Di-san junyi daxue xuebao (Sep 2020)
Circadian rhythms molecule BMAL1 promotes the prognosis of osteosarcoma via regulating immune cell cytotoxicity
Abstract
Objective To investigate the role and possible mechanism of the core rhythm molecule BMAL1 in the prognosis of osteosarcoma (OS). Methods After BMAL1 was overexpressed in U2OS cells by Lipofectamine3000, the expression of BMAL1 was detected with qRT-PCR, and the clone formation and invasion ability of the overexpressed cells were observed with clonogenic assay and Transwell assay. Then, the BMAL1 overexpressed U2OS cells or the cells with control vector transfection were cocultured with peripheral blood mononuclear cells (PBMCs), the direct killing effects of PBMCs on U2OS cells was observed with Calcein AM staining, and the CD107a expression by CD8+ T and NK cells was measured with flow cytometry. Results The OS patients with higher BMAL1 mRNA level had significantly longer survival time when compared with those with lower expression (P < 0.001). BMAL1 overexpression had no obvious effects on the invasion and clone formation of U2OS cells. However, cell death was significantly increased in BMAL1 overexpressed U2OS cells than the control vector transfected U2OS cells when co-cultured with PBMCs in vitro [PBMCs:U2OS cells=5:1, (81.00±0.58)% vs (73.33±0.67)%, P < 0.01; PBMCs:U2OS cells=10:1, (82.67±1.86)% vs (76.67±0.33)%, P < 0.01]. There was no significant difference in the expression level of CD107a between T cells and NK cells in the BMAL1 overexpressed U2OS cells than the control vector transfected U2OS cells when co-cultured with PBMCs (E:T=5:1, CD3+ CD56- T cells, P=0.46, CD3-CD56+ NK cells, P=0.96; E:T=10:1, CD3+ CD56- T cells, P=0.93; CD3-CD56+ NK cells, P=0.21). Conclusion The expression level of BMAL1 is positively correlated with the prognosis of OS patients, which might be mainly due to the enhanced immunological surveillance, but not by affecting the ability of invasion and clone formation of OS cells.
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