Effects of HDAC inhibitor Vorinostat and radiation on HTB4 and MDA‐MB‐435 cancer cells

Abstract

HDAC inhibitors have shown promise in the treatment of various types of cancer. The HDAC inhibitor vorinostat was first introduced during treatments for cutaneous T‐cell lymphoma and has been shown to cause an increase in the effectiveness of radiation on multiple cancer cell lines. For the purpose of these experiments, the effects of vorinostat and radiation on HTB4 cells (a human bladder cancer cell line) and MDA‐MB‐435 cells (a human melanoma cell line) are being investigated in order to determine the efficacy of this combined treatment. Using cell cycle analysis and MTT assays, we were able to analyze the effects of radiation and vorinostat alone compared to the combination of both. For cell cycle analysis, we plated the cells in four flasks and treated three of them with either vorinostat (2.5 μM) alone, radiation (~20Gy) alone or the combination of the two. The cells were harvested, stained and analyzed five hours after radiation and 24 hours after vorinostat treatment by flow cytometry. Preliminary results for the HTB4 cells treated with both radiation and vorinostat showed an increase in the percent of cells in G2 and a reduction in the percent of those in both G1 and S phase compared to either treatment alone or the control population. Results for the 435's did not show a similar trend with distribution of cells between the control and three treatments. The MTT assay was performed using two 96‐well microtiter plates with 16μM vorinostat serially diluted 1:2 across 10 columns, and only cells in the 11th column and medium alone in the 12th column. One plate was irradiated using a lower dose of 5 Gy based on a literature survey. MTT was added to both plates directly after the one plate was irradiated. Results of the MTT assay for HTB4's and 435's showed that increasing concentrations of vorinostat alone and when coupled with radiation resulted in less MTT product produced compared to the radiation treatment alone. Based on the MTT data, the HTB4 cell line appears to be more sensitive than the 435's to the effects of vorinostat. Future experiments will focus on the effects of radiation on multiple tumor cell lines and investigate the molecular mechanisms by which HDAC inhibition influences radiation‐based cancer treatment.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.