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Human hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide with a poor prognosis of limited survival. The role of regulatory B cell (Breg), a new important B cell subset, in HCC progression remains unclear. We firstly found that the percentage of B cells at tumor margin was significantly higher than that in tumor and non-tumor regions. Especially, increased intrahepatic B cells at tumor margin were positively associated with tumor invasive features and more tumor recurrence. Besides, HCC patients had a significantly higher percentage of circulating Bregs than healthy people. Increased circulating Bregs were correlated with advanced tumor staging, tumor multiplicity and venous infiltration. Next, we firstly revealed that human Bregs promoted HCC tumor growth independent of Tregs in SCID mice. The migration of Bregs from blood into tumor was also confirmed in mice. Finally, we further explored the molecular mechanism of Bregs promoting proliferation and migration of HCC cells in vitro . Bregs promoted HCC growth and invasiveness by directly interacting with liver cancer cells through the CD40/CD154 signaling pathway. [ABSTRACT FROM AUTHOR]

Background & Aims: Patients with hepatocellular carcinoma (HCC) receiving living donor liver transplantation appear to possess significantly higher tumor recurrence than the recipients receiving deceased donor liver transplantation. The underlying mechanism for HCC recurrence after transplantation remains unclear. Here, we aim to investigate the impact of small-for-size liver graft injury on HCC recurrence after transplantation. Methods: The correlation between tumor recurrence, liver graft injury, CXCL10 expression and endothelial progenitor cell (EPC) mobilization was studied in 115 liver transplant recipients and rat orthotopic liver transplantation (OLT) models. The direct role of CXCL10/CXCR3 signaling on EPC mobilization was investigated in CXCL10 −/− mice and CXCR3 −/− mice. The role of EPCs on tumor growth and angiogenesis was further investigated in an orthotopic liver tumor model. Results: Clinically, patients with small-for-size liver grafts (<60% of standard liver weight, SLW) had significantly higher HCC recurrence (p =0.04), accompanied by more circulating EPCs and higher early-phase intragraft and plasma CXCL10 levels, than the recipients with large grafts (⩾60% of SLW), which were further validated in rat OLT models. Circulatory EPC mobilization was reduced after liver injury both in CXCL10 −/− mice and CXCR3 −/− mice in comparison to wild-type controls. CXCL10 recruited EPCs in dose-dependent and CXCR3-dependent manners in vitro. Early-phase EPC/CXCL10 injection enhanced orthotopic liver tumor growth, angiogenesis and metastasis in nude mice. Conclusions: Post-transplant enhanced CXCL10/CXCR3 signaling in small-for-size liver grafts directly induced EPC mobilization, differentiation and neovessel formation, which further promotes tumor growth. Targeting CXCL10/CXCR3 signaling may attenuate early-phase liver graft injury and prevent late-phase tumor recurrence/metastasis after transplantation. [Copyright &y& Elsevier]