Purpose: Endosialin/CD248/tumor endothelial marker 1is expressed in stromal cells, endothelial cells, and pericytes in various tumors; however, few studies have focused on expression in malignant cells. Experimental Design: We studied expression of endosialin in clinical specimens, cell culture, and animal models and designed an anti-endosialin therapeutic prototype. Results: Fifty human tumor cell lines and 6 normal cell types in culture were assayed by reverse transcription-PCR and/or flow cytometry for endosialin. Cell surface protein was found on 7 sarcoma lines, 1neuroblastoma, and 4 normal cell types in culture. A fully human anti-endosialin antibody bound to human A-673 Ewing's sarcoma cells and SK-N-AS neuroblastoma cells but not HT-1080 cells. Exposure of cells to an anti-human IgG conjugated to saporin resulted in growth inhibition only of endosialin-expressing cells. Endosialin expression was assessed by immunohistochemistry in 250 clinical specimens of human cancer including 20 cancer subtypes. Endosialin is frequently found in human cancers. Endosialin expression is mainly a perivascular feature in carcinomas, with some expression in stromal cells. In sarcomas, endosialin is expressed by malignant cells, perivascular cells, and stromal cells. Development and characterization of experimental models for studying endosialin biology in sarcomas and evaluating anti-endosialin therapies is presented. Conclusions: Findings suggest that an anti-endosialin immunotoxin might be a promising therapeutic approach for endosialin-positive neoplasia, especially synovial sarcoma, fibrosarcoma, malignant fibrous histiocytoma, liposarcoma, and osteosarcoma. Thus, a diagnostic/therapeutic targeted therapeutic approach to treatment of endosialin-expressing tumors may be possible.

A 57 kDa protein (p57) was obtained during the study on phosphatidylinositol-specific phospholipase C. Its cDNA was isolated from calf spleen and human leukemia cell line HL60 libraries and cloned. In the primary structures of p57, they have two unique amino acid sequence motifs, a WD repeat and a leucine zipper motif. Furthermore, p57 shared sequence similarity (40%) with coronin, an actin-binding protein responsible for chemotaxis, cell motility, and cytokinesis of Dictyostelium discoideum, which has only the WD repeat, p57 also showed an actinbinding activity and was mainly expressed in immune tissues. From these results, we conclude that p57 is a coronin-like novel actin-binding protein in mammalian cells but may also have a different function from coronin.

Key Points• NOD-specific Sirpa polymorphism is the genetic determinant of highly efficient xenograft activity in NOD-based immunodeficient mouse models.Current mouse lines efficient for human cell xenotransplantation are backcrossed into NOD mice to introduce its multiple immunodeficient phenotypes. Our positional genetic study has located the NOD-specific polymorphic Sirpa as a molecule responsible for its high xenograft efficiency: it recognizes human CD47 and the resultant signaling may cause NOD macrophages not to engulf human grafts. In the present study, we established C57BL/6.Rag2 nullIl2rgnull mice harboring NOD-Sirpa (BRGS). BRGS mice engrafted human hematopoiesis with an efficiency that was equal to or even better than that of the NOD.Rag1 nullIl2rgnull strain, one of the best xenograft models. Consequently, BRGS mice are free from other NOD-related abnormalities; for example, they have normalized C5 function that enables the evaluation of complement-dependent cytotoxicity of antibodies against human grafts in the humanized mouse model. Our data show that efficient human cell engraftment found in NOD-based models is mounted solely by their polymorphic Sirpa. The simplified BRGS line should be very useful in future studies of human stem cell biology. (Blood. 2013;121(8):1316-1325) IntroductionImmunodeficient mice are widely used to reconstitute human hematopoiesis by xenotransplantation of hematopoietic stem cells (HSCs). 1,2 This "humanized" mouse model provides a powerful tool with which to evaluate the biologic properties of human HSCs and progenitors in vivo. 3,4 Such xenotransplantation systems have also been used to study human cancer stem cells. [5][6][7][8] Elimination of the lymphoid system is the first step to achieving reconstitution of human hematopoiesis. To deplete T and B cells, the scid mutation in the Prkdc gene [9][10][11] or disruption of the recombination activating gene 1 or 2 (Rag1 and Rag2) 12,13 has been introduced into various mouse strains. In addition, to deplete natural killer (NK) cells or their functions, the IL-2 receptor common ␥ chain subunit (Il2rg) [14][15][16] or beta-2-microglobulin (B2m) [17][18][19] is disrupted.However, depletion of lymphoid cells is not sufficient and it has been shown empirically that additional strain-specific factors modulate human hematopoietic engraftment in the xenotransplantation setting. For example, within the SCID strain, the SCID with the NOD background was the gold standard for the xenotransplantation assay based on its high efficiency. 11 In fact, recent studies have shown that among the lymphoid-depleted mouse strains, the NOD-scid Il2rg null (NSG/NOG) 14,15 and NOD.Rag1 null Il2rg null (NOD-RG) 20 strains are the most efficient; the BALB/c.Rag2 null Il2rg null (BALB-RG) strain is the next efficient 21,22 ; and the C57BL/6 strains with scid, 23 Rag2 null , Rag2 null B2m null , Rag2 null Prf null , 24 or Rag2 null Jak3 null25 mutations are unable to reconstitute human hematopoiesis. The NOD strain has multiple immune deficiencies, ...

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Src homology 2 domain-containing protein tyrosine phosphatase substrate 1 (SHPS-1) is a member of the signal regulatory protein family in which the extracellular region interacts with its ligand, CD47. Recent studies have demonstrated that SHPS-1 plays an important role in cell migration and cell adhesion. We demonstrate in this study, using immunohistochemical and flow cytometric analyses, that murine Langerhans cells (LCs) express SHPS-1. Treatment of mice ears with 2,4-dinitro-1-fluorobenzene significantly reduced the number of epidermal LCs, and that reduction could be reversed by pretreatment with mAb to SHPS-1 or the CD47-Fc fusion protein. Treatment with the SHPS-1 mAb in vivo reduced the number of FITC-bearing cells in the lesional lymph nodes after the application of FITC to the skin. The SHPS-1 mAb inhibited the in vivo TNF-α-induced migration of LCs. The emigration of dendritic cells expressing I-Ab+ from skin explants to the medium was also reduced by the SHPS-1 mAb. We further demonstrate that the chemotaxis of a murine dendritic cell line, XS52, by macrophage inflammatory protein-3β was significantly inhibited by treatment with the SHPS-1 mAb or CD47-Fc recombinant protein. Finally, we show that migration of LCs was attenuated in mutant mice that lack the intracellular domain of SHPS-1. These observations show that the ligation of SHPS-1 with the SHPS-1 mAb or with CD47-Fc abrogates the migration of LCs in vivo and in vitro, which suggests that the SHPS-1-CD47 interaction may negatively regulate LC migration.