RESULTS: The tumour cell line analysed showed a strong hypoxic CA9
mRNA expression pattern in response to prolonged severe
hypoxia with cell-line specific patterns and a marked induction of CA9
protein in response to severe
hypoxia. These results were paralleled by the results for HIF-1α
protein under identical oxygenation conditions with a similar expression tendency to that displayed during the CA9
protein expression experimental series. Continuous stimulation with the
cytokines,
IL-1,
IL-6, TNF-α and TGF-β, under normoxic conditions significantly increased the
carbonic anhydrase 9 expression level at both the
protein and
mRNA level, almost doubling the CA9
mRNA and CA9 and HIF-1α
protein expression levels found under
hypoxia. The findings from these experiments indicated that
hypoxia is a positive regulator of CA9 expression in HCC, and the four signal transduction pathways,
IL-1,
IL-6, TNF-α and TGF-β, positively influence CA9 expression under both normoxic and hypoxic conditions.
CONCLUSION: These findings may potentially be considered in the design of anti-
cancer therapeutic approaches involving
hypoxia-induced or
cytokine stimulatory effects on expression. In addition, they provide evidence of the stimulatory role of the examined
cytokine families resulting in an increase in CA9 expression under different oxygenation conditions in human
cancer, especially HCC, and on the role of the CA9 gene as a positive disease regulator in human
cancer.