SNS-032 prevents hypoxia-mediated glioblastoma cell invasion by inhibiting hypoxia inducible factor-1α expression

Hypoxia and hypoxia inducible factor-1α (HIF-1α) play a critical role in glioblastoma (GBM) which is characterized by highly aggressive and widespread cell invasion into adjacent normal brain tissue. The purpose of this study was to investigate the effect of the novel aminothiazole compound SNS-032 in glioblastoma cell invasion under hypoxic condition. SNS-032 is a potent and selective inhibitor of cyclin-dependent kinases 2, 7 and 9 and inhibits both cell cycle and transcription. We analyzed the effect of SNS-032 (0.5 μM) on HIF-1α expression and its major trans-regulating factors including COX-2, VEGF, MMP-2 and uPAR that are involved in cellular invasion in tumor hypoxia. Our observations demonstrate SNS-032: i) inhibited hypoxia-induced U87MG cell invasion and among all the other inhibitors tested, SNS-032 is the most effective, ii) blocked HIF-1α mediated transcription of COX-2, MMP-2, VEGF and uPAR expression in U87MG cells in response to hypoxia, iii) blocked HIF-1α expression by a proteasome independent pathway. The effects were similar to those observed with HIF-1α siRNA which prevented cellular invasion by blocking HIF-1α expression and its downstream effectors. Taken together, our data suggest that SNS-032 prevents hypoxia-mediated U87MG cell invasion by blocking the expression of HIF-1α and its trans-regulating factors. Our results present an opportunity in controlling highly invasive tumors such as glioblastoma using this novel class of compounds.