Melanoma/CSPG4-Enhanced Collagen-Mediated Contact Guidance Requires Mutant Active BRAF and the CSPG4 Core Protein Cytoplasmic Domain

Introduction: Chondroitin sulfate proteoglycan-4 (CSPG4) is a transmembrane cell surface proteoglycan that promotes malignant progression in melanoma. Elevated CSPG4 expression in melanoma cells is associated with several malignant phenotypic properties, including increased tumor cell invasion, tumorigenic potential, and metastasis. Methods: Magnetically aligned collagen gels with entrapped cells were used to model the aligned extracellular matrix in the tumor microenvironment and to identify the key role of CSPG4 in sensing contact guidance. Results: The data show that CSPG4-expressing WM1552C Radial Growth Phase (RGP) melanoma cells exhibit enhanced contact guidance along with increased migration speed in contrast to paired counterparts that lack CSPG4. This required the presence of a pERK 1,2 phospho-acceptor site on the cytoplasmic tail of the core protein. Furthermore, short-term treatment of CSPG4-expressing cells with the clinically used mutant active BRAF inhibitor vemurafenib reduced both guidance and speed. Conclusions: These findings support the role of CSPG4 overexpression and mutant active BRAF-in promoting increased contact guidance. The results are discussed in terms of expanding what is known about the potential tumor biology and clinical implications of CSPG4-related impact on malignant invasion during early phases of melanoma progression.