Functional Characterization of VS-186B, a Novel HDAC Inhibitor with Anticancer Activity

Histone acetylation and deacetylation are key regulators of gene expression and are frequently dysregulated in cancer, contributing to tumorigenesis and drug resistance. Overexpression of histone deacetylases (HDACs) in many cancer types leads to silencing of tumor suppressor genes and uncontrolled proliferation. Tumors often rely on epigenetic mechanisms to escape therapy and develop resistance. This study aimed to identify novel compounds that selectively target cancer cells while minimizing toxicity to non-cancerous cell lines. A series of novel HDAC inhibitors was evaluated using the Differential Nuclear Staining (DNS) assay, flow cytometry, and HDAC inhibition assays. These assays assessed cytotoxicity, selectivity, and mechanisms of cell death. Among seven compounds tested, VS-186B exhibited the highest cytotoxicity and Selective Cytotoxicity Index (SCI), particularly against the human Jurkat T-cell leukemia cell line. Flow cytometry experiments (Annexin V-FITC, ROS, JC-1, and Caspase-3/7 assays) revealed that VS-186B induced apoptosis. VS-186B was more cytotoxic than Curcumin and Vorinostat across most of the cell lines tested and was more specific to hematological cells. Connectivity Map (CMap) analysis showed strong similarity to genes affected by known HDAC inhibitors. Subsequently, HDAC enzymatic assays confirmed that VS-186B inhibits Class I and II HDACs in a dose-dependent manner. VS-186B exhibits promising anticancer potential as a selective HDAC inhibitor since it induces apoptosis in cancer cells without significant cytotoxicity to non-cancerous lines with a similar gene expression profile to known HDAC inhibitors. These findings support further development of VS-186B as an epigenetic treatment for leukemia/lymphoma.