Abstract 2939: Harnessing in vivo CRISPR screen to uncover metabolic dependencies during cancer progression

Abstract Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, with the worst prognosis and limited treatment options. TNBC cells undergo metabolic reprogramming in response to nutrient limitations and changes in the tumor microenvironment throughout cancer progression. In the early stages, tumor cells are found to prioritize nutrient uptake and biosynthesis, but as they grow, intensified competition for nutrients fosters the emergence of subpopulations of cancer cells that excel in utilizing specific nutrients. The substantial metabolic pathways and genes that regulate each phase of cancer progression remain poorly understood. To address this, we have developed a stable integration, site-specific, and inducible CRISPR-Cas9 system that allows for temporal control of genetic perturbation. We conducted an unbiased in vivo loss-of-function CRISPR screen aimed at identifying metabolic vulnerabilities at different phases of cancer progression of TNBC. The inducible CRISPR system was activated only at the desired study period of each phase, thus capable of uncovering metabolic dependencies for TNBC proliferation at each distinct phase of cancer progression. As many large-scale CRISPR screens have previously been performed to identify gene dependencies for cancer progression in vitro, our CRISPR screen could address the shortcomings of in vitro screens by identifying novel essential metabolic genes that are significantly important for cancer growth in vivo. Preliminary data from our CRISPR screen revealed different pathways to be significantly important for tumor growth and proliferation at different phases of TNBC progression. For example, we find that ferroptosis is altered during the early lag phase of TNBC cancer progression, whereas, at the later stage of cancer progression, metastatic tumors upregulate serine metabolism, suggesting that secondary tumors could have distinct metabolism from the primary sites. Altogether, the findings from this study could provide valuable insights into stepwise metabolic dependencies arising from microenvironmental limitations and identify potential therapeutic targets at each phase of cancer progression. Moreover, our CRISPR-Cas9 model holds promise for dissecting the complex mechanisms of other cancer progressions. Citation Format: Seow Qi Ng, Zhengwei Wu, Jessica A. Lidster, Wai Leong Tam. Harnessing in vivo CRISPR screen to uncover metabolic dependencies during cancer progression 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 2939.