Sodium butyrate-mediated HDAC inhibition under hypoxic conditions modulates redox balance and tumor cell behavior in MCF-7 human breast cancer cells

Abstract Hypoxia and epigenetic dysregulation are key contributors to breast cancer progression and therapeutic resistance. However, the interaction between histone deacetylase (HDAC) inhibition and hypoxia-associated signaling remains incompletely understood. This study therefore aimed to evaluate the combined effects of sodium butyrate (NaBu), an HDAC inhibitor, and cobalt chloride (CoCl 2 ), a chemical hypoxia-mimetic agent, on the biological behavior of MCF-7 breast cancer cells. To do this, cells were treated with NaBu, CoCl 2 , or their combination. Cell viability, proliferation, intracellular reactive oxygen species (ROS) generation, and cell-cycle distribution were assessed using MTT, cell counting, NBT, and flow cytometry, respectively. Quantitative real-time PCR was also performed to evaluate the expression of HDAC1 , HIF-1α , c-MET , and lncRNA-H19 . NaBu reduced cell viability and proliferation in a dose- and time-dependent manner, accompanied by increased ROS generation and HDAC1 downregulation. CoCl 2 induced a hypoxia-mimetic response characterized by HIF-1α and lncRNA-H19 upregulation and G2/Marrest, whereas prolonged or higher-dose exposure promoted ROS accumulation and growth inhibition. Combined treatment further reduced cell viability and proliferation, enhanced ROS accumulation, and modulated hypoxia-related gene expression compared with either treatment alone. Although G2/M arrest was also observed following combined treatment, the cell-cycle profile largely resembled that induced by CoCl 2 alone, suggesting that hypoxia-mimetic signaling predominantly drove this response. Overall, HDAC inhibition enhanced the cellular response to hypoxia-mimetic stress, highlighting the therapeutic potential of integrating epigenetic modulation with hypoxia-targeting strategies. Nevertheless, further mechanistic, drug-interaction, and in vivo studies are required to validate these findings.