Inhibition of neuroblastoma xenograft growth by Hsp90 inhibitors

Background: Advanced-stage neuroblastomas are often resistant to chemotherapy. Heat shock protein (Hsp) 90 is a molecular chaperons that maintains the stability of important signal transduction proteins. We have previously reported that geldanamycin (GA), an Hsp90 inhibitor, decreases Raf-1 and Akt protein expressions and induces apoptosis in neuroblastoma cells. We sought to determine the in vivo effects of Hsp90 inhibitor compounds on human neuroblastomas. Materials and Methods: Human neuroblastoma (LAN-1 and SK-N-SH) xenografts (4-mm³ tumor implants) were placed in the flanks of athymic nude mice. The mice received either Hsp90 inhibitors (17-AAG or EC5) or vehicle (control). The tumor dimensions were measured twice weekly. Proteins were extracted for Western immunoblotting. Results: Hsp90 inhibitor compounds significantly blocked both LAN-1 and SK-N-SH neuroblastoma growth in vivo. Drug-treated tumors showed decreases in Raf-1 and cleaved PARP expressions. Conclusion: Hsp90 inhibitors may prove to be important novel therapeutic agents for patients with advanced-stage neuroblastoma who fail to respond to current treatment regimens.