Sensitization of immunotherapeutic efficiency in HCC by polyinosinic-polycytidylic acid-triggered CXCL10 secretion in liver sinusoidal endothelial cells.

126 Background: Nowadays, the efficiency of immune checkpoint blockades (ICBs) in the treatment of advanced hepatocellular carcinoma (HCC) was low. The previous study we published in Hepatology demonstrated that polyinosinic-polycytidylic acid (PolyIC), a TLR3 agonist, could trigger the accumulation, proliferation and activation of CTLs, which contributes to the enhanced anti-tumor efficiency of PD-L1 Ab in HCC. However, the mechanism remains unclear. Methods: The mouse HCC model was established by hydrodynamic transfection of combinational c-Myc/N-Ras oncogenes. PolyIC, CTLA-4 Ab, PD-L1 Ab, CD8 Ab and CXCR3 Ab were all intraperitoneal injected. Mice liver non-parenchymal cells (NPCs) were isolated after liver perfusion and multistep centrifugation. The proliferation, activation and cytotoxic function of CTLs were assessed by flow cytometry. Liver sinusoidal endothelial cells (LSECs) were isolated by magnetic cell sorting. Expressions of TLR3 and CXCL10 were quantitatively analyzed by qRT-PCR and ELISA. LSECs were cultured in vitro by using DMEM medium. Results: Combination of polyIC and PD-L1 Ab (or CTLA-4 Ab) had a synergistic anti-tumor effect on the treatment of mouse HCC. PolyIC induced the accumulation, proliferation, activation and cytotoxic function of CTLs in liver, which were further enhanced when combined ICBs. And CTLs depletion by CD8 Ab attenuated the synergistic anti-tumor effect of polyIC when combined with ICBs. TLR3 expression was much higher in NPCs than other cells in liver, especially in LSECs. Also, polyIC dramatically induced the expressions of CXCL10 in LSECs both in vivo and in vitro. And in vitro, after treated by polyIC, the CXCL10 expression in the medium and cells were all elevated. What’s more, CXCL10/CXCR3 signaling blockade by CXCR3 Ab attenuated the combinational effects of polyIC and ICBs. Meanwhile, after CXCL10/CXCR3 signaling blockade, the accumulation, proliferation and activation of CTLs were all inhibited. Conclusions: PolyIC specifically targets LSECs to induce CXCL10 expression and secretion, which contributes to the CTLs transformation and enhanced efficiency of ICBs in the treatment of HCC.