Objective:To investigate the expression and clinical significance of hypoxia-inducible factor 1α(HIF-1α) in hypoxic human lung cancer cell lines and human lung carcinoma tissues. Methods:Transwell assay was used to test the invasive capacity of hypoxic lung cancer cells. The expression of HIF-1α mRNA and protein in hypoxic lung cancer cells in vitro was determined by reverse transcription-polymerase chain reaction(RT-PCR) and Western blot. The expression of HIF-1α was detected using immunohistochemistry and reverse transcription-polymerase chain reaction analyses(RT-PCR) in 60 specimens of lung carcinoma and 20 specimens of corresponding adjacent tissues. Results:The effect of hypoxia on the invasion of lung cancer cells increased. After hypoxia exposure,the HIF-1α mRNA and protein expression in lung cancer cells increased time-dependently. Compared with those in the control group,the mRNA and protein levels of HIF-1α in the hypoxic groups had more significant difference(P < 0.05 or P < 0.01). In lung carcinoma tissues,the positive expression rates of HIF-1α mRNA and proteins were 90.0% and 75.0% ,while 30.0% and 20.0% in normal lung tissues respectively,showing the expression of HIF-1α in cancer tissues were significantly different from that in normal tissues(P < 0.01). Comparing with the mRNA and protein levels of HIF-1α in lung cancer tissues of ⅠandⅡstage,there was marked increase in Ⅲ and Ⅳstage. The expression of HIF-1α in group of lymph node metastasis was higher than that in group without lymph node metastasis(P < 0.05). Conclusion:CoCl2 can up-regulate the expression of HIF-1α in lung cancer cell lines by inducing hypoxia. These hypoxia-mediated effects have the potential impact on lung cancer cells to promote its hypoxic tolerance. HIF-1-琢 overexpression plays important roles in invasion and metastasis of lung carcinoma. HIF-1-琢 may be a useful marker for evaluating the biological behaviors of lung carcinoma.