Clinical characteristics of a newly developed ovarian tumour marker, galactosyltransferase associated with tumour (GAT)

In this study clinical studies were conducted on galactosyltransferase associated with tumour (GAT) as a newly developed marker of ovarian cancers. The positive rates of GAT with a cut-off value of 16 U/ml (which corresponds to the mean + 2 standard deviations (S.D.) for healthy females) were 4.7% for benign ovarian tumours, 4.5% for endometriosis and 45.9% for ovarian cancers. GAT showed a positive rate comparable to that of CA546 or CA72-4 among other tumour markers (CA602, CA125, CA546, CA72-4, STN and SLX) examined in ovarian cancers. However, it showed lower positive rates for benign ovarian diseases and, in particular, it gave the lowest positive rate for endometriosis among the aforementioned tumour markers. Furthermore, the receiver operating characteristic (ROC) analysis for discriminating between ovarian cancer and endometriosis showed a significantly high area under the curve (AUC) for GAT compared with that of the other markers. GAT showed the lowest correlation coefficients with other markers, and the positive rate and the diagnostic efficiency were increased by its combination assay with CA602 and/or CA546. Furthermore, the accuracy of the diagnosis of ovarian cancer improved by examining GAT after screening with CA602 or ultrasonography. These results suggest that GAT is a suitable marker for distinguishing ovarian cancers from benign gynaecological diseases, particularly endometriosis, and is useful for combination assay or secondary screening for ovarian cancers.

Separation and partial characterization of two galactosyltransferase isoforms from malignant ascitic fluid

Galactosyltransferase was isolated from human malignant ascites by ammonium sulphate precipitation, alpha-lactalbumin affinity chromatography and by the removal of contaminating immunoglobulins with protein A chromatography. Two isoforms of galactosyltransferase were separated by DEAE chromatography, and partially characterised by gel filtration, non-denaturing polyacrylamide gel electrophoresis, concanavalin A binding and enzyme kinetics. The two forms isolated were compared with the isoenzymes previously described and the biochemical basis for the difference between the two forms discussed.

Evaluation of galactosyltransferase isoenzyme II in a human colon carcinoma-derived cell line, HCT-8

Polyacrylamide gel electrophoresis of galactosyltransferase (GT) extracted from a human colon adenocarcinoma cell line, HCT-8, demonstrated the presence of two peaks of activity: a slow-moving peak, referred to as GT-II, and a more anodally migrating peak, designated as GT-I, which was also found for normal human serum. However, if GT solubilized from HCT-8 cells was separated by isoelectric focusing, no unique isoenzymes could be detected. Total GT activity from HCT-8 cells was purified by alpha-lactalbumin-Sepharose affinity chromatography followed by ion exchange chromatography on either DEAE-cellulose or FPLC using a Mono Q anion exchange resin. Three major peaks of activity were resolved from anion exchange chromatography. Electrophoresis of each peak revealed a GT pattern identical with that originally observed for the crude (detergent) solubilized homogenate. No enrichment of either GT-I or GT-II was observed in the three enzyme fractions. The data suggest that GT-II may be an artifactual activity of cancer cells composed of GT-I associated with some contaminating protein.

The specificity of serum uridine 5'-phosphogalactose: glycoprotein galactosyl transferase activity in the diagnosis of ovarian cancer

Serum galactosyl transferase activity was measured in patients with ovarian cancer, non-ovarian cancer, inflammation and infection, miscellaneous control patients and a normal group. Patients with cancer had widely dispersed results, high and low results being recorded. The majority of patients with inflammation and infection had elevated results. Differences in methodology and selection of clinical material make it difficult to compare results from different groups of workers. We conclude that it is not possible at present to decide on the usefulness of serum galactosyl transferase measurements in the investigation of ovarian cancer.

Galactosyltransferases: physical, chemical, and biological aspects

Galactosyltransferases (GTs) are one of the members of a family of enzymes called glycosyltransferases involved in the biosynthesis of complex carbohydrates. These enzymes catalyze the transfer of galactose from UDP-galactose to an acceptor (glycoprotein, glycolipid) containing terminal N-acetylglucosamine or N-acetylgalactosamine residue. GTs occur in soluble (milk, serum, effusions, etc.) and insoluble (membrane) forms. The GT activities on the outer surface of the cells have been correlated with a host of cellular interactions, including fertilization, cell migration, embryonic induction, chondrogenesis, contact inhibition of growth, cell adhesion, hemostasis, intestinal cell differentiation, and immune recognition. GTs have been purified to homogeneity using affinity chromatography. Most GTs are found active in the pH range 6 to 8 and at temperatures between 35 to 40 degrees C. Manganese is an essential co-factor for GT activity. Isoenzymes of GT have been recognized, especially in tumor tissues, malignant effusions, and sera of cancer patients using polyacrylamide gel electrophoresis in the presence and absence of SDS. Depending on the source of the enzyme, the molecular weights of GTs range between 40,000 to 80,000 daltons. Carcinoma-associated GT isoenzyme has been reported to have a higher molecular weight than the normal GT isoenzyme. Development of monoclonal antibody against the cancer-specific GT isoenzyme will provide help in the development of an immunoassay for the measurement of this isoenzyme in the sera and an aid in the radioimmunolocalization of the tumors in cancer patients.

Serum galactosyltransferase isoenzymes as markers for solid tumours in humans

High resolution agarose isoelectric focusing was used to compare the galactosyltransferase isoenzyme patterns of serum from 9 healthy controls with those from 38 patients with either breast, lung, ovarian, stomach or colonic cancer. At least 12 peaks of enzyme activity were found in every sample, the healthy controls having major forms with isoelectric points of 4.74, 4.87, 4.96, 5.16 and 5.23. Thirty patients (79%) had elevated levels of at least one isoenzyme and 23 (61%) had at least 3 isoenzymes elevated compared to only 10 (26%) patients who had elevated total serum galactosyltransferase activity. The isoenzymes which were most often elevated in the cancer patient group had isoelectric points of 4.93, 5.16 and 4.61. One isoenzyme with an isoelectric point of 4.43 was preferentially elevated in patients with ovarian cancer. Those isoenzymes containing little or no sialic acid were rarely elevated in cancer patients. Although no cancer-associated isoenzyme was detected the quantitative differences observed in the cancer patient group were striking.