Targeting Melanoma-Associated Fibroblasts to Overcome Cancer Stem Cell-Driven Drug Resistance

Area of Science:

• Oncology
• Cancer Biology
• Melanoma Research

Background:

• Acquired resistance to BRAF V600E inhibitors is a significant challenge in melanoma treatment.
• Melanoma-initiating cells (MICs), influenced by cancer-associated fibroblasts (CAFs), are implicated in mediating drug resistance via stromal Notch1 signaling.

Purpose of the Study:

• To investigate if activating Notch1 signaling in CAFs can overcome BRAF inhibitor resistance in melanoma.
• To explore the role of stromal Notch1 signaling in regulating MICs and drug resistance.

Main Methods:

• Patient-derived melanoma-associated fibroblasts (MAFs) were engineered to activate Notch1 signaling (MAF N1IC-GFP).
• Drug resistance was assessed in BRAF inhibitor-resistant melanoma cells (451LuBR) using 3D spheroid co-culture assays with PLX4720.
• In vivo efficacy was evaluated in NSG mice co-grafted with 451LuBR cells and MAF N1IC-GFP or control MAF GFP, assessing tumor growth, angiogenesis, and CD271⁺ MIC populations.

Main Results:

• MAF N1IC-GFP suppressed drug-resistant melanoma spheroid formation in vitro.
• Co-grafting MAF N1IC-GFP significantly reduced tumor growth and bioluminescence in vivo.
• MAF N1IC-GFP selectively depleted CD271⁺ MICs, decreased their proliferation, and induced apoptosis.

Conclusions:

• Activating Notch1 signaling in MAFs overcomes BRAF inhibitor resistance by disrupting cancer stem cell niches.
• This stromal-targeted approach offers a novel therapeutic strategy for melanoma patients with drug-resistant disease, complementing existing therapies.