Abstract C033: Targeting PIKfyve-driven lipid metabolism in pancreatic cancer

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) subsists in a nutrient-deregulated microenvironment, making it particularly susceptible to treatments that interfere with cancer metabolism. For example, PDAC utilizes and is dependent on high levels of autophagy and other lysosomal processes including macropinocytosis. Although targeting these pathways has shown potential in preclinical studies, progress has been hampered by the challenge of identifying and characterizing favorable targets for drug development. In our study, we aimed to characterize PIKfyve, a lipid kinase integral to lysosomal functioning, as a novel and targetable vulnerability in PDAC. We first confirmed that PIKfyve inhibition disrupted autophagic flux and disrupted lysosomal function. Next, to understand the metabolic effects of PIKfyve inhibition in PDAC cells, we employed a metabolism-focused CRISPR screen. Through this, we identified that PIKfyve inhibition increases PDAC cells’ dependency on de novo fatty acid synthesis through genes such as FASN and ACACA. Accordingly, PIKfyve inhibition triggered an increase in SREBP1-driven transcriptional and metabolic signatures favoring de novo fatty acid synthesis through increasing expression of genes such as FASN and ACACA. Further, employing targeted lipidomics, we determined that PIKfyve inhibition triggered an SREBP1-dependent accumulation of long-chain sphingolipids and that knockout of serine palmitoyl transferase subunits SPTLC1 and SPTLC2 sensitized PDAC cells to PIKfyve inhibition. Taken together, PIKfyve inhibition disrupts PDAC lipid homeostasis such that PDAC cells upregulate de novo synthesis of sphingolipids as a compensatory mechanism, suggesting that co-targeting de novo fatty acid synthesis and PIKfyve would result in synergistic effects. Given the importance of KRAS-MAPK signaling in controlling PDAC metabolic homeostasis, we hypothesized that the KRAS-MAPK signaling pathway is a primary driver of de novo lipid synthesis, specifically enhancing FASN and ACACA levels. Utilizing chromatin immunoprecipitation sequencing, we determined that KRAS or MEK inhibition reduces MYC binding to FASN and ACACA promoters. In line with this observation, KRAS or MEK perturbation decreased FASN and ACACA transcript and protein levels, suggesting that KRAS or MEK inhibition may sensitize PDAC cells to PIKfyve inhibition. Indeed, the simultaneous targeting of PIKfyve and KRAS-MAPK resulted in the elimination of tumor burden in a syngeneic orthotopic model and tumor regression in a xenograft model of PDAC. Taken together, these studies suggest that disrupting lipid metabolism through PIKfyve inhibition induces synthetic lethality in conjunction with KRAS-MAPK-directed therapies for PDAC. Citation Format: Caleb Cheng, Jasmine P Wisniewski, Sydney Peters, Jing Hu, Rahul Mannan, Bailey Jackson, Rüya Pakkan, Pietro Morlacchi, Brian Magnuson, Tongchen He, Rupam Bhattacharyya, Yuanyuan Qiao, Costas A Lyssiotis, Arul M Chinnaiyan. Targeting PIKfyve-driven lipid metabolism in pancreatic cancer [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 C033.