Abstract 252: IRS2-driven modulation of PI3K/AKT signaling and tumorigenesis in estrogen receptor-positive breast cancer

Introduction: Insulin receptor substrate 2 (IRS2) is a critical adaptor protein mediating intracellular signaling pathways downstream of insulin and insulin-like growth factor 1 (IGF1) receptors. Through its involvement in the PI3K/AKT signaling cascade, IRS2 regulates key processes essential for tumor growth and progression. While high IRS2 expression is linked to tumor progression, low IRS2 expression is associated with poorer overall survival, particularly in estrogen receptor-positive (ER+) breast cancer. However, the underlying mechanisms remain unclear, prompting this investigation into the role of IRS2 in ER+ breast cancer. Method: IRS2 expression levels and overall survival across subtypes were analyzed using TCGA and METABRIC public data. IRS2 expression levels were analyzed by Western blot and qRT-PCR. In the ER+ MCF7 cell line, IRS2 knockdown was performed using shRNA, and its effects on tumor cell proliferation, migration, and invasion were assessed via MTT, wound healing and transwell assays. To examine the impact of IRS2 on the IGF1 pathway, cells were treated with IGF1, and Western blot was used to analyze alterations in PI3K/AKT signaling and EMT marker expression following IRS2 knockdown. Tumorigenesis and metastasis were studied using fat pad and tail vein injections in NOD.SCID mice. Results: Analysis of METABRIC and TCGA patient data revealed that in the Luminal A subtype, lower IRS2 expression correlated with poorer overall survival. Among the 12 breast cancer cell lines, the ER+ MCF7 cell line, which exhibited relatively high IRS2 expression, was selected for shRNA knockdown experiments. IRS2 knockdown resulted in reduced cell proliferation, migration, and invasion. Time-dependent IGF1 treatment revealed reduced p-AKT levels following IRS2 knockdown, demonstrating suppression of IGF1-mediated PI3K/AKT signaling. EMT marker analysis revealed reduced expression of mesenchymal markers associated with cancer metastasis. Animal experiments suggested a potential reduction in tumorigenesis and metastasis; however, results were inconclusive and required further validation. Conclusion: Our findings demonstrate that IRS2 knockdown reduces proliferation, migration, and invasion, emphasizing its critical role in tumor cell functions. IRS2 depletion also suppressed IGF1-induced activation of the PI3K/AKT pathway and downregulated mesenchymal EMT markers, highlighting its role in cancer progression and metastasis. However, the significant correlation between low IRS2 expression and poorer patient outcomes underscores the need for further investigation into its clinical implications. Citation Format: Seonmin Lee, Ju Hee Kim, Han-Byoel Lee, Wonshik Han. IRS2-driven modulation of PI3K/AKT signaling and tumorigenesis in estrogen receptor-positive breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 252.