Abstract 3008: Induction of necroptosis through caspase-independent mechanisms in MCF-7 breast cancer cells following HDAC inhibition

Abstract

Abstract Cell proliferation and cell death are essential for maintaining homeostatic balance in eukaryotic organisms. Many diseases develop when cellular homeostasis is disturbed. Currently, several anti-cancer drugs are known to induce apoptosis through activation of intrinsic or extrinsic pathways. However, many types of cancer cells have acquired resistance due to quick adaptation to resist pro-apoptotic mechanisms. Therefore, simultaneous induction of other forms of cell deaths such as necroptosis, autophagy, etc., in addition to apoptosis, is becoming an attractive strategy for controlling tumor growth and metastasis. For this purpose, we have explored the role of XIAP in caspase-independent mechanisms of cell death during HDAC (Histone Deacetylase) inhibition. Our experiments with HDAC inhibitor SAHA (Suberoylanilide hydroxamic acid) have revealed that the anti-apoptotic biomarkers, including survivin and XIAP, exhibit important regulatory functions for inducing necroptosis in cancer cells. Interestingly, many of the signal adaptors of apoptosis and necroptosis are known to show dual functions during drug-induced cancer cell death. For example, the formation of the survivin-XIAP complex prevents XIAP from undergoing proteasomal degradation and polyubiquitination, thereby stabilizing XIAP in cancer cells. When the survivin level is increased, it is also known to stop the inhibition of XIAP by Smac. In addition, since XIAP can inhibit caspase -9 and the executioner caspases -3 and -7, the apoptosis mechanisms will be blocked, and cell proliferation will continue to promote cell survival and tumorigenesis. Our western blot data revealed that the caspase -9, -3, -7, and -8 levels were significantly downregulated in MCF-7 breast cancer cells following SAHA treatment. Furthermore, SAHA treatment also increased the levels of necroptosis inducers such as phospho-RIP3 and MLKL in MCF-7 cells. However, treatment of the same MCF-7 cells with other drugs such as RG-7388, an MDM2 inhibitor, was able to induce apoptosis through activation of caspases. Our current results show that MCF-7 cells may switch to the necroptosis pathway due to the inhibition of caspases and increased levels of survivin and XIAP. (This research was supported by the Royal Dames of Cancer Research Inc., Ft. Lauderdale, Florida). Citation Format: Umamaheswari Natarajan, Grace Waldron, Thiagarajan Venkatesan, Appu Rathinavelu. Induction of necroptosis through caspase-independent mechanisms in MCF-7 breast cancer cells following HDAC inhibition [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3008.