Molecular Mechanism of TRAF6 in Malignant Proliferation of Human NK/T Cell Lymphoma Cell HANK1.

Background: Ubiquitination affects cancer progression by regulating both tumor-suppressing and tumor-promoting proteins in cancer. The current study sought to evaluate the role of TNF receptor-associated factor 6 (TRAF6) in the malignant proliferation of the human NK/T cell lymphoma cell line HANK1. Methods: TRAF6 and MST1 expression levels in HANK1, KHYG-1, and SNK-6 cells were determined by RT-qPCR and Western blot analysis, followed by transfection of si-TRAF6 into HANK1 cells. Cell viability and proliferation were assessed by cell-counting kit-8 and 5-Ethynyl-2'-deoxyuridine (EdU) assays, and proliferating cell nuclear antigen (PCNA) expression levels in cells were determined by Western blot analysis. After that, cells were treated with MG132, followed by analysis of the binding of TRAF6 to macrophage stimulating 1 (MST1) via co-immunoprecipitation and the ubiquitination level of MST1 via the ubiquitination assay. The functional rescue experiment was performed with si-MST1 and si-TRAF6 in cells. Results: TRAF6 was upregulated in HANK1 cells. Inhibition of TRAF6 reduced cell viability and the number of EdU-positive cells, and downregulated PCNA expression. TRAF6 binds to MST1 to promote ubiquitination-mediated degradation of MST1. After MG132 treatment, the ubiquitination level of MST1 declined. Silencing MST1 abolished the inhibition of TRAF6 on malignant proliferation of HANK1 cells. Conclusion: TRAF6 was upregulated in HANK1 cells and bound to MST1 to promote ubiquitination-mediated degradation of MST1, consequently facilitating the malignant proliferation of HANK1 cells.