Abstract 566: The anticancer effects of polyisoprenylated cysteinyl amide inhibitors involves interaction with the KRAS chaperone calmodulin

Abstract Pancreatic cancer is the third leading cause of cancer-related deaths with a 5-year survival rate of less than 10%. Approximately 90% of reported cases are driven by KRAS mutations. The mutant KRAS acquires its functional localization through interactions with chaperone proteins via its polybasic polyisoprenylated tail. Polyisoprenylated cysteinyl amide inhibitors (PCAIs) mimic this region possibly disrupting the polyisoprenylation-dependent interactions with chaperone proteins. Here, we determine the effect of newly developed PCAIs that were designed to be more water-soluble on cell viability, 3D spheroid invasion, spheroid degeneration and F-actin filaments on MIA PaCa-2 and PANC-1 cells. Of the seven new PCAIs analogs tested, NSL-AB-51 and NSL-AB-45 were the most potent, with EC50 values of 2.5 and 5.6 µM against MIA PaCa-2, and 1.7 and 4.5 µM against PANC-1 cells, respectively. At 5 and 10 µM, NSL-AB-51 decreased the invasion area of 3D spheroids by 98 and 99%, respectively. MIA PaCa-2 spheroids degenerated by 61% after 72 h treatment with 10 µM NSL-AB-51. Treatment with 1.0 μM NSL-AB-51 caused cell rounding and reduction of mean cell areas by 69% and F-actin filaments by 96%. Moreover, to identify the pharmacological target of the PCAIs, NSL-AB-45 was coupled to an epoxy-activated Sepharose resin for affinity trapping of PCAIs-interacting proteins. Affinity-analysis of supernatants and detergent membrane extracts from MIA PaCa-2 and PANC-1 cells revealed single Coomassie band of about 17 kDa that was identified as calmodulin by western blotting analysis. The calmodulin-PCAIs affinity interaction was found to be strongest in the presence of calcium and weakest in the presence of EDTA. These findings reveal that calmodulin is the likely target of PCAIs. Since calmodulin is the chaperone protein responsible for KRAS trafficking and localization to the inner surface of the plasma membrane, this finding strongly suggests, at least in part, an anticancer role for the PCAIs that involve disruption of KRAS functions. Citation Format: Kweku Ofosu-Asante, Jassy Mary Lazarte, Amarender Burra, Nazarius S. Lamango. The anticancer effects of polyisoprenylated cysteinyl amide inhibitors involves interaction with the KRAS chaperone calmodulin [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 566.