GD3s-mediated lipid metabolism reprograming promotes proliferation and metastasis of melanoma.

BACKGROUND: Melanoma is an aggressive malignant tumor with an increasing incidence worldwide. Ganglioside GD3 is recognized as a human melanoma-specific antigen and is highly expressed in melanoma tissues and cell lines. GD3 synthase (GD3s) is the rate-limiting enzyme for the synthesis of GD3. However, the function and mechanism of GD3s in melanoma remains poorly understood. METHODS: The expression of GD3s was evaluated by an in silico analysis and detected by melanoma tissue microarray. Cell loss-of-function and gain-of-function, proliferation, colony formation, wound healing assay, transwell assay, tumor xenograft mouse model and a tail vein-injection mouse model were conducted to determine the functional role of GD3s in melanoma progression. Proteomic analysis and metabolomic analysis were used to identify downstream targets of GD3s. Quantification of triglyceride and cholesterol, nile red staining, Western blot, Real-time quantitative PCR (RT-qPCR) and Co-immunoprecipitation (Co-IP) assays were employed to validate the underlying mechanisms of GD3s which aggravate progression of melanoma. High-throughput screening method was used to identify the inhibitor of GD3s. RESULTS: Dysregulated high levels of GD3s were correlated with advanced clinical stages and poor prognoses of melanoma. GD3s promoted the proliferation and metastasis of melanoma by reprograming lipid metabolism. GD3s induced extensive lipid accumulation and elevated expression levels of lipogenic enzymes in melanoma cells by regulating AMPK/SREBP1 signaling pathway. ENMD-2076 L-(+)-Tartaric acid was considered to be a novel GD3s inhibitor and exhibited good anti-tumor activity both in vivo and in vitro. Mechanistically, consistent with shRNA-mediated silencing of GD3s, ENMD-2076 L-(+)-Tartaric acid inhibited de novo fatty acid synthesis through AMPK/SREBP1 pathway. CONCLUSIONS: The current findings uncovered a novel mechanism by which GD3s modulated aberrant lipid metabolism and promoted the progression of melanoma. ENMD-2076 L-(+)-Tartaric acid was firstly discovered as a new inhibitor of GD3s and had good anti-tumor effect both in vitro and in vivo.