The stress protein BAG3 stabilizes Mcl-1 protein and promotes survival of cancer cells and resistance to antagonist ABT-737

J Biol Chem. 2013 Mar 8;288(10):6980-90. doi: 10.1074/jbc.M112.414177. Epub 2013 Jan 22.

Abstract

Members of the Bcl-2 family of proteins are important inhibitors of apoptosis in human cancer and are targets for novel anticancer agents such as the Bcl-2 antagonists, ABT-263 (Navitoclax), and its analog ABT-737. Unlike Bcl-2, Mcl-1 is not antagonized by ABT-263 or ABT-737 and is considered to be a major factor in resistance. Also, Mcl-1 exhibits differential regulation when compared with other Bcl-2 family members and is a target for anticancer drug discovery. Here, we demonstrate that BAG3, an Hsp70 co-chaperone, protects Mcl-1 from proteasomal degradation, thereby promoting its antiapoptotic activity. Using neuroblastoma cell lines, with a defined Bcl-2 family dependence, we found that BAG3 expression correlated with Mcl-1 dependence and ABT-737 resistance. RNA silencing of BAG3 led to a marked reduction in Mcl-1 protein levels and overcame ABT-737 resistance in Mcl-1-dependent cells. In ABT-737-resistant cells, Mcl-1 co-immunoprecipitated with BAG3, and loss of Mcl-1 after BAG3 silencing was prevented by proteasome inhibition. BAG3 and Mcl-1 were co-expressed in a panel of diverse cancer cell lines resistant to ABT-737. Silencing BAG3 reduced Mcl-1 protein levels and overcame ABT-737 resistance in several of the cell lines, including triple-negative breast cancer (MDA-MB231) and androgen receptor-negative prostate cancer (PC3) cells. These studies identify BAG3-mediated Mcl-1 stabilization as a potential target for cancer drug discovery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adaptor Proteins, Signal Transducing / metabolism*
  • Antineoplastic Agents / pharmacology*
  • Apoptosis / drug effects*
  • Apoptosis / genetics
  • Apoptosis Regulatory Proteins
  • Biphenyl Compounds / pharmacology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Drug Resistance, Neoplasm / genetics
  • Gene Expression Regulation, Neoplastic
  • HEK293 Cells
  • Humans
  • Immunoblotting
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasms / genetics
  • Neoplasms / metabolism
  • Neoplasms / pathology
  • Nitrophenols / pharmacology
  • Piperazines / pharmacology
  • Proteasome Endopeptidase Complex / metabolism
  • Protein Binding
  • Protein Stability
  • Proteolysis
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism*
  • RNA Interference
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sulfonamides / pharmacology
  • Ubiquitination

Substances

  • ABT-737
  • Adaptor Proteins, Signal Transducing
  • Antineoplastic Agents
  • Apoptosis Regulatory Proteins
  • BAG3 protein, human
  • Biphenyl Compounds
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Nitrophenols
  • Piperazines
  • Proto-Oncogene Proteins c-bcl-2
  • Sulfonamides
  • Proteasome Endopeptidase Complex