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PAK signalling drives acquired drug resistance to MAPK inhibitors in BRAF-mutant melanomas.

Nature | 2017

Targeted BRAF inhibition (BRAFi) and combined BRAF and MEK inhibition (BRAFi and MEKi) therapies have markedly improved the clinical outcomes of patients with metastatic melanoma. Unfortunately, the efficacy of these treatments is often countered by the acquisition of drug resistance. Here we investigated the molecular mechanisms that underlie acquired resistance to BRAFi and to the combined therapy. Consistent with previous studies, we show that resistance to BRAFi is mediated by ERK pathway reactivation. Resistance to the combined therapy, however, is mediated by mechanisms independent of reactivation of ERK in many resistant cell lines and clinical samples. p21-activated kinases (PAKs) become activated in cells with acquired drug resistance and have a pivotal role in mediating resistance. Our screening, using a reverse-phase protein array, revealed distinct mechanisms by which PAKs mediate resistance to BRAFi and the combined therapy. In BRAFi-resistant cells, PAKs phosphorylate CRAF and MEK to reactivate ERK. In cells that are resistant to the combined therapy, PAKs regulate JNK and β-catenin phosphorylation and mTOR pathway activation, and inhibit apoptosis, thereby bypassing ERK. Together, our results provide insights into the molecular mechanisms underlying acquired drug resistance to current targeted therapies, and may help to direct novel drug development efforts to overcome acquired drug resistance.

Pubmed ID: 28953887 RIS Download

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Associated grants

  • Agency: NCI NIH HHS, United States
    Id: P01 CA025874
  • Agency: NCI NIH HHS, United States
    Id: CA142928
  • Agency: NCI NIH HHS, United States
    Id: P30 CA010815
  • Agency: NHLBI NIH HHS, United States
    Id: R01 HL134923
  • Agency: NCI NIH HHS, United States
    Id: P01 CA114046
  • Agency: NCI NIH HHS, United States
    Id: P50 CA174523
  • Agency: NIGMS NIH HHS, United States
    Id: R01 GM085146
  • Agency: NCI NIH HHS, United States
    Id: CA174523
  • Agency: NCI NIH HHS, United States
    Id: CA025874
  • Agency: NCI NIH HHS, United States
    Id: CA114046
  • Agency: NCI NIH HHS, United States
    Id: U54 CA193417

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