Abstract 1655: Targeting lipid metabolism disrupts KRAS oncogenesis in pancreatic cancer
Authors: Arora Neha , Liang Hong , Reed Alex , Chang Jeffrey T. , Cravatt Benjamin F. , Zhou Yong 
Published: March 2024

Background: KRAS mutations are chief genetic event in pancreatic cancer. Recently approved inhibitors, sotorasib and adagrasib specifically target KRASG12C, a minor mutation in pancreatic cancer. Further, patients developed acquired resistance by generating secondary KRAS mutations, posing an added obstacle for allele specific inhibitors, warranting alternative strategies to tackle KRAS-dependent cancers. KRAS forms proteolipid signaling platforms on plasma membrane (PM) termed nanoclusters. We have shown mutant KRAS nanoclusters selectively enrich phosphatidylserine (PS) lipid, being particularly receptive to unsaturated PS, suggesting lipid acyl chain metabolism is crucial for KRAS function. In cells, lysophosphatidylcholine acyltransferases 3 (LPCAT3) preferentially catalyzes synthesis of unsaturated PS. We tested the hypothesis that inhibition of LPCAT3 depletes unsaturated PS in the PM, perturbs the PS-dependent PM interactions and oncogenic functions of KRAS.

Methods: LPCAT3 knockdown (KD) mediated by siRNA in doxycycline (Dox) inducible KRASG12D murine cells (iKRAS) and CRISPR-Cas9 in human pancreatic tumor line (MiaPaCa-2). LPCAT3 inhibition achieved using small molecule inhibitors (SMIs): HTS3 and HTS4. Shotgun lipidomics characterized re-modeling of PS lipidomes. PM distribution and nanoclustering of KRAS was evaluated by super-resolution electron microscopy (EM). Anti-tumor effect of LPCAT3 inhibition was examined in vitro by proliferation, colony formation and soft agar assays and cellular signaling by western blot.

Results: LPCAT3KD decreased polyunsaturated PS levels in MiaPaCa-2 and mislocalized mutant KRASG12V on the PM with a 4-fold reduction in KRAS PM distribution (p&lt;0.0013) and disrupted KRAS nanoclustering, without affecting that of HRASG12V in transformed MiaPaCa-2. LPCAT3KD reduced colony formation ability in MiaPaCa-2. LPCAT3 siRNA reduced KRAS-dependent MAPK signaling, and significantly reduced colony formation only upon Dox-induced expression of KRASG12D, while having no effect in uninduced iKRAS. An integrated knowledgebase tool canSAR.ai generated a druggability score of 77% suggesting LPCAT3 is highly druggable by chemistry-based assessment. Indeed, recently discovered LPCAT3 inhibitors, significantly reduced MAPK signaling, proliferation and colony formation in mutant KRAS-dependent tumor cells while having no significant effect in WT KRAS cells corroborating mutant KRAS specificity of LPCAT3.

Conclusion: We demonstrate targeting unsaturated PS lipid metabolism by inhibiting LPCAT3 disrupts KRAS signaling platform and perturbs its oncogenic functions in pancreatic cancer cells. Since various KRAS mutants require unsaturated PS to propagate signaling, our approach targets diverse KRAS mutants, uniquely addressing drug resistance issue. Further, we will optimize the LPCAT3 inhibitors and study their efficacy in xenograft mouse models.

Citation Format: Neha Arora, Hong Liang, Alex Reed, Jeffrey T. Chang, Benjamin F. Cravatt, Yong Zhou. Targeting lipid metabolism disrupts KRAS oncogenesis in pancreatic cancer [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 1655.