Isozymes of acid esterase and acid phosphatase in permanent human hematopoietic cell lines

Net enzyme activities of normal human blood cells were measured, and isoelectric focusing patterns of acid esterase (AcE) (EC 3.1.1.6) and acid phosphatase (AcP) (EC 3.1.3.2) were compared with corresponding data obtained for two acute T-lymphoblastic leukemia cell lines (JM, Molt-4), one acute B-lymphoblastic leukemia cell line (Ball-1), one acute non-B-non-T-lymphoblastic leukemia cell line (KM 3), and one promyelocytic leukemia cell line (HL-60). The AcE isozymes, found in the individual blood cell types, were regularly expressed by the corresponding cell lines. AcP was regularly expressed by lines HL-60 and KM 3, but lines JM, Molt-4, and Ball-1 showed additional isozymes and/or reduction of the intensity of the typical isozymes found in the presumed normal counterparts. This phenomenon resulted partly in an obscuration of the typical isozyme patterns. Our study documents the applicability of isozyme mapping to the characterization of permanent hematopoietic cell lines. The results suggest that long-term culture conditions can repress phenotypic properties and/or derepress gene activities.