De novo accelerated phase of chronic myeloid leukemia should be recognized even in the era of tyrosine kinase inhibitors.

Overall survival of patients classified according to the European LeukemiaNet 2020 classification. Chronic phase (CP), accelerated phase (AP), blast crisis (BC), low risk (LR), intermediate risk (IR), high risk (HR).

Technical Note Cell Dysplasia - Cell Dysplastic Features (A Morphological Note).

Cell dysplasia is a currently used term describing various cellular developmental abnormalities visible by microscopy. However, detailed description of these developmental abnormalities might provide useful information not only on the cell state but also on the abnormal developmental steps of cell lineages, tissues and organs. The frequently noted visualized cell dysplastic features reflect nuclear- or nucleolar-cytoplasmic anarchy (asynchrony), premature heterochromatin condensation state, marked aneuploidy, abnormal nucleus-cytoplasm ratio, abnormality of cell organelles including mitochondria, abnormal presence or absence of cell lineage-specific granules, and formation of peripheral buds or blebbing on the cell surface. The description of these frequently occurring cell dysplastic features might also be helpful in recognizing and studying defined specific disorders of the "whole macro-body" expressed as a disease.

BCR-ABL1 mediated miR-150 downregulation through MYC contributed to myeloid differentiation block and drug resistance in chronic myeloid leukemia.

The fusion oncoprotein BCR-ABL1 exhibits aberrant tyrosine kinase activity and it has been proposed that it deregulates signaling networks involving both transcription factors and non-coding microRNAs that result in chronic myeloid leukemia (CML). Previously, microRNA expression profiling showed deregulated expression of miR-150 and miR-155 in CML. In this study, we placed these findings into the broader context of the MYC/miR-150/MYB/miR-155/PU.1 oncogenic network. We propose that up-regulated MYC and miR-155 in CD34+ leukemic stem and progenitor cells, in concert with BCR-ABL1, impair the molecular mechanisms of myeloid differentiation associated with low miR-150 and PU.1 levels. We revealed that MYC directly occupied the -11.7 kb and -0.35 kb regulatory regions in the MIR150 gene. MYC occupancy was markedly increased through BCR-ABL1 activity, causing inhibition of MIR150 gene expression in CML CD34+ and CD34- cells. Furthermore, we found an association between reduced miR-150 levels in CML blast cells and their resistance to tyrosine kinase inhibitors (TKIs). Although TKIs successfully disrupted BCR-ABL1 kinase activity in proliferating CML cells, this treatment did not efficiently target quiescent leukemic stem cells. The study presents new evidence regarding the MYC/miR-150/MYB/miR-155/PU.1 leukemic network established by aberrant BCR-ABL1 activity. The key connecting nodes of this network may serve as potential druggable targets to overcome resistance of CML stem and progenitor cells.

Intracellular Cytokines Produced by Stimulated CD3+ Cells from Chronic Myeloid Leukemia Patients.

Our work examined the production of intracellular interferon (INF)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-2, and IL-4 by in vitro stimulated CD3+ cells from 38 chronic myeloid leukemia (CML) patients. At the time of diagnosis the percentages of cells producing INF-γ, TNF-α, and IL-2 were strongly suppressed compared to those in healthy control subjects. Hematological remission achieved through treatment with tyrosine-kinase inhibitors was associated with a highly significant increase in the ratio of cells producing all 4 cytokines. The percentages of CD3+ cells producing cytokines were dependent on age, more so in CML patients than in healthy controls, and they negatively correlated with the number of leukocytes. Patients with an optimal therapy outcome possessed higher percentages of cytokine-producing CD3+ cells at diagnosis than those with nonoptimal outcomes. This difference was statistically significant in the case of INF-γ-producing cells, and it was on the brink of significance in the case of IL-2-producing cells.

Simplifying procedure for prediction of resistance risk in CML patients - Test of sensitivity to TKI ex vivo.

Tyrosine kinase inhibitors (TKIs) targeting BCR-ABL have dramatically improved chronic myeloid leukemia therapy. While imatinib remains to be the first line therapy, about 30% of patients develop resistance or intolerance to this drug and are recommended to switch to other TKIs. Nilotinib and dasatinib are currently implemented into the first line therapy and other inhibitors have already entered the clinical practice. This opens further questions on how to select the best TKI for each patient not only during the therapy but also at diagnosis. The individualized therapy concept requires a reliable establishment of prognosis and prediction of response to the available TKIs. We tested the ex vivo sensitivity of patient primary leukocytes to imatinib, nilotinib and dasatinib - two concentrations of each inhibitor for 48h incubation - and we evaluated the usefulness of such tests for the clinical practice. Besides reflecting the actual sensitivity to the therapy, our optimized simple tests were able to predict the outcome in 90/87% of patients, for the next 12/24months, respectively. According to these results, the presented ex vivo testing could help clinicians to select the appropriate drug for each patient at diagnosis and also at any time of the therapy.

Characterization of 46 patient-specific BCR-ABL1 fusions and detection of SNPs upstream and downstream the breakpoints in chronic myeloid leukemia using next generation sequencing.

In chronic myeloid leukemia, the identification of individual BCR-ABL1 fusions is required for the development of personalized medicine approach for minimal residual disease monitoring at the DNA level. Next generation sequencing (NGS) of amplicons larger than 1000 bp simplified and accelerated a process of characterization of patient-specific BCR-ABL1 genomic fusions. NGS of large regions upstream and downstream the individual breakpoints in BCR and ABL1 genes, respectively, also provided information about the sequence variants such are single nucleotide polymorphisms.

Unraveling the complexity of tyrosine kinase inhibitor-resistant populations by ultra-deep sequencing of the BCR-ABL kinase domain.

In chronic myeloid leukemia and Philadelphia chromosome-positive acute lymphoblastic leukemia, tyrosine kinase inhibitor (TKI) therapy may select for drug-resistant BCR-ABL mutants. We used an ultra-deep sequencing (UDS) approach to resolve qualitatively and quantitatively the complexity of mutated populations surviving TKIs and to investigate their clonal structure and evolution over time in relation to therapeutic intervention. To this purpose, we performed a longitudinal analysis of 106 samples from 33 patients who had received sequential treatment with multiple TKIs and had experienced sequential relapses accompanied by selection of 1 or more TKI-resistant mutations. We found that conventional Sanger sequencing had misclassified or underestimated BCR-ABL mutation status in 55% of the samples, where mutations with 1% to 15% abundance were detected. A complex clonal texture was uncovered by clonal analysis of samples harboring multiple mutations and up to 13 different mutated populations were identified. The landscape of these mutated populations was found to be highly dynamic. The high degree of complexity uncovered by UDS indicates that conventional Sanger sequencing might be an inadequate tool to assess BCR-ABL kinase domain mutation status, which currently represents an important component of the therapeutic decision algorithms. Further evaluation of the clinical usefulness of UDS-based approaches is warranted.

No clinical evidence for performing trough plasma and intracellular imatinib concentrations monitoring in patients with chronic myelogenous leukaemia.

This multicentre study focused on monitoring imatinib mesylate (IMA) trough plasma (Ctrough ) and intracellular (IMA Cintrac ) concentrations in 228 chronic myelogenous leukaemia patients. The median of measured IMA Ctrough in our patient group was 905.8 ng ml (range: 27.7-4628.1 ng/ml). We found a correlation between IMA Ctrough and alpha 1-acid glycoprotein plasma concentrations (rS = 0.42; p < 0.001). All other analysed parameters revealed only weak (gender, dose of IMA per kg) or not significant (age, albumin, creatinine plasma concentration or body mass index) impact on measured IMA Ctrough. The IMA Ctrough decreased during the first 6 months and significantly increased later during treatment. The IMA Ctrough at the first month of therapy did not differ between patients with and without an optimal response at the 12th (p = 0.724) and 18th month (p = 0.135) of therapy. There were no significant differences in medians of IMA Ctrough between both groups measured during the first year of treatment. The IMA Cintrac during the first month were not different between patients with and without an optimal response at the 6th (p = 0.273) and the 12th month (p = 0.193) of therapy. Our data obtained from real life clinical practice did not find a benefit of routine and regular IMA Ctrough nor IMA Cintrac therapeutic drug monitoring in chronic myelogenous leukaemia patients or for subsequent adjustments of the IMA dose based on these results. Moreover, actual alpha 1-acid glycoprotein plasma concentration should be used for proper interpretation of IMA Ctrough results.

Health-related quality of life and symptoms of chronic myeloid leukemia patients after discontinuation of tyrosine kinase inhibitors: results from the EURO-SKI Trial.

Limited data is available on the health-related quality of life (HRQoL) and symptoms of patients with chronic myeloid leukemia (CML) who are in treatment-free remission (TFR). We herein report HRQoL results from the EURO-SKI trial. Patients who had been on tyrosine kinase inhibitors (TKIs) therapy for at least 3 years and achieved MR4 for at least 1 year were enrolled from 11 European countries, and the EORTC QLQ-C30 and the FACIT-Fatigue questionnaires were used to assess HRQoL and fatigue respectively. Patients were categorized into the following age groups: 18-39, 40-59, 60-69 and ≥70 years. Of 728 patients evaluated at baseline, 686 (94%) completed HRQoL assessments. The median age at TKI discontinuation was 60 years. Our findings indicate that HRQoL and symptom trajectories may vary depending on specific age groups, with younger patients benefiting the most. Improvements in patients aged 60 years or older were marginal across several HRQoL and symptom domains. At the time of considering TKI discontinuation, physicians could inform younger patients that they may expect valuable HRQoL benefits. Considering the marginal improvements observed in patients aged 60 years or above, it may be important to further investigate the value of TFR compared to a lowest effective dose approach in this older group of patients.

The SNP rs460089 in the gene promoter of the drug transporter OCTN1 has prognostic value for treatment-free remission in chronic myeloid leukemia patients treated with imatinib.

Membrane transporters are important determinants of drug bioavailability. Their expression and activity affect the intracellular drug concentration in leukemic cells impacting response to therapy. Pharmacogenomics represents genetic markers that reflect allele arrangement of genes encoding drug transporters associated with treatment response. In previous work, we identified SNP rs460089 located in the promotor of SLC22A4 gene encoding imatinib transporter OCTN1 as influential on response of patients with chronic myeloid leukemia treated with imatinib. Patients with rs460089-GC pharmacogenotype had significantly superior response to first-line imatinib treatment compared to patients with rs460089-GG. This study investigated whether pharmacogenotypes of rs460089 are associated with sustainability of treatment-free remission (TFR) in patients from the EUROpean Stop Kinase Inhibitor (EURO-SKI) trial. In the learning sample, 176 patients showed a significantly higher 6-month probability of molecular relapse free survival (MRFS) in patients with GC genotype (73%, 95% CI: 60-82%) compared to patients with GG (51%, 95% CI: 41-61%). Also over time, patients with GC genotype had significantly higher MRFS probabilities compared with patients with GG (HR: 0.474, 95% CI: 0.280-0.802, p = 0.0054). Both results were validated with data on 93 patients from the Polish STOP imatinib study. In multiple regression models, in addition to the investigated genotype, duration of TKI therapy (EURO-SKI trial) and duration of deep molecular response (Polish study) were identified as independent prognostic factors. The SNP rs460089 was found as an independent predictor of TFR.

Management and outcome of patients with chronic myeloid leukemia in blast phase in the tyrosine kinase inhibitor era - analysis of the European LeukemiaNet Blast Phase Registry.

Blast phase (BP) of chronic myeloid leukemia (CML) still represents an unmet clinical need with a dismal prognosis. Due to the rarity of the condition and the heterogeneity of the biology and clinical presentation, prospective trials and concise treatment recommendations are lacking. Here we present the analysis of the European LeukemiaNet Blast Phase Registry, an international collection of the clinical presentation, treatment and outcome of blast phases which had been diagnosed in CML patients after 2015. Data reveal the expected heterogeneity of the entity, lacking a clear treatment standard. Outcomes remain dismal, with a median overall survival of 23.8 months (median follow up 27.8 months). Allogeneic stem cell transplantation (alloSCT) increases the rate of deep molecular responses. De novo BP and BP evolving from a previous CML do show slightly different features, suggesting a different biology between the two entities. Data show that outside clinical trials and in a real-world setting treatment of blast phase is individualized according to disease- and patient-related characteristics, with the aim of blast clearance prior to allogeneic stem cell transplantation. AlloSCT should be offered to all patients eligible for this procedure.

Hsp90 - a potential prognostic marker in CML.

Heat shock proteins (Hsp) are important for the stability and function of cell proteins and thus for cell survival under physiological as well as stress conditions. Hsps were also reported to play an important role in tumorogenesis including leukemias. In this study we followed up Hsp70 and 90 protein levels in samples from patients with chronic myeloid leukemia (CML) to evaluate these Hsps with regard to their ability to characterize the disease status and disease prognosis. We analyzed 68 samples of total leukocytes of CML patients with different response to therapy with tyrosine kinase inhibitors. The results of Western blot analyses showed that the level of Hsp70 did not change in the course of the disease and did not correlate with response to therapy. In contrast, Hsp90 levels showed good correlation with the disease state. Patients with good response to therapy (major molecular response-MMR, molecular remission-CMR) had low expression levels of Hsp90, similar to those in healthy individuals. High Hsp90 levels were found in patients with resistance to therapy (hematological relapse-HR, accelerated phase or blast crisis), and in leukemic cell line K562. The results of the study suggested that not the kinetics but the particular level of Hsp90 at any time point since therapy start is of prognostic value: Hsp90 level above 0.27 significantly predicted poor response to TKI therapy (relapse, progression) and the level below 0.085 good response (MMR, CMR). In conclusion, Hsp90 level in total leukocytes could serve as a risk factor at diagnosis as well as during therapy and might help in clinical decision making especially in cases where BCR-ABL monitoring is of low predictive value. Our data suggest that high expression of HSP90 contributes to the aggressivity of the disease and should be considered as an important target for specialized CML therapy.

Current survival measures reliably reflect modern sequential treatment in CML: correlation with prognostic stratifications.

Using the data of 723 chronic myeloid leukemia (CML) patients in the chronic phase, we analyzed the prognostic value of the Sokal, Euro, and EUTOS scores as well as the level of BCR-ABL1 and the achievement of complete cytogenetic response (CCgR) at 3 months of imatinib therapy in relation to the so-called current survival measures: the current cumulative incidence (CCI) reflecting the probability of being alive and in CCgR after starting imatinib therapy; the current leukemia-free survival (CLFS) reflecting the probability of being alive and in CCgR after achieving the first CCgR; and the overall survival. The greatest difference between the CCI curves at 5 years after initiating imatinib therapy was observed for the BCR-ABL1 transcripts at 3 months. The 5-year CCI was 94.3% in patients with BCR-ABL1 transcripts ≤ 10% and 57.1% in patients with BCR-ABL1 transcripts > 10% (P = 0.005). Therefore, the examination of BCR-ABL1 transcripts at 3 months may help in early identification of patients who are likely to perform poorly with imatinib. On the other hand, CLFS was not significantly affected by the considered stratifications. In conclusion, our results indicate that once the CCgR is achieved, the prognosis is good irrespective of the starting prognostic risks.

Inhibition of casein kinase 2 induces cell death in tyrosine kinase inhibitor resistant chronic myelogenous leukemia cells.

Chronic myelogenous leukemia (CML) is a myeloproliferative disease characterized by the BCR-ABL oncogene. Despite the high performance of treatment with tyrosine kinase inhibitors (TKI), about 30% of patients develop resistance to the therapy. To improve the outcomes, identification of new targets of treatment is needed. Here, we explored the Casein Kinase 2 (CK2) as a potential target for CML therapy. Previously, we detected increased phosphorylation of HSP90ß Serine 226 in patients non-responding to TKIs imatinib and dasatinib. This site is known to be phosphorylated by CK2, which was also linked to CML resistance to imatinib. In the present work, we established six novel imatinib- and dasatinib-resistant CML cell lines, all of which had increased CK2 activation. A CK2 inhibitor, CX-4945, induced cell death of CML cells in both parental and resistant cell lines. In some cases, CK2 inhibition also potentiated the effects of TKI on the cell metabolic activity. No effects of CK2 inhibition were observed in normal mononuclear blood cells from healthy donors and BCR-ABL negative HL60 cell line. Our data indicate that CK2 kinase supports CML cell viability even in cells with different mechanisms of resistance to TKI, and thus represents a potential target for treatment.

Expression of four major WT1 splicing variants in acute and chronic myeloid leukemia patients analyzed by newly developed four real-time RT PCRs.

Although the mechanism of action of leukemic oncogene Wilms' tumor gene 1 (WT1) remains unclear, WT1 has already been used in monitoring of patients with acute myeloid leukemia (AML) and it is being tested for immunotherapy. More detailed understanding of the role of WT1 in leukemia may improve its utilization. At least 36 isoforms may be produced. Four major variants denoted as -5/-KTS, -5/+KTS, +5/-KTS and +5/+KTS are produced by combining splicing of exon 5 and KTS sequence. In this study, we report applicability of newly developed real-time RT PCRs enabling for the first time full quantification of the four major WT1 splicing variants. Following careful optimization and testing of quantification reliability of four assays, we analyzed 34 samples of patients with AML and 12 samples of patients with chronic myeloid leukemia (CML) at the time of diagnosis. Analyses of five more CML patients provided insight into WT1 variants expression kinetics. We found predominance of +5/+KTS in both diagnoses. Comparison of WT1 variant expression in AML and CML patients' groups differing in response to therapy suggested possible importance of particular WT1 variant levels as markers of further disease course.

Impact of BCR::ABL1 transcript type on RT-qPCR amplification performance and molecular response to therapy.

Several studies have reported that chronic myeloid leukaemia (CML) patients expressing e14a2 BCR::ABL1 have a faster molecular response to therapy compared to patients expressing e13a2. To explore the reason for this difference we undertook a detailed technical comparison of the commonly used Europe Against Cancer (EAC) BCR::ABL1 reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) assay in European Treatment and Outcome Study (EUTOS) reference laboratories (n = 10). We found the amplification ratio of the e13a2 amplicon was 38% greater than e14a2 (p = 0.015), and the amplification efficiency was 2% greater (P = 0.17). This subtle difference led to measurable transcript-type dependent variation in estimates of residual disease which could be corrected by (i) taking the qPCR amplification efficiency into account, (ii) using alternative RT-qPCR approaches or (iii) droplet digital PCR (ddPCR), a technique which is relatively insensitive to differences in amplification kinetics. In CML patients, higher levels of BCR::ABL1/GUSB were identified at diagnosis for patients expressing e13a2 (n = 67) compared to e14a2 (n = 78) when analysed by RT-qPCR (P = 0.0005) but not ddPCR (P = 0.5). These data indicate that widely used RT-qPCR assays result in subtly different estimates of disease depending on BCR::ABL1 transcript type; these differences are small but may need to be considered for optimal patient management.

Expression patterns of microRNAs associated with CML phases and their disease related targets.

BACKGROUND: MicroRNAs are important regulators of transcription in hematopoiesis. Their expression deregulations were described in association with pathogenesis of some hematological malignancies. This study provides integrated microRNA expression profiling at different phases of chronic myeloid leukemia (CML) with the aim to identify microRNAs associated with CML pathogenesis. The functions of in silico filtered targets are in this report annotated and discussed in relation to CML pathogenesis. RESULTS: Using microarrays we identified differential expression profiles of 49 miRNAs in CML patients at diagnosis, in hematological relapse, therapy failure, blast crisis and major molecular response. The expression deregulation of miR-150, miR-20a, miR-17, miR-19a, miR-103, miR-144, miR-155, miR-181a, miR-221 and miR-222 in CML was confirmed by real-time quantitative PCR. In silico analyses identified targeted genes of these miRNAs encoding proteins that are involved in cell cycle and growth regulation as well as several key signaling pathways such as of mitogen activated kinase-like protein (MAPK), epidermal growth factor receptor (EGFR, ERBB), transforming growth factor beta (TGFB1) and tumor protein p53 that are all related to CML. Decreased levels of miR-150 were detected in patients at diagnosis, in blast crisis and 67% of hematological relapses and showed significant negative correlation with miR-150 proved target MYB and with BCR-ABL transcript level. CONCLUSIONS: This study uncovers microRNAs that are potentially involved in CML and the annotated functions of in silico filtered targets of selected miRNAs outline mechanisms whereby microRNAs may be involved in CML pathogenesis.

Estimation of current cumulative incidence of leukaemia-free patients and current leukaemia-free survival in chronic myeloid leukaemia in the era of modern pharmacotherapy.

BACKGROUND: The current situation in the treatment of chronic myeloid leukaemia (CML) presents a new challenge for attempts to measure the therapeutic results, as the CML patients can experience multiple leukaemia-free periods during the course of their treatment. Traditional measures of treatment efficacy such as leukaemia-free survival and cumulative incidence are unable to cope with multiple events in time, e.g. disease remissions or progressions, and as such are inappropriate for the efficacy assessment of the recent CML treatment. METHODS: Standard nonparametric statistical methods are used for estimating two principal characteristics of the current CML treatment: the probability of being alive and leukaemia-free in time after CML therapy initiation, denoted as the current cumulative incidence of leukaemia-free patients; and the probability that a patient is alive and in any leukaemia-free period in time after achieving the first leukaemia-free period on the CML treatment, denoted as the current leukaemia-free survival. The validity of the proposed methods is further documented in the data of the Czech CML patients consecutively recorded between July 2003 and July 2009 as well as in simulated data. RESULTS: The results have shown a difference between the estimates of the current cumulative incidence function and the common cumulative incidence of leukaemia-free patients, as well as between the estimates of the current leukaemia-free survival and the common leukaemia-free survival. Regarding the currently available follow-up period, both differences have reached the maximum (12.8% and 20.8%, respectively) at 3 years after the start of follow-up, i.e. after the CML therapy initiation in the former case and after the first achievement of the disease remission in the latter. CONCLUSIONS: Two quantities for the evaluation of the efficacy of current CML therapy that may be estimated with standard nonparametric methods have been proposed in this paper. Both quantities reliably illustrate a patient's disease status in time because they account for the proportion of patients in the second and subsequent disease remissions. Moreover, the model is also applicable in the future, regardless of what the progress in the CML treatment will be and how many treatment options will be available, respectively.