Effect of retinoic acid and interferon alpha on granulocyte-macrophage colony forming cells in chronic myeloid leukemia: increased inhibition by all-trans- and 13-cis-retinoic acids in advanced stage disease

Phase II study of all-trans retinoic acid in the accelerated phase or early blastic phase of chronic myeloid leukemia: a study of the Eastern Cooperative Oncology Group (E1993)

The aims of this study were to evaluate the safety and efficacy of all-trans retinoic acid (ATRA) in the treatment of the accelerated and blastic phase of chronic myeloid leukemia (CML) and to evaluate in vitro correlates of biological activity. ATRA was administered in an intermittent schedule to patients with CML in the accelerated or blastic phases for a 6 week induction period, which was continued if there was evidence of clinical response or stable disease. If the patient was progressing at 6 weeks, interferon-alpha could be added to the ATRA. Laboratory correlative studies were performed prior to treatment and at intervals during treatment to evaluate effects on maturation and differentiation, and on CML progenitor cell growth by assessment of colony-forming cells (CFC). Eighteen patients were enrolled. There was 1 complete response, 1 partial response and 2 with hematological improvement. A fifth patient was stable on ATRA and interferon for several months. Laboratory data for the responders demonstrated high sensitivity of primary CFC to ATRA prior to treatment and low serial CFC counts on ATRA therapy. ATRA demonstrated clinical and hematological activity in 5 of 18 patients with the accelerated phase of CML, and there was evidence of a biological effect in laboratory studies of 3 of the 5 patients' progenitor cells. Combination therapy with other differentiating agents may be useful in this disease.

Chronic myelogenous leukemia: elements of conventional chemotherapy and an overview of autografting in the treatment of the chronic phase

Chronic myelogenous leukemia (CML) consists of a clonal malignancy that arises from a pluripotent hematopoietic stem call. In most cases, neoplastic cells are characterized by the formation of a shortened chromosome 22 called the Philadelphia chromosome. It results from a reciprocal translocation between long arms of chromosomes 9 and 22. A rearranged gene (bcr-abl) is the consequence of this translocation, and it may be considered as the first step toward leukemic transformation. Conventional chemotherapy of CML in the chronic phase is unable to suppress the Ph+ leukemic clone. The treatment with the IFNalpha may induce an overall cytogenetic response rate of 40-50% of patients. Autografting for patients with CML in chronic phase may induce a 53% overall cytogenetic response rate with a duration of disease-free time and survival from the autograft ranging, respectively, from 4 to 24 mo and from 8 to 40 mo.

AraC-based pharmacotherapy of chronic myeloid leukaemia

In interferon-alpha (IFN) treated chronic phase chronic myeloid leukaemia (CML) patients, survival depends on individual risk profile and achievement of a complete haematological response (CHR) and a major cytogenetic response (MCR) (< 35% Philadelphia-chromosome-positive metaphases). The highest cytogenetic response rates have been achieved with the combination of IFN and low-dose sc. AraC (10 mg daily to 10-20 mg/m2 for 10-14 days/month). Whether the higher cytogenetic response rates are also associated with a significant improvement of survival still remains controversial. The different results obtained from large randomised and observational trials may be due to the numbers of patients enrolled, distribution of risk profiles and the treatment schedule, which is influenced greatly by the haematological and gastrointestinal toxicity of AraC. An oral formulation (YNK01), which is lipophilic and resistant to deamination, is currently under investigation. Clinically, it has similar activity, but toxicity leads to discontinuation of treatment in a considerable proportion of patients. The clinical benefits may therefore be outweighed by the dose-limiting toxicity for both application forms. Combinations with other drugs, e.g., STI571 or homoharringtonine, have shown promising early results in vitro and in vivo.

Growth advantage of chronic myeloid leukemia CFU-GM in vitro: survival to growth factor deprivation, possibly related to autocrine stimulation, is a more common feature than hypersensitivity to GM-CSF/IL3 and is efficiently counteracted by retinoids +- alpha-interferon

Bcr/abl fusion gene, in experimental models, induces survival to growth factor deprivation and hypersensitivity to IL3. However, conflicting data were reported about chronic myeloid leukemia (CML) progenitors. We investigated the responsiveness of purified CML CFU-GM to GM-CSF/IL3 and their survival to growth factor deprivation. CFU-GM hypersensitivity to IL3 and/or GM-CSF was found in 3/11 CML cases only. CML CFU-GM survived well in stroma-free 'mass' culture (5 x 10(4) cells/ml) without cytokine addition, up to day 11, average recovery being around 95% in medium + 10% fetal bovine serum and 67-81% in serum-free medium. Conversely, normal progenitors declined steadily, particularly after extensive purification (18 +/- 10% recovery at the 7th day), and in serum-free medium (4 +/- 6% recovery). By contrast, normal and CML CFU-GM declined in a similar way in limiting dilution cultures (1-10 cells/50 microl). We also investigated the effects of retinoic acid and alpha-interferon on CFU-GM survival. Both all-trans- and 13-cis retinoic acid, particularly in combination with alpha-interferon, reduced CML CFU-GM recovery down to normal progenitors' values. In conclusion, hypersensitivity to CSFs is rare in CML, whereas resistance to growth factor deprivation has been confirmed in mass, but not in limiting, dilution cultures. Both stereoisomers of retinoic acid, at therapeutic concentrations and in combination with alpha-interferon, can overcome the survival advantage of CML progenitors.

Unexpected high incidence of severe toxicities associated with alpha interferon, low-dose cytosine arabinoside and all-trans retinoic acid in patients with chronic myelogenous leukemia

Preclinical data have shown that all-trans retinoic acid (ATRA) with interferon-alpha (IFN-alpha) can exert significant suppressive effects on Philadelphia-chromosome (Ph)-positive cells. The aim of this study combining IFN-alpha, low-dose cytosine arabinoside (ara-C) and ATRA was to increase the proportion of patients achieving a major cytogenetic response, in comparison with a group of 140 patients previously treated with IFN-alpha plus low-dose ara-C. Forty three patients with Ph-positive CML in early chronic phase were treated with IFN-alpha 5 MU/m2 s.c. daily, low-dose ara-C 10 mg s.c. daily and ATRA 45 mg/m2 orally daily, for 7 consecutive days every other week. Overall, 76% of patients achieved a complete hematologic response (CHR). A cytogenetic response was in observed 59% (major in 38% and complete in 17%). Compared with patients treated with IFN-alpha and low-dose ara-C, those receiving additional ATRA had a lower CHR rate (p. 014), but other response rates were similar. Severe toxicities were common with the triple regimen (64%), mostly related to ATRA therapy. Two patients experienced pseudotumor cerebri; two patients had leukocytosis during the week on ATRA treatment, decreasing during the week off (one suffered a severe asthma-like reaction followed by pulmonary edema, resembling ATRA syndrome). Six patients had other unusual side-effects: aseptic necrosis of the hip (1 patient), ataxic syndrome (1 patient), paranoid syndrome (2 patients), syncopal episodes (1 patient), pure red cell aplasia (1 patient). In conclusion the results of IFN-alpha and low-dose ara-C combined with ATRA in patients with early CML-chronic phase were disappointing, due to excessive toxicity. Whether different ATRA dose schedules may result in fewer side-effects and improve hematologic and cytogenetic response remains to be determined.

Detection of BCR-ABL transcripts in chronic myeloid leukaemia by nested PCR

Polymerase chain reaction (PCR) is a powerful and rapid method for specifically detecting BCR-ABL rearrangement by amplification of the complementary DNA (cDNA) produced by reverse transcription of BCR-ABL mRNA. We studied 29 patients for detecting the presence of BCR-ABL transcripts before and after bone marrow transplantation (BMT). Our sample was composed of two different groups of patients: one group (n = 18) was studied by serial follow-ups before and after BMT; a second group (n = 11) was studied several years after BMT. Detection of BCR-ABL was carried out with different primer sets at different periods of the clinical outcome of chronic myeloid leukaemia (CML). A comparison of PCR data and clinical-haematological conditions showed clear differences between patients. In the first group, eight patients showed a positive correlation between a favourable clinical outcome and molecular remission. Conversely, in the second group, six patients were BCR-ABL positive between 20 and 117 months after BMT, while only two of these patients showed signs of clinical relapse. Among all patients whose isoforms were known at some time during the course of CML, the more frequent isoform was b3a2. These results were compared to previous findings in the literature on diagnosis, outcome and prognosis of CML.

Novel biologic approaches to hematologic malignancies

Biologic agents have made a major impact on the treatment of hematologic malignancies and will continue to play a major role as we better understand their function in normal and malignant cell regulation. The examples provided in this chapter are a brief introduction to the potential of these agents. Many have yet to be used in conjunction with current cytotoxic therapy in these diseases, and perhaps combinations will prove even more successful. This possibility provides substantial ground for further investigation and therapy.

All-trans retinoic acid combined with interferon-alpha effectively inhibits granulocyte-macrophage colony formation in chronic myeloid leukemia

We investigated the effect of all-trans retinoic acid (ATRA) alone and in combination with interferon-alpha (IFN-alpha) on the granulocyte-macrophage (GM) colony formation of peripheral blood progenitors isolated from patients with chronic myeloid leukemia (CML) (n = 12) or other myeloproliferative disorders (n = 10) as well as from healthy controls (n = 7). The ATRA or IFN-alpha alone inhibited slightly, but not significantly, the GM colony growth in CML. Granulocyte-macrophage colony formation decreased significantly (P<0.05) when ATRA and IFN-alpha were combined (114 +/- 96 versus 74 +/- 53 colonies/10(4) mononuclear cells). The combination did not have any inhibitory effect on the other MPDs. In healthy controls, ATRA or IFN-alpha alone or their combination stimulated GM colony growth, the increase being from 22 +/- 9 to 39 +/- 16 colonies for ATRA (P<0.05), up to 47 +/- 12 colonies for IFN-alpha (P<0.05) and up to 50 +/- 19 colonies for the combination (P<0.05). In conclusion, ATRA combined with IFN-alpha inhibits GM colony growth in CML. This combination may be worth testing clinically as a treatment of CML.