Dang Yang ‘s team found that H2S can down-regulate IDO1 expression by blocking NF-κB and STAT3 pathways and inhibit IDO1 activity through H2S/NO cross-talk, which has an immunotherapeutic effect on H22 hepatocellular carcinoma (HCC) tumor-bearing mice [105]. Here, STAT3 is linked to hepatocellular carcinoma.