Abstract 5328: Novel KRAS-specific in-well lysis ELISA for high throughput screening

Abstract

Abstract RAS is one of the most frequently mutated genes in cancer. Gain–of–function missense mutations promoting oncogenesis cluster at codons 12, 13, and 61 of KRAS, NRAS and HRAS. These result in enhanced GTP binding due to fast exchange of nucleotide and/or impairment of GAP (GTPase Activating Protein) binding. Although these mutants are all activating, they are not equal in their oncogenic potential and differences in patient survival are associated with different RAS mutants and which RAS allele is affected, with KRAS being the most prevalent. Current RAS therapeutic approaches have migrated to be isoform specific. With this in mind, we have developed an activation state specific high throughput screening compatible (HTS) assay that is specific for KRAS. A novel rabbit anti–KRAS recombinant antibody was isolated via cloning of immunoglobulin variable regions from antigen positive B cells isolated from rabbits immunized with a peptide immunogen targeting a region of low homology between the RAS isoforms. Antibody specificity was validated with recombinant HRAS, KRAS and NRAS proteins over a wide concentration range by both immunoblotting and by a bead–based multiplex ELISA where all three RAS isoforms were present. The new assay allows for direct in–well lysis of cells cultured in 96–well plate format, either directly in media or following a PBS wash step. Activated KRAS in the lysate is captured on the assay plate and detected via chemiluminescence using the KRAS specific antibody. Preliminary assay validation has included EGF treatment of HeLa cells to show activation in cells expressing wildtype KRAS and inhibition with the selective non–covalent KRASG12D inhibitor MRTX1133 in Aspc1 cells known to express KRASG12D over a wide range of cell seeding densities. We anticipate that this assay will further the discovery of novel KRAS specific therapeutics. Citation Format: Hyun Min Park, Jason Poole, Mary Anne Jelinek. Novel KRAS-specific in-well lysis ELISA for high throughput screening. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5328.