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.