Abstract 5535: Intracellular negative regulators of RTK-Ras-ERK signaling alter breast cancer perception of metastatic niche-derived growth factors

Abstract Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype that commonly metastasizes to distant organs, such as the lung, resulting in the poor clinical outcomes. TNBC cells commonly overexpress epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK) which when bound by microenvironmental growth factors, results in the activation of downstream effector kinases ERK-AKT and initiates transcriptional programs that control cell fate. Tumor cells, however, simultaneously receive many growth factor inputs from their respective microenvironments, many of which stimulate RTKs other than EGFR, that converge at ERK and AKT resulting in different transcriptional and cell fate outputs. This raises questions as to how tumor cells perceive, decode, and respond to a complex set of microenvironmental signals and what the relevance of this process may be for disease pathogenesis and treatment. To this end, our study aimed to determine how disseminated breast cancer cells perceive and respond to a complex growth factor milieu upon seeding and engraftment in the lung. Using live-cell microscopy techniques and TNBC cells carrying biosensors for ERK and Akt signaling pathways, we monitored the dynamic signaling behaviors of single tumor cells, in real-time, as they adapted to the environment in living human lung tissue. Strikingly, we found that individual disseminated tumor cells are less responsive to growth factors once seeded in the lung, as compared to outside this tissue, despite the presence of RTK stimulating ligands. We showed that partial activation of EGFR is necessary for complete activation of ERK signaling by other growth factor-RTK pairs, and expression of downstream ERK target genes, whereas AKT signaling was unaffected. Using quantitative modeling and experimentation, we showed that reshaping of ERK signaling response dynamics occurred via dysregulation of negative regulators that are dominantly controlled by EGFR signaling. Together, these results provide novel insight into how tumor cells perceive and respond to complex microenvironmental signals, which has important implications for drug targeting strategies. Citation Format: Vaibhav Murthy, Cemal Erdem, Jeremy Copperman, Marc Birtwistle, Alexander Davies. Intracellular negative regulators of RTK-Ras-ERK signaling alter breast cancer perception of metastatic niche-derived growth factors [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 5535.