Abstract 2819: Novel drug resistant CDX models for anti-cancer drugs discovery

Abstract

Abstract Oncogene BRAF is located on chromosome 7q34, consisting of 766 amino acids and 22 exons, encoding a serine/threonine protein kinase belonging to the RAF family and plays a critical role in the MAPK signaling pathway. The mutation of BRAF was documented in nearly 8% of all human cancers including melanoma (60%), thyroid (60%), and lung adenocarcinoma (10%). The most common mutation of BRAF is V600E (Class I), which was found in more than 70% in these cancers. Despite the clinical success of approved small molecule inhibitors of BRAF V600E (vemurafenib, dabrafenib and encorafenib), this remains an area of unmet medical need because of primary or acquired drug resistance. The construction of BRAF drug-resistant cell lines plays a pivotal role in cancer research. It serves as a crucial tool for discovery of the mechanisms of drug resistance. In this study, we have developed a systematic approach for constructing drug-resistant cell lines, inducing resistance through the gradual escalation of drug concentrations. The validation of drug resistance involves morphological recordings of parent and drug-resistant cell lines, drug resistance index in vitro through IC50 measurements and in vivo through the inhibition of tumor growth (TGI) which compare to those in the parental cell line. We successfully established Vemurafenib and Dabrafenib resistant A375 cell lines (A375 Vemurafenib R, A375 Dabrafenib R) with 21 and 31.5 folds of resistance index, respectively. The in vivo drug resistance efficacy was also tested by implanting Vemurafenib resistant cells subcutaneously into NOD-SCID mice and showed that A375 Vemurafenib R exhibited robust tolerance to 50 mg/kg Vemurafenib treatment (P.O.21 days, 50mpk, TGI=17.4%), whereas the parental cells were nearly completely inhibited (P.O.21 days, 50mpk, TGI=92.3%). In addition, single-cell sequencing of A375 Vemurafenib R revealed significant gene expression differences in the MAPK and EGFR signaling pathways, aiding in the identification of new targets, and signaling pathways associated with drug resistance, thereby providing potential targets for new drug development. Citation Format: Hai-Ting Dai, Tie-Jun Bing, Zhi-Da An, Jie Yang, Tian-Yu Pang, Jia-Wei Gao, Yun-Yi Bo, Wen-Jen Yu. Novel drug resistant CDX models for anti-cancer drugs discovery [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 2819.