Human Anti-Human ASGPR1 monoclonal Antibody, clone SFB709 [APC]

Twenty-three human colorectal carcinoma cell lines were examined for the binding of recombinant hepatic asialoglycoprotein receptor 1 (ASGR1), which is known to be exclusively expressed on hepatic parenchymal cells. The effects of the binding were assessed by adhesion to and proliferation on immobilized recombinant ASGR1. Recombinant ASGR1 bound strongly to six cell lines and moderately to 15 cell lines out of 23 lines tested, as shown by flow cytometric analysis. The first six cell lines (group A) also exhibited strong adherence to immobilized ASGR1, whereas 11 of the 15 cell lines of the second group (group B) showed significant adhesion with smaller enhancement by ASGR1 than the cell lines in group A. With a representative cell line (DLD-1 cells categorized in group B), a significant portion of the adhesion was inhibited by preincubation of ASGR1 with asialofetuin, a competitive inhibitor of the carbohydrate recognition by ASGR1. The growth rates of 13 cell lines (two of group A and 11 of group B) were significantly accelerated when they were cultured on immobilized recombinant ASGR1. The results indicate that ASGR is a potential organ-specific microenvironmental factor for colorectal carcinoma growth and metastasis formation in livers.

Background. A profound thrombocytopenia limits hepatic xenotransplantation in the pig-to-primate model. Porcine livers also have shown the ability to phagocytose human platelets in the absence of immune-mediated injury. Recently, inactivation of the porcine ASGR1 gene has been shown to decrease this phenomenon. Inactivating GGTA1 and CMAH genes has reduced the antibody-mediated barrier to xenotransplantation; herein, we describe the effect that these modifications have on xenogeneic consumption of human platelets in the absence of immune-mediated graft injury. Methods. Wild type (WT), ASGR1(-/-), GGTA1(-/-), and GGTA1(-/-) CMAH(-/-) knockout pigs were compared for their xenogeneic hepatic consumption of human platelets. An in vitro assay was established to measure the association of human platelets with liver sinusoidal endothelial cells (LSECs) by immunohistochemistry. Perfusion models were used to measure human platelet uptake in livers from WT, ASGR1(-/-), GGTA1(-/-), and GGTA1(-/-) CMAH(-/-) pigs. Results. GGTA1(-/-), CMAH(-/-) LSECs exhibited reduced levels of human platelet binding in vitro when compared with GGTA1(-/-) and WT LSECs. In a continuous perfusion model, GGTA1(-/-) CMAH(-/-) livers consumed fewer human platelets than GGTA1(-/-) and WT livers. GGTA1(-/-) CMAH(-/-) livers also consumed fewer human platelets than ASGR1(-/-) livers in a single-pass model. Conclusions. Silencing the porcine carbohydrate genes necessary to avoid antibody-mediated rejection in a pig-to-human model also reduces the xenogeneic consumption of human platelets by the porcine liver. The combination of these genetic modifications may be an effective strategy to limit the thrombocytopenia associated with pig-to-human hepatic xenotransplantation.