Molecular Basis of BRAF Inhibitor Resistance in Melanoma: A Systematic Review.

Background: Melanoma, the deadliest human skin cancer, frequently harbors activating BRAF mutations, with V600E being the most prevalent. These alterations drive constitutive activation of the MAPK pathway, promoting uncontrolled cell proliferation, survival, and dissemination. The advent of BRAFi and MEKi has significantly improved outcomes in BRAF V600-mutant melanoma. However, therapeutic resistance remains a major clinical barrier. Methods: This review integrates recent findings from preclinical and clinical studies to delineate resistance mechanisms to BRAF-targeted therapy. It categorizes resistance into primary (intrinsic), adaptive, and acquired forms, and analyzes their molecular underpinnings, including genetic and epigenetic alterations, pathway reactivation, and microenvironmental interactions. Results: Primary resistance is linked to pre-existing genetic and epigenetic changes that activate alternative signaling pathways, such as PI3K-AKT. Adaptive and acquired resistance includes secondary BRAF mutations, pathway redundancy, phenotype switching, and immune and stromal interactions. High-throughput sequencing has revealed novel mutations, including NRAS, NF1, and PTEN alterations, that contribute to resistance. Discussion: Understanding the multifaceted nature of resistance is critical to improving outcomes in advanced melanoma. This review highlights emerging strategies to overcome resistance, including combinatorial therapies, metabolic targeting, and biomarker-driven approaches, aiming to inform future therapeutic development and precision oncology strategies.