Fibroblast nemosis arrests growth and induces differentiation of human leukemia cells.

Interactive signaling between cancer cells and stroma plays an important role in determining tumor development. We recently found tumor cell-derived factors to induce fibroblast clustering, and that the high amounts of hepatocyte growth factor/scatter factor (HGF/SF) produced by these cell-cell contact-activated fibroblasts enhanced the invasiveness of c-Met-expressing cancer cells. We now observed that leukemia cells lacking c-Met respond to this novel type of fibroblast activation, nemosis, with growth arrest and differentiation to a dendritic cell-like phenotype. This effect was counteracted by introduction of c-Met expression into these cells. Moreover, those leukemia cell lines harboring properly processed c-Met showed no effect in response to nemosis. We propose this effect to be mediated by nemosis-derived cytokine signals, and present the potential candidates induced in the nemotic fibroblasts: interleukins-1, -6, -8, -11, leukemia inhibitory factor and granulocyte-macrophage-colony-stimulating factor. Our results emphasize the role of activated stromal fibroblasts in controlling progression of certain hematologic malignancies in a c-Met expression-dependent manner.

Hematogones in acute leukemia during and after therapy.

After each leukemia therapy phase, characteristics of normal regenerating B-cells may be reminiscent of and mistaken for a relapse. We compared the incidence and phenotypic characteristics of hematogone stages in a total of 669 bone marrow aspirates from 107 patients with B-ALL, 97 patients of AML, and 27 patients with T-ALL at diagnosis, during, and after therapy. The three individual physiological maturation phases of B-lymphocytes (hematogone stages 1, 2, and 3) were studied by four-color flow cytometry in the course of bone marrow regeneration in leukemia patients. Multiple stages of hematogones were observed twice as frequently in B-ALL (73.8%) and T-ALL (69.2%) samples as in AML aspirates (34.1%). Stage 3 hematogones were found usually in children and were thus frequent in B-ALL. The hematogones had an extremely high phenotypic stability unaffected by disease or therapy or by their coincidence with leukemia cells.