Biotherapy of chronic myelogenous leukemia

Effects of chemotherapy (busulfan-hydroxyurea) and interferon-alfa on bone marrow morphologic features in chronic myelogenous leukemia. Histochemical and morphometric study on sequential trephine biopsy specimens with special emphasis on dynamic features

We performed a retrospective clinicopathologic study on sequential biopsy specimens from 90 patients with Philadelphia chromosome-positive chronic myelogenous leukemia to study therapy-specific effects of busulfan (28 patients), hydroxyurea (32 patients), and interferon-alfa (IFN-alfa; 30 patients). Bone marrow specimens were evaluated by morphometry after silver impregnation and staining with monoclonal antibodies to identify reticulin fibers, nucleated erythroid precursors, megakaryocytes, and macrophages. To compute dynamics of histopathology implicating corresponding changes in time, relevant indices were calculated. Quantification of megakaryocytopoiesis and its precursor cell population showed a significant increase in the IFN-alfa and busulfan groups compared with the hydroxyurea group. These changes were associated with a development of myelofibrosis during therapy. Although a significant increase in fiber density was detectable in the busulfan group, the progression index proved to be twice as high after IFN-alfa therapy. In contrast, a considerable number of patients displayed a regression of myelofibrosis after hydroxyurea treatment. The general association of the megakaryocyte lineage with myelofibrosis was in line with experimental findings. The mature macrophage population and its activated subfraction revealed a marked proliferation (IFN-alfa group) during treatment. Growth and activation of macrophages may be compatible with their putative function during erythrocytopoietic regeneration and with stimulation of their phagocytic properties.

Interferon alpha2b directly induces fibroblast proliferation and transforming growth factor beta secretion of macrophages

To elucidate the effects of interferon alpha2b (IFN-alpha) on normal human bone marrow, fibroblasts from patients without haematopoietic pathology were cultivated and used in stimulation experiments. Further, co-cultures with highly enriched fractions of megakaryocytes and bone marrow macrophages were analysed. In this context, the influence of cell-to-cell interactions and humoral factors was determined in transwell and neutralization studies. Finally, secretion of platelet-derived growth factor (PDGF) and transforming growth factor beta1 (TGF-beta1) by single megakaryocytes and macrophages was examined by using the reverse haemolytic plaque assay (RHPA). Following these experimental designs, a direct proliferative activity of IFN-alpha on bone marrow fibroblasts could be demonstrated. In the unstimulated co-cultures, the megakaryocyte- but not the macrophage-enriched fraction induced fibroblast growth and [3H]-thymidine uptake. This effect was dependent on cell-to-cell contact and also on the influence of TGF-beta and PDGF. In the megakaryocyte-enriched co-cultures, the fibroblast proliferation was not altered by IFN-alpha, but in the macrophage fibroblast cultures addition of IFN-alpha enhanced fibroblast growth and [3H]-thymidine uptake was distinctively higher than in the monocultures. This effect was not obvious in the transwell or neutralization experiments. Finally, IFN-alpha treatment exerted a significantly elevated TGF-beta1 secretion in single macrophages. Our findings are in keeping with the assumption that several pathomechanisms participate in IFN-alpha-induced myelofibrosis, including direct and indirect effects.

Detection of the bcr/abl gene in bone marrow macrophages in CML and alterations during interferon therapy--a fluorescence in situ hybridization study on trephine biopsies

A fluorescence in situ hybridization (FISH) study was performed on trephine biopsies of the bone marrow in chronic myelogenous leukaemia (CML) to evaluate the bcr/abl translocation in macrophages before and during interferon (IFN) therapy. Mature macrophages and osteoclasts were identified by the monoclonal antibody PG-M1, which recognizes a fixative-resistant epitope of the CD68 molecule. In contrast to a control group, in 145 of 479 (30 per cent) macrophages of the CML bone marrow, a positive fusion signal was found, together with corresponding translocation sites in the surrounding myeloid cells. In patients following IFN treatment for approximately 12 months and with haematological/cytogenetic remission by clinical standards, this number was reduced to 10 of 136 (9 per cent) macrophages. In addition, the few multinucleated osteoclasts of the untreated CML bone marrow displayed positive translocation spots. This finding supports the hypothesis that stromal macrophages and osteoclasts are of haematogenic stem cell origin. Moreover, clinical remission and reduction of bcr/abl-positive macrophages under IFN therapy lend support to the hypothesis that the presence of malignant stromal macrophages may contribute to the selective expansion of leukaemic precursors and the suppression of normal haematopoiesis in CML.

Influence of interferon-alpha on cytokine expression by the bone marrow microenvironment--impact on treatment of myeloproliferative disorders

Myeloproliferative disorders (MPD) are characterized by several common clinical and biological features, although at the molecular level, each disease entity exhibits distinct abnormalities. IFN-alpha exerts beneficial therapeutic effects in chronic myelogenous leukemia, polycythemia vera and essential thrombocythemia, resulting in control of hematopoietic hyperplasia and, in a minority of patients, in induction of cytogenetic remission. The mechanism of action of IFN-alpha in MPD is poorly defined. Recently published in vitro findings suggest that IFN-alpha interacts with the regulation of hematopoiesis by multiple ways. Its antiproliferative activity is well known for more than a decade, however, substantial growth inhibition is achieved only at relatively high concentrations. Defective adhesion of hematopoietic progenitor cells in CML to bone marrow stromal cells is corrected by IFN-alpha, which might expose CML progenitors to inhibitory cytokines produced by the bone marrow microenvironment. Recent work from our group demonstrated, that IFN-alpha potently interacts with the production of hematopoietic cytokines in bone marrow stromal cells. Expression of stimulatory cytokines, such as GM-CSF, G-CSF, IL-1 and IL-11 is inhibited by IFN-ct, whereas the production of negative regulators, such as IL-1RA and MIP-1 alpha, is stimulated. The combined action of IFN-alpha on paracrine expression of cytokines suggests an indirect antihematopoietic effect, which might contribute to its clinical activity in MPD.

Interferon-alpha and its effects on the cytokine cascade: a pro- and anti-inflammatory cytokine

Interferon-alpha (IFN alpha) has emerged as an important regulator of growth and differentiation, affecting cellular communication and signal transduction pathways as well as immunological control. The efficacy of IFN alpha has been demonstrated in many different diseases of viral, malignant, angiogenic, allergic, inflammatory, and fibrotic origin. Cytokines are pleiotropic and redundant molecules showing a wide variety of biologic functions on various tissues and cells, and several different cytokines exert similar and overlapping functions on certain cells. Data gained in the last years support this view also for IFN alpha. Initially thought to have mainly immunomodulating and proinflammatory effects, recent data suggest that IFN alpha has several anti-inflammatory properties. These newly identified anti-inflammatory and immunosuppressive functions may help to explain some of the IFN mechanisms.

Effect of interferon therapy on bone marrow morphology in chronic myeloid leukemia: a cytochemical and immunohistochemical study of trephine biopsies

The effect of interferon (IFN) therapy on bone marrow features in chronic myeloid leukemia (CML) has been studied on successive trephine biopsies (mean interval 13 +/- 8 months) by cytochemical and immunohistochemical methods in combination with morphometry and in comparison with a control group of patients who received monotherapy by busulfan (BU). Following IFN administration (IFN-alpha frequently in combination with IFN-gamma), there was a decrease in neutrophil granulopoiesis accompanied by a significant expansion of erythroid precursors and increased numbers of hemosiderin-laden macrophages. These changes corresponded with the hematologic response in 21 of the 25 patients investigated. Numbers of megakaryocytes and reticulin/collagen fiber density increased during treatment. Most conspicuously, in responding patients atypical micromegakaryocytes, usually characterizing CML, were partially replaced by normal-sized cells of this lineage. These features are in keeping with the assumption of a reappearance of the normal hematopoietic cell clone as the result of IFN therapy, which was not found in the BU-treated control group. On the other hand, a relevant subpopulation of micromegakaryocytes (about 30%) was still maintained. This result probably relates to the failure to improve myelofibrosis more effectively. Analysis of cell proliferation (proliferating cell nuclear antigen-PCNA) and apoptosis (in situ end labeling) revealed a reduction in PCNA labeling and increased numbers of cells undergoing programmed death. Identification of the activated subset of macrophages (alpha-D-galactosyl residues expression) by appropriate lectin histochemistry disclosed an increase in the number of GSA-I binding cells. These findings were exclusively limited to IFN administration and reflect an inhibitory effect of IFN on cell proliferation and stimulation of programmed cell death. The latter phenomenon probably results in increased phagocytosis of clonally transformed myeloid cells by GSA-I-positive (activated) macrophages.