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The effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on megakaryocytopoiesis and platelet production was investigated in patients with normal hematopoiesis. Three findings indicated that GM-CSF plays a role in megakaryocytopoiesis. During treatment with GM-CSF (recombinant mammalian, glycosylated; Sandoz/Schering-Plough, 5.5 μg protein/kg/d, subcutaneously for 3 days) the percentage of megakaryocyte progenitors (megakaryocyte colony forming unit [CFU-Mk]) in S phase (evaluated by the suicide technique with high 3H-Tdr doses) increased from 31% ± 16% to 88% ± 11%; and the maturation profile of megakaryocytes was modified, with a relative increase in more immature stage I—III forms. Moreover, by autoradiography (after incubation of marrow cells with 125I-labeled GM-CSF) specific GM-CSF receptors were detectable on megakaryocytes. Nevertheless, the proliferative stimulus induced on the progenitors was not accompanied by enhanced platelet production (by contrast with the marked granulo-monocytosis). It may be suggested that other cytokines are involved in the regulation of the intermediate and terminal stages of megakaryocytopoiesis in vivo and that their intervention is an essential prerequisite to turn the GM-CSF–induced proliferative stimulus into enhanced platelet production.

By analyzing a total of 107 patients affected by chronic myelogenous leukemia (CML; chronic and blast crisis) or lymphoid and myeloid Philadelphia chromosome (Ph′) positive acute leukemias, we have investigated the relationship between the molecular defect on the Ph′ chromosome and the associated hematologic phenotype. As expected, approximately half of the Ph′ positive acute leukemias showed a breakpoint on chromosome 22 falling outside the “breakpoint cluster region” (bCr) known to be involved in CML. Surprisingly, seven of 80 CML cases in chronic phase also showed rearrangements falling outside the bcr region. In two of these cases the breakpoint on chromosome 22 was mapped between 9 and 12 kb upstream to the bcr region. In another case, the breakpoint was located approximately 16 kb downstream to bcr. In the remaining four cases, the precise position of the rearrangement could not be localized with the available bcr probes. DNAs from patients with CML blast crises showed classical bcr rearrangements. No molecular changes were observed during the progression of the disease in six patients whose DNA from both a chronic and acute phase was available. Our results seem to indicate a greater degree of veriability of chromosome 22 breakpoints in CML than previously observed, and the lack of additional rearrangements on the Ph′ chromosome in CML blast crises with respect to chronic phase.

Antibodies against phosphotyrosine are a powerful tool with which to identify proteins phosphorylated on tyrosine residues, such as viral oncogene-encoded transforming proteins and their cellular protein substrates. Probed on human leukemia cell lines, phosphotyrosine antibodies recognized a 210,000-molecular-weight protein (p210) in K562 cells, a cell line derived from a Philadelphia (Ph)'-positive chronic myelogenous leukemia (CML), but recognized no protein in control Ph'-negative non-CML leukemia cells. The p210 protein was also recognized by antisera against v-abl-encoded polypeptides and displayed kinase activity, phosphorylating itself on tyrosine, in an immunocomplex kinase assay. These data are consistent with reported findings of the expression of a recombined bcr-abl gene in Ph'-positive CML cells, leading to the synthesis of an altered p210c-abl protein endowed with tyrosine kinase activity. Phosphotyrosine antibodies also detected the expression of the p210c-abl protein in fresh bone marrow cells harvested from CML patients in blast crisis. Besides the p210c-abl protein kinase, phosphotyrosine antibodies recognized other proteins with molecular weights of 110,000, 68,000, and 36,000 (p110, p68, and p36) in K562 cells. When [gamma-32P]ATP was added to nonionic detergent-extracted cells, these proteins became phosphorylated on tyrosine, as confirmed by phosphoamino acid analysis. A comparison with fibroblasts transformed by the v-abl, v-src, and v-fps oncogenes suggested the identity of the p36 protein with the common 36-kilodalton protein substrate of viral oncogene-encoded tyrosine kinases. Enhanced tyrosine phosphorylation of cellular proteins is thus a feature shared by cells transformed by v-abl and cells expressing a rearranged bcr-abl gene.

Human gamma interferon (HuIFN gamma) was evaluated for its effects on the release from human peripheral blood T lymphocytes (greater than 98% pure) stimulated by phytohemagglutinin (PHA) of activities that can stimulate granulocyte-macrophage (CFU-GM) colonies and clusters, erythroid (BFU-E) bursts, and mixed (CFU-GEMM) colonies. T lymphocytes did not release these activities in the absence of PHA with or without HuIFN gamma. In the presence of PHA, pure natural HuIFN gamma at concentrations of 0.1 to 100 U/mL significantly enhanced release of these colony-stimulating activities. Although enhanced release of granulocyte-macrophage colony-stimulating activities were noted when T lymphocytes were added to the conditioning medium in the presence of 0.1%, 0.5%, and 1% PHA, enhanced release of burst-promoting and mixed colony activities was seen only in the presence of 0.1% and 0.5% PHA. The enhanced release of colony-stimulating activities was not due to HuIFN gamma-suppression of the release from PHA-stimulated T lymphocytes of suppressor molecules. The enhancing effects of natural HuIFN gamma were neutralized with a monoclonal anti-natural HuIFN gamma, and recombinant HuIFN gamma mimicked the enhancing effects of the natural HuIFN gamma. This enhancing effect was noted only when HuIFN gamma was added with the T lymphocytes and PHA during the first 24 hours of incubation. T lymphocytes were separated into T4+, T8-, T8+, and T4- subsets (greater than 98% pure for the appropriate phenotypes) after incubation with OKT4- and OKT8- monoclonal antibodies and sorting on a fluorescence-activated cell sorter (FACS). All types of colony-stimulating activities were released from each population after stimulation with PHA, but enhanced release of these activities in the presence of HuIFN gamma was only detected with the T4+ or T8- subsets of lymphocytes. It cannot be concluded from these studies whether HuIFN gamma is enhancing the release of one or several types of colony-stimulating activities, but these studies suggest a role for HuIFN gamma and T4+ lymphocyte subsets in the regulation in vitro of the release of colony-stimulating activities.

The dynamic cell processes connected with liver regeneration have been studied as follows: 1) ribonucleic and desoxyribonucleic contents; 2) transamination reactions (glutamic-oxalacetic transaminase and glutamic-piruvic transaminase); 3) reactions related to the peptides constitution and demolition (dipeptidase); 4) reactions involved in the hydrolytic release of phosphoric bounds (alkaline phosphomonoesterase, acid pyrophosphatase, gluco-6-phosphatase); 5) reactions entering in nucleotides splitting and formation (nucleotidase).It has been particularly observed that the metabolic differences between normal and regenerating liver are mainly quantitative and that the enhancement of proteosynthesis does not necessarily imply a simultaneous enhancement of all the related biochemical activities.