Correlation of VEGF and HIF-1 alpha Expression in Human Oral Cancer Cell Lines

The switch to the angiogenic phenotype represents a critical checkpoint during tumor progression. The transcription factor hypoxia-Inducible factor [HIF]-1 alpha is an important mediator of hypoxic adaptation of tumor cells thus controlling several genes involved in tumor angiogenesis such as vascular endothelial growth factor (VEGF). Objective: This study investigates the effect of hypoxia on both [HIF]-1 alpha and VEGF expression and the correlation of both these molecules, in normal human oral keratinocytes and oral cancer cell lines. Methods: Oral cancer cell lines [Cal33, SCC-4 & SCC-9] and normal oral human keratinocytes [NHOK] were grown in normoxia (20% O2, 5%-CO2) and hypoxia (2% O2-5%CO2). Immunocytochemial analysis was performed on Nunc Lab-Tek chamber slides to analyze the expression of vascular endothelial growth factor [VEGF] and hypoxia-Inducible factor [HIF]-1 alpha. Comparative analysis of VEGF and [HIF]-1 alpha expression in these oral cancer cell lines was examined using Western and Northern analysis. Results: 1) Hypoxia up-regulated VEGF and [HIF]-1 alpha at both transcriptional and translational levels. 2) Higher levels of VEGF and [HIF]-1 alpha were expressed in cancer cells as compared to NHOK. 3) A parallel increase in VEGF and [HIF]-1 alpha is apparent in all the oral cancer cell lines studied as compared to normal keratinocytes. Conclusion: These findings suggest that [HIF]-1 alpha may play an essential role in the hypoxia-induced upregulation of VEGF expression and subsequent tumor progression in oral carcinogensis.