Toward Minimal Residual Disease-Directed Therapy in Melanoma

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Advanced cancers often achieve initial treatment responses but retain minimal residual disease (MRD), leading to relapse.
• Understanding the biological mechanisms underlying MRD is crucial for developing effective therapeutic strategies.
• BRAF-mutant melanomas are a significant focus in cancer research due to their response to targeted therapies.

Purpose of the Study:

• To investigate the biological characteristics of minimal residual disease (MRD) in BRAF-mutant melanoma.
• To identify drug-tolerant transcriptional states within MRD following RAF/MEK inhibition.
• To explore the role of specific transcriptional programs and their drivers in therapy resistance.

Main Methods:

• Single-cell RNA sequencing was applied to malignant cells from patient-derived xenograft (PDX) melanoma models.
• These models were treated with concurrent RAF/MEK inhibitors.
• Transcriptional states within MRD from PDXs and patient biopsies were analyzed.

Main Results:

• Distinct drug-tolerant transcriptional states were identified within MRD.
• A neural crest stem cell (NCSC) transcriptional program, driven by the nuclear receptor RXRG, was found in MRD.
• Inhibition of RXR (retinoid X receptor) reduced NCSC accumulation in MRD and delayed resistance development.

Conclusions:

• Neural crest stem cells (NCSCs) are identified as key drivers of therapy resistance in minimal residual disease (MRD).
• Targeting RXRG and NCSC programs represents a potential therapeutic strategy for MRD-directed therapy.
• Reprogramming gene regulatory network architecture can be exploited to limit cellular heterogeneity and overcome resistance.