Glucocorticoid Receptor α and β Variant Expression Is Associated with ASF/SF2 Splicing Factor Upregulation in HT-29 Colon Cancer and MCF-7 Breast Carcinoma Cells

Background and AimsTranscriptional activity of NF-κB is inhibited by the liganded glucocorticoid receptor (GR), which exists mainly in two splice variants as functional GRα and nonfunctional GRβ. We investigated the effect of 5-aza-2′-deoxycytidine (5-dAzaC), trichostatin A (TSA), and sodium butyrate (NaBu) on GRα,GRβ and ASF/SF2 splicing factor expression in HT-29 colon and MCF-7 breast carcinoma cells.MethodsHT-29 and MCF-7 cells were cultured in the absence or in the presence of 5-dAzaC, TSA, and NaBu, followed by RNA and protein isolation. The transcript and protein levels of GRα, GRβ ASF/SF2 were determined by reverse transcription, real-time quantitative PCR and Western blot analysis.ResultsWe found that 5-dAzaC, TSA, and NaBu lead to an increase in GRα and ASF/SF2 transcript levels and a decrease in GRβ transcript levels in HT-29 and MCF-7 cells. The 5-dAzaC, TSA, and NaBu resulted in increased GRα and ASF/SF2 protein levels and GRβ protein downregulation in HT-29 cells. The most increased GRα protein expression in MCF-7 cells was observed with NaBu. However, all of these compounds inhibited GRβ protein expression in MCF-7 cells. The MCF-7 cells treated with NaBu demonstrated a remarkable increase in ASF/SF2 protein expression.ConclusionsBecause NF-κB is considered to be a factor in the augmentation of malignant properties of cells, treatment of tumors with 5-dAzaC, TSA, and NaBu may provide a novel approach to the enhancement of therapeutic effects of glucocorticoids in epithelial carcinomas.