Abstract C047: Autophagy-mediated proline-supply is important for cell survival in pancreatic cancers

Abstract Oncogenic KRAS mutations present in 90–95% of pancreatic cancer patients. KRAS mutation in pancreatic cancer increased the dependency on glutamine and consumption of proline. Proline is a non-essential amino acid but it is important for the synthesis of proteins such as collagen, and also for precursors of antioxidant molecules. Several enzymes such as P5CS(ALDH18A1),PYCR1 and PYCR2 are involving proline synthesis. The effects of proline synthesis enzymes on pancreatic cancer cells are relatively less studied than that of enzymes catalyzing proline. Here, we examined the impact of proline synthesis enzymes on pancreatic cancer cell survival and proliferation. We first examined that exogenous proline promotes cell survival under low glutamine conditions in various pancreatic cancer cells. Exogenous proline supplementation increased some pancreatic cell survival even when glutamine was not sufficiently available, whereas proline supplement is dispensible for certain cell types of pancreatic cancer. Next, to investigate the importance of proline synthesis enzymes in cell survival, we measured the cell proliferation of pancreatic cancer with knock-down the proline synthesis enzymes. The knockdown of ALDH18A1 and PYCR1,2, which are proline biosynthesis enzyme genes, reduced cell survival in pancreatic cancer cells, suggesting that in PDAC cells, the enzymes that synthesize proline from glutamine are crucial for cancer cell survival and growth. To test the effect of proline-sysnthesis enzymes on autophagy, we measured autophagy flux in the cell harboring GFP-RFP-LC3 or GFP-LC3 as a reporter. Knockdown of proline synthesis enzymes, particularly ALDH18A1 or PYCR1 led to an increase in autophagy levels, indicating that proline-independent cells can bypass proline synthesis by autophagy induction in the absence of proline synthesis genes. Furthermore gemcitabine-resistant cells showed reduced levels of proline synthesis enzymes. In pancreatic cancer cell lines, proline promotes cancer cell survival, generated by both biosynthesis from glutamine and starvation-induced autophagy, which also critically important for supporting cellular drug resistance. Taken together, these results indicate that proline synthesis is mechanistically associated with autophagy induced by glutamine-starvation, which is pivotal for supplying proline in pancreatic cancer cells. Citation Format: Ji hyeon Kim, Heesun Cheong. Autophagy-mediated proline-supply is important for cell survival in pancreatic cancers [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr C047.