Abstract 539: LN18-MRTX1719R cell line, a useful cell model for the discovery of the new PRMT5 inhibitors

Abstract

Abstract In recent years, the PRMT5-MTA complex has emerged as a "synthetic lethal" novel target for the treatment of MTAP (methylthioadenosine phosphorylase)-deficient cancers. Kryukov et al. first reported the "synthetic lethal" effect of inhibiting PRMT5 in MTAP-deficient tumors, and they identified MTAP as the synthetic lethal partner of PRMT5 in 2016. MTAP is a tumor suppressor gene frequently lost in various cancers, including pancreatic cancer, non-small cell lung cancer, and mesothelioma. Furthermore, the loss of MTAP leads to the accumulation of MTA in cancer cells, which competes with PRMT5's co-factor SAM for binding and forms the PRMT5-MTA complex. Cancer cells lacking MTAP show enhanced sensitivity to PRMT5 loss. Therefore, this complex has emerged as a potential therapeutic target, particularly for the treatment of MTAP-deficient cancers. MRTX1719 is a highly effective selective inhibitor of the PRMT5-MTA complex, capable of selectively inhibiting PRMT5 activity in MTAP-deficient cells. As the most promising candidate drug, MRTX1719 is undergoing Phase I/II clinical evaluation for patients with MTAP-deficient cancers. Drug resistance is an inevitable problem with small molecule inhibitors. Currently, the mechanism of resistance to MRTX1719 is not clear, as MTAP/CDKN2A loss is an early driver event in most cancers. To further explore the resistance mechanism of MRTX1719, our group used the MTAP-deficient LN-18 cell line and induced mutagenesis using the mutagen ENU. We then used a drug low-concentration gradient method to establish the LN-18-MRTX1719R-resistant cell line. Specifically, LN-18 cells were treated with increasing doses of MRTX1719 for 6 months, and mixed clones that tolerated MRTX1719 were selected. Subsequently, single clones were selected, and a stable MRTX1719-resistant clone was obtained, named LN-18-MRTX1719R. Cell proliferation inhibition assay showed that the IC50 of LN-18-MRTX1719R was over 1000nM, which is 100-fold more resistant than the parental LN-18 cells (9.87 nM). We explored the resistance mechanisms using RNA-Seq and WES methods. The resistance to MRTX1719 of the LN-18-MRTX1719R cell line was highly stable after 20 cell passages. The LN-18-MRTX1719R cell line can be a useful cell line mode in the development of future PRMT5·MTA inhibitors. Citation Format: Yao Tang, Liping Wang, Guoqian Wang, Jinying Ning, Feng Hao. LN18-MRTX1719R cell line, a useful cell model for the discovery of the new PRMT5 inhibitors [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 539.