Hypoxia inducible factor-1a-mediated activation of survivin in cervical cancer cells

Aim: Hypoxia, a characteristic of almost all types of solid tumors, has been associated with poor outcome in a number of human malignancies. The aim of this study was to investigate the molecular mechanisms involved in hypoxia-induced activation of the human survivin gene promoter in cervical HeLa cells. Material and Methods: Immunohistochemical staining was used to detect the expression of HIF-1a and survivin in cervical cancer samples and normal cervical samples. Under normoxic and hypoxic conditions, the expression of hypoxia inducible factor (HIF)-1a and survivin in cervical cancer HeLa cells was detected by quantitative reverse transcription polymerase chain reaction and Western blotting. Luciferase reporter assays was used to investigate the molecular mechanisms in hypoxia-induced survivin activation. We also studied the effect of HIF-1a overexpression on the expression of survivin in cervical cancer HeLa cells. Results: Significant HIF-1a and survivin overexpression is associated with cervical cancer, and HIF-1a protein expression is strongly correlated with survivin protein expression. In cervical cancer cell line (HeLa), hypoxia upregulated both HIF-1a and survivin expression. Moreover, luciferase reporter assays using survivin core promoter demonstrated that survivin transcription was activated under hypoxia conditions and was associated with HIF-1a overexpression. The transcriptional activation of reporter genes in response to hypoxia is independent of potential HIF-1a-responsive element, located between -86 and -82 regions. HIF-1a overexpression significantly activated survivin expression. Conclusion: Our results demonstrate that survivin expression is upregulated following the induction of HIF-1a by hypoxia resulting from tumor formation, possibly leading to tumor progression. These findings have potential implication in developing novel cancer therapy targeting HIF-1.