STAT3 and hepatocellular carcinoma: Our previous studies indicated that PTPRO suppresses JAK2 activation in HCC cells, and other research has also indicated that activation of c-MYC, a downstream regulator of STAT3,23 can enhance PD-L1 expression.24 Therefore, we postulated that PTPRO might suppress PD-L1 expression by suppression of both the JAK2/STAT1 and JAK2/STAT3/c-MYC signaling pathways.