HBP1 and hepatocellular carcinoma: We found that HCC cells with high expression levels of circ-0044539 released exosomes containing miR-29a-3p, which were then taken up by recipient PMN-MDSCs, and these miR-29a-3p targeted Hbp-1 mRNA, resulting in improved functions of PMN-MDSCs and the formation of an immunosuppressive LN microenvironment that promotes LNM.