Abstract 2339: Targeting ICMT in pancreatic cancer

Abstract

Abstract Introduction: Pancreatic Cancer remains one of the most difficult to treat human cancers with the 5-year survival as low as 5%. No targeted therapy yet developed against Pancreatic cancer. Here we want to target Isoprenylcysteine carboxylmethyltransferase (ICMT), an enzyme that post translationally modifies a group of proteins including several small GTPases against Pancreatic Cancer. Method: ICMT inhibition was achieved using lentivirus expressing ICMT shRNA and a pharmacological inhibitor named Cysmethynil. We evaluated a panel of human pancreatic cancer cell lines and identified those that are sensitive to ICMT inhibition by cell viability assay. This responsiveness to ICMT inhibition was confirmed in in vivo xenograft tumor mouse models using both Cysmethynil and shRNA-targeting ICMT. Flow cytometry analysis after DAPI or PI staining is used to detect cell cycle arrest and apoptosis. We used western blot analysis to study autophagy, apoptosis and cell cycle markers. ShRNA for P21 is used for p21 knock down studies. SiRNA for p53 is used to study whether p21 induction is p53 dependent. BNIP3, ULK1 and ATG5 knock down was done using specific shRNAs to study their role in ICMT inhibition induced autophagy and apoptosis. BCL-xL is over expressed in the cells using retroviral vectors to study the role of apoptosis in ICMT inhibition induced cell death. Cell and mitochondrial respiration was determined by oxygen consumption rate analysis using Seahorse XF24 analyzer. Summary: In sensitive pancreatic cancer cells, ICMT inhibition induces mitochondrial respiratory deficiency and cellular energy depletion, leading to significant upregulation of p21 and p21 dependent induction of BNIP3 leading to autophagy and apoptosis. But unlike in prostate and liver cancer, ICMT inhibition induced apoptosis not the autophagy responsible for inhibition of cell viability in pancreatic cancer. Conclusion: These findings suggest ICMT is a potential therapeutic target against pancreatic cancers and atleast in pancreatic cancer, ICMT inhibition induced apoptosis but not autophagy responsible for its therapeutic efficacy. Citation Format: Kanjoormana A. Manu, Tin F. Chai, Jing T. Teh, Wan Zhu, Patrick J. Casey, Mei Wang. Targeting ICMT in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2339.