Chu et al. (2016) used CoCl2 to establish a hypoxia model of breast cancer cells and found that the expression of HIF-1α mRNA was increased in those cells. In this study, human glioma U251 cells were treated with 400 μM CoCl2. Compared with the blank control group and MgCl2 group, the cell proliferation level decreased, and the expression of HIF-1α mRNA and protein increased in a CoCl2 group, suggesting that a hypoxia cell model was successfully established. The gene discussed is HIF1A; the disease is central nervous system cancer.