PIWIL1 and hepatocellular carcinoma: Indeed, several previous studies have suggested the immunosuppressive population of immune cells, such as Treg and M2-like TAMs, did not directly infiltrate into the HCC tumors but harbored at surrounding hepatic tissues of mice and human, which sufficiently developed a microenvironment favoring HCC growth.56,57 We observed an increased population of TAMs in PIWIL1-overexpressing HCC tumors (data not shown).