Anti-tumor immunity and ferroptosis of hepatocellular carcinoma are enhanced by combined therapy of sorafenib and delivering modified GO-based PD-L1 siRNAs

Programmed cell death receptor ligand 1 (PD-L1)/PD-1 signaling has been exploited to design inhibitors that deliver promising clinical outcome albeit with limited efficacy. Herein, we prepare graphene oxide (GO)-PEI-PEG with low cytotoxicity and long stability and GO-PEI-PEG delivers PD-L1 siRNAs to hepatocellular carcinoma (HCC) cells by the endocytosis-lysosome pathway. The functional GO-PEI-PEG/PD-L1 siRNAs decrease PD-L1 and PD-1 abundance, increase pro-inflammation cytokine IFN-γ and TNF-α release, and improve the proliferation activity of Jurkat T cells. Since GO-PEI-PEG targets the mouse liver effectively, the intrahepatic tumors in C57BL/6 mice are treated with GO-PEI-PEG/Pd-l1 siRNAs via the tail vein, resulting in shrinkage of the HCC tumors and boosting the anti-tumor efficacy in combination with oral sorafenib. A single treatment improves the total CD3⁺ and cytotoxic CD8⁺ T cell infiltration in the HCC tumor tissues and even spleen and upregulates the expression of Perforin, Gzmb, Ifng, Il-1b and Tnfa in the tumors after the combined treatment. Both the single and combined treatments enhance reactive oxygen species (ROS) accumulation, and improved HCC ferroptosis. The results suggest that GO-PEI-PEG delivered PD-L1 siRNAs combined with oral sorafenib can activate the adaptive immunity and tumor ferroptosis and reveal an effective therapy to treat advanced HCC patients.