Hexosaminidase isoenzyme profiles in leukemic cells

beta-N-acetylhexosaminidases in the spleen of a patient with hairy-cell leukaemia

The spleen from a patient with hairy-cell leukaemia had beta-N-acetylhexosaminidase activity that could be resolved into three isoenzymes by chromatography on phenyl boronate agarose. Two of these were the major forms, A and B, found in normal tissues but, in addition, there was an 'extra' form that accounted for 15% of total activity. The 'extra' form hydrolysed the synthetic substrate 4-methylumbelliferyl-beta-N-acetylglucosamine 6-sulphate, indicating the presence of alpha-subunits. It was more acidic than A, was less heat-stable and showed no generation of B on denaturation under a variety of conditions. These findings and the immunoblot (Western blotting) analysis demonstrate that the 'extra' form is entirely composed of alpha-subunits, and most closely resembles S, the residual activity in Sandhoff's disease.

Alpha-L-fucosidase isoenzyme pattern in hairy cell leukaemia

alpha-L-Fucosidase isoenzymes pattern in hairy cell leukaemia (HCL) is characterized by the disappearance of the more acidic form when compared to normal lymphocytes. Our data seem to indicate that this profile could not be related to the T or B phenotype because in normal lymphocytes (mainly T), MO cells possessing T markers, as well as lymphocytes from chronic lymphoid leukaemia (CLL) known to exhibit normal-like B phenotypes two alpha-L-fucosidase forms are identified and especially the more acidic one.

Enzyme immunoassay of beta-hexosaminidase isoenzymes using monoclonal antibodies

Purified beta-hexosaminidase A (Hex A) and beta-hexosaminidase B (Hex B) were used as immunogens in mice, with the purpose of obtaining isoenzyme-specific monoclonal antibodies (mabs). A total of 60 mabs were developed, 23 specific for Hex A and 37 recognizing both isoenzymes. At low pH, two of the latter mabs reacted only with Hex B, and it was, therefore, possible to develop enzyme immunoassays for the specific determination of Hex A and Hex B. The precision of the methods was adequate with intra- and interassay coefficients of variation below 3%.

Malignant cell glycoproteins and glycolipids

The cell surface is involved in cell growth and division, cell-cell interaction, communication, differentiation and migration, and other processes likely to be involved in malignant transformation and/or the metastatic spread of cancer. Although there are many alterations of glycoproteins and glycolipids on the malignant cell surface, it is unclear whether these alterations are epiphenomena or an integral part of the malignancy process. This article reviews the recent literature and some earlier studies relevant for understanding emerging concepts and trends with respect to malignant cell glycoconjugates. Emphasis is on structural alterations of the carbohydrate portions of malignant cell glycoproteins and glycolipids and on the enzymes (glycosyltransferases and glycosidases) involved in their metabolism. Practical applications derived from malignant cell glycoconjugate studies are discussed briefly with respect to the diagnosis, staging, monitoring, and treatment of malignant disease. The review concludes by indicating which research areas on malignant cell glycoconjugates are likely to be fruitful in increasing our basic understanding of, and ability to deal effectively with, malignant disease.

Genes for tumor markers are clustered with cellular proto-oncogenes on human chromosomes

We have analyzed the relative mapping positions of genes for polypeptides expressed abnormally in tumors (tumor markers) and cellular proto-oncogenes and find a remarkable degree of co-mapping of tumor marker genes with oncogenes in the human karyotype. We propose that aberrant expression of marker genes in tumors may be related to their proximity in the human genome to oncogenes expressed during the development of malignancy, and we suggest ways to test this hypothesis of concerted abnormal gene expression in mammalian tumor cells.

Occurrence of particular isoenzymes in fresh and cultured leukemia-lymphoma cells. II. Hexosaminidase I isoenzyme

The isoenzyme profiles of hexosaminidase (N-acetyl-beta-D-glucosaminidase) were analyzed by isoelectric focusing on horizontal polyacrylamide thin-layer gel with special emphasis on the intermediate isoenzyme (Hex I). The expression of Hex I was examined in 87 leukemia-lymphoma cell lines, in 14 B-lymphoblastoid cell lines, in 441 cases of leukemia-lymphoma (specimens containing 80% or more tumor cells), in 22 leukemia cell lines and in 14 cases of leukemia that had been treated with phorbolesters (TPA) for induction of differentiation, and in the mononuclear cell preparations separated from peripheral blood, lymph node, thymus, bone marrow, tonsil, liver, and spleen specimens from normal donors. Hex I was detected in the leukemia cell lines arrested at early, immature or at late, mature stages of B- and T-cell differentiation, but not in cell lines blocked at intermediate stages of maturation. Most myelomonocytic leukemia cell lines and the erythroleukemia cell lines showed Hex I, whereas the B-lymphoblastoid cell lines were negative for this marker. During induction of differentiation, the expression of Hex I was lost in 13 of 15 leukemia cell lines that were originally Hex I-positive. Among the panel of the "fresh" leukemia-lymphoma cells, Hex I was found predominantly in cases of acute lymphoblastic leukemia and acute myeloblastic/monoblastic leukemia, but rarely or not at all in the mature T-, B- or myeloid malignancies. However, two out of two cases of multiple myeloma were Hex I-positive, and the Hex I expression could be induced by TPA in three of six B-cell chronic lymphocytic leukemia cases. Chronic myelocytic leukemia cells remained Hex I-negative during induction of differentiation. Hex I-positivity was not detected in the cell preparations from normal tissues, and peripheral blood indicating that the normal cellular counterpart of the Hex I-positive tumor cells are present at only low percentages within the respective cell populations. It is suggested that Hex I is a marker of early lymphoid and myeloid hematopoiesis that is no longer expressed in intermediate stages of lymphoid differentiation and in later or terminal stages of myeloid differentiation, but that is again detectable in terminally differentiated B-cells. Further studies will focus on identification and isolation of normal Hex I-positive cells.

Isoenzyme studies in human leukemia-lymphoma cell lines--III. beta-Hexosaminidase (E.C. 3.2.1.30)

The hexosaminidase (beta-N-acetylglucosaminidase) isoenzyme profiles of 86 human hematopoietic cell lines grown actively in suspension culture were analysed by isoelectric focusing and by conventional disc electrophoresis on horizontal thin-layer polyacrylamide gels. A maximum of three hexosaminidase (Hex) isoenzymes (A = anodic, I = intermediate, B = basic) could be demonstrated. The immunological phenotyping of 74 leukemia-lymphoma derived cell lines had led to a categorization into four groups with a subclassification of the T- and B-cell lines into several stages of differentiation: 26 T-cell, 34 B-cell, 6 myelomonocytic and 8 Non-T, Non-B cell leukemia-lymphoma cell lines. Twelve so-called 'normal' B-lymphoblastoid cell lines were also available. Distinct isoenzyme profiles were seen in the different stages of differentiation in the T- and B-leukemia-lymphoma cell lines. Among the 12 normal B-lymphoblastoid cell lines heterogeneity in the isoenzymatic phenotypes was detected. Hex isoenzyme expression in normal and neoplastic lymphoid cell lines represents hypothetically sequential stages of T- and B-cell differentiation. Myelomonocytic cell lines displayed strongly stained bands of all three isoenzymes. Heterogeneity was seen in the group of Non-T, Non-B cell lines. Four out of 5 pre B-cell lines and 4 out of 4 Non-T, Non-B cell lines which are comparable to cases of pre B- and common ALL revealed a high Hex I/Hex A ratio in terms of intensity of the isoenzyme bands. The analysis of Hex isoenzymes is useful for characterizing lymphoid and myeloid populations (both normal and malignant, cultured or fresh), particularly with regard to their stage of differentiation. But this enzyme should be part of a multiple enzyme study where the information obtained is complementary. In turn, enzyme marker analysis should be included in the multiple marker analysis for an optimized characterization of leukemic cells.