Serum beta-(1----4)-galactosyltransferase activity with synthetic low molecular weight acceptor in human ovarian cancer

Evaluation of beta1,4-galactosyltransferase as a potential biomarker for the detection of subclinical disease after the completion of primary therapy for ovarian cancer

OBJECTIVE

Approximately 50% of patients with ovarian cancer who have normal CA 125 levels at the completion of therapy have persistent disease. In an effort to improve the ability to detect small volume disease, we have evaluated the usefulness of N-acetylglucosamine:beta1,4-galactosyltransferase as a potential biomarker for the detection of subclinical disease after the completion of primary therapy for ovarian cancer.

STUDY DESIGN

The sera of 33 patients with stage IIIC epithelial ovarian cancer in complete clinical remission after chemotherapy (CA 125 <35 units/mL and negative computed tomography scan) who underwent second-look surgery were examined for N-acetylglucosamine:beta1,4-galactosyltransferase activity. The values were determined from sera that had been obtained before primary cytoreductive operation and before second-look surgery after the completion of platinum-based chemotherapy. Determinations of the levels of CA 125 were performed with the Bayer Immuno ITM CA-125 II assay. N-acetylglucosamine:beta1,4-galactosyltransferase activity was determined by measuring the transfer of galactose from uridine diphosphate- carbon 14-labeled galactose to the terminal N-acetylglucosamine residue of a very well-defined synthetic acceptor, N-acetylglucosamine:beta1,6GalNAc(alpha)-o-benzyl, which is a portion of the core structure of mucin glycoproteins. The cutoff value of N-acetylglucosamine:beta1,4-galactosyltransferase was determined to be 22,000 counts/min, based on the analysis of 25 healthy control subjects. Correlation between serum CA 125 and N-acetylglucosamine:beta1,4-galactosyltransferase levels was determined with the use of the Pearson correlation coefficient. The ability of galactosyltransferase to identify small volume disease correctly was also evaluated.

RESULTS

There was a significant correlation between serum CA 125 and N -acetylglucosamine:beta1,4-galactosyltransferase levels before the operation (r = 0.57; P =.03) but not before second-look surgery (r = 0.10; P =.57). Thirteen patients (39.4%) had residual disease at second-look surgery. Elevated N-acetylglucosamine:beta-1,4galactosyltransferase activity >22,000 cpm correctly identified 10 of these patients (76.9%). The sensitivity, specificity, and positive and negative predictive values of N-acetylglucosamine:beta1,4-galactosyltransferase activity (>22,000 counts/min) for the prediction of residual disease at second-look surgery were 77%, 45%, 48%, and 77%, respectively.

CONCLUSION

Our comparative study of serum CA 125 and N -acetylglucosamine:beta1,4-galactosyltransferase levels showed a significant correlation between the two tumor markers before the beginning of ovarian cancer therapy. This correlation disappeared before second-look surgery because 60% of patients with normal serum CA 125 and N-acetylglucosamine:beta1,4-galactosyltransferase levels. CA 125 antigen appears to be inferior to N -acetylglucosamine:beta1,4-galactosyltransferase in the detection of small-volume residual disease. N-acetylglucosamine:beta1,4-galactosyltransferase may be useful as a biomarker in the monitoring of patients with ovarian cancer when the serum CA 125 level is normal. These findings require confirmation in larger studies.

Human ovarian cancer, lymphoma spleen, and bovine milk GlcNAc:beta1,4Gal/GalNAc transferases: two molecular species in ovarian tumor and induction of GalNAcbeta1,4Glc synthesis by alpha-lactalbumin

Affinity Gel-UDP was utilized to purify GlcNAc:beta1,4Gal/GalNAc transferases (Ts) from human lymphoma spleen, ovarian tumor, and ovarian cancer sera. Mn(2+) was found to be an absolute requirement for activity. Two molecular species containing both beta1,4Gal/GalNAc-T activities were discernible when the purified ovarian tumor microsomal enzyme was subjected to Sephacryl S-100 HR column chromatography as well as native polyacylamide gel-electrophoresis. Acceptor specificity studies of the affinity-purified lymphoma spleen and ovarian tumor microsomal enzymes and the conventionally purified, as well as the cloned, bovine milk GlcNAc:beta1,4Gal-Ts using a number of synthetic acceptors showed that the beta(1,6)-linked GlcNAc moiety to alpha-GalNAc was the most efficient acceptor. As compared to the purified milk enzyme, the recombinant form exhibited sixfold GlcNAc:beta1,4 GalNAc-T activity and up to eightfold GlcNAc6SO3beta-:beta1,4Gal-T activity. Further, the recombinant enzyme catalyzed the transfer of GalNAc to the terminal beta-linked GlcNAc6SO3 moiety. Alpha-lactalbumin (alpha-LA) inhibited up to 85%, the transfer of Gal to the GlcNAc moiety linked either to Man or GlcNAc. On the contrary, alpha-LA had no significant influence on the transfer of GalNAc to the above acceptors. alpha-LA had no appreciable effect on the recombinant enzyme, except for the transfer of Gal or GalNAc to Glc. Both alpha- and beta-glucosides, as well as alpha-N-acetylglucosaminide, did not serve as acceptors.

Clinical aspects of glycoprotein biosynthesis

Glycoproteins are widely distributed among species in soluble and membrane-bound forms, associated with many different functions. The heterogenous sugar moieties of glycoproteins are assembled in the endoplasmic reticulum and in the Golgi and are implicated in many roles that require further elucidation. Glycoprotein-bound oligosaccharides show significant changes in their structures and relative occurrences during growth, development, and differentiation. Diverse alterations of these carbohydrate chains occur in diseases such as cancer, metastasis, leukemia, inflammatory, and other diseases. Structural alterations may correlate with activities of glycosyltransferases that assemble glycans, but often the biochemical origin of these changes remains unclear. This suggests a multitude of biosynthetic control mechanisms that are functional in vivo but have not yet been unraveled by in vitro studies. The multitude of carbohydrate alterations observed in disease states may not be the primary cause but may reflect the growth and biochemical activity of the affected cell. However, knowledge of the control mechanisms in the biosynthesis of glycoprotein glycans may be helpful in understanding, diagnosing, and treating disease.

Synthetic antigens as immunogens: Part IV. Specificity of antisera developed to Gal beta 1-3(GlcNAc beta 1-6)GalNAc and GlcNAc beta 1-6GalNAc

Antisera to the chemically synthesized trisaccharide, Gal beta 1-3(GlcNAc beta 1-6)GalNAc, and disaccharide, GlcNAc beta 1-6GalNAc, were developed using the diazophenyl bovine serum albumin derivatives. The binding specificity of the antisera were analyzed by enzyme immunoassays with structurally related, chemically synthesized oligosaccharides. The anti-trisaccharide antibody showed no reactivity to T antigenic structures which bear the Gal beta 1-3GalNAc moiety. The immunodominant area of the Gal beta 1-3(GlcNAc beta 1-6)GalNAc was contained in the GlcNAc beta 1-6GalNAc region of the molecule. The reactivity pattern of the anti-trisaccharide antibody, although directed to the disaccharide, did not exactly duplicate the reactivity pattern of the anti-disaccharide.

A simple serum galactosyltransferase assay method suitable for routine use

UDP-Galactose: N-acetylglucosaminyl glycoprotein beta 1-4 galactosyltransferase (GT) catalyzes the transfer of galactose to N-acetylglucosamine from UDP-[3H]Gal. The uncharged reaction product (tritiated N-acetyllactosamine) is separated from the unreacted UDP-[3H]Gal by ion-exchange chromatography. The major advantage of this method is its rapidity compared to other isotopic techniques.

Alteration in isoenzyme patterns of serum galactosyltransferase activity in ovarian cancer patients: preliminary results

Isoelectric focusing on agarose gel was used to separate the isoenzymes of serum galactosyltransferase (uridine diphosphogalactose: N-acetylglucosaminyl galactosyltransferase, EC 2.4.1.22) from 8 healthy women, and 11 ovarian cancer patients of whom 4 were in clinical remission. In all cases, we found 7 major peaks with isoelectric points ranging from 4.0-5.4. The most acidic peaks were preferentially elevated in the tumor-bearing patients, particularly the peak with pI 4.44.

Serum galactosyltransferase activity with three acceptors in ovarian cancer patients

Several laboratories have demonstrated the usefulness of serum galactosyltransferase as a biological marker for ovarian neoplasms. However, contradictory results have been published recently, which might be partially explained by differences in methodology. We thus decided to measure serum galactosyltransferase activity in patients with ovarian cancer and benign gynecological diseases using three different assay systems. A very good correlation was obtained between the results of these assays. Furthermore, we confirm that serum GT is frequently elevated in cancer patients, and is of potential value for their follow-up.