Hsp70 silencing with siRNA in nanocarriers enhances cancer cell death induced by the inhibitor of Hsp90

Inducers of heat shock protein 70 (Hsp70) commonly promote cancer cell viability whereas inhibitors of Hsp90 reduce it. The anticancer agent celastrol, interferes with signal transduction pathways involving these heat shock proteins. The objective of this in vitro study was to silence inducible Hsp70 and to promote celastrol-induced tumor cell death. Hsp70 siRNA loaded chitosan-TPP carriers were prepared by ionic gelation and characterized by photon correlation spectroscopy and asymmetric flow field-flow fractionation combined with dynamic light scattering. Viability of human leukemia and glioblastoma cells and Hsp70 silencing was determined following treatment with chitosan-TPP-Hsp70 siRNA particles. The results showed that silencing of Hsp70 by chitosan-TPP-Hsp70 siRNA treatment significantly reduced cell viability, and enhanced antiproliferative effects of celastrol in leukemia and glioblastoma cells. In glioblastoma spheroids, higher concentrations of celastrol and Hsp70 siRNA in chitosan-TPP nanocarriers were necessary to induce cell death. (C) 2013 Elsevier B.V. All rights reserved.