Abstract:

BACKGROUND: We previously found that enhanced expression of hepatocyte nuclear factor 4alpha (HNF-4alpha) is associated with hyper-proliferation of colon carcinoma cells. Here, the effect of histone deacetylase (HDAC) inhibitors on proliferation and the expression of HNF-4alpha and its downstream target genes were assessed in HM7, LS174T, HT29 and Caco-2 colon carcinoma cell lines. RESULTS: HNF-4alpha expression was found to vary in the different colon carcinoma cell lines tested, being highest in HM7. Additionally, a direct correlation with proliferation was observed. In HM7 cells, the weak HDAC inhibitor butyrate significantly inhibited the transcription of HNF-4alpha, its downstream target gene MUC4, and genes associated with proliferation, including the proliferating cell nuclear antigen gene PCNA. siRNA-mediated silencing of HNF-4alpha exerted an effect similar to butyrate on HM7 cell proliferation. The stronger HDAC inhibitor trichostatin A (TSA) exerted an effect similar to that of siRNA-mediated HNF-4alpha silencing and, concomitantly, inhibited the expression of the transcription factor gene SP1. Also, siRNA-mediated silencing of HDAC3 and HDAC4 reduced HNF-4alpha expression. Chromatin immunoprecipitation (ChIP) assays revealed that TSA induces hyperacetylation of histones H3 and H4 and, concomitantly, inhibits SP1 binding to the HNF-4alpha promoter. Subsequent electromobility shift assays supported these latter findings. CONCLUSIONS: HNF-4alpha transcriptional expression and activity are tightly controlled by epigenetic mechanisms. HDAC inhibitor targeting of HNF-4alpha may serve as an effective treatment for advanced colon carcinomas, since downstream cancer-associated target genes such as MUC4 are significantly down-regulated by this treatment.

Notes:

Algamas-Dimantov, Anna Yehuda-Shnaidman, Einav Peri, Irena Schwartz, Betty eng Research Support, Non-U.S. Gov't Netherlands Cell Oncol (Dordr). 2013 Apr;36(2):155-67. doi: 10.1007/s13402-012-0123-3. Epub 2013 Jan 11.