Participation of Gas6 ligand in the interaction of melanoma cells and fibroblasts

Abstract

Growth arrest-specific factor 6 (Gas6), is a secreted protein part of the Vitamin K-Dependent (VKD) protein family that exerts its biological activity through the TAM tyrosine kinase receptors (Tyro3, Axl and Mertk). In cancer, Gas6/TAM promotes cell survival, invasion and metastasis. This study aims to elucidate the role of Gas6 in the context of melanoma metastasis to the lung and its interaction with lung fibroblasts. The tumoral microenvironment, including the contribution of fibroblasts, has emerged as a critical factor in melanoma progression and treatment response. We examined the interaction of mouse B16F10 melanocytes with lung fibroblasts from wild-type (expressing Gas6 constitutively) and Gas6 knockout mice to assess the impact of Gas6 on melanoma progression. Metabolic activity assays revealed lower and more heterogeneous metabolic activity in the absence of Gas6 compared to Gas6-expressing fibroblasts. Stimulation of wild-type and Gas6 knockout fibroblasts with B16-conditioned media activated the MAPK/ERK and PI3K/AKT pathways. Gas6 knockout fibroblasts displayed increased AKT content, suggesting an adaptation to Gas6 deficiency. To understand the effect of Gas6 on melanocytes and melanospheres, a B16F10 transgenic clone expressing murine Gas6 was generated. Gas6 expression induces melanin production, resulting in darker melanospheres. Evaluation of two inhibitors, Cabozantinib/XL184 and Bemcentinib/BGB324, demonstrated that Bemcentinib, an Axl-selective inhibitor, effectively induced fibroblast cytotoxicity and apoptosis and reduced melanosphere growth. Cabozantinib, a multi-kinase inhibitor, exhibited limited efficacy in inducing apoptosis of B16F10 Gas6-expressing melanospheres.