PTPRD Affects The Expression Of PD-L1 In Human Hepatocellular Carcinoma By Down-regulating STAT3

Objective1.To determine the correlation between tumors suppressor factor PTPRD gene and the immune checkpoint PD-L1 in HCC tissues.2.To observe the mechanism of the tumor suppressor PTPRD on the expression of the immune checkpoint PD-L1 in the HepG2 cells,and provide the new targets for HCC immunotherapy.3.To observe the tumor suppressor activity of PTPRD in nude mouse HCC model.Methods1.The positive expressions of PTPRD and PD-L in HCC tissues and adjacent tissues were detected by immunohistochemically,and the correlation between PTPRD and PD-L1 were analyzed by spearman.2.The mRNA and protein expressions levels of PTPRD and PD-L1 in HCC tissues were detected by RT-PCR and Western blot,and the correlation between the mRNA and protein of PTPRD and PD-L1 were analyzed by spearman.3.HepG2 cell lines with PTPRD gene overexpression and silencing were constructed by PTPRD overexpression adenovirus and shRNA-PTPRD lentivirus,respectively.The mRNA and protein expressions PD-L1 in PTPRD gene overexpression and silencing were detected by RT-PCR and Western blot,and the protein expressions STAT3 and p-STAT3 in PTPRD gene overexpression and silencing were detected by Western blot.The effects of PTPRD changes on the proliferation and cloning ability of HCC cells were detected in vitro.4.ShRNA-PTPRD lentivirus was used to construct stable HepG2 cell lines with PTPRD gene silencing,and the effect of PTPRD silencing on the tumor formation rate of nude mices were observed.Results1.The expression of PTPRD were significantly down-regulated in HCC tissues compared with adjacent tissues,however PD-L1was significantly higher in HCC tissues compared with the adjacent tissues.There was a negative correlation between PTPRD and PD-L1 expressions in HCC tissues.2.The mRNA and protein expressions of PTPRD were significantly down-regulated in HCC tissues compared with adjacent tissues,however the levels of PD-Llwere significantly higher in HCC tissues compared with adjacent tissues(p<0.05).3.Compared with the negative control group,the mRNA and protein level of PD-L1 in the overexpressed with PTPRD were down-regulated,and the protein levels of STAT3 and p-STAT3 were down-regulated too(P<0.05).On the contrary,the mRNA and protein level of PD-L1 in HepG2 cell with PTPRD gene silencing were increased(P<0.05),and the protein levels of STAT3 and p-STAT3 were also increased.Furthermore,PTPRD overexpression can inhibit the proliferation and cloning of HCC cells.However PTPRD silencing can significantly promote the proliferation and cloning.4.Compared with the negative control group,the growth of nude mouse was promoted in HepG2 cell with PTPRD gene silencing.Conclusions1.The expression of PTPRD and PD-L1 on HCC was negatively correlated.2.PTPRD gene may affect the expression of PD-L1 in HCC cells by regulating STAT3 signaling pathway.