A differential sensitivity to recombinant human interferon-alpha 2a between normal and chronic myeloid leukaemic peripheral blood granulocyte-macrophage colony-forming units

Retroviral coexpression of IFN-alpha and IFN-gamma genes and inhibitory effects in chronic myeloid leukemia cells

Interferon (IFN) is an effective treatment for chronic myeloid leukemia (CML) in chronic phases, and a number of in vitro antileukemic effects of IFN on CML cells have been reported. The transfer of cytokine genes into tumor cells is reportedly a valuable approach to improve the antitumor activity of cytokines in various models. We first investigated the possibility of transducing CML cells with the retroviral vectors LIalpha2SN and LIgammaSN, encoding the IFN-alpha2 and IFN-gamma genes, respectively, and with the bicistronic vector LIalpha2IrIgammaSN coexpressing the IFN-alpha2 and IFN-gamma genes. We then analyzed the effects of IFN-alpha2 and IFN-gamma produced alone or simultaneously on the proliferation of CML cells. We optimized the transduction efficiency by using the CML-derived K562 cell line. We then introduced IFN genes into CML CD34+ cells. Secretion of IFN-alpha and IFN-gamma was demonstrated in K562 and CML CD34+ cells transduced with the different vectors. The MHC class I antigens were overexpressed in both K562 and CML CD34+ transduced cells. Inhibition of the proliferation of LIalpha2IrIgammaSN-transduced CML cells was greater than with the LIalpha2SN and the LIgammaSN-transduced CML cells. We demonstrate an additive effect of IFN-alpha and IFN-gamma on the inhibition of K562 and CML CD34+ cell proliferation.

Differential effect of interferon alpha on chronic myelogenous leukaemia and normal haematopoietic progenitors in a stromal cell co-culture context: role of the flt3 ligand

Interferon alpha (IFN-alpha) is used to treat chronic myelogenous leukaemia (CML) patients. However, its target(s) remain(s) unknown. One possibility is that there is a differing sensitivity of the leukaemic from the normal colony-forming cell (CFC) compartments to IFN-alpha. Co-cultures of progenitors with stromal cells provide a valuable tool to dissect direct and indirect activities of IFN-alpha. In this study, we have used endothelial cells (EC) as a source of stromal cells. In co-cultures of normal progenitors with EC, IFN-alpha increased the generation of clonogenic cells, mainly via an increased production of flt3 ligand (FL) by EC. In contrast, in co-cultures of CML progenitors with EC, IFN-alpha inhibited the generation of clonogenic cells, mainly by direct inhibition on the progenitors, the up-regulation of FL production by stromal cells being unable to compensate for the direct inhibitory effects of IFN-alpha. These data provide evidence for a differential effect of IFN-alpha on the growth of CML and normal CFC cells in a stromal context and suggest that an alteration in the response of CML progenitor cells to FL is important in the explanation of this differential effect.

New drugs in essential thrombocythemia and polycythemia vera

Among the chronic myeloproliferative disorders, polycythemia vera and essential thrombocythemia are unique because of their association with thrombohemorrhagic manifestations and their relatively indolent clinical course. Patients with essential thrombocythemia may not have a significant shortening of life-expectancy and most may not require specific therapy. However, patients with polycythemia vera have a significant risk of transformation of polycythemia vera into acute leukemia or postpolycythemic myelofibrosis (or both). 'High-risk-for-thrombosis' patients with either polycythemia vera or essential thrombocythemia require specific therapy with a platelet-lowering agent to prevent thrombotic complications. Currently, the standard agent used for this is hydroxyurea. However, its tetratogenic and leukemogenic potential has been of concern. As a result, new platelet-lowering agents are being evaluated in the treatment of polycythemia vera and essential thrombocythemia. Anagrelide and interferon alfa are two such agents and have been shown to be effective in reducing platelet counts in patients with chronic myeloproliferative disorders. The putative mechanism of action of these drugs, their specific activity in polycythemia vera and essential thrombocythemia, side-effect profile, and current indications are discussed herein.

Biotherapy of chronic myelogenous leukemia

The aim of this review is to summarize the current knowledge on the clinical results of biotherapy of chronic myelogenous leukemia (CML) and potential mechanisms of the antitumor action of interferon alpha. IFN alpha treatment induces hematologic and cytogenetic remissions in patients with chronic phase CML. In addition, the duration of the chronic phase is prolonged by IFN alpha resulting in a significant survival benefit. In two randomized clinical trials this survival benefit was demonstrated in all chronic phase CML patients independent of their risk scores. Moreover, IFN treatment also delays the onset of clinical relapse after allogeneic bone marrow transplantation. The critical mechanisms of IFN action have not yet been identified. Both direct and indirect antiproliferative mechanisms have been described. In particular, differential regulation of growth promoting and growth inhibiting cytokines represents an attractive hypothetical mechanism of IFN action. Nevertheless, no leukemia specific IFN activities explaining cytogenetic remissions and/or delay of disease progression have been identified. Further research on that field are required to further improve biological CML therapies.

Modulation of growth and differentiation of eosinophils from human peripheral blood CD34+ cells by IL5 and other growth factors

Small numbers of CD34+ primitive hematopoietic progenitors are found in normal human peripheral blood. These cells differentiate to myeloid or lymphoid lineage under the influence of different growth factors. We investigated the effects of IL5 and other growth factors on the production of eosinophils from peripheral blood CD34+ cells. CD34+ cells were enriched from normal donors by apheresis and positive selection using an affinity column and plated in agarose with different combinations of cytokines. At 14 days of growth a triple stain technique was used to identify eosinophil, monocyte, and neutrophil colonies. IL5 alone did not support colony growth from CD34+ cells. In contrast, GM-CSF and IL3 alone or together without added IL5 supported the generation of more than 50% pure eosinophil colonies. Addition of IL5 did not change the total number of colonies, but increased the fraction of pure eosinophil colonies to over 70%. Addition of G-CSF reduced the percentage of eosinophil colonies and increased the percentage of neutrophil colonies. Under the best conditions for eosinophil colony growth (IL3+GM-CSF+IL5), the addition of interferon-alpha or bacterial lipopolysaccharide inhibited colony growth by 51 and 58%, respectively. Addition of interferon-gamma, tumor necrosis factor-alpha, or dexamethasone had no effect on eosinophil colonies. Since IL5 alone did not support colony growth from CD34+ cells, we determined when IL5-responsive cells appeared in culture. Cells were grown initially with IL3 + GM-CSF in suspension, washed, and plated in agarose with IL5 alone. Only when progenitors were grown at least 3 days could IL5 serve as the single growth factor supporting pure eosinophil colony growth (47 colonies/10(4) cells plated at Day 3 and 134 colonies/10(4) cells at Day 7). We used neutralizing anti-IL5 antibodies to demonstrate that this late acting IL5 growth effect was specific, and that differentiation of eosinophils in the presence of IL3 + GM-CSF was IL5 independent. Using reverse-transcriptase polymerase chain reaction, the mRNA encoding the eosinophil-specific protein eosinophil peroxidase (EPO) was not detected in Day 0 CD34+ cells, but was demonstrated by Day 3 of culture. We conclude that within 3 days of culture, peripheral blood CD34+ cells can become committed to the eosinophil lineage as demonstrated by responsiveness to IL5 and production of EPO transcripts.

Interferon-alpha-induced biologic modifications in patients with chronic myelogenous leukemia

Serum neopterin (Np), beta 2-microglobulin (beta 2-M), and 2',5'-adenylate (2',5'A) levels and intracellular 2',5'A and human Mx (Hu-Mx) protein synthesis were measured in 20-24 chronic myeloid leukemia patients before and during 1 year of IFN-alpha treatment and in a further 8-9 patients before and at the end of the first and second treatment weeks only. Univariate analysis showed that IFN-alpha increased Np and 2',5'A serum levels and intracellular concentrations of 2',5'A and Hu-Mx significantly from the end of the first week to month 12 of therapy. The biologic marker profiles were similar in cytogenetic responders and nonresponders, as well as in patients treated with IFN-alpha early (< 12 months from diagnosis) or late (after > 12 months standard chemotherapy). Further, there were no differences in the short-term (first 14 days) or long-term (during 12 month therapy) induction of the biologic markers irrespective of whether IFN-alpha 2a or IFN-alpha 2b was given. Because multivariate analysis revealed no significant interactions between cytogenetic response, time to treatment, and type of IFN-alpha used, increments in intracellular 2',5'A and Hu-Mx protein were similar at all study times for all factor combinations tested. Np levels varied significantly only during the first 14 therapy days; changes in serum 2',5'A were never statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction of 2-chlorodeoxyadenosine (2-CDA) and interferon alpha (IFN-alpha) on normal and myeloid leukemia hematopoiesis in vitro

The influence of 2-CDA and interferon alpha (IFN-alpha) on the CFU-GM cells from ten normal individuals as well as on the CFU-GM from ten patients with chronic myeloid leukemia (CML) and on clonogenic leukemic blasts (CFU-L) from ten patients with acute myeloid leukemia (AML) in semi-solid cultures in vitro was investigated. The agents were added to the cultures alone and in combinations at concentrations of 20, 40 and 80 nM/l of 2-CDA and 10(2), 10(3) and 10(4) U/ml of IFN-alpha. A dose-dependent growth inhibition of CFU-GM as well as of CFU-L was observed. The inhibitory effect of both drugs used alone was significantly greater on the CFU-GM cells from patients with CML than on cells from normal donors. However, 2-CDA and IFN-alpha used together showed greater additive effect on the CFU-L than on the CFU-GM from normal donors and from CML patients.

Clonogenic assay is not predictive but reflects therapeutic efficacy of interferons in the treatment of chronic myelogenous leukemia

Patients with chronic myelogenous leukemia (CML) have been treated with interferon (IFN) alpha-2b alone or in combination with IFN gamma. In order to predict clinical response to IFN, bone marrow samples from 15 CML patients were incubated with serial dilutions of IFN alpha-2b to obtain the IC50 values for erythroid burst forming units (BFU-E) and granulocyte-macrophage colony forming units (CFU-GM). A dose-dependent inhibition of at least one lineage was observed in all but one sample. An inhibitory effect of greater than 50% was reached for BFU-E in 8/14 patients and for CFU-GM in 10/14 patients. All three patients with no response (NR) to IFN treatment had IFN-sensitive BFU-E and CFU-GM. In four patients with hematologic remission (HR) or partial hematologic remission (PHR), BFU-E or CFU-GM were affected very little by the inhibitory effect of IFN. These observations suggest no predictive value for pretesting IFN sensitivity in vitro. The in vivo effect of IFN on the hemopoietic progenitor cells BFU-E and CFU-GM was evaluated in patients treated with either IFN alpha-2b alone (n = 11), or in combination with low dose IFN gamma (n = 10). All patients were newly diagnosed and not pretreated. After a median treatment duration of 11 months (range 3-25) a significant decrease in BFU-E and CFU-GM was observed in both groups of patients. We conclude that in vitro colony growth reflects the therapeutic efficacy of IFN.