Effect of LncRNA HCG18 on PD-L1 Expression in Nasopharyngeal Carcinoma Cells and CD8+T Cell Cytotoxic Activity
Objective:To investigate the regulatory mechanism of LncRNA HCG18 on the function of CD8+T cells against nasopharyngeal carcinoma(NPC)cells.Methods:The expression of HCG18 in NPC tis-sues and paracancerous tissues was detected by qRT-PCR.The expression of HCG18 in human nasal mucosal epithelial cells(HNEpC)and NPC cell lines(CNE1,CNE2,HONE-1,HNE-2)was also detected.CNE1 cells were divided into si-HCG18 group,si-NC group,and si-HCG18+PD-L1 group;HNE-2 cells were di-vided into HCG18 group,Vector group,and HCG18+sh-PD-L1 group.CNE1 and HNE-2 cells in each group were co-cultured with CD8+T cells for 24 h(si-HCG18+CD8+T group,si-NC+CD8+T group,si-HCG18+PD-L1+CD8+T group,HCG18+CD8+T group,Vector+CD8+T group,and HCG18+sh-PD-L1+CD8+T group).The concentrations of INF-γ,TNF-α,and IL-2 in the co-culture system were detected by enzyme-linked immunosorbent assay(ELISA),and the tumor cell lysis rate was detected by a cytotoxicity as-say kit.Western blot was used to detect PD-L1 protein expression.Dual luciferase reporter gene assay was used to verify the targeting relationship between HCG18 and miR-20b-5p,and the targeting relationship be-tween miR-20b-5p and PD-L1.Results:The expression of HCG18 in NPC tissues was significantly higher than that in paracancerous tissues,and the expression of HCG18 in CNE1,CNE2,HONE-1,and HNE-2 cells was significantly higher than that in HNEpC cells(P＜0.05).The expression of PD-L1 in CNE1 cells of the si-HCG18 group was significantly lower than that in the si-NC group(P＜0.05),and the expression of PD-L1 in HNE-2 cells of the HCG18 group was significantly higher than that in the Vector group(P＜0.05).Compared with the si-NC+CD8+T group,the concentrations of INF-γ,TNF-α,and IL-2 in the co-culture system of the si-HCG18+CD8+T group were significantly increased(P＜0.05),and the CNE1 cell ly-sis rate was significantly increased(P＜0.05).Compared with the si-HCG18+CD8+T group,the concentra-tions of INF-γ,TNF-α,and IL-2 in the co-culture system of the si-HCG18+PD-L1+CD8+T group were significantly decreased(P＜0.05),and the CNE1 cell lysis rate was significantly decreased(P＜0.05).Com-pared with the Vector+CD8+T group,the concentrations of INF-γ,TNF-α,and IL-2 in the co-culture sys-tem of the HCG18+CD8+T group were significantly decreased(P＜0.05),and the HNE-2 cell lysis rate was significantly decreased(P＜0.05).Compared with the HCG18+CD8+T group,the concentrations of INF-γ,TNF-α,and IL-2 in the co-culture system of the HCG18+sh-PD-L1+CD8+T group were significantly in-creased(P＜0.05),and the HNE-2 cell lysis rate was significantly increased(P＜0.05).miR-20b-5p is a target gene of HCG18,and PD-L1 is a target gene of miR-20b-5p.Conclusion:HCG18 upregulates PD-L1 expression in NPC cells and suppresses the anti-tumor activity of CD8+T cells.
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