STAT3 and hepatocellular carcinoma: Among these PARP1-related studies, the one that caught our attention the most was a recent study that showed that intrinsic TLR9 activation in hepatocellular carcinoma cells downregulates PARP1 expression, which in turn downregulates STAT3 PARylation, leading to increased STAT3 phosphorylation, resulting in upregulation of PD-L1 and ultimately inducing immune escape [24].