PURPOSE OF REVIEW: BRAF inhibitors achieve outstanding clinical response rates in BRAF-mutated melanoma patients but therapeutic resistance is common. Although combinatorial targeted therapy has recently improved patient survival, resistance still occurs, which might be because of the plasticity and heterogeneity of melanoma. Proteomics complements the mostly genomics-based approaches used so far to gain additional insights into the pathophysiological mechanisms driving melanoma progression under treatment.

RECENT FINDINGS: Few proteomics studies have investigated mitogen-activated protein kinase inhibitor (MAPKi) resistance. Three technologies have been described: shotgun analysis, pressure cycling technology-sequential window acquisition of all theoretical masses (which offers an optimized protein extraction by the pressure cycling technology), and selected reaction monitoring for selected candidate evaluation. Preliminary data demonstrate that BRAFi resistance might be associated with enhanced expression of the lysosomal compartment, cell adhesion, and epithelial-mesenchymal transformation. Melanoma cells change the phenotype in response to targeted therapy with MAPKi from a proliferative to an invasive state gaining epithelial-mesenchymal transformation features, which are associated with drug resistance.

SUMMARY: Performing proteomics may lead to an enhanced understanding of the underlying mechanisms of MAPKi resistance and might offer new insights for rational therapies. Selected reaction monitoring can be used to evaluate predictive or pharmacodynamic biomarkers for monitoring therapeutic response and early identification of resistance.