Upregulation of PD-L1 expression promotes epithelial-to-mesenchymal transition in sorafenib-resistant hepatocellular carcinoma cells

Background:The epithelial-to-mesenchymal transition(EMT)status is associated with programmed death-1 ligand 1(PDL1)expression in various cancers.However,the role and molecular mechanism of PD-L1 in the EMT of sorafenib-resistant hepatocellular carcinoma(HCC)cells remain elusive.In this study,we aimed to investigate the regulation of PD-L1 on the EMT in sorafenib-resistant HCC cells.Methods:Initially,the sorafenib-resistant HCC cell lines HepG2 SR and Huh7 SR were established.Western-blot assays were used to detect the expression of PD-L1,E-cadherin,and N-cadherin.The intervention and overexpression of PD-L1 were used to explore the role of PD-L1 in the regulation of EMT in HepG2 SR and Huh7 SR cells.Cell migration and invasion were assessed by transwell assays.PD-L1 or Sterol regulatory element-binding protein 1(SREBP-1)overexpression and knockdown were performed in order to study the mechanism of PD-L1 in sorafenib-resistant HCC cells.Results:PD-L1 expression was upregulated,whereas E-cadherin levels were downregulated and N-cadherin expression was increased in HepG2 SR and Huh7 SR cells.The cell viabilities of HepG2 and Huh7 cells were lower than those of HepG2 SR and Huh7 SR cells.PD-L1 overexpression reduced E-cadherin expression and increased N-cadherin levels,whereas PD-L1 knock-down increased E-cadherin expression and decreased N-cadherin expression.PD-L1 expression promoted EMT and the migratory and invasive abilities of HepG2 SR and Huh7 SR cells.PD-L1 promoted the EMT of sorafenib-resistant HCC cells via the PI3K/Akt pathway by activating SREBP-1 expression in HepG2 SR and Huh7 SR cells.Conclusions:The findings reveal that PD-L1 expression promotes EMT of sorafenib-resistant HCC cells.

Cryptotanshinone increases the sensitivity of liver cancer to sorafenib by inhibiting the STAT3/Snail/ epithelial mesenchymal transition pathway

Objective:Sorafenib resistance has been a major factor limiting its clinical use as a targeted drug in liver cancer.The present study aimed to investigate whether cryptotanshinone can enhance the sensitivity of liver cancer and reduce the resistance to sorafenib.Methods:Sorafenib-resistant cells were established based on HepG2 and Huh7 cell lines.And the anti-tumor effect of sorafenib combined with cryptotanshinone on the sorafenib-resistant cells was verified by MTT,colony formation,transwell assays and tumor growth xenograft model.Moreover,the effects of the combined treatment on the expression of phosphorylated(p)-STAT3,as well as epithelial mesenchymal transition(EMT)and apoptosis related proteins of cells were evaluated by western blot analysis.Results:It was identified that cryptotanshinone inhibited the viability of both HepG2 and Huh7 cells in a dose-and time-dependent manner,and decreased p-STAT3 expression rather than total STAT3 expression at a concentration of 40μmol/L.In the sorafenib-resistant cells,sorafenib in combination with cryptotanshinone markedly inhibited cell viability,invasion and migration compared with sorafenib alone.In contrast,increased p-STAT3 level by colivelin led to the inhibition of the synergistic effect of cryptotanshinone and sorafenib not only on cell viability,but also on EMT and apoptosis,suggesting that cryptotanshinone and sorafenib may act by downregulating STAT3 signaling.Further,the inhibition of carcinogenicity effect was also verified in xenografted tumor models.Conclusion:The present results indicated that cryptotanshinone could synergize with sorafenib to inhibit the proliferative,invasive,and migratory abilities of sorafenib-resistant cells by downregulating STAT3 signaling.