Tumors glycoproteins

The preparation methods for the glycoprotein antigens were varied. Myeloma protein was obtained from ascite fluid [25], The glucoamylase was from A niger [26], the erythropoietin was from recombinant hampster cells [27] and tumor glycoprotein was from colon tumor tissue [28]. 

Fig. 37.—Antibodies directed at colon-tumor glycoprotein antigens. A Carcinoembryonic antigen on gel electrophoresis (I), gel embedded in agar (2). precipitin area (3), tumor antibody (4). B Tumor colon KC1HC1 extract (6), embedded gel (7), precipitin area (8), antibodies (9), extract of normal colon (5). C Agar diffusion of tumor-colon antibodies, C = carcinoembryonic antigen, E = new tumor colon antigens, S, = serum to C EA, S2 = serum to E x indicates periodate-oxidized antigens. [Data from J. H. Pazur, J. Chromatogr. B., 663 (1995) 51-57.)...

Tissue-type plasminogen activator (tPA) is a glycoprotein (68 kDa), synthesized by endothelial and tumor-cells. As a serine protease, tPA hydrolyses Arg561-Val562 peptide bond in plasminogen, resulting in plasmin formation. It needs cofactors for efficient plasminogen activation. 

Urokinase-type plasminogen activator (uPA, urokinase) is synthesized by endothelial and tumor cells as a single-chain glycoprotein (scuPA) without catalytic activity. When it is converted to a two-chain protein (tcuPA) by plasmin, an active serine protease center develops, which activates plasminogen. Thus, uPA (55 kDa) results in the amplification of fibrinolysis. 

IFNs are natural glycoproteins produced by the cells of most vertebrates in response to the challenge by foreign agents, such as infectious organisms (viruses, bacteria, fungi, and parasites), and by tumor cells. IFNs can be produced by cells of the innate and adaptive immune systems and by non-immune cells such as fibroblasts and epithelial cells. 

Tumor cells may become resistant when genetic changes occur during cell proliferation. Resistant cancer cells with the mdr-1 gene may possess a membrane-associated protein, p-glycoprotein, that facilitates efflux of chemotherapy agents out of the cells. Numerous attempts at blocking this efflux pump have been unsuccessful. 

Monoclonal antibody-defined antigens, such as tumor-associated glycoproteins, CA-125 and CA 15-3... 

P-glycoprotein) in human normal and tumor tissues, J. Histochem. Cytochem. 1990, 38, 1277-1287. 

ATPase activity of P-glycoprotein related to emergence of drug resistance in Ehrlich ascites tumor cell lines, Biochim. Biophys. Acta 1997,... 

P-glycoprotein is not only expressed in tumor cells, but also in cells of several healthy tissues. In liver it was detected in the biliary canalicular surface of hepato-cytes and the apical surface of small biliary ductules. In the small intestine and colon, it is localized in the apical surface of columnar epithelial cells, and in kidneys it is found in the brush border membrane of proximal tubules. Moreover, it is detectable on the apical surface of small ductules in the pancreas and on the surface of cells in the medulla and cortex of adrenals [2]. 

The 80 kDa glycoprotein transferrin (Tf) is responsible for intracellular iron transport via the transferrin receptor (TfR), using a clathrin-dependent endocytosis process. Tumor tissues frequently overexpress the TfR. While natural Tf recycles to... 

---