The histone deacetylase inhibitors (HDACi), such as PXD101 or SAHA, inhibit the proliferation and stimulate the apoptosis in tumors. The enhanced effect of HDACi combined with chemotherapy or radiotherapy has been reported in several cancers. In this study, we investigated the antitumor effect of HDACi PXD101 combined with irinotecan in colon cancer.
PXD101 and SN38, active form of irinotecan, had a dose-dependent anti-proliferative activity in HCT116 and HT29 colon cancer cells. PXD101 combined with SN38 had a synergistic effect in colon cancer cell lines, as shown by combination index. The combination of PXD101 with SN38 had an effect on XIAP and p21 protein expressions with time- and dose-dependent manner, more prominently in HCT116 than HT29 cells. These effects were further enhanced by the addition of PXD101 than irinotecan alone in both cell lines. In xenograft mice, PXD101 in combination with irinotecan dramatically inhibited tumor growth without additive toxicity. In addition, antiumor effect was more prominent in HCT116 than HT29 xenografts. Apoptotic effects of tumor in xenografts treated with these combinations were better than irinotecan alone. Combination of PXD101 and irinotecan resulted in 63 % of relative SUV mean in [18F]FLT-PET in mice with established HCT116 xenograft. Early response to these agents can be detected with [18F]FLT-PET. These data suggest that PXD101 increases the cytotoxic activity of iriontecan in colon cancer and these drug combinations should be explored in the treatment of colon cancer.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5371.
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