Biochemical characterization of a leukemia-associated inhibitor (LAI) suppressing normal granulopoiesis in vitro.
Low-density (less than 1.077 g/ml) marrow or blood cells from patients with acute or chronic leukemia release a high molecular weight substance called "leukemia-associated inhibitor" (LAI) that reduces the fraction of normal marrow CFU-c in S-phase as measured with the 3H-TdR suicide technique. LAI from conditioned media or 3M KCl extracts of subcellular fractions behaved homogeneously on gel chromatography, showing an apparent molecular weight greater than 500,000. However, ion-exchange chromatography and isoelectric focusing indicated considerable charge heterogeneity for LAI molecules. Results from SDS-polyacrylamide gel electrophoresis indicated that the biologic activity resides in a subunit of 150,000-170,000 daltons. The findings of marked affinity for Con-A-Sepharose, marked susceptibility to mild periodate treatment, partial susceptibility to protease digestion, and relative resistance to heating suggest that LAI is a glycoprotein. Data from radiolabeling of cell surface components and sucrose density gradient centrifugation are consistent with LAI being a peripheral cell membrane glycoprotein, which may suppress normal granulopoiesis in leukemia.
D002499:Centrifugation, Density Gradient; D055598:Chemical Phenomena; D002621:Chemistry; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D006098:Granulocytes; D006410:Hematopoiesis; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D007525:Isoelectric Focusing; D007945:Leukemia, Lymphoid / Q000097:blood; D007951:Leukemia, Myeloid / Q000097:blood; D015470:Leukemia, Myeloid, Acute / Q000097:blood; D010447:Peptide Hydrolases / Q000494:pharmacology; D010504:Periodic Acid / Q000494:pharmacology
D007106:Immune Sera; D010504:Periodic Acid; D010447:Peptide Hydrolases