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Proc Natl Acad Sci U S A. 2010 Apr 20;107(16):7497-502. doi: 10.1073/pnas.0907696107. Epub 2010 Apr 5.

IKK{gamma} protein is a target of BAG3 regulatory activity in human tumor growth.

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Laboratory of Gene Regulation and Signal Transduction, Department of Pharmacology and Cancer Center, School of Medicine, University of California, San Diego, La Jolla, CA 92093-0723, USA.


BAG3, a member of the BAG family of heat shock protein (HSP) 70 cochaperones, is expressed in response to stressful stimuli in a number of normal cell types and constitutively in a variety of tumors, including pancreas carcinomas, lymphocytic and myeloblastic leukemias, and thyroid carcinomas. Down-regulation of BAG3 results in cell death, but the underlying molecular mechanisms are still elusive. Here, we investigated the molecular mechanism of BAG3-dependent survival in human osteosarcoma (SAOS-2) and melanoma (M14) cells. We show that bag3 overexpression in tumors promotes survival through the NF-kappaB pathway. Indeed, we demonstrate that BAG3 alters the interaction between HSP70 and IKKgamma, increasing availability of IKKgamma and protecting it from proteasome-dependent degradation; this, in turn, results in increased NF-kappaB activity and survival. These results identify bag3 as a potential target for anticancer therapies in those tumors in which this gene is constitutively expressed. As a proof of principle, we show that treatment of a mouse xenograft tumor model with bag3siRNA-adenovirus that down-regulates bag3 results in reduced tumor growth and increased animal survival.

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