Aim: To elucidate the effects of dexamethasone on hypoxia-induced epithelial-to-mesenchymal transition (EMT) in colon cancer.
Methods: Human colon cancer HCT116 and HT29 cells were exposed to normoxic (21%) and hypoxic (1%) conditions. First, the effect of dexamethasone on cell viability was examined by MTT cell proliferation assay. In order to measure the expression levels of EMT markers (Snail, Slug, Twist, E-cadherin, and integrin αVβ6) and hypoxia-related genes [Hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial growth factor (VEGF)] by dexamethasone, quantitative real-time polymerase chain reaction and western blot analysis were performed. Furthermore, the morphological changes of colon cancer cells and the expression pattern of E-cadherin by dexamethasone were detected through immunocytochemistry. Finally, the effects of dexamethasone on the invasiveness and migration of colon cancer cells were elucidated using matrigel invasion, migration, and wound healing migration assays.
Results: Under hypoxia, dexamethasone treatment inhibited HIF-1α protein level and its downstream gene, VEGF mRNA level in the colon cancer cell lines, HCT116 and HT29. In addition, the presence of dexamethasone down-regulated the mRNA levels of hypoxia-induced Snail, Slug, and Twist, all transcriptional factors of EMT, as well as hypoxia-induced integrin αVβ6 protein level, a well-known EMT marker for colon cancer cells. Furthermore, reduced E-cadherin in hypoxic condition was found to be recoverable by treating with dexamethasone in both colon cancer cell lines. Similarly, under hypoxic conditions, dexamethasone restored the growth pattern and morphological phenotype reminiscent of colon cancer cells grown under normoxic conditions; dexamethasone blocked the migration and invasion of both colorectal cancer cell lines in hypoxia.
Conclusion: Our study suggested that dexamethasone has inhibitory effects on cell migration and invasion by suppressing EMT of colon cancer cell lines in hypoxic condition.
Keywords: Colon cancer; Dexamethasone; Epithelial-mesenchymal transition; Hypoxia; Hypoxia-inducible factor-1α.