Multi‐Target Inhibitor CUDC‐101 Impairs DNA Damage Repair and Enhances Radiation Response in Triple Negative Breast Cell Line

Since the discovery that Histone deacetylase inhibitors (HDCAi) could enhance radiation response, a number of HDACi, mainly pan-HDAC inhibitors, have been studied either as monotherapy or in combination with photon irradiation or chemotherapeutic drugs in the management of breast cancer. Studies on combination of HDACi and particle type of radiation remain limited. CUDC-101 is a multitarget inhibitor of Histone deacetylases (HDACs), epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2(HER-2). In this paper, the effectiveness of CUDC-101 in enhancing radiation response to protons irradiation was studied in MCF-7, MDA-MB-231 and MCF-10A cell lines, using X-rays as reference radiation. γ-H2AX foci assays showed increased sensitivity to CUDC-101 in MDA-MB-231 cell line compared to the MCF-7 cell line. In both cell lines, induction of apoptosis was enhanced in CUDC-101 pre-treated cells compared to radiation (protons or X-rays) alone. Increased apoptosis was also noted in CUDC-101 pre-treated cells in the MCF-10A cell line. Cell cycle analysis showed increased G2/M arrest by CUDC-101 mono-treatment as well as combination of CUDC-101 and X-irradiation in the MDA-MB-231 cell line. Collectively, the findings indicate that CUDC-101 effectively enhances response to both X-radiation and proton irradiation, in the triple negative MDA-MB-231 cell line. The study highlights that CUDC-101 holds potential in the management of triple negative breast cancer as monotherapy or in combination with X-irradiation.