Cobalt chloride, a chemical inducer of hypoxia-inducible factor-1α in U251 human glioblastoma cell line

Tumor hypoxia has been described to increase the resistance of cancer cells to radiation therapy and chemotherapy. Hypoxia-inducible factor-1α (HIF-1α) is the main transcriptional factor activated by hypoxia and it plays a key role in reprogramming tumor growth. We examined in this study whether cobalt chloride induce HIF-1α in different concentrations. U251 human glioblastoma cell line was incubated at 16 h under normoxia with or without CoCl2 at 1, 5, 10, 20, 25, 50, 100, 150 and 200 μM treatments. In proliferation assay, CoCl2 have shown an increase in cellular induction between 50 and 200 μM, proportionally. CoCl2 have also shown at 50 μM the maximum induction effect. In addition, CoCl2 at 50 μM displayed maximum response at 20,000, 30,000 and 40,000 U251 cells, respectively. In HIF-1 expression assay, CoCl2 increases HIF-1α gene expression between 50 and 200 μM. Western analysis revealed sharp protein band at 118 KDa which represented the HIF-1α protein with high band density at 50 μM CoCl2. The present paper reports the adaptive response of human glioblastoma cells to CoCl2, a chemical hypoxia-mimicking agent. The effects of the treatment were evaluated on cell proliferation, and HIF-1α gene expression.