Abstract 2977: Novel HSP90 inhibitors with senolytic activity for a targeted therapy in a hormone-induced breast cancer senescence model

Abstract Background: The research into senescent cells, particularly their accumulation and contribution to aging and age-related diseases, has gained significant momentum in recent years. This interest is primarily driven by findings in mouse models, where the excessive buildup of senescent cells is linked to various age-related pathologies. Consequently, there has been a concerted effort in the scientific community to identify and develop senolytics. A notable development in this field is the identification of senolytics within the class of HSP90 inhibitors. These inhibitors, initially investigated for their potential in cancer therapy, have been repurposed due to their high selectivity for senescent cells. Our research has led to new compounds with mild inhibitory activity against HSP90α in response to these challenges. These compounds stand out for their lack of toxic side effects and their demonstrated senolytic activity across multiple cellular models. Objective: The primary objective of this research is to identify and characterize innovative HSP90 inhibitors that exhibit senolytic properties, specifically in the context of hormone-driven cancers. Methods and Results: Utilizing a structure-based virtual screening technique, we identified several compounds displaying strong affinity and predicted inhibitory activity against the target protein, HSP90α. Among these, two inhibitors designated K4 and K5, demonstrated notable senolytic activity in vitro without inducing cytotoxic effects in non-senescent cells. These compounds were tested for their efficacy in senolytic activity and displayed half-maximal inhibitory concentrations (IC50) of 155 nM and 111 nM, respectively. The experimental model for this study was the MCF7 cell line, which was treated with 4-Hydroxytamoxifen (Tam, 10uM for 96 hours) to induce a state of senescence. Subsequent growth curve analyses and beta-galactosidase assays established that Tam treatment effectively halted cell proliferation and induced a senescence state in about 40% of the cell population compared to the ethanol control. When treated with K4 and K5 (10 uM for an additional 96 hours), a significant reduction in the senescent cell population was observed, with K5 showing a particularly pronounced increase in the mortality rate of these cells (up to 2.5-fold compared to the DMSO control). Western blot analysis supported these results, suggesting the effectiveness of K5 combined with Tam in inhibiting proliferation and inducing cell death in MCF7 cells. Conclusion: Our findings propose a novel therapeutic approach for hormone-dependent breast cancer, combining the dual roles of tamoxifen and HSP90 inhibitors to target senescent cancer cells. This strategy could reduce tumor recurrence and contribute to the advancement of cancer treatment methods. Citation Format: Luca Cis, Michela Gottardi Zamperla, Veronica Barbi, Pietro Cigala Fulgosi, Sara De Martino, Aurora Aiello, Simona Nanni, Chiara Cencioni, Davide Pirolli, Paola Tabarelli De Fatis, Giovanni Battista Ivaldi, Marco Malavolta, Christian Steinkühler, Maria Cristina De Rosa, Antonella Farsetti, Sandra Atlante, Carlo Gaetano. Novel HSP90 inhibitors with senolytic activity for a targeted therapy in a hormone-induced breast cancer senescence model [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 2977.