Mutant B-RAF-Mcl-1 survival signaling depends on the STAT3 transcription factor

Oncogene. 2014 Feb 27;33(9):1158-66. doi: 10.1038/onc.2013.45. Epub 2013 Mar 4.

Abstract

Approximately 50% of melanomas depend on mutant B-RAF for proliferation, metastasis and survival. The inhibition of oncogenic B-RAF with highly targeted compounds has produced remarkable albeit short-lived clinical responses in B-RAF mutant melanoma patients. Reactivation of signaling downstream of B-RAF is frequently associated with acquired resistance to B-RAF inhibitors, and the identification of B-RAF targets may provide new strategies for managing melanoma. Oncogenic B-RAF(V600E) is known to promote the stabilizing phosphorylation of the anti-apoptotic protein Mcl-1, implicated in melanoma survival and chemoresistance. We now show that B-RAF(V600E) signaling also induces the transcription of Mcl-1 in melanocytes and melanoma. We demonstrate that activation of STAT3 serine-727 and tyrosine-705 phosphorylations is promoted by B-RAF(V600E) activity and that the Mcl-1 promoter is dependent on a STAT consensus-site for B-RAF-mediated activation. Consequently, suppression of STAT3 activity disrupted B-RAF(V600E)-mediated induction of Mcl-1 and reduced melanoma cell survival. We propose that STAT3 has a central role in the survival and contributes to chemoresistance of B-RAF(V600E) melanoma.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line, Tumor
  • Cell Survival / genetics*
  • Humans
  • Interleukin-6 / genetics
  • Interleukin-6 / metabolism
  • Melanocytes / metabolism
  • Melanoma / genetics
  • Melanoma / metabolism
  • Mutation / genetics*
  • Myeloid Cell Leukemia Sequence 1 Protein / genetics*
  • Myeloid Cell Leukemia Sequence 1 Protein / metabolism
  • Phosphorylation / genetics
  • Promoter Regions, Genetic / genetics
  • Proto-Oncogene Proteins B-raf / genetics*
  • Proto-Oncogene Proteins B-raf / metabolism
  • STAT3 Transcription Factor / genetics*
  • STAT3 Transcription Factor / metabolism
  • Signal Transduction / genetics*
  • Transcription Factors / genetics*
  • Transcription Factors / metabolism
  • Transcriptional Activation / genetics

Substances

  • IL6 protein, human
  • Interleukin-6
  • MCL1 protein, human
  • Myeloid Cell Leukemia Sequence 1 Protein
  • STAT3 Transcription Factor
  • STAT3 protein, human
  • Transcription Factors
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf