PURPOSE: Despite recent advances, approximately 50% of patient with metastatic melanoma eventually succumb to the disease. Patients with melanomas harboring a BRAF mutation (BRAFMut) have a worse prognosis than those with wildtype (BRAFWT) tumors. Unexpectedly, interim AVAST-M Phase III trial data reported benefit from adjuvant anti-VEGF bevacizumab only in the BRAFMut group. We sought to find mechanisms underpinning this sensitivity. METHODS: We investigated this finding in vitro and in vivo using melanoma cell lines and clones generated by BRAFV600E knock-in on a BRAFWT background. RESULTS: Compared with BRAFWT cells, isogenic BRAFV600E clones secreted more VEGF and exhibited accelerated growth rates as spheroids and xenografts, which were more vascular and proliferative. Recapitulating AVAST-M findings, bevacizumab affected only BRAFV600E xenografts, inducing significant tumor growth delay, reduced vascularity and increased necrosis. We identified 814 differentially expressed genes in isogenic BRAFV600E/BRAFWT clones. Of 61 genes concordantly deregulated in clinical melanomas ROR2 was one of the most upregulated by BRAFV600E. ROR2 was shown to be RAF-MEK regulated in BRAFV600E cells and its depletion suppressed VEGF secretion down to BRAFWT levels. The ROR2 ligand WNT5A was also overexpressed in BRAFMut melanomas, and in ROR2-overexpressing BRAFV600E cells MEK inhibition downregulated WNT5A and VEGF secretion. CONCLUSIONS: These data implicate WNT5A-ROR2 in VEGF secretion, vascularity, adverse outcomes and bevacizumab sensitivity of BRAFMut melanomas, suggesting that this axis has potential therapeutic relevance.
Journal article
Cell Oncol (Dordr)
04/2023
46
391 - 407
BRAF, Bevacizumab, Melanoma, ROR2, WNT5A, Humans, Bevacizumab, Cell Line, Tumor, Melanoma, Mitogen-Activated Protein Kinase Kinases, Mutation, Proto-Oncogene Proteins B-raf, Receptor Tyrosine Kinase-like Orphan Receptors, Wnt-5a Protein, Vascular Endothelial Growth Factor A