Search

Imatinib is actively transported by organic cation transporter-1 (OCT-1) influx transporter, and low OCT-1 activity in diagnostic chronic myeloid leukemia blood mononuclear cells is significantly associated with poor molecular response to imatinib. Herein we report that, in diagnostic chronic myeloid leukemia mononuclear cells and BCR-ABL1 + cell lines, peroxisome proliferator-activated receptor γ agonists (GW1929, rosiglitazone, pioglitazone) significantly decrease OCT-1 activity; conversely, peroxisome proliferator-activated receptor γ antagonists (GW9662, T0070907) increase OCT-1 activity. Importantly, these effects can lead to corresponding changes in sensitivity to BCR-ABL kinase inhibition. Results were confirmed in peroxisome proliferator-activated receptor γ-transduced K562 cells. Furthermore, we identified a strong negative correlation between OCT-1 activity and peroxisome proliferator-activated receptor γ transcriptional activity in diagnostic chronic myeloid leukemia patients (n=84; P <0.0001), suggesting that peroxisome proliferator-activated receptor γ activation has a negative impact on the intracellular uptake of imatinib and consequent BCR-ABL kinase inhibition. The inter-patient variability of peroxisome proliferator-activated receptor γ activation likely accounts for the heterogeneity observed in patient OCT-1 activity at diagnosis. Recently, the peroxisome proliferator-activated receptor γ agonist pioglitazone was reported to act synergistically with imatinib, targeting the residual chronic myeloid leukemia stem cell pool. Our findings suggest that peroxisome proliferator-activated receptor γ ligands have differential effects on circulating mononuclear cells compared to stem cells. Since the effect of peroxisome proliferator-activated receptor γ activation on imatinib uptake in mononuclear cells may counteract the clinical benefit of this activation in stem cells, caution should be applied when combining these therapies, especially in patients with high peroxisome proliferator-activated receptor γ transcriptional activity., (Copyright© Ferrata Storti Foundation.)

ALOX5 is implicated in chronic myeloid leukemia development in mouse leukemic stem cells, but its importance in human chronic myeloid leukemia is unknown. Functional ALOX5 was assessed using an LTB4 ELISA and ALOX5, and LTB4R1 mRNA expression was determined via a TaqMan gene expression assay. LTB4R1 and 5-LOX protein levels were assessed by cell surface flow cytometry analysis. At diagnosis ALOX5 was below normal in both blood and CD34(+) stem cells in all patients. On treatment initiation, ALOX5 levels increased in all patients except those who were destined to progress subsequently to blast crisis. LTB4 levels were increased despite low ALOX5 expression, suggesting that the arachidonic acid pathway is functioning normally up to the point of LTB4 production. However, the LTB4 receptor (BLT1) protein in newly diagnosed patients was significantly lower than after a period of treatment (P<0.0001). The low level of LTB4R1 at diagnosis explains the downregulation of ALOX5. In the absence of LTB4R1, the arachidonic acid pathway intermediates (5-HEPTE and LTA4) negatively regulate ALOX5. ALOX5 regulation is aberrant in chronic myeloid leukemia patients and may not be important for the development of the disease. Our data suggest caution when extrapolating mouse model data into human chronic myeloid leukemia., (Copyright© Ferrata Storti Foundation.)

Radotinib (IY5511HCL), a novel and selective BCR-ABL1 tyrosine kinase inhibitor, has shown pre-clinical and phase I activity and safety in chronic myeloid leukemia. This phase II study investigated the efficacy and safety of radotinib in Philadelphia chromosome-positive chronic phase-chronic myeloid leukemia patients with resistance and/or intolerance to BCR-ABL1 tyrosine kinase inhibitors. Patients received radotinib 400 mg twice daily for 12 cycles based on results from the phase I trial. The primary end point was rate of major cytogenetic response by 12 months. A total of 77 patients were enrolled. Major cytogenetic response was achieved in 50 (65%; cumulative 75%) patients, including 36 (47%) patients with complete cytogenetic response by 12 months. Median time to major cytogenetic response and complete cytogenetic response were 85 days and 256 days, respectively. Major cytogenetic response and complete cytogenetic response rates were similar between imatinib-resistant and imatinib-intolerant patients, but were higher in patients without BCR-ABL1 mutations. Overall and progression-free survival rates at 12 months were 96.1% and 86.3%, respectively. All newly-occurring or worsening grade 3/4 hematologic abnormalities included thrombocytopenia (24.7%) and anemia (5.2%); grade 3/4 drug-related non-hematologic adverse events included fatigue (3.9%), asthenia (3.9%), and nausea (2.6%). The most common biochemistry abnormality was hyperbilirubinemia (grade 3/4 23.4%), and 12 of 18 cases were managed with dose modification. Study findings suggest radotinib is effective and well tolerated in chronic phase-chronic myeloid leukemia patients with resistance and/or intolerance to BCR-ABL1 tyrosine kinase inhibitors and may represent a promising alternative for these patients. (clinicaltrials.gov identifier: 01602952)., (Copyright© Ferrata Storti Foundation.)

The BCR-ABL T315I mutation confers resistance to currently licensed tyrosine kinase inhibitors in chronic myelogenous leukemia. However, the impact of this mutation on survival in early stages of disease, in chronic phase, has never been detailed. Using matched pair analysis, a cohort of 64 patients with chronic phase chronic myelogenous leukemia harboring a T315I mutation and resistant to imatinib mesylate was compared to a similar cohort of 53 chronic phase patients resistant to imatinib, but with no detectable T315I mutation, in the pre-ponatinib era. These patients were matched according to age at diagnosis, interval between disease diagnosis and start of imatinib treatment, and duration of imatinib therapy. Kaplan-Meier survival analyses demonstrated the significant negative impact of the presence of the T315I mutation on overall survival (since imatinib-resistance: 48.4 months for T315I(+) patients versus not reached for T315I(-) ones; P=0.006) and failure-free survival (since imatinib-resistance: 34.7 months for T315I(+) patients versus not reached for T315I(-) patients; P=0.003). In addition, Cox proportional hazard models adjusted on overall survival demonstrated the negative influence of the T315I mutation (P=0.02, HR=2.54). These results confirm early assumptions concerning the poor prognosis of chronic phase chronic myelogenous leukemia patients with the T315I mutation who are not eligible for allogeneic transplantation, and demonstrate the need for more therapeutic options.

Before the introduction of imatinib, interferon alpha-based regimens were the gold standard for treatment of early chronic phase chronic myeloid leukemia patients. The combination of IFN-alpha with imatinib is currently being investigated in at least two large clinical trials, the German CML Study IV and the French SPIRIT trial. We reviewed the cytogenetic and molecular responses of 76 early chronic phase chronic myeloid leukemia patients who were treated with imatinib and interferon-alpha and of 419 early chronic phase chronic myeloid leukemia patients treated with imatinib alone front-line. The complete cytogenetic response rate was higher in the IM+IFN-alpha group than in the imatinib group at six months (60% vs. 42%; P=0.003), but not at 48 months (88% vs. 88%). The durability of the complete cytogenetic response was similar in the two groups with 94% and 91% of complete cytogenetic responders in continuous complete cytogenetic response at 48 months (P=0.56). The major molecular response rate was higher in the IM+IFN-alpha group at six months (58% vs. 34%; P=0.0001) and 12 months (67% vs. 47%; P=0.001) but not later on (65% vs. 57% at 48 months; P=0.25). Overall and progression free survival were comparable in the two groups; a significant trend to a better event free survival was observed in patients treated with PegIFNalpha (91% vs. 78%; P=0.02). These data suggest that the response to the combination treatment is more rapid. It is not yet known how much a rapid reduction will influence the longer-term overall and progression free survival, and the cure rate.

Here we describe how we detected the BCR/ABL fusion gene on the short arm of der(9) combining classical GTG banding and Fluorescence In Situ Hybridization (FISH) in a case of chronic myeloid leukemia (CML). To our knowledge, variant translocations involving the short arm of chromosome 9, in literature, are almost rare in chronic myeloid leukemia. It is not clear if this complex genetic translocation represents clonal evolution or a unique, initial presentation variant of the Philadelphia chromosome (Ph).