Objective: To explore the characters of expression of cytoglobin in tumor cells after hypoxia.
Methods: Human pulmonary tumor cells of the line A549 were cultured and divided into 4 groups to be cultured under 5% CO2 and 95% air and exposed to 2% O2, 5% CO2, and 93% N(2) for 4, 12, or 24 hours respectively. The distribution of cytoglobin was examined by immunohistochemistry and the expression of cytoglobin was detected by Western blotting. The mRNA level of cytoglobin in the A549 cells was assayed by reverse-transcription PCR.
Results: Immunohistochemistry showed that cytoglobin was located in the plasma of the A549 cells, and the staining strength of cytoglobin was enhanced in the hypoxic groups in comparison with the normoxic group. Western blotting showed significantly stronger expression of protein of cytoglobin in the 3 hypoxic groups than in the normoxic group (all P < 0.05). The expression of cytoglobin was upregulated significantly in the hypoxic 12- and 24-hour groups than in the hypoxic 4-hour group (both P < 0.05). The cytoglobin mRNA levels of the 3 hypoxic groups were all significantly higher than that of the normoxic group (all P < 0.05). The cytoglobin mRNA levels of the hypoxic 12- and 24-hour groups were significantly higher than that of the hypoxic 4-hour group (both P < 0.05), however, without a significant difference between the hypoxic 12- and 24-hour groups (P > 0.05).
Conclusion: Hypoxia upregulates the expression of cytoglobin in tumor cells.