Christian Binet

The Role of Platelet/Endothelial Cell Adhesion Molecule–1 (CD31) and CD38 Antigens in Marrow Microenvironmental Retention of Acute Myelogenous Leukemia Cells

In acute myelogenous leukemia (AML), leukemic cell-microenvironment interactions within various niches (stromal/osteoblastic or sinusoidal endothelial cell niches) have a role in leukemia cell survival and drug resistance. The AML leukemic cells express platelet/endothelial cell adhesion molecule-1 (CD31) and CD38, two adhesion molecules that could interact with microenvironmental elements, i.e., CD31 on the surface of marrow endothelial cells (CD31/CD31 and CD38/CD31 interactions) and hyaluronate (CD38/hyaluronate interactions). We report a physical association of these two antigens on the plasma membrane of myeloid leukemic cells. In this context, in vitro experiments done using interaction-blocking anti-CD31 and anti-CD38 monoclonal antibodies (CLB-HEC75 and OKT10, respectively) indicate that an excess of CD31 on the cell membrane of leukemic cells (CD31/CD38 MFI ratio >1) promotes a homotypic interaction with marrow endothelial cells, resulting in higher transendothelial migration. Conversely, an excess of CD38 (CD31/CD38 MFI ratio <1) allows leukemic cells to be entrapped within the bone marrow microenvironment through hyaluronate adhesion. The results obtained in vitro using fluorescence resonance energy transfer, co-capping, and co-immunoprecipitation experiments, and hyaluronate adhesion and transendothelial migration assays, are supported by immunophenotypic characterization of marrow leukemic cells from 78 AML patients on which CD38 expression levels were found to be positively correlated with those of CD31. Importantly, the excess of CD31 in those samples was associated with a higher peripheral WBC count. These findings indicate that bone marrow retention of AML cells depends on CD31 and CD38 coexpression levels.

Cytokines released in vitro by stromal cells from autologous bone marrow transplant patients with lymphoid malignancy

Abstract: Marrow stromal cells of patients treated by autologous bone marrow transplantation (ABMT) for malignancies have been assessed for their ability to secrete granulocyte colony‐stimulating factor (G–CSF), granulocyte‐macrophage colony‐stimulating factor (GM–CSF), stem cell factor (SCF), leukemia inhibitory factor (LIF), interleukin‐6 (IL‐6), transforming growth factor β1 (TGFβ1) and macrophage inflammatory protein‐1α (MIP‐1α). Long‐term marrow cultures were established from 10 patients prior to and 3 months after ABMT, from 7 patients 1 yr after ABMT and from 11 controls. Cytokines in culture supernatants of stromal layers (SL) were evaluated by enzyme‐linked immunosorbent assay (ELISA). Significant differences between patient groups and controls were apparent in baseline production of GM–CSF, SCF, MlP‐1α and TGFβ1. After IL‐1β addition in cultures, G–CSF production was reduced in pretransplant and post‐transplant patients compared to controls. The production of TGFβ1, LIF, IL‐6 and more particularly SCF were reduced in post‐transplant patients, while elevated levels of GM–CSF and MIP‐1α were observed in these patients only when the values were corrected for the number of cells growing in the SL. These results indicate a prolonged stromal defect in growth factor production following ABMT for the early‐stage acting cytokines IL‐6, LIF and SCF as well as for G–CSF, but not for GM–CSF, while the production of the 2 inhibitors shows different pathways.

In vitro effect of stem cell factor on human clonogenic marrow progenitors after myeloablative treatments

Abstract: Abnormal hematopoiesis, including a deficiency of marrow progenitors and particularly of erythroid progenitors, has been described after autologous stem cell transplantation (ASCT), persisting for several years. In order to explain this deficiency, a resistance of marrow progenitors to stem cell factor (SCF) after ASCT was investigated. Marrow samples were harvested from pregraft patients at graft collection prior to ASCT, transplanted patients 6–24 months after high‐dose therapy and control patients. CD34+ cells were cultured in a serum‐free clonogenic assay with increasing doses of SCF. The clonogenic efficiency without SCF was lower for BFU‐E in treated groups than in controls, whereas it was not different for CFU‐GM. With increasing doses of SCF a dose‐dependent effect was found on the numbers of both CFU–GM and BFU–E in all groups, although the maximal number of BFU–E remained lower in treated groups. However, the SCF dose that induced 50% of maximal BFU–E growth (D50) was similar in all groups. Furthermore, a dose‐dependent effect on the size of BFU–E was found in all groups, with no difference in the proportion of large colonies. Thus, clonogenic erythroid progenitors from patients who have received myelotoxic treatments remain sensitive to SCF, with no evidence for a chemotherapy‐related resistance.