Chronic myeloid leukemic granulocytes exhibit reduced and altered binding to P-selectin: modification in the CD15 antigens and sialylation

Lack of the adhesion molecules P-selectin and intercellular adhesion molecule-1 accelerate the development of BCR/ABL-induced chronic myeloid leukemia-like myeloproliferative disease in mice

In vitro studies show that BCR/ABL-expressing hematopoietic cells exhibit altered adhesion properties. No in vivo studies show whether the altered adhesion properties affect BCR/ABL leukemogenesis. Using mice with homozygous inactivation of genes encoding the 2 adhesion molecules P-selectin and intercellular adhesion molecule-1 (ICAM1), we show that the mutant mice develop BCR/ABL-induced chronic myeloid leukemia (CML)-like leukemia at a significantly faster rate than do wild-type (WT) mice. Lack of P-selectin and ICAM1 did not have a significant effect on the development of B-cell acute lymphoblastic leukemia (BALL) induced by BCR/ABL. Using mice deficient for P-selectin or ICAM1 alone, we show that P-selectin plays a major role in the acceleration of CML-like leukemia. Lack of P-selectin resulted in early release of BCR/ABL-expressing myeloid progenitors from bone marrow, appearing to alter the biologic properties of leukemic cells rather than their growth rate by increasing their homing to the lungs, causing fatal lung hemorrhages. These results indicate that adhesion of BCR/ABL-expressing myeloid progenitors to marrow stroma through P-selectin and ICAM1 play an inhibitory role in the development of CML-like disease, suggesting that improvement of adhesion between BCR/ABL-expressing myeloid progenitor cells and bone marrow stroma may be of therapeutic value for human CML.

Expression profiles of I and sialosyl-I antigens on blood cells: the sialosyl-I antigen is expressed along the monocytic differentiation

Expression of I and sialosyl-I antigens was examined using specific monoclonal antibodies. The anti-I antibody C6 reacted with monocytes (24%), T cells (55%), B cells (80%) but not with neutrophils (4%), bone marrow (BM) CD34+ cells (2%) or mobilized peripheral blood (PB) CD34+ cells (1%). The anti-sialosyl-I antibody NUH2 reacted with monocytes (38%) and BM CD34+ cells (41%) but not with T cells (2%), B cells (0%) or neutrophils (1%) and it hardly reacted with mobilized PB CD34+ cells (8%). Flow cytometric analyses of CD34+ cells enriched from BM showed that most of the sialosyl-I cells expressed CD13, CD33, CD117, and HLA-DR. Sialosyl-I+ CD34+ cells isolated from BM produced a large number of granulocyte-macrophage colonies and macrophage colonies. Therefore, sialosyl-I+ CD34+ cells are suggested to be colony-forming units granulocyte-macrophage (CFU-GM) and colony-forming units macrophage (CFU-M). BM CD34+ cells cultured in medium containing cytokines produced I+ CD14+ monoblasts and sialosyl-I+ CD14+ monoblasts. Leukemic cells from patients with acute myeloid leukemia were I-negative (32/32) and sialosyl-I-positive (one/32). Leukemic cells from patients with acute lymphoid leukemia were I-positive (four/ten) and sialosyl-I-negative (ten/ten). These results indicate that (1) the I antigen is broadly expressed by monoblasts, monocytes, lymphocytes, and leukemic lymphoblasts, and (2) the sialosyl-I antigen is expressed along the normal differentiation of CFU-GM to monocytes.

Protein kinase C isoforms in normal and chronic myeloid leukemic neutrophils. Distinct signal for PKC alpha by immunodetection on PVDF membrane, decreased expression of PKC alpha and increased expression of PKC delta in leukemic neutrophils

Neutrophils from patients with Chronic Myeloid Leukemia (CML) exhibit defects in several functions. They also show altered phosphorylation-dephosphorylation patterns of several proteins on stimulation with phorbol myristate acetate--a direct activator of protein kinase C (PKC). Since PKC mediates several functions of the neutrophil, in this study we investigate the PKC isoform profile and subcellular distribution in normal and CML neutrophils in an attempt to elucidate their role in CML signalling. Our results show the presence of PKC alpha, betaI, betaII and delta in both the cell types. A distinct and clear signal was obtained for PKC alpha, the isoform reported to be absent or present in very low amounts in normal neutrophils. In addition, PKC alpha was present in significantly lower levels in CML neutrophils while the PKC delta isoform was found in significantly higher amounts in the CML cytosol as compared to that in normal cells. PKC alpha, betaI, betaII and delta isoforms could not be detected in the nucleus of unstimulated normal and CML neutrophils. The altered levels of PKC alpha and delta may be one of the causes for the defects in function exhibited by the leukemic cells.

Expression and modulation of the Lewis x antigen (CD15) on the T cell line Molt-4

The T cell lines Molt-4 and H9 exhibited a characteristic distribution of the cell adhesion molecule Lewis x (CD15, lacto-N-fucopentanose III) showing an unusually broad peak by flow cytometry ranging from cells without CD15 to cells with high expression. The cytokines IL-1, IL-2, IFN-beta, IFN-gamma, and TNF-alpha, known to activate T cells, did not affect CD15 expression. However, phorbol myristate acetate and the thymic peptide extract Thymex-L were able to enhance both the number of CD15-positive cells and the median fluorescence. The effects of both inducers were dose- and time-dependent. An additive or synergistic effect was not seen. These data suggest that phorbol esters and distinct thymic peptides can modulate the expression of the cell surface antigen CD15.