Abstract 507: Nebivolol induces autophagy and inhibits cell proliferation in triple negative breast cancer

Abstract Background: Among various types of breast cancer (BC), triple negative BC (TNBC) has a high-risk of recurrence and poorer prognosis. Chemotherapy, which is associated with many acute and chronic toxicities, remains the primary treatment for TNBC. Despite aggressive therapy, about one-third of early-stage TNBC patients develop metastasis within 5 years of diagnosis and have a median survival of only 12 months. Therefore, identifying safe and effective novel treatment for TNBC is of utmost importance. Using 2 cell models, our group recently reported the repurposing potential of nebivolol (NEB) in TNBC cells. Here, we aimed to confirm the effects of NEB using a panel of 10 TNBC cell lines and identify its mechanism of action. Methods: The half-maximal inhibitory concentrations of NEB (IC50) were determined across 10 cell lines by a concentration-response curve using non-linear regression analysis fitted to a 3-parameter logistic equation. MDA-MB-231 and SUM159 cells were chosen for subsequent experiments. RNA-seq followed by enrichment analysis using KEGG database and reverse phase protein array (RPPA) followed by two-way Analysis of Variance (ANOVA) with multiple comparisons were conducted to identify downstream pathways and target proteins impacted by NEB. To assess the effect on autophagy, lysosome formation, and cell proliferation, autophagy and lysosome fluorescent dyes and EdU proliferation assay were used, respectively, after treating the cells with various NEB concentrations. Fluorescent images from these experiments were imaged using a Nikon confocal microscope and analyzed in ImageJ. Differential expression of protein candidates from RPPA and autophagy related markers was confirmed using western blotting (WB). A p-value < 0.05 was considered statistically significant by student’s t-test and one-way ANOVA, as appropriate. Results: NEB inhibited the growth of all 10 TNBC cell lines in a concentration-dependent manner. The IC50 of NEB for TNBC cell lines ranged from 6.1 to 13.9 µM. Integrative RNA-seq analysis of both cell line models suggested significant upregulation of autophagy pathway (FDR < 0.05) after NEB treatment. NEB induced autophagy and lysosome formation in a concentration- and time-dependent manner, significantly inhibited cell proliferation, and significantly upregulated autophagy markers p62 and LC3B-II. In RPPA, DNMT3B and pTRAP220/MED1 were the most significantly downregulated proteins after NEB treatment in both cell lines (FDR < 0.05), which was further confirmed using WB. Conclusion: NEB inhibits TNBC growth and proliferation and induces autophagy and lysosome formation by modulating key proteins. Ongoing studies include the analysis of NEB’s effects on inducing apoptosis and its role in clonogenic and tumorigenic potential of TNBC cells. Citation Format: Wangjia Cao, Tagari Samanta, Benny A. Kaipparettu, Meghana V. Trivedi. Nebivolol induces autophagy and inhibits cell proliferation in triple negative 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 507.