Histone Deacetylase Inhibitors Have a Profound Antigrowth Activity in Endometrial Cancer Cells

Purpose: HDAC inhibitors (HDACIs) have been shown to inhibit cancer cell proliferation, stimulate apoptosis, and induce cell cycle arrest. Our purpose was to investigate the antiproliferative effects of the HDACIs [suberoyl anilide bishydroxamine, valproic acid (VPA), trichostatin A, and sodium butyrate] against six endometrial cancer cell lines. Experimental Design: Endometrial cancer cells were treated with a variety of HDACIs, and the effect on cell growth, cell cycle, and apoptosis was measured. The ability of VPA to inhibit the growth of endometrial tumors growing in immunodeficient mice was also assessed. Results: Clonogenic assays showed that all cancer cell lines were sensitive to the growth inhibitory effect of HDA-CIs. Cell cycle analysis indicated that treatment with HDA-CIs decreased the proportion of cells in S phase and increased the proportion of cells in the G₀-G₁ and/or G₂-M phases of the cell cycle. Terminal deoxynucleotidyl transferase-mediated nick end labeling assays showed that HDA-CIs induced apoptosis. This was concomitant with altered expression of genes related to malignant phenotype, including an increase in p21^Waf1, p27 ^Kip7, and E-cadherin and a decrease in Bcl-2 and cyclin-D1 and -D2. Chromatin immunoprecipitation analysis revealed a remarkable increase in levels of acetylated histones associated wiith the p21 promoter after suberoyl anilide bishydroxamine treatment. In nude mice experiments, VPA inhibited significantly human uterine tumor growth without toxic side effects. Conclusions: These results suggest that HDACIs are effective in inhibiting growth of endometrial cancer cells in vitro and in nude mice, without toxic side effects. The findings raise the possibility that HDACIs may prove particularly effective in treatment of endometrial cancers.