Combination Treatment of Renal Cell Carcinoma with Belinostat and 5-Fluorouracil: A Role for Oxidative Stress Induced DNA Damage and HSP90 Regulated Thymidine Synthase

Abstract

Despite several therapeutic options renal cell carcinoma is associated with a poor clinical outcome. Therefore, we investigated whether combining 5-fluorouracil with the histone deacetylase inhibitor belinostat would exert a synergistic effect on renal cell carcinoma cells invitro and invivo. We used SN12C cells treated with 5-fluorouracil and/or belinostat invitro and in xenograft experiments invivo. Cell viability and death mechanisms were assessed by MTS assay and Western blot. To investigate the role of reactive oxygen species we used H2DCF-DA, reactive oxygen species scavengers and the roGFP2 construct. Belinostat potentiated the anticancer effect of 5-fluorouracil. It synergistically induced apoptosis by activating caspases and increasing the subG1 cell population. Effects on reactive oxygen species mediated DNA damage included decreased thioredoxin expression and increased levels of TBP-2, γ-H2AX and Ac-H3. Furthermore, belinostat attenuated the 5-fluorouracil mediated induction of thymidylate synthase via HSP90 hyperacetylation. Co-administration of 5-fluorouracil with belinostat similarly reduced tumor volume and weight, and increased γ-H2AX and Ac-H3 levels in the SN12C xenograft model. In combination with 5-fluorouracil the targeted inhibitor of histone deacetylase synergistically inhibited renal cancer cell growth by the blockade of thymidylate synthase induction and the induction of reactive oxygen species mediated DNA damage invitro and invivo. Our results suggest that combined treatment with belinostat and 5-fluorouracil may represent a promising new approach to renal cancer.