Mechanism of TC2N gene promoting the growth of melanoma

To investigate the effect and mechanism of TC2N in skin cutaneous melanoma（SKCM）.

Using the Human Protein Atlas（HPA）and The Cancer Genome Atlas（TCGA）databases to analyze the expression and correlation of clinicopathologic feature of TC2N in SKCM. Human melanoma A375 cells were used to construct an overexpression cell model of TC2N. CCK-8 assay method was used to detect the effect of TC2N on cell proliferation. Cutaneous melanin xenograft model was constructed in TC2N knockout mice, and the tumor growth was observed and measured. Based on the animal model, the expression of Ki67 was detected in transplanted tumor by immunohistochemistry to analyze the proliferation of tumor cells. In addition, Gene Set Enrichment Analysis（GSEA）was performed to investigate the correlation between TC2N expression and ERK/MAPK signaling pathway. RT-qPCR and Western blot assay were used to detect mRNA and protein expression levels of related genes（CyclinD1, c-Myc, CDK2 and CyclinE1 in vitro and in vivo）.

Compared with normal skin tissues, the expression level of TC2N protein in SKCM tissues was higher, which was significantly associated with clinicopathological stages and lymphatic node metastasis in patients with SKCM（P<0.05）. In vitro cell experiments demonstrated that the proliferation ability of A375 cells were significantly increased after TC2N overexpression（P<0.05）. The results of skin melanin xenograft model of knockout mouse revealed that compared with TC2N^＋/＋ mice, the tumor weight and tumor volume of TC2N^-/- mice were significantly decreased（P<0.05）, suggesting that TC2N knockout significantly inhibited the growth of SKCM. GSEA enrichment analysis indicated that TC2N was significantly correlated with MAPK signaling pathway（P<0.01）, and TC2N was positively correlated with ERK/MAPK downstream gene expression（all P<0.01）. Experiments in vivo and in vitro showed TC2N expression significantly promoted the expression of ERK and p-ERK, and exerted effect on the mRNA and protein expression levels of ERK-related molecues, CyclinD1, c-Myc, CDK2 and CyclinE1（P<0.01）.

TC2N gene may promote the growth of cutaneous melanoma through activating ERK/MAPK signaling pathway.