calyculin-a and Leukemia--Myelogenous--Chronic--BCR-ABL-Positive

The proteolytic modification of plasminogen activator inhibitor 2 (PAI-2) was studied during apoptosis in the human promyelocytic leukaemic NB4 cell line during treatment with the phosphatase inhibitors okadaic acid and calyculin A as well as the protein synthesis inhibitor cycloheximide. The apoptic type of cell death was ascertained by morphological and biochemical criteria. In cell homogenates PAI-2 was probed by [125I]urokinase plasminogen activator (uPA) and detected as a sodium dodecyl sulphate-stable M(r) 80,000 complex after reducing sodium dodecyl sulphate-polyacrylamide gel electrophoresis and autoradiography. During apoptosis a smaller (M(r) 70,000) uPA-PAI-2 complex was consistently detected. The modification was in the PAI-2 moiety, as the [125I]uPA tracer could be extracted in its intact form from the complex. Thus the cleaved PAI-2 isoform is a biochemical marker of apoptosis in the promyelocytic NB4 cell line. The modified PAI-2 isoform was also detected in homogenates made from purified human mononuclear leukaemic cells aspirated from the bone marrow of patients suffering from acute and chronic myeloid leukaemia.

Topics: Apoptosis; Biomarkers, Tumor; Bone Marrow; Cell Death; Ethers, Cyclic; Humans; Intracellular Fluid; Isomerism; Leukemia, Myelogenous, Chronic, BCR-ABL Positive; Leukemia, Promyelocytic, Acute; Marine Toxins; Okadaic Acid; Oxazoles; Phosphoprotein Phosphatases; Plasminogen Activator Inhibitor 2; Tumor Cells, Cultured