The interplay between telomeric complex members and BCR::ABL1 oncogenic tyrosine kinase in the maintenance of telomere length in chronic myeloid leukemia.

PURPOSE: Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by recurrent genetic aberration in leukemic stem cells, namely Philadelphia chromosome caused by reciprocal translocation t(9;22)(q34;q11). In our study, we analyzed the telomeric complex expression and function in the molecular pathogenesis of CML. METHODS: We employed CD34+ primary leukemic cells, comprising both leukemic stem and progenitor cell populations, isolated from peripheral blood or bone marrow of CML patients in chronic and blastic phase to analyze the telomere length and telomeric-associated proteins. RESULTS: The reduction in telomere length during disease progression was correlated with increased expression of BCR::ABL1 transcript and the dynamic changes were neither associated with the enzymatic activity of telomerase nor with gene copy number and expression of telomerase subunits. Increased expression of BCR::ABL1 was positively correlated with expression of TRF2, RAP1, TPP1, DKC1, TNKS1, and TNKS2 genes. CONCLUSIONS: The dynamics of telomere length changes in CD34+ CML cells is dependent on the expression level of BCR::ABL, which promotes the expression of certain shelterins including RAP1 and TRF2, as well as TNKS, and TNKS2, and results in telomere shortening regardless of telomerase activity. Our results may allow better understanding of the mechanisms responsible for the genomic instability of leukemic cells and CML progression.

Analysis of Predictive Factors for Early Response to Ruxolitinib in 320 Patients with Myelofibrosis From the Polish Adult Leukemia Group (PALG) Registry.

INTRODUCTION: Ruxolitinib is widely used in myelofibrosis (MF). However, some patients do not optimally respond and require more efficacious treatment. Our analysis aimed to establish predictors of ruxolitinib response. PATIENTS AND METHODS: We designed a multicenter, retrospective analysis of the efficacy of ruxolitinib treatment in patients with MF in 15 Polish hematology centers. As responses to ruxolitinib occur within the first 6 months, we used this point to evaluate the efficacy of treatment. Symptoms response was defined as ≥50% reduction of the MF constitutional symptoms assessed by Myeloproliferative Neoplasm Symptom Assessment Form Total Symptom Score (MPN-SAF TSS). Spleen response was defined as ≥50% reduction of the difference between the spleen's baseline length and the upper limit norm measured by ultrasonography. RESULTS: 320 MF patients were enrolled. At 6 months of therapy, the spleen response was detected in 140 (50%) patients, and symptoms response in 241 patients (76%). Multivariable analysis identified leukocytosis <25 G/L (OR 2.06, 95%CI: 1.12-3.88, P = .0200), and reticulin fibrosis MF 1 (OR 2.22, 95%CI: 1.11-4.46, P = .0249) contributed to better spleen response. The time interval between MF diagnosis and ruxolitinib administration shorter than 3 months, and platelets ≥150 G/L (OR 1.69, 95% CI 1.01-2.83, P = .0466) influenced symptoms response. CONCLUSION: Establishing predictive factors for ruxolitinib response is particularly important given the potential for new therapies in MF. In patients with a low likelihood of responding to ruxolitinib, using other JAK inhibitors or adding a drug with a different mechanism of action to ruxolitinib may be of clinical benefit.

Targeting integrated stress response with ISRIB combined with imatinib treatment attenuates RAS/RAF/MAPK and STAT5 signaling and eradicates chronic myeloid leukemia cells.

The integrated stress response (ISR) facilitates cellular adaptation to unfavorable conditions by reprogramming the cellular response. ISR activation was reported in neurological disorders and solid tumors; however, the function of ISR and its role as a possible therapeutic target in hematological malignancies still remain largely unexplored. Previously, we showed that the ISR is activated in chronic myeloid leukemia (CML) cells and correlates with blastic transformation and tyrosine kinase inhibitor (TKI) resistance. Moreover, the ISR was additionally activated in response to imatinib as a type of protective internal signaling. Here, we show that ISR inhibition combined with imatinib treatment sensitized and more effectively eradicated leukemic cells both in vitro and in vivo compared to treatment with single agents. The combined treatment specifically inhibited the STAT5 and RAS/RAF/MEK/ERK pathways, which are recognized as drivers of resistance. Mechanistically, this drug combination attenuated both interacting signaling networks, leading to BCR-ABL1- and ISR-dependent STAT5 activation. Consequently, leukemia engraftment in patient-derived xenograft mice bearing CD34+ TKI-resistant CML blasts carrying PTPN11 mutation responsible for hyperactivation of the RAS/RAF/MAPK and JAK/STAT5 pathways was decreased upon double treatment. This correlated with the downregulation of genes related to the RAS/RAF/MAPK, JAK/STAT5 and stress response pathways and was associated with lower expression of STAT5-target genes regulating proliferation, viability and the stress response. Collectively, these findings highlight the effect of imatinib plus ISRIB in the eradication of leukemic cells resistant to TKIs and suggest potential clinical benefits for leukemia patients with TKI resistance related to RAS/RAF/MAPK or STAT5 signaling. We propose that personalized treatment based on the genetic selection of patients carrying mutations that cause overactivation of the targeted pathways and therefore make their sensitivity to such treatment probable should be considered as a possible future direction in leukemia treatment.

Real-world study of children and young adults with myeloproliferative neoplasms: identifying risks and unmet needs.

Myeloproliferative neoplasms (MPNs) are uncommon in children/young adults. Here, we present data on unselected patients diagnosed before 25 years of age included from 38 centers in 15 countries. Sequential patients were included. We identified 444 patients, with median follow-up 9.7 years (0-47.8). Forty-nine (11.1%) had a history of thrombosis at diagnosis, 49 new thrombotic events were recorded (1.16% patient per year [pt/y]), perihepatic vein thromboses were most frequent (47.6% venous events), and logistic regression identified JAK2V617F mutation (P = .016) and hyperviscosity symptoms (visual disturbances, dizziness, vertigo, headache) as risk factors (P = .040). New hemorrhagic events occurred in 44 patients (9.9%, 1.04% pt/y). Disease transformation occurred in 48 patients (10.9%, 1.13% pt/y), usually to myelofibrosis (7.5%) with splenomegaly as a novel risk factor for transformation in essential thrombocythemia (ET) (P= .000) in logistical regression. Eight deaths (1.8%) were recorded, 3 after allogeneic stem cell transplantation. Concerning conventional risk scores: International Prognostic Score for Essential Thrombocythemia-Thrombosis and new International Prognostic Score for Essential Thrombocythemia-Thrombosis differentiated ET patients in terms of thrombotic risk. Both scores identified high-risk patients with the same median thrombosis-free survival of 28.5 years. No contemporary scores were able to predict survival for young ET or polycythemia vera patients. Our data represents the largest real-world study of MPN patients age < 25 years at diagnosis. Rates of thrombotic events and transformation were higher than expected compared with the previous literature. Our study provides new and reliable information as a basis for prospective studies, trials, and development of harmonized international guidelines for the specific management of young patients with MPN.

Gene expression and mutation-guided synthetic lethality eradicates proliferating and quiescent leukemia cells.

Quiescent and proliferating leukemia cells accumulate highly lethal DNA double-strand breaks that are repaired by 2 major mechanisms: BRCA-dependent homologous recombination and DNA-dependent protein kinase-mediated (DNA-PK-mediated) nonhomologous end-joining, whereas DNA repair pathways mediated by poly(ADP)ribose polymerase 1 (PARP1) serve as backups. Here we have designed a personalized medicine approach called gene expression and mutation analysis (GEMA) to identify BRCA- and DNA-PK-deficient leukemias either directly, using reverse transcription-quantitative PCR, microarrays, and flow cytometry, or indirectly, by the presence of oncogenes such as BCR-ABL1. DNA-PK-deficient quiescent leukemia cells and BRCA/DNA-PK-deficient proliferating leukemia cells were sensitive to PARP1 inhibitors that were administered alone or in combination with current antileukemic drugs. In conclusion, GEMA-guided targeting of PARP1 resulted in dual cellular synthetic lethality in quiescent and proliferating immature leukemia cells, and is thus a potential approach to eradicate leukemia stem and progenitor cells that are responsible for initiation and manifestation of the disease. Further, an analysis of The Cancer Genome Atlas database indicated that this personalized medicine approach could also be applied to treat numerous solid tumors from individual patients.

Treatment adherence in chronic myeloid leukaemia patients receiving tyrosine kinase inhibitors.

Failure to comply with treatment recommendations is very common in patients, but still poorly recognised by doctors. The current practice of using oral therapy on a large scale has been increasingly adopted for cancer patients. Chronic myeloid leukaemia (CML) is just such an example, where the introduction of taking new oral medications, the tyrosine kinase BCR-ABL inhibitors (TKI), has now revolutionised the treatment. The aim of our study was to assess treatment adherence in a group of Polish CML patients (a survey was conducted on 140 patient aged ≥18 years) treated with oral TKI (imatinib, dasatinib and nilotinib) taking into account the following variables: gender, age, education, place of residence, family circumstances and duration of therapy. In addition, we evaluated whether there is a relationship between how patients perceive their level of adherence to treatment recommendations with how subjectively the required dosage regimen was followed. Half the patients admitted to skipping at least one drug dose during the entire course of treatment and 39% did so within their last treatment month. Patients were also found to overestimate their own adherence assessment; around 60% of those missing at least 1 drug dose within the last treatment month believed they 'always' followed recommendations. The study demonstrated that adherence deteriorates over time. Furthermore, patients aged >65 years and patients suffering at least one comorbid disease had better adherence (p < 0.011). There were no differences in adherence among patients treated with imatinib, dasatinib and nilotinib (p = 0.249).

Statins inhibit ABCB1 and ABCG2 drug transporter activity in chronic myeloid leukemia cells and potentiate antileukemic effects of imatinib.

Despite undisputed success of tyrosine kinase inhibitors in the therapy of chronic myeloid leukemia (CML), development of drug resistance and inability to cure the disease challenge clinicians and researchers. Additionally, recent reports regarding cardiovascular toxicities of second and third generation tyrosine kinase inhibitors prove that there is still a place for novel therapeutic combinations in CML. We have previously shown that statins are able to modulate activity of chemotherapeutics or antibodies used in oncology. Therefore, we decided to verify that statins are able to potentiate antileukemic activity of imatinib, still a frontline treatment of CML. Lovastatin, a cholesterol lowering drug, synergistically potentiates antileukemic activity of imatinib in cell lines and in primary CD34+ CML cells from patients in different phases of the disease, including patients resistant to imatinib with no detectable mutations. This effect is related to increased intracellular concentration of imatinib in CD34+ CML cells and cell lines measured using uptake of (14)C-labeled imatinib. Lovastatin does not influence influx but significantly inhibits efflux of imatinib mediated by ATP-binding cassette (ABC) transporters: ABCB1 and ABCG2. The addition of cholesterol completely reverses these effects. Statins do not affect expression of ABCB1 and ABCG2 genes. The effects are drug-class specific, as observed with other statins. Our results suggest that statins may offer a valuable addition to imatinib in a select group of CML patients.

Genomic instability may originate from imatinib-refractory chronic myeloid leukemia stem cells.

Genomic instability is a hallmark of chronic myeloid leukemia in chronic phase (CML-CP) resulting in BCR-ABL1 mutations encoding resistance to tyrosine kinase inhibitors (TKIs) and/or additional chromosomal aberrations leading to disease relapse and/or malignant progression. TKI-naive and TKI-treated leukemia stem cells (LSCs) and leukemia progenitor cells (LPCs) accumulate high levels of reactive oxygen species (ROS) and oxidative DNA damage. To determine the role of TKI-refractory LSCs in genomic instability, we used a murine model of CML-CP where ROS-induced oxidative DNA damage was elevated in LSCs, including quiescent LSCs, but not in LPCs. ROS-induced oxidative DNA damage in LSCs caused clinically relevant genomic instability in CML-CP-like mice, such as TKI-resistant BCR-ABL1 mutations (E255K, T315I, H396P), deletions in Ikzf1 and Trp53, and additions in Zfp423 and Idh1. Despite inhibition of BCR-ABL1 kinase, imatinib did not downregulate ROS and oxidative DNA damage in TKI-refractory LSCs to the levels detected in normal cells, and CML-CP-like mice treated with imatinib continued to accumulate clinically relevant genetic aberrations. Inhibition of class I p21-activated protein kinases by IPA3 downregulated ROS in TKI-naive and TKI-treated LSCs. Altogether, we postulate that genomic instability may originate in the most primitive TKI-refractory LSCs in TKI-naive and TKI-treated patients.

Immune thrombocytopenia in patients with chronic lymphocytic leukemia treated with cladribine-based regiments or chlorambucil--follow-up of PALG-CLL randomized trials.

OBJECTIVES: The relationship between treatments of chronic lymphocytic leukemia (CLL) with cladribine (2-CdA) or chlorambucil and immune thrombocytopenia (IT) has not been yet determined. METHODS: The records of 777 patients in two randomized Polish Adult Leukemia Group (PALG)-CLL programs treated with these agents were retrospectively analyzed. RESULTS: Immune thrombocytopenia occurred in 55 of 777 (7.1%) patients. No significant differences in IT prevalence were seen between patients on chlorambucil or 2-CdA-based regiments (P = 0.33). IT developed at a median time of 0.499 yr (0.06-4.8) from the start of CLL therapy. This time was significantly longer in patients treated with chlorambucil (2.03 yr, 95% CI: 0.06-4.22) in relation to patients treated with 2-CdA-based regiments (0.52 yr, 95%CI: 0.34-0.69, P = 0.049). Overall survival (OS) of patients with IT and those without IT were similar (2.65 yr vs. 3.2 yr P = 0.23) but the severity of bleeding was more pronounced in the 2-CdA group. The responses to IT therapy were 35%, 54% and 75% for steroids, chemotherapy and splenectomy, respectively. CONCLUSIONS: In this study, an unexpectedly high percentage of IT incidence was demonstrated in patients with CLL requiring chemotherapy. Although no marked differences were seen in IT frequency in patients treated with 2-CdA-based regiments compared to chlorambucil regimen, the clinical course of hemorrhagic diathesis was more severe in 2-CdA group. Also, the time elapsed from study screening to IT diagnosis was significantly shorter in the 2-CdA group than in the chlorambucil group suggesting a causative relationship. The appearance of IT did not influence the median time of OS.

Diverse mechanisms of mTOR activation in chronic and blastic phase of chronic myelogenous leukemia.

Chronic myelogenous leukemia (CML) is a stem cell disorder, and leukemia stem cells (LSCs) can contribute to the relapse of the disease. Quiescent LSCs are BCR-ABL independent and resistant to imatinib; therefore, there is an unmet need to identify new therapeutic targets in LSCs. Inhibition of the mammalian target of rapamycin (mTOR) in imatinib-resistant BCR-ABL1-positive cells was effective in vitro, but in a pilot clinical trial, only a few patients responded to the treatment. In this study, we demonstrate that mTOR activation in CML CD34(+) progenitor cells is ERK dependent in chronic phase of the disease and ERK independent in blast crisis. Rapamycin effectively inhibits mTOR in all phases of CML, but does not reduce number of LSC-enriched CD34(+) blast crisis (BC) cells, neither alone nor in combination with imatinib in CML-BC cells. These results show that potential therapeutic benefits of mTOR inhibition may be the result of effects on differentiated leukemic cells and may be potentially achieved only in the chronic phase of the disease.

The PERK-eIF2α phosphorylation arm is a pro-survival pathway of BCR-ABL signaling and confers resistance to imatinib treatment in chronic myeloid leukemia cells.

Activation of adaptive mechanisms plays a crucial role in cancer progression and drug resistance by allowing cell survival under stressful conditions. Therefore, inhibition of the adaptive response is considered as a prospective therapeutic strategy. The PERK-eIF2α phosphorylation pathway is an important arm of the unfolded protein response (UPR), which is induced under conditions of endoplasmic reticulum (ER) stress. Our previous work showed that ER stress is induced in chronic myeloid leukemia (CML) cells. Herein, we demonstrate that the PERK-eIF2α phosphorylation pathway is upregulated in CML cell lines and CD34+ cells from CML patients and is associated with CML progression and imatinib resistance. We also show that induction of apoptosis by imatinib results in the downregulation of the PERK-eIF2α phosphorylation arm. Furthermore, we demonstrate that inactivation of the PERK-eIF2α phosphorylation arm decreases the clonogenic and proliferative capacities of CML cells and sensitizes them to death by imatinib. These findings provide evidence for a pro-survival role of PERK-eIF2α phosphorylation arm that contributes to CML progression and development of imatinib resistance. Thus, the PERK-eIF2α phosphorylation arm may represent a suitable target for therapeutic intervention for CML disease.

Elevation of pulmonary artery pressure as a complication of nilotinib therapy for chronic myeloid leukemia.

We present the case of a 72-year-old male with chronic phase myeloid leukemia. Elevation of the pulmonary artery pressure due to nilotinib therapy was noted. This effect on pulmonary artery pressure was nilotinib dose dependent.

Comparison of cladribine plus cyclophosphamide with fludarabine plus cyclophosphamide as first-line therapy for chronic lymphocytic leukemia: a phase III randomized study by the Polish Adult Leukemia Group (PALG-CLL3 Study).

PURPOSE Little is known about comparison of the activity of different purine nucleoside analogs in chronic lymphocytic leukemia (CLL). We conducted a randomized phase III trial to compare efficacy and safety of cladribine and fludarabine, each combined with cyclophosphamide, in previously untreated progressive CLL. PATIENTS AND METHODS Patients received cladribine at 0.12 mg/kg combined with cyclophosphamide at 250 mg/m(2) for 3 days intravenously (CC regimen) or fludarabine at 25 mg/m(2) combined with cyclophosphamide at 250 mg/m(2) for 3 days intravenously (FC regimen), every 28 days for up to six cycles. The primary end point was complete response (CR) rate. Secondary end points included overall response rate (ORR), progression-free survival (PFS), overall survival (OS), and treatment-related toxicity. RESULTS Of 423 randomly assigned patients (211 to CC and 212 to FC), 395 were evaluated in the final analysis. The CR and ORR reached 47% and 88% in the CC arm and 46% and 82% in the FC arm (P = .25 and P = .11, respectively). The median PFS was 2.34 years with CC and 2.27 years with FC (P = .51). OS and grade 3/4 treatment-related toxicity were also comparable. Moreover, we did not observe any significant differences in CC and FC efficacy across different patient prognostic subgroups that included patients with 17p13 (TP53 gene) deletion who had poor survival in both study arms. CONCLUSION Cladribine and fludarabine in combination with cyclophosphamide are equally effective and safe first-line regimens for progressive CLL. Both combinations have unsatisfactory activity in patients with 17p13 (TP53 gene) deletion.

Clinical characteristics of patients with chronic eosinophilic leukaemia (CEL) harbouring FIP1L1-PDGFRA fusion transcript--results of Polish multicentre study.

A small subgroup of patients with hypereosinophilic syndrome (HES) demonstrates imatinib-sensitive fusion transcript-the FIP1L1-PDGFRA (F/P+). These cases are currently diagnosed as chronic eosinophilic leukaemia (CEL). In this paper, we screened 77 patients to estimate the frequency of FIP1L1-PDGFRA transcript among patients with unexplained, long-term hypereosinophilia exceeding 1.5 x 10(9)/L and to analyse the clinical and serological features in F/P+ CEL population. The FIP1L1-PDGFRA chimeric protein was detectable in 16 (14 males and 2 females) out of 77 examined HES patients (20%) by RT-PCR. Two patients suffered from cough at diagnosis. Three out of 16 (18%) patients had no organ involvements, in 5-one organ was affected and in the remaining eight cases-at least two. Eosinophilic organ damage/dysfunction identified splenomegaly in the majority of studied patients. We compared clinical and serological features between CEL F/P+ (n = 16) and HES (n = 61) patients. F/P+ cases had significantly increased WBC and absolute eosinophil count (AEC) at diagnosis (p = 0.008 and 0.02), whereas platelet count was decreased in this population (p = 0.03). Serum B12 and tryptase levels were increased (p = 0.002 and 0.004) in CEL F/P+ patients when compared to HES cases whereas serum IL-5 levels were significantly increased in the latter group (p = 0.01). Male gender and splenomegaly occurred more frequent in CEL F/P+ population (p = 0.002 and 0.0007, respectively). Additionally, patients with F/P+ CEL (n = 16) were compared with F/P- CEL (n = 8). The latter group, was significantly older, had lower AEC and higher platelet count. In conclusion, significant clinical symptoms are infrequent present and splenomegaly remains the most common organ involvement in patients with CEL expressing F/P fusion transcript. Our study confirmed the long-term remission on imatinib in this patient population.

Karyotype changes during long-term targeted therapy of chronic myeloid leukemia with imatinib.

The main risk factors during imatinib therapy of chronic myeloid leukemia are still subject to discussion. A group of 39 patients was cytogenetically examined and monitored before and during long-term treatment with imatinib. The cytogenetic response was investigated using karyotype analysis and fluorescence in situ hybridisation method. Different therapy effects were shown for three subgroups distinguished before the start of treatment: patients with the sole translocation t(9;22) with a typical pattern of BCR/ABL fusion vs. patients with submicroscopic deletion in the fusion region ABL/BCR of the sole t(9;22) vs. patients with aberrations additional to t(9;22) and without submicroscopic deletion. Of the two group with sole t(9;22) the group with deletion in the ABL/BCL region suffered a poorer treatment outcome than the group without deletion. The risk of progression of cytogenetic changes in group with deletion was more than nine times higher than in patients with sole t(9;22) without deletion (statistically significant).