Tumor-associated CD75s gangliosides and CD75s-bearing glycoproteins with Neu5Acalpha2-6Galbeta1-4GlcNAc-residues are receptors for the anticancer drug rViscumin.

The anticancer drug rViscumin, currently under clinical development, has been shown in previous studies to be a sialic acid specific ribosome inactivating protein (RIP). Comparative binding assays with the CD75s-specific monoclonal antibodies HB6 and J3-89 revealed rViscumin to be a CD75s-specific RIP due to identical binding characteristics toward CD75s gangliosides. The receptor gangliosides are IV6nLc4Cer, VI6nLc6Cer, and the newly characterized ganglioside VIII6nLc8Cer, all three carrying the Neu5Acalpha2-6Galbeta1-4GlcNAc motif. To elucidate the clinical potential of the rViscumin targets, CD75s gangliosides were determined in several randomly collected gastrointestinal tumors. The majority of the tumors showed an enhanced expression of CD75s gangliosides compared with the unaffected tissues. The rViscumin binding specificity was further investigated with reference glycoproteins carrying sialylated and desialylated type II N-glycans. Comparative Western blots of rViscumin and ricin, an rViscumin homologous but galactoside-specific RIP, revealed specific recognition of type II N-glycans with CD75s determinants by rViscumin, whereas ricin failed to react with terminally sialylated oligosaccharides such as CD75s motifs and others. This strict binding specificity of rViscumin and the increased expression of CD75s gangliosides in various tumors suggest this anticancer drug as a promising candidate for an individualised adjuvant therapy of human tumors.

[Clinical application of cancer-associated carbohydrate antigens in the diagnosis and therapy of human cancers].

Cell surface carbohydrates are important cancer-associated antigens. The carbohydrate antigens which have been proved to be useful for the serum diagnosis of human cancers are classified from their biochemical primary structure into three categories; the type 1 chain antigens, type 2 chain antigens, and core structure-associated antigens. The SPan-1 antigen, the newly-introduced tumor marker for human pancreas cancers, seems to be a type 1 chain antigen, judging from its distribution pattern among human cancers and its good correlation with other type 1 chain antigens. Another newly-introduced tumor marker, the CA54/61 antigen, which is specific for ovarian cancers, seems to belong to the family of the core-structure-associated antigens, since both antibodies (MA54 and MA61) used for the detection of the CA54/61 antigen are shown to recognize the antigen molecule which is closely related to sialyl Tn antigen, the well-known carbohydrate core structure of mucins. There are two approaches for the therapy of human cancers employing carbohydrate antigens as target molecules. One is the direct application of the specific monoclonal antibodies (alone, or in the drug-conjugated forms) in cancer patients. In this case, special attention is paid to the use of murine antibodies in human patients. The other approach is to induce specifically an effective immune response against the cancer-associated carbohydrate antigens. For this approach, further methodological development is necessary to determine how to obtain an effective immune response to carbohydrate antigens, since they have long been known as very poor immunogens which are T-independent.

Glycopeptide dendrimers, part III: a review. Use of glycopeptide dendrimers in immunotherapy and diagnosis of cancer and viral diseases.

Glycopeptide dendrimers containing different types of tumor associated-carbohydrate antigens (T(N), TF, sialyl-T(N), sialyl-TF, sialyl-Le(x), sialyl-Le(a) etc.) were used in diagnosis and therapy of different sorts of cancer. These dendrimeric structures with incorporated T-cell epitopes and adjuvants can be used as antitumor vaccines. Best results were obtained with multiantigenic vaccines, containing, e.g. five or six different TAAs. The topic of TAAs and their dendrimeric forms at molecular level are reviewed, including structure, syntheses, and biological activities. Use of glycopeptide dendrimers as antiviral vaccines against HIV and influenza is also described. Their syntheses, physico-chemical properties, and biological activities are given with many examples.

Behavior of tumor markers CA19.9, CA195, CAM43, CA242, and TPS in the diagnosis and follow-up of pancreatic cancer.

We compared the recently proposed tumor markers CA195, CA242, and CAM43 with a widely used antigen, CA19.9, and a circulating marker of cellular proliferation, TPS, to define their specificity, sensitivity, and cost-benefit ratio. The tumor markers were measured in 41 pancreatic carcinoma patients and in two control groups, the first comprising 19 patients with benign pancreatic diseases, the second comprising 41 healthy blood donors. Sensitivities were 79% for CA19.9, 57% for CA242, 60% for CAM43, 76% for CA195, and 98% for TPS. Specificities calculated for the group with pancreatic diseases were 60% for CA19.9, 84% for CA242, 95% for CAM43, 53% for CA195, and 22% for TPS. Specificities for the blood donor group were 100% for CA19.9, 93% for CA242, 98% for CAM43, 85% for CA195, and 88% for TPS. Positive values for the tumor markers appeared from second stage (Hermreck classification). Metastases, invasion of lymph nodes, and coupling of cancer-associated antigens did not significantly modify marker sensitivity. In pancreatic carcinoma, CA19.9 showed good sensitivity (79%) and high specificity (60-100%). In view of their own advantages (e.g., high specificity of CAM43, high sensitivity of TPS in recurrences) and limits (e.g., low sensitivity of CAM43, very low sensitivity of TPS), the other markers could be used alone or with CA19.9. Two pairs of tumor markers showed high similarity in our study: CA19.9 and CA195, and CAM43 and CA242.

[Heterogeneity of CA 125 antigens released from human endometrial heterotopic epithelium and ovarian cancer].

We purified CA125 antigen from the conditioned media (CM) of eutopic and heterotopic endometrial epithelial cells (EC) as well as ovarian cancer cell lines, SHIN-3 and HOC-I, to determine what molecular weight forms of CA125 antigen were identifiable. Treatment of the high-molecular-weight CA125 antigen with 6M urea yielded a much lower molecular mass peak. After purification by OC125 affinity column chromatography, samples were applied to 3 to 7% polyacrylamide gradient gel and analyzed by Western blot. A single band with a molecular weight (MW) of 200KDa was identified in eutopic EC materials. The CA125 polypeptide of the 110KDa molecule could be detected in all of the CM obtained from heterotopic EC, irrespective of the length of time in the cell culture. A MW of approximately 200 KDa was also observed in some heterotopic EC samples. On the other hand, although the multiple bands with a MW equal to orless than 200KDa were observed in the CM of two ovarian cancer cells, the CA125 polypeptide of 110KDa molecules could not be detected. This preliminary finding offers promise that the 110KDa molecule detection method may be a useful adjunct in the differential diagnosis of heterotopic EC and ovarian cancer.