Abstract: Abstract:Objective To explore whether hypoxia could promote epithelial-mesenchymal transition (EMT) in various differentiated colorectal cancer cells, and analyse the effect of hypoxia on invasion and migration of colorectal cancer cells. Methods HCT116 (poorly differentiated) and HT-29 (highly differentiated) colorectal adenocarcinoma cells were selected respectively. The morphological changes of two cell lines were observed after 0， 10， 25， 50， 100 and 150 mg/L cobalt chloride (CoCl2) treatment for 48 h. The expression of hypoxia-inducible factor-1α (HIF-1α) protein was analysed after 0， 10， 25， 50， 100 and 150 mg/L CoCl2 treatment for 48 h. An optimal concentration of CoCl2 was then selected. Methylthiazolyl tetrazolium (MTT) assay was used to detect the proliferation of two kinds of colorectal cancer cells induced by CoCl 2 at different time points (0, 24, 48, 72 and 96 h), and to select an optimal time. Under the optimal concentration and time conditions, the HCT116 and HT- 29 cells were processed by hypoxia (hypoxia group) and normoxia (normoxic group). Transwell invasion assay and Wound healing assay were used to detect cell invasion and migration in two groups. Western blot assay and RT-PCR were used to detect protein and mRNA expression levels of HIF-1α, E-cadherin and Vimentin in two groups. Results Two kinds of cells showed obvious morphological changes after 50 mg/L CoCl2 treatment for 48 h. HIF- 1α protein level first increased and then decreased in two groups of cells with the increased concentration of CoCl2, and 50mg/L CoCl2 was the optimal concentration (P＜0.05). The cell proliferation showed a tendency to decrease after the increase in both kinds of cells with or without hypoxia for 0-96 h (P＜0.05), and 48 h was the optimal time. The transmembrane number and cell migration rate were significantly more in hypoxia group than those of normoxic group (P＜0.05). The protein and mRNA levels of HIF- 1α and Vimentin were significantly higher in hypoxia group than those of normoxic group in HCT116 and HT-29 cell lines (P＜0.05). E-cadherin protein and mRNA levels were significantly lower in hypoxia group than those of normoxic group (P＜0.05). Conclusion Hypoxia can promote EMT in different differentiated colorectal cancer cells, and can enhance invasion and migration of two kinds of colorectal cancer cells.

Key words: hypoxia-inducible factor1,α subunit, colorectal neoplasms, epithelial-mesenchymal transition, cell prolifer? ation, neoplasm invasion, cell movement