Abstract 3300: Dual inhibition of PIKfyve and KRAS/MAPK as a potential for therapeutic strategy for pancreatic ductal adenocarcinoma
Authors: Wisniewski Jasmine P. , Cheng Caleb , Jackson Bailey , Korkaya Ahmet , Peters Sydney , Qiao Yuanyuan , Lyssiotis Costas A. , Chinnaiyan Arul M. 
Published: March 2024

Abstract
Background: PIKfyve is a lipid kinase that serves as the single source for PI(3,5)P2, a critical molecule for lysosome functions, including autophagy. Pancreatic Ductal Adenocarcinoma (PDAC) is known to utilize autophagy as well as other lysosome functions to survive in its harsh microenvironment. Considering the role of PIKfyve in autophagy, we hypothesized that PIKfyve is important for PDAC pathophysiology. Indeed, we screened multiple cell lines of different cancer lineages and found that PDAC cell lines were highly sensitive to PIKfyve inhibitors apilimod and ESK981. Given these results, we aimed to establish PIKfyve inhibition as a therapeutic strategy for PDAC. Importantly, this idea is rapidly translatable as both apilimod and ESK981 have both cleared phase-1 clinical trials. Additionally, PDAC nearly ubiquitously harbors a mutation in KRAS, leading to the overactivation of the KRAS-RAF-MEK-ERK pathway, which is known to be the driver of PDAC. Recent reports showed that inhibition of this pathway results in induction of autophagic flux as a protective mechanism in PDAC. Thus, we aimed to investigate the therapeutic potential of PIKfyve inhibition in blocking protective autophagy induced by KRAS/MAPK inhibition.
Methods and results: In order to determine the potential of PIKfyve inhibition as a therapeutic for PDAC treatment, we first established that PIKfyve inhibition disrupts the autophagic flux in cells. Specifically, we used PIKfyve inhibitors ESK981 and apilimod as well as CRISPRi-mediated knockdown and saw a decrease in autophagic flux through western blot and GFP-LC3-RFP-LC3∆G-based autophagic flux probe analyses. Finally, PIKfyve inhibition decreased cell viability with IC50s in the nanomolar range.To evaluate the potential of combined inhibition of KRAS/MAPK and PIKfyve, we first confirmed that genetic or pharmacological KRAS/MAPK perturbation indeed increases autophagic flux utilizing the autophagic flux probe. Importantly, we found that PIKfyve inhibition attenuates the autophagic flux induced by KRAS/MAPK inhibition. Moreover, we determined that dual inhibition of PIKfyve and KRAS/MAPK resulted in synergistic growth inhibition employing CellTiter-Glo-based synergy assays. Further, to investigate the in vivo potential of this combination, we utilized a syngeneic orthotopic model of PDAC. Surprisingly, most mice were cured when treated with both ESK981 and trametinib while each individual treatment only modestly decreased tumor burden. Additionally, we established a patient-derived xenograft model where mice treated with a combination of ESK981 and trametinib (MEK inhibitor) or ESK981 and MRTX-1133 (KRASG12D inhibitor) displayed substantial tumor regression in comparison to single treatment or control groups. Taken together, the dual inhibition of PIKfyve and KRAS holds promise as a therapeutic strategy for PDAC treatment.
Citation Format: Jasmine P. Wisniewski, Caleb Cheng, Bailey Jackson, Ahmet Korkaya, Sydney Peters, Yuanyuan Qiao, Costas A. Lyssiotis, Arul M. Chinnaiyan. Dual inhibition of PIKfyve and KRAS/MAPK as a potential for therapeutic strategy for pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3300.