Targeting p63 Upregulation Abrogates Resistance to MAPK Inhibitors in Melanoma

Cancer Res. 2020 Jun 15;80(12):2676-2688. doi: 10.1158/0008-5472.CAN-19-3230. Epub 2020 Apr 14.

Abstract

Targeting the MAPK pathway by combined inhibition of BRAF and MEK has increased overall survival in advanced BRAF-mutant melanoma in both therapeutic and adjuvant clinical settings. However, a significant proportion of tumors develop acquired resistance, leading to treatment failure. We have previously shown p63 to be an important inhibitor of p53-induced apoptosis in melanoma following genotoxic drug exposure. Here, we investigated the role of p63 in acquired resistance to MAPK inhibition and show that p63 isoforms are upregulated in melanoma cell lines chronically exposed to BRAF and MEK inhibition, with consequent increased resistance to apoptosis. This p63 upregulation was the result of its reduced degradation by the E3 ubiquitin ligase FBXW7. FBXW7 was itself regulated by MDM2, and in therapy-resistant melanoma cell lines, nuclear accumulation of MDM2 caused downregulation of FBXW7 and consequent upregulation of p63. Consistent with this, both FBXW7-inactivating mutations and MDM2 upregulation were found in melanoma clinical samples. Treatment of MAPK inhibitor-resistant melanoma cells with MDM2 inhibitor Nutlin-3A restored FBXW7 expression and p63 degradation in a dose-dependent manner and sensitized these cells to apoptosis. Collectively, these data provide a compelling rationale for future investigation of Nutlin-3A as an approach to abrogate acquired resistance of melanoma to MAPK inhibitor targeted therapy. SIGNIFICANCE: Upregulation of p63, an unreported mechanism of MAPK inhibitor resistance in melanoma, can be abrogated by treatment with the MDM2 inhibitor Nutlin-3A, which may serve as a strategy to overcome resistance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Antineoplastic Combined Chemotherapy Protocols / pharmacology*
  • Antineoplastic Combined Chemotherapy Protocols / therapeutic use
  • Cell Line, Tumor
  • Dose-Response Relationship, Drug
  • Drug Resistance, Neoplasm / drug effects*
  • F-Box-WD Repeat-Containing Protein 7 / genetics
  • F-Box-WD Repeat-Containing Protein 7 / metabolism
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Gene Expression Regulation, Neoplastic / genetics
  • Humans
  • Imidazoles / pharmacology
  • Imidazoles / therapeutic use
  • Male
  • Melanoma / drug therapy*
  • Melanoma / genetics
  • Melanoma / pathology
  • Middle Aged
  • Mitogen-Activated Protein Kinase Kinases / antagonists & inhibitors
  • Mitogen-Activated Protein Kinase Kinases / metabolism
  • Mutation
  • Piperazines / pharmacology
  • Piperazines / therapeutic use
  • Protein Kinase Inhibitors / pharmacology
  • Protein Kinase Inhibitors / therapeutic use
  • Proteolysis / drug effects
  • Proto-Oncogene Proteins B-raf / antagonists & inhibitors
  • Proto-Oncogene Proteins B-raf / metabolism
  • Proto-Oncogene Proteins c-mdm2 / antagonists & inhibitors
  • Proto-Oncogene Proteins c-mdm2 / metabolism
  • Skin / pathology
  • Skin Neoplasms / drug therapy*
  • Skin Neoplasms / genetics
  • Skin Neoplasms / pathology
  • Transcription Factors / antagonists & inhibitors*
  • Transcription Factors / metabolism
  • Tumor Suppressor Proteins / antagonists & inhibitors*
  • Tumor Suppressor Proteins / metabolism
  • Up-Regulation / drug effects
  • Young Adult

Substances

  • F-Box-WD Repeat-Containing Protein 7
  • FBXW7 protein, human
  • Imidazoles
  • Piperazines
  • Protein Kinase Inhibitors
  • TP63 protein, human
  • Transcription Factors
  • Tumor Suppressor Proteins
  • nutlin 3
  • MDM2 protein, human
  • Proto-Oncogene Proteins c-mdm2
  • BRAF protein, human
  • Proto-Oncogene Proteins B-raf
  • Mitogen-Activated Protein Kinase Kinases