Abstract 5830: A first-of-its-kind model that reconstitutes targeted drug-induced cellular transdifferentiation

Abstract Introduction: Lung tumors treated with targeted therapies ultimately relapse due to intra-genic resistance mutations, bypass pathway activation, or cellular lineage changes. Newer precision therapies have higher selectivity and potency against both resistant and activating gene mutations, resulting in a significant increase in incidence of cellular transdifferentiation. The most common form of transdifferentiation is the change from lung adenocarcinomas (LUADs) to small cell lung cancer (t-SCLC) upon drug treatment which remains very poorly understood. Methods: We have combined patient derived xenografts (PDX) and ex vivo lines with multi-omic characterization, high-content image-based morphometry and fluorescence tracking, and single-cell barcode tracing to better understand the process of lung tumor transdifferentiation. Results: We have developed a first-of-its-kind t-SCLC model that reconstitutes ex vivo LUAD to SCLC transdifferentiation. Genomic and transcriptomic analyses of our NSCLC PDX collection identified tumors with mutation in TP53 and RB1, two genes that are altered in virtually all de novo SCLCs. PDX sample CBX336 was identified as having mutations in both TP53 and RB1, in addition to expressing the KRASG12C oncogene. Upon treatment with Sotorasib, CBX336 tumors initially demonstrated slow tumor growth, followed by a dramatic increase in the growth after prolonged drug exposure. Our experimental and computational data suggest a highly coordinated procession toward transdifferentiation with the parallel upregulation of the neuroendocrine transcription factor NEUROD1 across numerous epithelial cellular clones. Conclusions: Our new experimental system allows characterization at the single-cell level. Ongoing work includes the integration of new resources to study lineage reprogramming, and advancing new therapeutic strategies. Citation Format: Priyanka Gopal, Mohamed Abazeed. A first-of-its-kind model that reconstitutes targeted drug-induced cellular transdifferentiation 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 (6Suppl): Abstract nr 5830.