# Inter-Relationship Between Melanoma Vemurafenib Tolerance Thresholds and Metabolic Pathway Choice

## TL;DR

This study explores how melanoma cells develop resistance to vemurafenib and how this resistance affects their metabolism, suggesting new treatment strategies.

## Contribution

The study reveals how drug tolerance thresholds directly influence specific metabolic shifts in vemurafenib-resistant melanoma cells.

## Key findings

- Vemurafenib-resistant models show upregulated β-catenin, MITF, and ABCB5, with sensitivity to Wnt/β-catenin inhibitor ICG-001.
- Highly drug-tolerant cells shift to TCA cycle and OXPHOS, while low-tolerant cells activate the pentose phosphate pathway, both inhibited by ICG-001.
- Wnt/β-catenin signaling plays a key role in metabolic plasticity in vemurafenib-resistant melanoma cells.

## Abstract

Melanomas quickly acquire resistance to vemurafenib, an important therapeutic for BRAFV600 mutant melanomas. Although combating vemurafenib resistance (VemR) to counter mitochondrial metabolic shift using mitochondria-targeting therapies has promise, no studies have analyzed the relationship between vemurafenib tolerance levels and metabolic plasticity. To determine how vemurafenib endurance levels drive metabolic plasticity, we developed isogenic BRAFV600E VemR melanoma models with variant vemurafenib tolerances and performed an integrative analysis of metabolomic and transcriptome alterations using metabolome, Mitoplate-S1, Seahorse, and RNA-seq assays. Regardless of drug tolerance differences, both VemR models display resistance to MEK inhibitor and sensitivity to Wnt/β-catenin inhibitor, ICG-001. β-catenin, MITF, and ABCB5 levels are upregulated in both VemR models, and ICG-001 treatment restored vemurafenib sensitivity with reductions in MITF, ABCB5, phospho-ERK1/2, and mitochondrial respiration. Whereas β-catenin signaling induced TCA cycle and OXPHOS in highly drug tolerant A2058VemR cells, it activated pentose phosphate pathway in M14VemR cells with low vemurafenib tolerance, both of which are inhibited by ICG-001. These data implicate an important role for Wnt/β-catenin signaling in VemR-induced metabolic plasticity. Our data demonstrate that drug tolerance thresholds play a direct role in driving metabolic shifts towards specific routes, thus providing a new basis for delineating VemR melanomas for metabolism-targeting therapies.