Abstract 2391 Novel HDAC Inhibitors as Potential Anticancer Drugs

Introduction/background: Histone deacetylases (HDACs) are known to be overexpressed in many cancer types. This overexpression drives the proliferation of cancer cells and can repress tumor suppressor genes such as p53 and p21. HDAC inhibitors are relatively new in the field of cancer research, with some already approved by the Food and Drug Administration (FDA) to treat cancer patients, and others currently ongoing clinical trials. In this study, we evaluated the anti-cancer activity of seven novel HDAC inhibitors received from our collaborator, which included VS-169B, VS-183A, VS-183D, VS-186A, VS-186B, VS-186C, VS-186E, and compared them to their controls Curcumin and 5-fluorouracil. Experiments were conducted using two Acute Lymphoblastic Leukemia (ALL) cell lines, CEM and Jurkat, and one non-cancerous cell line, HS-27. The objective of this study is to see if these HDAC inhibitors display any cytotoxic activity, and if so, compare the activity in two human lymphoma cell lines. We also want to identify the mechanism of action that these drugs use to induce cell death, as well as find a drug treatment that targets cancer cells with minimal cytotoxicity to normal cells. Materials and Methods: The Differential Nuclear Staining (DNS) Assay was performed by growing the cells in flasks, plating them in 96 well plates, treating them with various concentrations of the drugs, incubating them for 72 hours, and reading them using a bioimager multi-well plate reader (Molecular Devices ImageXpress Pico). This instrument generates data that is used to calculate the CC50, or concentration that kills fifty percent of the cells. Flow Cytometry was used to check cell viability and perform assays such as the Annexin V FITC Assay, which determines the mechanism of action that the drug uses to induce cell death, whether that be apoptosis or necrosis. Results: All HDAC inhibitors displayed some anti-cancer activity. The compound VS-186B showed to have the most cytotoxic activity, with a CC50 of 2.9uM in the Jurkat cell line, and 4.6uM in the CEM cell line. The compounds displayed more cytotoxic activity than their controls Curcumin, and 5-fluorouracil. VS-186B was also tested on the human fibroblast HS-27 cell line to observe the cytotoxicity of the drug against non-cancerous cells. VS-186B exhibited a high selective cytotoxic index of 16.09 against Jurkat and 10.17 against CEM. Conclusion: Our cellular and molecular analyses indicate that the HDAC inhibitors displayed anti-cancer activity, with VS-186B being the most cytotoxic. Annexin V FITC analysis verified that this compound induced cell death by apoptosis. The high selective cytotoxic indexes confirmed that VS-186B was cytotoxic to cancer cells with minimal cytotoxicity to non-cancerous cells. We are currently using VS-186B in other assays such as mitochondrial depolarization, reactive oxygen species, and cell cycle analysis. Future experiments could include RNAseq gene expression analysis to compare the expression of tumor suppressor genes with and without HDAC inhibitor treatment. This research is funded by G-RISE at The University of Texas at El Paso Grant NIGMS 1T32GM144919 from National Institutes of Health.