HSP27 knockdown produces synergistic induction of apoptosis by HSP90 and kinase inhibitors in glioblastoma multiforme.

The heat-shock proteins HSP27 and HSP90 perpetuate the malignant nature of glioblastoma multiforme (GBM) and offer promise as targets for novel cancer therapeutics. The present study sought to define synergistic antitumor benefits of concurrent HSP27-knockdown and the HSP90 inhibitor, 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) or, comparatively, the non-selective kinase inhibitor, staurosporine, in GBM cells. Dose-response relations were determined for 17-AAG and staurosporine in three GBM cell lines. HSP27-targeted siRNA was administered alone or in combination with subtherapeutic concentrations of each drug and cells were evaluated for viability, proliferation and apoptosis. Adjuvant HSP27 knockdown with 17-AAG or staurosporine produced marked and synergistic decrease in GBM cell viability and proliferation, with robust elevation of apoptotic fractions and caspase-3 activation. HSP27 knockdown confers potent chemosensitization of GBM cells. These novel data support the development of HSP-targeting strategies and, specifically, anti-HSP27 agents for the treatment of GBM.