442 CLEC12B a new gene implicated in melanoma

Abstract

A transcriptomic analysis from vitiligo patient skins allowed us to discover that CLEC12B is selectively and strongly expressed by melanocytes. The objective of this study was to investigate the role of CLEC12B in melanoma. Expression of CLEC12B was assessed in melanoma cell lines, nevi and melanoma samples. Using a lentivirus construct we overexpressed (Ov) or downregulated (Sh) CLEC12B in melanoma cells lines to assess the effect of its modulation on proliferation and cell cycle. The signaling pathway involved was then studied. Tumorigenic properties of CLEC12B were finally analyzed in nude mice, with tumor xenograft experiments. Firstly, patients with high CLEC12B expression have a significantly higher median survival than those with low expression (TCGA database). CLEC12B expression was significantly decreased in melanoma cells and melanoma tissues as compared to normal melanocytes and nevi. Ov decreased the cell proliferation, while Sh did the opposite. Using co-immunoprecipitation assay and after generating a mutant of CLEC12B ITIM domain we demonstrated that CLEC12B recruits the tyrosine phosphatase SHP2. Ov induces a dephosphorylation of pSHP2Y542 and downstream of pSTAT3. The mutant reverses these effects. The effects on proliferation are linked to a slow-down in G0/G1 with an increase of p53/p21and p27 after Ov. In accordance with in vitro results, the tumor growth in Ov group was significantly decreased compared to vehicle group and associated with a decreased expression of pSTAT3 and an increase of p53 within the tumors (opposite with Sh). CLEC12B appears as a potent suppressor gene in melanoma by regulating cell cycle and repressing STAT3 activation.