
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.
Proto-Oncogene Proteins B-raf, STAT3 Transcription Factor, Transcriptional Activation, Cell Survival, Interleukin-6, B-RAF, Mcl-1, MAPK, 333, STAT3, anoikis, Cell Line, Tumor, Mutation, Humans, Melanocytes, Myeloid Cell Leukemia Sequence 1 Protein, Phosphorylation, Promoter Regions, Genetic, Melanoma, Signal Transduction, Transcription Factors
Proto-Oncogene Proteins B-raf, STAT3 Transcription Factor, Transcriptional Activation, Cell Survival, Interleukin-6, B-RAF, Mcl-1, MAPK, 333, STAT3, anoikis, Cell Line, Tumor, Mutation, Humans, Melanocytes, Myeloid Cell Leukemia Sequence 1 Protein, Phosphorylation, Promoter Regions, Genetic, Melanoma, Signal Transduction, Transcription Factors
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