The MAPKs signaling has been found to primarily mediate the immunosuppressive functions through both regulating Arginase/iNOS balance and cytokine production.41 As in our study, we observed MDSCs sorted from PIWIL1-overexpressing HCC tumors exhibited higher levels of both Arginase/iNOS and IL10 cytokine, we focused on the regulation of MAPKs signaling. Here, PIWIL1 is linked to hepatocellular carcinoma.