Targeting the p300/NONO axis sensitizes melanoma cells to BRAF inhibitors

Area of Science:

• Oncology
• Molecular Biology
• Cancer Research

Background:

• BRAF inhibitors (BRAFi) are effective against BRAF V600E-mutant melanoma but acquired resistance is a major clinical challenge.
• Reactivation of the ERK1/2 pathway through abnormal RAF isoform expression is implicated in melanoma resistance to BRAFi.

Purpose of the Study:

• To elucidate the mechanisms underlying RAF isoform dysregulation in melanoma cells resistant to BRAF inhibitors.
• To identify novel therapeutic targets for overcoming BRAF inhibitor resistance in melanoma.

Main Methods:

• Co-immunoprecipitation assays to identify protein interactions.
• Western blotting to assess protein levels and modifications (acetylation, ubiquitination).
• In vitro and in vivo experiments using BRAFi-resistant melanoma models and p300 inhibitor C646.

Main Results:

• NONO was identified as a key protein interacting with and stabilizing CRAF and ARAF in melanoma cells.
• NONO acetylation by p300 at 198K stabilized NONO against RNF8-mediated degradation.
• Upregulation of p300 and NONO promoted pERK1/2 reactivation, leading to BRAFi resistance, forming a positive feedback loop.
• A positive correlation between p300 and NONO was observed in resistant melanoma cells and clinical samples.
• The p300 inhibitor C646 effectively overcame BRAFi resistance in vitro and in vivo.

Conclusions:

• The p300-NONO axis plays a critical role in stabilizing RAF isoforms and reactivating ERK1/2, driving BRAFi resistance in melanoma.
• Targeting the positive feedback loop involving p300, NONO, RAF isoforms, and ERK1/2 presents a promising strategy to overcome BRAFi resistance in melanoma patients.