Cancer-associated isoenzyme of serum galactosyltransferase.

Abstract

Galactosyltransferase activity was assayed in sera from 58 patients with various types of cancer. On discontinuous polyacrylamide gel electrophoresis a slow-moving peak of galactosyltransferase activity (isoenzyme II) was found to be present in the serum of 43 Galactosyltransferase activity has been identified with intracellular membranes, primarily the Golgi membrane fraction (1). Recent reports have also demonstrated the presence of galactosyltransferase activity on the cell surface membrane of :various cell types which include rat intestinal crypt cells (2), human fetal cells (2), and chemically induced rat tumor cells (3). Bosmann and Hall (4) reported elevated levels of sialyltransferases in homogenates of tumor cells from human breast and colon. Kessel and Allen reported elevated sialyltransferase activity in the plasma of cancer patients (5). Galactosyltransferase activity has also been detected in rat and human serum as a soluble activity (6, 7), but the total activity was not previously found to be elevated in cancer patients unless liver disease was also present (8). However, by means of discontinuous polyacrylamide gel electrophoresis Podolsky and Weiser were able to detect in cancer patients a slower moving peak of activity that separated well from the major, more anodally directed peak of activity found in all patients (9). The present report describes the cancer patients who were tested for serum galactosyltransferase isoenzymes, compares them with disease and normal controls, and examines possible clinical and laboratory correlations with serum levels of these isoenzymes. MATERIALS AND METHODSBiochemical Assays. Galactosyltransferase activity in whole serum was measured as previously described (9). The glycoprotein acceptor used for this enzyme assay was fetuin minus its terminal sialic acid and penultimate galactose residues (10).Polyacrylamide gel electrophoresis of sera and detection of galactosyltransferase activity from slices of polyacrylamide gels were performed by the method of Podolsky and Weiser (9). It was observed that the cancer-associated cathodal peak of activity (isoenzyme II) could not be detected * To whom reprints should be addressed. unless the gel reagents were first re-crystallized. N-acetylglucosamine (1 mM) was added to the gel eluting solution to stabilize the enzyme; it did not affect galactosyltransferase activity with fetuin acceptor. Polyacrylamide electrophoresis appeared to separate two peaks of galactosyltransferase (fetuin) activity which entered the gel. No galactosyltransferase activity with endogenous acceptor was detected. The major peak, which was found in all sera, was the more anodal one, while the smaller peak (isoenzyme II) was near the origin but separated from the activity remaining at the origin (9). These isoenzymes have been separated and partially purified and shown to have their original RF values on reelectrophoresis (unpublished observations).Serum. Serum samples were obtained primarily from patients hospitalized on the surgical service ...

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