Abstract 27: Characterizing 3q26 copy number gain in lung squamous cell carcinoma through a novel genetically engineered mouse model
Authors: Meneses Kayleah M. , Weems Capella , Liu Yi , Justilien Verline , Murray Nicole R. , Fields Alan P. 
Published: April 2023

Abstract
Lung squamous cell carcinoma (LUSC) is a major histological subtype of lung cancer accounting for ~30% of all lung cancer diagnoses. LUSC patients suffer from poor therapeutic response, high relapse rate, and poor prognosis. A major reason for this bleak outcome is the lack of well characterized oncogenic drivers of LUSC. This has stalled the generation of relevant genetic pre-clinical mouse models amenable to studying LUSC tumorigenesis in vivo and developing targeted therapeutics to treat LUSC patients. Our group has identified concomitant 3q26 copy number gain (CNG) and TP53 loss as defining genetic alterations present in ~90% of LUSC tumors. Furthermore, we have identified three 3q26 oncogenes (PRKCI, ECT2 and SOX2) that genetically and biochemically collaborate to drive LUSC tumor formation. Coordinate overexpression of Prkci, Ect2 and Sox2, and loss of Trp53 in ex vivo cultures of lung basal stem cells (LBSCs; a potential cell of origin for LUSC) is both necessary and sufficient to transform these cells into orthotopic LUSC tumors in syngeneic mice. These findings indicate that 3q26 amplification and TP53 loss play a critical role in the initiation and progression of LUSC. Based on these data, we have developed the first autochthonous genetically engineered mouse model (GEMM) to study the role of 3q26 CNG in LUSC tumorigenesis in vivo. Our GEMM allows inducible overexpression of Prkci, Ect2, and Sox2 and knockout of Trp53 (PES/Trp53−/−) in lung tissue. Tumorigenesis will be initiated in PES/Trp53−/− mice using an established protocol to target transgene recombination to LBSCs in vivo. These mice will be assessed for tumor latency, survival, tumor burden, and metastatic potential. In related studies, we used bioinformatics analyses on primary LUSC tumors from the Cancer Genome Atlas’ database to identify 13 genes in addition to PRKCI, ECT2 and SOX2, whose expression is driven by 3q26 amplification. These genes were functionally characterized by assessing the effect of shRNA-mediated gene silencing on soft-agar growth of human H520 LUSC cells, a cell line that harbors 3q26 amplification. Our results revealed that knockdown of each of these genes independently resulted in a significant decrease in soft agar colony formation. We further assessed these genes through RT-qPCR mRNA expression profiling comparing PES/Trp53−/- transformed LBSCs to non-transformed LBSCs. These genes were significantly upregulated in PES/Trp53−/- transformed LBSCs, suggesting that they play important roles in LBSC transformation. Future work will further assess the molecular mechanisms by which these additional 3q26 genes contribute to LUSC cell transformation and assess the role of alternate cells of origin (Club and AT2) in 3q26-driven LUSC tumor formation using our PES/Trp53−/− GEMM.
Citation Format: Kayleah M. Meneses, Capella Weems, Yi Liu, Verline Justilien, Nicole R. Murray, Alan P. Fields. Characterizing 3q26 copy number gain in lung squamous cell carcinoma through a novel genetically engineered mouse model [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 27.