Plectin promotes melanoma tumor formation by regulation of Rous sarcoma oncogene activity

Abstract

Background Melanoma is a malignant tumor that is characterized by high proliferation and aggressive metastasis. To address the efficient treatment of melanoma, the molecular mechanisms of the proto-oncogene, Rous sarcoma oncogene (Src), which is highly activated and promotes cell proliferation, migration, adhesion, and metastasis in melanoma, should be understood. Plectin has recently been identified as an Src-binding protein that regulates Src activity in osteoclasts. Plectin, a cytoskeleton-regulatory protein, is a candidate biomarker of certain tumors because of its high expression and the target of anti-tumor reagents such as ruthenium pyridinecarbothioamide, although the molecular mechanisms by which plectin works in melanoma are still unclear. In this study, we examined its pathological role in melanoma tumor formation. Methods We established plectin knock-out B16 cells, the mouse melanoma cell line, with CRISPR/Cas9 system. The expression of plectin and activity of Src were examined by western blotting analysis. The tumors were formed at 2 weeks after subcutaneous injection of B16 cells in nude mice and analyzed by Hematoxylin-Eosin (H-E) staining. Cell proliferation was evaluated by cell counting kit-8, expression of cyclin D1 and Ki-67. Cell aggregation and adhesion were assessed by spheroid formation and cell adhesion assay.Results Depletion of plectin induced low-density and sparce tumor formation by melanoma cells in vivo. In vitro experiments revealed that plectin-deficient melanomas exhibit reduced cell proliferation and suppressed cell-to-cell adhesion. Because Src activity is reduced in plectin-deficient melanomas, we examined the relationship between plectin and Src signaling. Src overexpression restored Src activity and rescued cell proliferation and cell-to-cell adhesion in plectin-deficient melanomas. Conclusion: These results suggest that plectin is required for tumor formation by promoting cell proliferation and cell-to-cell adhesion through Src signaling activity in melanoma cells.