Teruo Miyauchi

Chromosomal localization of two cell surface-associated molecules of potential importance in development: midkine (Mdk) and basigin (Bsg).

Midkine (protein symbol: MK, proposed gene symbol: Mdk) is the first member of a family of heparin binding growth factors (Kadomatsu et al. 1988; Tomomura et al. 1990a, 1990b). MK has mitogen activity on PC12 pheochromocytoma cells (Tomomura et al. 1990b), while heparin binding growth associated molecule (HB-GAM), another member of the family, has neurite extension activity and is mitogenic for fibroblasts (Merenmies and Rauvala 1990; Li et al. 1990). MK has a molecular weight of 14,000 and is rich both in basic amino acids and cysteine (Tomomura et al. t990a). MK and HB-GAM have 50% homology and all cysteines are conserved (Merenmies and Rauvala 1990; Li et al. 1990; Tsutsui et al. 1991). Since MK has a strong affinity for heparin it should be mainly localized at the surface of the cell either in a matrix-bound form or in a membrane-bound form. Mdk, the gene coding for MK, is a retinoic acid responsive gene and it is expressed during the mid-gestation period of mouse embryogenesis (Kadomatsu et al. 1988, 1990; Huang et al. 1990). In adult mice, only the kidney expresses Mdk significantly (Kadomatsu et al. 1988). Basigin (gene symbol: Bsg) is a member of the immunoglobulin superfamily, and displays strong homology with both immunoglobulin V domain and the C-domain-like sequence of major histocompatibility antigen class II 13 chain (Miyaushi et al. 1990). The immunoglobulin-like domain of basigin may be closely related to the primordial form of the immunoglobulin domains. As other molecules of the immunoglobulin superfamily, basigin is expected to be involved in cell surface interactions as an adhesion molecule or as a receptor (Williams and Barclay 1988). Although basigin was found as a molecule bearing a carbohydrate marker of embryonic nature, the gene coding for bas-

Metanestin, a glycoprotein with metastasis-associated expression in transitional cell carcinoma of the urinary bladder

A 60‐kDa glycoprotein named metanestin was identified by molecular cloning. The glycoprotein had a twice‐repeated motif of Pro‐Gly‐Pro‐Gly and carried metastasis‐associated carbohydrate epitopes. The antibody to the protein portion of metanestin strongly reacted with lymph‐node metastasis of transitional‐cell carcinoma of the urinary bladder, but the reactivity to the primary tumor was generally weaker and the normal urothelium was scarcely reactive. Thus both metanestin and the carbohydrate on it showed metastasis‐associated expression. In addition, we identified a 100‐kDa glycoprotein with a 4‐times‐repeated motif of Pro‐Ala‐Pro‐Ala. The antibody to the 100‐kDa glycoprotein showed reactivity similar to that to metanestin. Int. J. Cancer 74:7–14.

New carbohydrate antigen found in large glycopeptides of teratocarcinoma cells

Abstract From rabbit antiserum against Dolichos agglutinin receptors of murine teratocarcinoma OTT6050, an antibody preparation has been isolated by affinity chromatography on the large glycopeptides of the teratocarcinoma. The antibody recognized carbohydrate antigen(s), which was expressed on embryonal carcinoma cells and primitive endodermal cells of teratocarcinomas, 2- to 4- cell embryos, and on GRSL leukemia cells, but not on many adult cells. The antigen was different from several carbohydrate antigens such as ABH, Forssman, Ii and SSEA-1 and will be useful as a marker of differentiation and tumorigenesis in a certain system.