
authors.initials: D
authors.lastname: Song
authors.affiliation: Institute of Medicinal Biotechnology, Chinese Academy of Medical Sciences &Peking Union Medical College, Beijing 100050, China.
authors.forename: Hongbin
authors.initials: H
authors.lastname: Deng
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis; D001343:Autophagy; D000071187:Autophagy-Related Protein 5 / Q000235:genetics / Q000378:metabolism; D002403:Cathepsins / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D008247:Lysosomes / Q000187:drug effects* / Q000378:metabolism; D009588:Nitrogen Mustard Compounds / Q000494:pharmacology*; D010190:Pancreatic Neoplasms / Q000378:metabolism*
chemical_list: C502778:ATG5 protein, human; D000970:Antineoplastic Agents; D000071187:Autophagy-Related Protein 5; C000628942:IMB-6G; D009588:Nitrogen Mustard Compounds; D002403:Cathepsins