TREATMENT WITH siRNA AND ANTISENSE OLIGONUCLEOTIDES TARGETED TO HIF-1

TREATMENT WITH siRNA AND ANTISENSE OLIGONUCLEOTIDES TARGETED TO HIF-1

TREATMENT WITH siRNA AND ANTISENSE OLIGONUCLEOTIDES TARGETED TO HIF-1

Overexpression of hypoxia inducible factor-1 (HIF-1) in cancers has been correlated to a more aggressive tumor phenotype. We investigated the effect of HIF-1knockout on the in vitro survival and death of human tongue squamous cell carcinomas (SCC-4 and SCC-9). Under normoxic condition, a basal level of HIF-1protein was constitutively expressed in SCC-9 cells, albeit an undetectable level of HIF-1 messages. Exposure to hypoxia induced only a transient increase in mRNA transcript but a prolonged elevation of HIF-1 protein and its immediate downstream target gene product, VEGF. Under normoxic or hypoxic conditions, treatment of SCC-9 cells with AS-HIF-1 ODN suppressed both constitutive and hypoxia-induced HIF-1 expression at both mRNA and protein levels. Knockout of HIF-1 gene expression via either AS-HIF-1 ODN or siRNA (siRNAHIF-1) treatment resulted in inhibition of cell proliferation and induced apoptosis in SCC-4 and SCC-9 cells. We also demonstrated that exposure of SCC-9 cells to hypoxia led to a time-dependent increase in the expression of bcl-2 and IAP-2, but not p53. The attenuated levels of bcl-2 and IAP-2, and the enhanced activity of caspase-3 after treatment with AS-HIF-1 ODN may contribute partly to the effects of HIF-1 blockade on SCC-9 cell death. Collectively, our data suggest that a constitutive or hypoxia-induced expression of HIF-1 in SCC-9 and SCC-4 cells is sufficient to confer target genes expression essential for tumor proliferation and survival. As a result, interfering with HIF-1 pathways by antisense or siRNA strategy may provide a therapeutic target for human tongue squamous cell carcinomas.
© 2004 Wiley-Liss, Inc.
Key words: antisense; siRNA; apoptosis; HIF-1; Bcl-2; IAP-2

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