Hypoxia and cytokines regulate carbonic anhydrase 9 expression in hepatocellular carcinoma cells in vitro

AIM: To study the expression of carbonic anhydrase(CA) 9 in human hepatocellular carcinoma(HCC) cells.METHODS: We studied CA9 protein, CA9 m RNA and hypoxia-inducible factor-1 alpha(HIF-1α) protein levels in Hep3 B cells exposed in different parallel approaches. In one of these approaches, HCC cells were exposed to extreme in vitro hypoxia(24 h 0.1% O2) without or with interleukin(IL)-1, IL-6, tumor necrosis factoralpha(TNF-α) and transforming growth factor-beta(TGF-β) stimulation for the same hypoxic exposure time or exposed to normoxic oxygenation conditions without or with cytokine stimulation.RESULTS: The tumour cell line analysed showed a strong hypoxic CA9 m RNA 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 m RNA level, almost doubling the CA9 m RNA 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 provideevidence 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.

Inhibition of N-Myc down regulated gene 1 in in vitro cultured human glioblastoma cells

AIM: To study short ds RNA oligonucleotides(si RNA)as a potent tool for artificially modulating gene expression of N-Myc down regulated gene 1(NDRG1) gene induced under different physiological conditions(Normoxia and hypoxia) modulating NDRG1 transcription, m RNA stability and translation. METHODS: A cell line established from a patient with glioblastoma multiforme. Plasmid DNA for transfections was prepared with the Endofree Plasmid Maxi kit. From plates containing 5 × 107 cells, nuclear extracts were prepared according to previous protocols. The p SUPERNDRG1 vectors were designed, two sequences were selected from the human NDRG1 c DNA(5'-GCATTATTGGCATGGGAAC-3' and 5'-ATGCAGAGTAACGTGGAAG-3'. reverse transcription polymerase chain reaction was performed using primers designed using published information on β-actin and hypoxia-inducible factor(HIF)-1α m RNA sequences in Gen Bank. NDRG1 m RNA and protein level expression results under different conditions of hypoxia or reoxygenation were compared to aerobic control conditions using the Mann-Whitney U test. Reoxygenation values were also compared to the NDRG1 levels after 24 h of hypoxia(P < 0.05 was considered significant).RESULTS: si RNA- and iodoacetate(IAA)-mediated downregulation of NDRG1 m RNA and protein expression in vitro in human glioblastoma cell lines showed a nearly complete inhibition of NDRG1 expression when compared to the results obtained due to the inhibitory role of glycolysis inhibitor IAA. Hypoxia responsive elements bound by nuclear HIF-1 in human glioblastoma cells in vitro under different oxygenation conditions and the clearly enhanced binding of nuclear extracts from glioblastoma cell samples exposed to extreme hypoxic conditions confirmed the HIF-1 Western blotting results. CONCLUSION: NDRG1 represents an additional diagnostic marker for brain tumor detection, due to the role of hypoxia in regulating this gene, and it canrepresent a potential target for tumor treatment in human glioblastoma. The si RNA method can represent an elegant alternative to modulate the expression of the hypoxia induced NDRG1 gene and can help to monitor the development of the cancer disease treatment outcome through monitoring the expression of this gene in the patients undergoing the different therapeutic treatment alternatives available nowadays.