The BCR-ABL1 transcript type influences response and outcome in Philadelphia chromosome-positive chronic myeloid leukemia patients treated frontline with imatinib

Atypical BCR-ABL1 transcript in mixed phenotype acute leukemia with bone marrow necrosis

Mixed phenotype acute leukemia (MPAL) is a type of acute leukemia in which encompasses mixed features of myeloid, T-lymphoid, and/or B-lymphoid differentiation. Philadelphia chromosome-positive (Ph+) MPAL is a rare subgroup with a poor prognosis and accounts for ＜1% of adult acute leukemia. Until now, there is still no consensus on how to best treat Ph+ MPAL. Here, we report a 62-year-old male with Ph+ (atypical e13a2 BCR-ABL1 fusion protein) MPAL. This patient presented with recurrent and intense bone pain due to bone marrow necrosis (BMN). Besides, he did not achieve a complete remission for the first two chemotherapies, until he received flumatinib combined with hyper-CVAD (B) (a dose-intensive regimen include methotrexate and cytarabine). To our knowledge, this is the first report to describe the coexistence of BMN and atypical e13a2 BCR-ABL1 transcripts in patients with MPAL. This finding will bring new understandings in the diagnosis and treatment of Ph+ MPAL.

Variant-specific BCR::ABL1 quantification discrepancy in chronic myeloid leukemia

INTRODUCTION

Accurate quantification of the BCR::ABL1 fusion gene in whole blood is pivotal for the clinical management of chronic myeloid leukemia (CML) patients. The fusion protein encoded by BCR::ABL1 can vary in size, depending on the BCR and/or ABL1 gene breakpoint. The vast majority of CML patients have a p210 BCR::ABL1 fusion gene (M-BCR), which can be attributed to the presence of either e14a2 (b3a2) or e13a2 (b2a2) mRNA transcript junctions.

METHODS

Twenty-five CML samples were analyzed in two different ISO15189-accredited centers that both use an Europe Against Cancer-based quantitative polymerase chain reaction (qPCR) protocol. Reanalysis of the sample set with transcript-specific standard curves and digital droplet PCR (ddPCR) were performed.

RESULTS

qPCR quantification revealed a significant (up to 1 log) difference specifically for the e13a2 transcript variant in contrast to e14a2 transcripts (Hodges-Lehman 4.29; p < 0.001). Reanalysis of the sample set with transcript-specific standard curves abolishes the initial transcript-specific difference (Hodges-Lehman 0.003; p = 0.8192). Comparison of transcript-specific qPCR results of both centers with ddPCR, an absolute quantification method, showed a statically significant association, especially in the lower range, indicating the clinical utility of transcript-specific or absolute quantification methods.

CONCLUSION

Our data show that differences between transcript-specific quantification might exist between centers, leading to potential clinical impact on the follow-up of CML patients. The use of transcript-specific standard curves for qPCR quantification, or absolute quantification, can significantly reduce these differences. Specific attention should be applied to the interpretation of quantification differences of CML patients that switch between diagnostic centers.

Chronic myeloid leukaemia: Biology and therapy

Chronic myeloid leukaemia (CML) is caused by BCR::ABL1. Tyrosine kinase-inhibitors (TKIs) are the initial therapy. Several organizations have reported milestones to evaluate response to initial TKI-therapy and suggest when a change of TKI should be considered. Achieving treatment-free remission (TFR) is increasingly recognized as the optimal therapy goal. Which TKI is the best initial therapy for which persons and what depth and duration of molecular remission is needed to achieve TFR are controversial. In this review we discuss these issues and suggest future research directions.

High Level of CD8+PD-1+ Cells in Patients with Chronic Myeloid Leukemia Who Experienced Loss of MMR after Imatinib Discontinuation

Treatment-free remission (TFR) is achieved in approximately half of chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors. The mechanisms responsible for TFR maintenance remain elusive. This study aimed to identify immune markers responsible for the control of residual CML cells early in the TFR (at 3 months), which may be the key to achieving long-term TFR and relapse-free survival (RFS) after discontinuation of imatinib. Our study included 63 CML patients after imatinib discontinuation, in whom comprehensive analysis of changes in the immune system was performed by flow cytometry, and changes in the BCR::ABL1 transcript levels were assessed by RQ-PCR and ddPCR. We demonstrated a significant increase in the percentage of CD8+PD-1+ cells in patients losing TFR. The level of CD8+PD-1+ cells is inversely related to the duration of treatment and incidence of deep molecular response (DMR) before discontinuation. Analysis of the ROC curve showed that the percentage of CD8+PD-1+ cells may be a significant factor in early molecular recurrence. Interestingly, at 3 months of TFR, patients with the e13a2 transcript had a significantly higher proportion of the PD-1-expressing immune cells compared to patients with the e14a2. Our results suggest the important involvement of CD8+PD-1+ cells in the success of TFR and may help in identifying a group of patients who could successfully discontinue imatinib.

Frequencies of BCR::ABL1 Transcripts in Patients with Chronic Myeloid Leukemia: A Meta-Analysis

Chronic myeloid leukemia (CML) is associated with the Philadelphia chromosome and distinct BCR::ABL1 gene transcripts. We assessed the frequencies of these transcripts in Mexico, Latin America, and worldwide. We determined the prevalence of BCR::ABL1 transcripts in CML patients and intercontinental or regional variations using specialized databases and keywords. We analyzed 34 studies from 20 countries, encompassing 5795 patients. Keyword-based searches in specialized databases guided data collection. ANOVA was employed for transcript distribution analysis. The b3a2 transcript was most prevalent globally, followed by b2a2, with e1a2 being the least frequent. Interestingly, Mexico City exhibited a higher incidence of b2a2, while b3a2 predominated in the remaining country. Overall, no significant intercontinental or regional variations were observed. b3a2 was the most common BCR::ABL1 transcript worldwide, with b2a2 following closely; e1a2 was infrequent. Notably, this trend remained consistent in Mexico. Evaluating transcript frequencies holds clinical relevance for CML management. Understanding the frequency of transcript informs personalized CML treatments.

e14a2 Transcript Favors Treatment-Free Remission in Chronic Myeloid Leukemia When Associated with Longer Treatment with Tyrosine Kinase Inhibitors and Sustained Deep Molecular Response

e13a2 and e14a2 are the most frequent transcript types of the BCR::ABL1 fusion gene in chronic myeloid leukemia (CML). The current goal with tyrosine kinase inhibitors (TKI) is to achieve sustained deep molecular response (DMR) in order to discontinue TKI treatment and remain in the so-called treatment-free remission (TFR) phase, but biological factors associated with these goals are not well established. This study aimed to determine the effect of transcript type on TFR in patients receiving frontline treatment with imatinib (IM) or second-generation TKI (2G-TKI). Patients treated at least 119 months with IM presented less post-discontinuation relapse than those that discontinued IM before 119 months (p = 0.005). In addition, cases with the e14a2 transcript type treated at least 119 months with IM presented a better TFR (p = 0.024). On the other hand, the type of transcript did not affect the cytogenetic or molecular response in 2G-TKI treated patients; however, the use of 2G-TKI may be associated with higher and earlier DMR in patients with the e14a2 transcript.

Exploration of treatment-free remission in CML, based on molecular monitoring

BACKGROUND

Typical chronic myelogenous leukemia (CML) is a myeloproliferative neoplasm caused by t(9; 22)(q34; q11) translocation. This chromosomal translocation forms the BCR::ABL1 fusion gene. The tyrosine kinase encoded by the BCR::ABL1 is considered to be the main pathogenic diver. BCR::ABL1 is not only a therapeutic target, but also a monitoring target. Monitoring of BCR::ABL1 reveals the progression of the disease and guides the next treatment. Now for CML, the target of treatment has been focused on treatment-free remission (TFR).

METHODS

We conducted a literature review of current developments of treatment-free remission and molecular monitoring methods.

RESULTS

More effective and sensitive CML monitoring methods such as digital droplet PCR (ddPCR) and next generation sequencing (NGS) have further studied the measurable residual disease (MRD) and clonal heterogeneity, which provides strong support for the exploration of TFR. We discussed some of the factors that may be related to TFR outcomes at the molecular level, along with some monitoring strategies.

CONCLUSION

Currently, predictive indicators for treatment-free remission outcomes and recurrence are lacking in clinical practice. In future, treatment-free remission research should focus on combining the clinical indicators with molecular monitoring and biological markers to personalize patient conditions and guide clinicians to develop individualized treatment plans, so that more patients with CML can achieve safer and stabler treatment-free remission.

Effect of BCR::ABL1 transcript type and droplet digital polymerase chain reaction on successful treatment-free remission in chronic myeloid leukemia patients who discontinued tyrosine kinase inhibitor

Background

Droplet digital polymerase chain reaction (ddPCR) is an exact method of measurement.

Objectives

We conducted this study to identify the prognostic factors for successful treatment-free remission in patients with chronic-phase chronic myeloid leukemia who discontinued tyrosine kinase inhibitors (TKIs). We also aimed to validate ddPCR for predicting molecular relapse.

Design

This is a prospective, multicenter study.

Methods

We enrolled patients treated with TKIs for at least 3 years with a confirmed sustained deep molecular response (DMR) for at least 1 year. TKI was re-administered in patients who experienced the loss of major molecular response (MMR).

Results

A total of 66 patients from five institutions in South Korea were enrolled. During a median follow-up period of 16.5 months, 29/66 (43.9%) patients experienced molecular relapse; the probability of molecular relapse-free survival (RFS) at 6 or 12 months after TKI discontinuation was 65.6% or 57.8%, respectively, with most molecular relapses occurring within the first 7 months. All patients who lost MMR were re-treated with TKI, and all re-achieved MMR at a median of 2.8 months. E14a2 transcript type (p = 0.005) and longer DMR duration (⩾48 months) prior to TKI discontinuation (p = 0.002) were associated with prolonged molecular RFS and with sustained DMR. Patients with both e13a2 transcript type and detectable BCR::ABL1 (⩾MR5.0) by ddPCR at the time of TKI discontinuation showed shorter duration of molecular RFS (p = 0.015).

Conclusion

Our data suggest that transcript type and BCR::ABL1 transcript levels on ddPCR should be taken into consideration when deciding whether to discontinue TKI therapy.

European LeukemiaNet laboratory recommendations for the diagnosis and management of chronic myeloid leukemia

From the laboratory perspective, effective management of patients with chronic myeloid leukemia (CML) requires accurate diagnosis, assessment of prognostic markers, sequential assessment of levels of residual disease and investigation of possible reasons for resistance, relapse or progression. Our scientific and clinical knowledge underpinning these requirements continues to evolve, as do laboratory methods and technologies. The European LeukemiaNet convened an expert panel to critically consider the current status of genetic laboratory approaches to help diagnose and manage CML patients. Our recommendations focus on current best practice and highlight the strengths and pitfalls of commonly used laboratory tests.

Prognosis in Chronic Myeloid Leukemia: Baseline Factors, Dynamic Risk Assessment and Novel Insights

The introduction of tyrosine kinase inhibitors (TKIs) has changed the treatment paradigm of chronic myeloid leukemia (CML), leading to a dramatic improvement of the outcome of CML patients, who now have a nearly normal life expectancy and, in some selected cases, the possibility of aiming for the more ambitious goal of treatment-free remission (TFR). However, the minority of patients who fail treatment and progress from chronic phase (CP) to accelerated phase (AP) and blast phase (BP) still have a relatively poor prognosis. The identification of predictive elements enabling a prompt recognition of patients at higher risk of progression still remains among the priorities in the field of CML management. Currently, the baseline risk is assessed using simple clinical and hematologic parameters, other than evaluating the presence of additional chromosomal abnormalities (ACAs), especially those at "high-risk". Beyond the onset, a re-evaluation of the risk status is mandatory, monitoring the response to TKI treatment. Moreover, novel critical insights are emerging into the role of genomic factors, present at diagnosis or evolving on therapy. This review presents the current knowledge regarding prognostic factors in CML and their potential role for an improved risk classification and a subsequent enhancement of therapeutic decisions and disease management.

Chronic-phase chronic myeloid leukemia: Incidence of BCR/ABL transcript and its correlation with presenting features, response to treatment, and survival

Introduction

Chronic myeloid leukemia (CML) is characterized by Philadelphia chromosome resulting in the fusion between the BCR gene, located on chromosome 22, and the ABL gene on chromosome 9. The prognostic significance of BCR-ABL transcript variants in CML is controversial. The aim of the current study was to evaluate the clinico-hematological presentation and evolution of the disease, response to treatment and survival according to transcript type in chronic phase CML patients.

Results

The median age of our population was 50 years with a slight female predominance (sex-ratio 0.78). Sixty percent had the b3a2 transcript and 34% had the b2a2 type. Patients with the co-expression of these two transcripts (4.5%) and those with e19a2 were excluded from the analysis. Patients with b3a2 subtype were associated significantly with thrombocytosis (p = 0.006) and higher Sokal score (p = 0.038) compared to those with b2a2 transcript. The two isolated transcripts were not significantly associated with gender, age group, blast cell percentage or the identified ranges of spleen size. Complete cytogenetic response at 12 months for b3a2 patients and b2a2 patients was 78.6% and 21.4% respectively. This difference was statistically significant (p = 0.001, HR = 9.5, 95% CI 6.5-13.7). Patients with b3a2 transcript had a higher rate of optimal molecular response at 3 months (p = 0.04, HR = 4.2, 95% CI 1-17.3) and major molecular response at 12 months (p = 0.004, HR = 4.9, 95%CI 1.5-15.1). At the date of last follow-up, most patients achieving deep molecular response (MR4 or deeper) belonged to b3a2 group (79%) (p = 0.003, HR = 5.2, 95% CI 1.6-16.4). We did not find a significant difference in OS and EFS between the two groups.

Conclusion

Our study concluded that b2a2 transcript is a prognostic factor in cytogenetic and molecular response but further studies are needed to complete this aspect.

Genetic alterations in the BCR-ABL1 fusion gene related to imatinib resistance in chronic myeloid leukemia

Use of the potent tyrosine kinase inhibitor imatinib as the first-line treatment in chronic myeloid leukemia (CML) has decreased mortality from 20% to 2%. Approximately 30% of CML patients experience imatinib resistance, however, largely because of point mutations in the kinase domain of the BCR-ABL1 fusion gene. The aim of this study was to use next-generation sequencing (NGS) to identify mutations related to imatinib resistance. The study included 22 patients diagnosed with CML and experiencing no clinical response to imatinib. Total RNA was used for cDNA synthesis, with amplification of a fragment encompassing the BCR-ABL1 kinase domain using a nested-PCR approach. Sanger and NGS were applied to detect genetic alterations. HaplotypeCaller was used for variant calling, and STAR-Fusion software was applied for fusion breakpoint identification. After sequencing analysis, F311I, F317L, and E450K mutations were detected respectively in three different participants, and in another two patients, single nucleotide variants in BCR (rs9608100, rs140506, rs16802) and ABL1 (rs35011138) were detected. Eleven patients carried e14a2 transcripts, nine had e13a2 transcripts, and both transcripts were identified in one patient. One patient had co-expression of e14a2 and e14a8 transcripts. The results identify candidate single nucleotide variants and co-expressed BCR-ABL1 transcripts in cellular resistance to imatinib.

Measurable residual disease in chronic myeloid leukemia

Chronic myeloid leukemia is characterized by a single genetic abnormality resulting in a fusion gene whose mRNA product is easily detected and quantified by reverse-transcriptase polymerase chain reaction analysis. Measuring residual disease was originally introduced to identify patients relapsing after allogeneic stem cell transplantation but rapidly adopted to quantify responses to tyrosine kinase inhibitors. Real-time quantitative polymerase chain reaction is now an essential tool for the management of patients and is used to influence treatment decisions. In this review we track this development including the international collaboration to standardize results, discuss the integration of molecular monitoring with other factors that affect patients' management, and describe emerging technology. Four case histories describe varying scenarios in which the accurate measurement of residual disease identified patients at risk of disease progression and allowed appropriate investigations and timely clinical intervention.

Molecular Changes in Chronic Myeloid Leukemia During Tyrosine Kinase Inhibitors Treatment. Focus on Immunological Pathways

Introduction

The aim of our research was to investigate changes in the molecular background of the immune response in the chronic phase (CP) of chronic myeloid leukaemia (CML) during treatment with tyrosine kinase inhibitors (TKIs).

Methods

Global gene and miRNA expression profiles were assessed using genome-wide RNA and miRNA microarray technology in bone marrow mononuclear cells. Fifty-one patients were recruited, and bone marrow samples were taken at diagnosis before treatment with TKIs and after 3, 6, and 12 months of treatment with TKIs. The largest number of upregulated genes was observed when the 0-month group (time of diagnosis) was compared to the 3-month group; 1774 genes were significantly upregulated, and 390 genes were significantly downregulated.

Discussion

Upregulated biological processes according to gene ontology (GO) classification involved basic cellular processes such as cell division, cell cycle, cell-cell adhesion, protein transport, mitotic nuclear division, apoptosis, and DNA replication. Differentially expressed miRNAs were annotated using GO classification to several immunity-related processes, including the T cell receptor signalling pathway, T cell costimulation, immune response, and inflammatory response. TKI therapy exerts a significant impact on cellular cycle processes and T-cell activation, which was proven at the molecular level.

Real-world efficacy and safety outcomes of imatinib treatment in patients with chronic myeloid leukemia: An Australian experience

Tyrosine kinase inhibitors (TKI) have revolutionized the treatment of chronic myeloid leukemia (CML), but patients still experience treatment-limiting toxicities or therapeutic failure. To investigate the real-world use and outcomes of imatinib in patients with CML in Australia, a retrospective cohort study of patients with CML commencing imatinib (2001-2018) was conducted across two sites. Prescribing patterns, tolerability outcomes, and survival and molecular response were evaluated. 86 patients received 89 imatinib treatments. Dose modifications were frequently observed (12-month rate of 58%). At last follow-up, 62 patients (5-year rate of 55%) had permanently discontinued imatinib treatment, of which 44 switched to another TKI (5-year rate of 46%). Within 3 months of starting imatinib, 43% (95% CI, 32%-53%) of patients experienced imatinib-related grade ≥3 adverse drug reactions (ADRs). Higher comorbidity score, lower body weight, higher imatinib starting dose, and Middle Eastern or North African ancestry were associated with a higher risk of grade ≥3 ADR occurrence on multivariable analysis (MVA). Estimated overall survival and event-free survival rates at 3 years were 97% (95% CI, 92%-100%) and 81% (95% CI, 72%-92%), respectively. Cumulative incidence of major molecular response (MMR) at 3 years was 63% (95% CI, 50%-73%). On MVA, imatinib starting dose, ELTS score, BCR-ABL1 transcript type, pre-existing pulmonary disease, and potential drug-drug interactions were predictive of MMR. In conclusion, imatinib induced deep molecular responses that translated to good survival outcomes in a real-world setting, but was associated with a higher incidence of ADRs, dose modifications and treatment discontinuations than in clinical trials.

Association between the BCR-ABL gene transcripts and the laboratory hematological profile

Objective: This study describes the hematological parameters associated with the BCR-ABL gene transcripts in patients with chronic myeloid leukemia (CML). Methods: We reviewed the results of 100 detectable patients for one of the BCR-ABL gene transcripts. The eligibility criteria were based on the presence of one of the leukemic transcripts (b2a2, b3a2, and b2a2/b3a2) and complete epidemiological and hematological data. The data were obtained from the LabMaster computerized system. The Kruskal-Wallis test was used to compare the medians of the quantitative variables between the transcripts of the BCR-ABL gene and the chi-square test to compare the qualitative ones, adopting the p-value with a level of significance less than or equal to 0.05. Results: Forty-five patients (45%) presented the b2a2 transcript, 24 (24%) the b3a2 transcript and 31 (31%) a b2a2/b3a2 coexpression. Individuals who expressed the b3a2 transcript had higher leukocyte counts and platelet levels, but we found no differences compared with individuals who expressed the other transcript. Conclusion: In this study, the BCR-ABL gene transcripts did not influence the hematological parameters of patients with CML.

Comparison of molecular responses and outcomes between BCR‐ABL1 e14a2 and e13a2 transcripts in chronic myeloid leukemia

Several studies have compared the molecular responses between e14a2 and e13a2 BCR::ABL1 transcripts in chronic myeloid leukemia (CML) patients treated with front‐line imatinib, but there were very limited studies on nilotinib or dasatinib‐treated patients. We retrospectively analyzed the molecular responses in 1124 CML patients with the e14a2 or e13a2 transcript receiving front‐line imatinib, nilotinib or dasatinib treatment. Patients with the e14a2 transcript had higher optimal response rates than those with the e13a2 transcript at 12 months in the imatinib‐treated group, and 6 and 12 months in the nilotinib‐treated group. The optimal response rates were not significantly different between the two transcripts in the dasatinib‐treated group at landmark molecular responses. With a median follow‐up time of 48.4 months, higher cumulative incidences of BCR::ABL1 International Scale ≤1% and major molecular response were observed in patients with the e14a2 rather than the e13a2 transcript receiving front‐line imatinib or nilotinib treatment, but not in dasatinib‐treated patients. The progression‐free survival and overall survival did not differ between the two transcripts in all three treatment groups. In view of the speed and depth of molecular responses, BCR::ABL1 transcript subtypes might provide helpful information in selecting a front‐line tyrosine kinase inhibitor for individual young patients with future potential treatment‐free remission.

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.

The Outcomes of Ponatinib Therapy in Patients With Chronic Myeloid Leukemia Resistant or Intolerant to Previous Tyrosine Kinase Inhibitors, Treated in Poland Within the Donation Program

INTRODUCTION

Tyrosine kinase inhibitors (TKIs) have greatly improved the treatment outcome for most patients with chronic myeloid leukemia (CML). Ponatinib is a new pan-inhibitor of TK active in resistant CML. This study aimed to evaluate the efficacy and safety of ponatinib in patients suffering from CML.

PATIENTS AND METHODS

This multicenter, non-randomized, observational, retrospective study evaluated the efficacy and safety of ponatinib administered in adult CML patients in any disease phase, including those with a detected ABL T315I mutation, which were resistant or intolerant to previous-generation TKIs. The study comprised 43 patients benefiting from the ponatinib donation program who were treated in 16 Polish centers.

RESULTS

For patients who started treatment with ponatinib in chronic phase (CP) (n = 23) and in accelerated phase (AP) (n = 3) the median time on ponatinib was 19.5 months (range: 1.0-35.4), and 31.7 months (range: 31.0-34.1), respectively. All these patients were in CP after 1 month of treatment and at the end of observation - none of them progressed to AP or blastic phase (BP) during the study, meaning that progression-free survival was 100% at the end of observation (35.4 months). The estimated 2-year survival in this group of patients was 84%. For all 43 patients, median survival was not reached (lower quartile 6.3 months), and estimated 2-year survival was 60%.

CONCLUSION

Our analysis confirmed ponatinib efficacy in a significant proportion of patients heavily pre-treated with TKIs achieving durable responses in both CP and AP/BP CML groups.

Predictive scoring systems for molecular responses in persons with chronic phase chronic myeloid leukemia receiving initial imatinib therapy

It is vital for physicians and persons with chronic myeloid leukemia (CML) to accurately predict the likelihood of achieving a major molecular response (MMR) and a deep molecular response (DMR; at least MR⁴) at the start of imatinib-therapy, which could help in decision making of treatment goals and strategies. To answer this question, we interrogated data from 1369 consecutive subjects with chronic phase CML receiving initial imatinib-therapy to identify predictive co-variates. Subjects were randomly-assigned to training (n = 913) and validation (n = 456) datasets. Male sex, higher WBC concentration, lower haemoglobin concentration, higher percentage blood blasts and larger spleen size were significantly-associated with lower cumulative incidences of MMR and MR⁴ in training dataset. Using Fine-Gray model, we developed the predictive scoring systems for MMR and MR⁴ which classified subjects into the low-, intermediate- and high-risk cohorts with significantly-different cumulative incidences of MMR and MR⁴ with good predictive discrimination and accuracy in training and validation cohorts with high area under the receiver-operator characteristic curve (AUROC) values. These data may help physicians decide appropriateness of initial imatinib therapy.

Impact of BCR-ABL1 Transcript Type on Outcome in Chronic Myeloid Leukemia Patients Treated With Tyrosine Kinase Inhibitors: A Pairwise and Bayesian Network Meta-Analysis

PURPOSE

To evaluate the impact of BCR-ABL1 transcript type on outcome in chronic myeloid leukemia (CML) patients treated with tyrosine kinase inhibitors (TKIs).

METHODS

PubMed, Embase and Cochrane library were systematically searched for relevant studies. Outcomes assessed were: major molecular response (MMR) at 6, 12, 18 and 60 months, deep molecular response (DMR) at 6, 12, 18 and 60 months, event-free survival (EFS), progression-free survival (PFS), overall survival (OS) and treatment-free remission (TFR). Odds ratios (ORs) and hazard ratios (HRs) were estimated and pooled using a random effect model.

RESULTS

A total of 16 retrospective cohort studies involving 5,411 patients were included in this study. Compared with e13a2 transcripts, there was a statistically significant advantage for patients with e14a2 (alone or with co-expressed e13a2) in terms of MMR and DMR at 6, 12 and 18 months. This benefit was sustained up to 5 years for patients with e14a2 transcripts (OR 1.60, 1.23-2.07 and 2.21, 1.71-2.87, respectively), but not for patients with both transcripts. The expression of e14a2 also improved EFS (HR 0.71, 0.53-0.94) and OS (HR 0.76, 0.57-1.00) throughout treatment period. Importantly, having e14a2 transcripts were associated with a higher rate of TFR (OR 2.94, 1.70-5.08) in CML patients attempting TKI discontinuation. Bayesian network meta-analysis showed that e14a2 had the highest probability to be the most favorable transcript type for all outcomes, followed by both and e13a2.

CONCLUSIONS

The expression of e14a2 had a positive impact on MMR, DMR, EFS, OS and TFR. We suggest that in the future, the e14a2 transcript can be added to the list of prognostic factors to guide clinical decisions in treating CML.

SYSTEMATIC REVIEW REGISTRATION

[https://www.crd.york.ac.uk/PROSPERO/#myprospero], identifier PROSPERO (CRD42021288440).

Discontinuation of Tyrosine Kinase Inhibitors in Patients with Chronic Myeloid Leukemia: a Review of the Biological Factors Associated with Treatment-Free Remission

Purpose of Review

Clinical factors alone do not enable us to differentiate which patients will maintain treatment-free remission (TFR) from those who are likely to relapse. Thus, patient-specific factors must also play a role. This review will update the reader on the most recent studies presenting biological factors that can help predict tyrosine kinase inhibitor (TKI) discontinuation success.

Recent Findings

Cellular and molecular factors with a suggested role in TFR include immune factors and leukemic stem cell (LSC) persistence; the BCR::ABL1 transcript type, halving time, and BCR::ABL1 DNA and RNA positivity; as well as other molecular factors such as somatic mutations, RNA expression, and telomere length.

Summary

Our review presents several biomarkers with predictive value for TFR but also highlights areas of unmet need. Future discontinuation guidelines will likely include biological factors for the personalization of TFR prediction. However, it will be important that such advances do not prevent more patients from making a TKI discontinuation attempt.

Genomic Mechanisms Influencing Outcome in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) represents the disease prototype of genetically based diagnosis and management. Tyrosine kinase inhibitors (TKIs), that target the causal BCR::ABL1 fusion protein, exemplify the success of molecularly based therapy. Most patients now have long-term survival; however, TKI resistance is a persistent clinical problem. TKIs are effective in the BCR::ABL1-driven chronic phase of CML but are relatively ineffective for clinically defined advanced phases. Genomic investigation of drug resistance using next-generation sequencing for CML has lagged behind other hematological malignancies. However, emerging data show that genomic abnormalities are likely associated with suboptimal response and drug resistance. This has already been supported by the presence of BCR::ABL1 kinase domain mutations in drug resistance, which led to the development of more potent TKIs. Next-generation sequencing studies are revealing additional mutations associated with resistance. In this review, we discuss the initiating chromosomal translocation that may not always be a straightforward reciprocal event between chromosomes 9 and 22 but can sometimes be accompanied by sequence deletion, inversion, and rearrangement. These events may biologically reflect a more genomically unstable disease prone to acquire mutations. We also discuss the future role of cancer-related gene mutation analysis for risk stratification in CML.

Combined Inhibition of Bcl2 and Bcr-Abl1 Exercises Anti-Leukemia Activity but Does Not Eradicate the Primitive Leukemic Cells

Background: The management of Philadelphia Chromosome-positive (Ph+) hematological malignancies is strictly correlated to the use of BCR-ABL1 tyrosine kinase inhibitors (TKIs). However, these drugs do not induce leukemic stem cells death and their persistence may generate a disease relapse. Published reports indicated that Venetoclax, a selective BCL2 inhibitor, could be effective in Ph+ diseases, as BCL2 anti-apoptotic activity is modulated by BCR-ABL1 kinase. We, therefore, investigated if BCL2 inhibition, alone or combined with Nilotinib, a BCR-ABL1 inhibitor, affects the primitive and committed Ph+ cells survival. Methods: We used Ph+ cells isolated from leukemic patients at diagnosis. To estimate the therapeutic efficacy of BCL2 and BCR-ABL1 inhibition we employed long-term culture, proliferation and apoptosis assay. Immunoblot was used to evaluate the ability of treatment to interfere with the down-stream targets of BCR-ABL1. Results: Blocking BCL2, we observed reduced proliferation and clonogenic potential of CML CD34-positive cells and this cytotoxicity was improved by combination with BCR-ABL1 inhibitor. However, BCL2 inhibition, alone or in combination regiment with BCR-ABL1 inhibitor, did not reduce the self-renewal of primitive leukemic cells, while strongly induced cell death on primary Ph+ Acute Lymphoblastic Leukemia (ALL). Conclusion: Our results suggest that primitive CML leukemic cells are not dependent on BCL2 for their persistence and support that committed CML and Ph + ALL cells are dependent by BCL2 and BCR-ABL1 cooperation for their survival. The antileukemic activity of BCL2 and BCR-ABL1 dual targeting may be a useful therapeutic strategy for Ph+ ALL patients.

Clinicopathological Variables and Outcome in Chronic Myeloid Leukemia Associated With BCR-ABL1 Transcript Type and Body Weight: An Outcome of European LeukemiaNet Project

Objective

It is debatable whether BCR-ABL1 transcript type has an impact on outcome of treatment of patients with CML, and it is not widely studied whether body weight influences response to treatment. In this study, we tried to find out if any of these factors has an impact on response to treatment and outcome.

Methodology

We conducted a retrospective analysis of the files of 79 patients being treated in our center for CML with known BCR-ABL1 breakpoints, and patients’ management and response assessment was done based on ELN 2013 guidelines. The analysis was performed based on two main groups, obese vs. normal BMI, and then based on BCR-ABL1 transcripts: e13a2 vs. e14a2. Cumulative incidence of MMR, CCyR, and DMR were estimated using the Kaplan–Meier survival curve method, and comparisons between groups were performed by the Log-rank/Gray test methods.

Results/conclusion

In the patient-cohort studied, there was no statistically significant difference in molecular response between patients with CML based on body weight or transcript type although patients in the obesity group achieved higher and faster MMR with no statistical significance.

Making Treatment-Free Remission (TFR) Easier in Chronic Myeloid Leukemia: Fact-Checking and Practical Management Tools

In chronic-phase chronic myeloid leukemia (CML), tyrosine kinase inhibitors (TKIs) are the standard of care, and treatment-free remission (TFR) following the achievement of a stable deep molecular response (DMR) has become, alongside survival, a primary goal for virtually all patients. The GIMEMA CML working party recently suggested that the possibility of achieving TFR cannot be denied to any patient, and proposed specific treatment policies according to the patient's age and risk. However, other international recommendations (including 2020 ELN recommendations) are more focused on survival and provide less detailed suggestions on how to choose first and subsequent lines of treatment. Consequently, some grey areas remain. After literature review, a panel of Italian experts discussed the following controversial issues: (1) early prediction of DMR and TFR: female sex, non-high disease risk score, e14a2 transcript and early MR achievement have been associated with stable DMR, but the lack of these criteria is not sufficient to exclude any patient from TFR; (2) criteria for first and subsequent line therapy choice: a number of patient and drug characteristics have been proposed to make a personalized decision; (3) monitoring of residual disease after discontinuation: after the first 6 months, the frequency of molecular tests can be reduced based on MR4.5 persistence and short turnaround time; (4) prognosis of TFR: therapy and DMR duration are important to predict TFR; although immunological control of CML plays a role, no immunological predictive phenotype is currently available. This guidance is intended as a practical tool to support physicians in decision making.

Treatment-Free Remission in Chronic Myeloid Leukemia: Can We Identify Prognostic Factors?

Simple Summary

Chronic myeloid leukemia (CML) is a blood cancer. Unlike other cancers CML treatment is lifelong and many patients experience side effects. For those patients who respond well to treatment and achieve deep molecular remission, quality of life is impacted because of continuous treatment. In this review, we look at emerging clinical trials which aim to investigate which patients can safely stop treatment. Treatment-free remission is the ultimate goal for CML patients, but there is still a gap in our knowledge as to why some patients can achieve treatment-free remission, while others relapse when treatment is stopped. Here we discuss if there are any prognostic factors that can predict the best candidates who qualify for treatment discontinuation, with a view to keeping them in remission.

Abstract

Following the development of tyrosine kinase inhibitors (TKI), the survival of patients with chronic myeloid leukaemia (CML) drastically improved. With the introduction of these agents, CML is now considered a chronic disease for some patients. Taking into consideration the side effects, toxicity, and high cost, discontinuing TKI became a goal for patients with chronic phase CML. Patients who achieved deep molecular response (DMR) and discontinued TKI, remained in treatment-free remission (TFR). Currently, the data from the published literature demonstrate that 40–60% of patients achieve TFR, with relapses occurring within the first six months. In addition, almost all patients who relapsed regained a molecular response upon retreatment, indicating TKI discontinuation is safe. However, there is still a gap in understanding the mechanisms behind TFR, and whether there are prognostic factors that can predict the best candidates who qualify for TKI discontinuation with a view to keeping them in TFR. Furthermore, the information about a second TFR attempt and the role of gradual de-escalation of TKI before complete cessation is limited. This review highlights the factors predicting success or failure of TFR. In addition, it examines the feasibility of a second TFR attempt after the failure of the first one, and the current guidelines concerning TFR in clinical practice.

Early BCR-ABL1 kinetics are predictive of subsequent achievement of treatment-free remission in chronic myeloid leukemia

With treatment-free remission (TFR) rapidly becoming the ultimate goal of therapy in chronic myeloid leukemia (CML), there is a need to develop strategies to maximize sustained TFR by improving our understanding of its key determinants. Chronic-phase CML patients attempting TFR were evaluated to identify the impact of multiple variables on the probability of sustained TFR. Early molecular response dynamics were included as a predictive variable, assessed by calculating the patient-specific halving time of BCR-ABL1 after commencing tyrosine kinase inhibitor (TKI) therapy. Overall, 115 patients attempted TFR and had ≥12 months of follow-up. The probability of sustained TFR, defined as remaining in major molecular response off TKI therapy for 12 months, was 55%. The time taken for the BCR-ABL1 value to halve was the strongest independent predictor of sustained TFR: 80% in patients with a halving time of <9.35 days (first quartile) compared with only 4% if the halving time was >21.85 days (last quartile) (P < .001). The e14a2 BCR-ABL1 transcript type and duration of TKI exposure before attempting TFR were also independent predictors of sustained TFR. However, the BCR-ABL1 value measured at 3 months of TKI was not an independent predictor of sustained TFR. A more rapid initial BCR-ABL1 decline after commencing TKI also correlated with an increased likelihood of achieving TFR eligibility. The association between sustained TFR and the time taken for BCR-ABL1 to halve after commencing TKI was validated using an independent dataset. These data support the critical importance of the initial kinetics of BCR-ABL1 decline for long-term outcomes.

Impact of BCR-ABL1 Transcript Type on Response, Treatment-Free Remission Rate and Survival in Chronic Myeloid Leukemia Patients Treated with Imatinib

The most frequent BCR-ABL1-p210 transcripts in chronic myeloid leukemia (CML) are e14a2 and e13a2. Imatinib (IM) is the most common first-line tyrosine–kinase inhibitor (TKI) used to treat CML. Some studies suggest that BCR-ABL1 transcript types confer different responses to IM. The objective of this study was to correlate the expression of e14a2 or e13a2 to clinical characteristics, cumulative cytogenetic and molecular responses to IM, acquisition of deep molecular response (DMR) and its duration (sDMR), progression rate (CIP), overall survival (OS), and treatment-free remission (TFR) rate. We studied 202 CML patients, 76 expressing the e13a2 and 126 the e14a2, and correlated the differential transcript expression with the above-mentioned parameters. There were no differences in the cumulative incidence of cytogenetic responses nor in the acquisition of DMR and sDMR between the two groups, but the e14a2 transcript had a positive impact on molecular response during the first 6 months, whereas the e13a2 was associated with improved long-term OS. No correlation was observed between the transcript type and TFR rate.

Effect of HSP90AB1 and CC domain interaction on Bcr-Abl protein cytoplasm localization and function in chronic myeloid leukemia cells

Background

The fusion oncoprotein Bcr-Abl is mostly located in the cytoplasm, which causes chronic myeloid leukemia (CML). After moving into the nucleus, the fusion protein can induce apoptosis of CML cells. The coiled-coil domain (CC domain) of Bcr-Abl protein plays a central role in the subcellular localization. However, how CC domain affects subcellular localization of Bcr-Abl remains unclear.

Methods

Herein, the key proteins interacting with the Bcr-Abl CC domain were screened by immunoprecipitation binding mass spectrometry. The specific site of Bcr-Abl CC domain binding to target protein was predicted by Deep Viewer. Immunoprecipitation assay was used to confirmed the specific sites of protein binding. IF and western blot were used to observe the subcellular localization of target protein. Western blot was used to examine the protein changes. CCK-8, clonal formation test and FCM cycle detection were used to observe the effect of inhibitor on the proliferation ability of CML cells. FCM apoptosis detection was used to observe the level of cells apoptosis.

Results

HSP90AB1 interacts with Bcr-Abl CC domain via N-terminal domain (NTD), preventing the transport of Bcr-Abl protein to the nucleus and maintaining the activation of Bcr-Abl tyrosine kinase. The nucleus-entrapped Bcr-Abl markedly inhibits the proliferation and induces apoptosis of CML cells by activating p73 and repressing the expression of cytoplasmic oncogenic signaling pathways mediated by Bcr-Abl. Moreover, the combination of 17AAG (Tanespimycin) with Leptomycin B (LMB) considerably decreased the proliferation of CML cells.

Conclusion

Our study provides evidence that it is feasible to transport Bcr-Abl into the nucleus as an alternative strategy for the treatment of CML, and targeting the NTD of HSP90AB1 to inhibit the interaction with Bcr-Abl is more accurate for the development and application of HSP90 inhibitor in the treatment of CML and other Bcr-Abl-addicted malignancies.

Measuring prognosis in chronic myeloid leukemia: what's new?

Introduction: The outcome of chronic myeloid leukemia (CML) patients in chronic phase has changed after the introduction of tyrosine kinase inhibitors (TKIs). The life expectancy is actually similar to that of the general population. Prognostic stratification at baseline is part of a patient-centered approach to decide the best therapeutic approach.Areas covered: In this review, the current prognostic factors examined at baseline are detailed and the meaning is explained. A broad research on Medline, Embase and archives from EHA and ASH congresses, was performed. Prognostic factors have been divided into patient-related (age, gender, comorbidities, etc.) and disease-related (additional cytogenetic abnormalities, type of transcript, etc). New information about genomic data and the potential role of patient-reported outcomes is also discussed.Expert Opinion: Prognostic factors at baseline should be considered to evaluate the long-term probability of disease-related death, the possible toxicity, and the projected long-term overall survival. The genomic assessment would provide the basis for a genomic-based risk and help in oriented decision-making process.

Long-term follow-up of late chronic phase chronic myeloid leukemia patients treated with imatinib after interferon failure: a single center experience

We report the long-term outcome of 139 patients treated with imatinib in late chronic phase after IFN failure. Median follow-up was 16.6 years and the estimated 18-year OS was 64.8%. 18-year EFS and PFS were 69% and 64.4%, respectively. Fifty (36%) patients stopped imatinib, 72% received a second line. b2a2 transcript was associated with a significantly inferior 18-year OS (p = 0.008), FFS (p = 0.036), PFS (p = 0.013) compared to the b3a2 type, whilst the type of transcript did not influence the time to response achievement. Failure to achieve MMR at 12 months significantly reduced the chance of reaching a DMR (p = 0.001). Imatinib discontinuation after achieving a sustained deep molecular response was attempted in 14 patients; 12 (86%) are still in treatment-free remission (TFR) at the last follow-up. Our experience confirms the long-term efficacy of imatinib after IFNα failure in real-life setting and documents the possibility of attempting a TFR in this subset of patients.

Higher Red Blood Cell Distribution Width is a Poor Prognostic Factor for Patients with Chronic Myeloid Leukemia

Purpose

Red blood cell distribution width (RDW) has been considered as a potential indicator of the effects of treatment or as a prognostic indicator for various malignancies. Most chronic myeloid leukemia (CML) patients are in the chronic phase, but some have transformed to accelerated phase or blast phase (blast crisis). However, the clinical significance of RDW in CML remains limited.

Patients and Methods

In the present study, detailed clinical information and the RDW of 168 healthy people and 153 CML patients (106 patients for the training cohort and 47 patients for the validation cohort) were retrospectively assessed.

Results

Multivariate analysis demonstrated that patient age (OR, 1.081; 95CI% 1.039~1.125; p < 0.001), platelet counts (OR, 0.997; 95CI% 0.994~0.999; p = 0.001) and RDW at admission (OR,1.469; 95CI% 1.121~1.925; p = 0.005) were significantly associated with the patients with advanced phase. Among CML patients in the chronic phase, higher RDW was significantly associated with overall survival (OS; p = 0.0008) and the event-free survival (EFS; p = 0.0221) among CML patients with chronic phase, but not with Transformation-free survival (TFS; p = 0.0821). Furthermore, higher RDW was associated with higher mortality compared to patients with low RDW (CML-associated deaths; p < 0.0001). In addition, a decline in RDW is associated with the treatment of CML patients with tyrosine kinase inhibitors, especially at 6 and 12 months after the start of treatment.

Conclusion

Higher RDW is a potential prognostic biomarker for chronic CML patients.

The prognostic importance of BCR-ABL transcripts in Chronic Myeloid Leukemia: A systematic review and meta-analysis

BACKGROUND

Chronic Myeloid Leukemia (CML) is characterized by the overproduction of BCR-ABL, a tyrosine kinase with constitutive activity, in which the majority of CML patients have e13a2 or e14a2 transcripts. Reckoned the possible associations between the hematologic and molecular features of the disease, a profound understanding of different aspects of this neoplasm would be provided.

METHOD

The authors implemented a systematic literature search, utilizing the terms published articles or internationally accepted abstracts from PubMed, Embase, Medline, Cochrane library before January 2019. Weighted mean proportion and 95 % confidence intervals (CIs) of CML prevalence calculated using a fixed-effects and a random-effects model. Statistical heterogeneity was evaluated using the I2 statistic.

RESULTS

34 studies for a total of 54,034 Patients were selected and included in the review. Results revealed that compared to e13a2 group, the overall estimated prevalence is much higher in the e14a2 (39 % and 54 %, respectively). Besides, the overall estimated prevalence ratio of male to female was higher in the e13a2 group in comparison to e14a2 (1.08 and 0.856 respectively). The overall estimated prevalence of dual transcription of e13a2/e14a2 was 1.11 %, and male/female overall estimated prevalence ratio was 1.18.

CONCLUSION

This meta-analysis of CML patients demonstrated the e14a2 as the more common transcript type. Usually, the e14a2 transcript is prevalent in females, whereas e13a2 and dual transcription of e13a2/e14a2 are more common in men. These data explicate that the differences in proportion are not by chance. This is crucial, as the transcript type is a variable suspected to be of prognostic importance for the treatment-related response, the outcome of treatment, and the rate of treatment-free remission.

NPM1 Mutated, BCR-ABL1 Positive Myeloid Neoplasms: Review of the Literature

Breakpoint cluster region - Abelson (BCR-ABL1) chimeric protein and mutated Nucleophosmin (NPM1) are often present in hematological cancers, but they rarely coexist in the same disease. Both anomalies are considered founder mutations that inhibit differentiation and apoptosis, but BCR-ABL1 could act as a secondary mutation conferring a proliferative advantage to a pre-neoplastic clone. The 2016 World Health Organization (WHO) classification lists the provisional acute myeloid leukemia (AML) with BCR-ABL1, which must be diagnosed differentially from the rare blast phase (BP) onset of chronic myeloid leukemia (CML), mainly because of the different therapeutic approach in the use of tyrosine kinase inhibitors (TKI). Here we review the BCR/ABL1 plus NPMc+ published cases since 1975 and describe a case from our institution in order to discuss the clinical and molecular features of this rare combination, and report the latest acquisition about an occurrence that could pertain either to the rare AML BCR-ABL1 positive or the even rarer CML-BP with mutated NPM1 at the onset. Differential diagnosis is based on careful analysis of genotypic and phenotypic features and anamnestic, clinical evolution, and background data. Therapeutic decisions must consider the broader clinical aspects, the comparatively mild effects of TKI therapy versus the great benefit that might bring to most of the patients, as may be incidentally demonstrated by our case history.

Distribution of BCR-ABL1 Transcript Variants in Nigerians with Chronic Myeloid Leukemia

The distribution of BCR-ABL1 transcript variants e13a2 ("b2a2") and e14a2 ("b3a2") in Nigerians with chronic myeloid leukemia (CML) had not been previously studied. In addition, there is paucity of data on the impact of BCR-ABL1 transcript variants on clinical presentation and survival in CML patients in Nigeria. The BCR-ABL1 transcript variants were analyzed in 230 Imatinib-treated CML patients at diagnosis. Patients with incomplete data (n = 28), e19a2 (n = 3) and e1a2 (n = 1) were excluded from analysis of transcript variant on disease presentation and survival leaving only 198. The frequencies of BCR-ABL1 transcript variants were 30 (13.0%), 114 (49.6%), 82 (35.7%), three (1.3%) and one (0.4%) for e13a2, e14a2, co-expression of e13a2/e14a2, e19a2 and e1a2, respectively. A significantly higher platelet count was found in patients with e13a2 variant (531.1 ± 563.4 × 10⁹/L) than in those expressing e14a2 (488.2 ± 560.3 × 10⁹/L) or e13a2/e14a2 (320.7 ± 215.8 × 10⁹/L); p = 0.03. No significant differences were found between the variants with regards to gender, age, phase of disease at diagnosis, total white blood cell count, neutrophil percentage, hematocrit, splenomegaly or hepatomegaly. Overall survival was higher but not statistically significant (p = 0.4) in patients with e14a2 variant (134 months) than in e13a2 (119 months) and co-expression of e13a2/e14a2 (115 months). Nigerian CML patients have the highest incidence of co-expression of e13a2 and e14a2. Distinct disease characteristics which contrast with findings from the Western countries were also identified in Nigerians which may be due to genetic factors.

Chronic Myeloid Leukemia, Version 2.2021, NCCN Clinical Practice Guidelines in Oncology

Chronic myeloid leukemia (CML) is defined by the presence of Philadelphia chromosome (Ph) which results from a reciprocal translocation between chromosomes 9 and 22 [t(9;22] that gives rise to a BCR-ABL1 fusion gene. CML occurs in 3 different phases (chronic, accelerated, and blast phase) and is usually diagnosed in the chronic phase. Tyrosine kinase inhibitor therapy is a highly effective first-line treatment option for all patients with newly diagnosed chronic phase CML. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with chronic phase CML.

Impact of the major BCR-ABL1 transcript type on clinical and biological parameters and molecular response in patients with chronic myeloid leukemia

AIM

In chronic myeloid leukemia (CML), the impact of MBCR-ABL1 major transcript type on disease phenotype and response to treatment still controversial to date. This work aims to study the influence of Mb3a2 and Mb2a2 transcripts on clinico-biological parameters and the molecular response in patients with chronic phase chronic myeloid leukemia (CP-CML) treated with Imatinib as frontline therapy.

METHODS

This is six years prospective study started in March 1 st, 2013. 67 patients with newly CP-CML were treated by Imatinib as frontline therapy. Clinical and biological characteristics disease were collected for all patients. Molecular typing was performed by multiplex RT-PCR and quantification of transcripts by real-time quantitative PCR (qRT-PCR). The cumulative incidence of deep molecular response (DMR) was estimated by the Kaplan-Meier method. The comparison was made using the parametric Log-Rank test. A value of P ≤ 0.05 is considered significant.

RESULTS

61% of patients expressed b3a2, 35.82% b2a2 and 2.98% expressed a rare transcript of type e19a2. At diagnosis, the b2a2 type had a higher level of expression than that of b3a2 (67.92 vs 53.79%; P = 0.03). This insignificant difference between the two transcript subgroups was also observed for rates below 1% at 6 months (54 vs 39; P = 0.26) and below 0.1% (54 vs 44 %; P = 0.50), (77 vs 50%; P = 0.09) and (81 vs 78 %; P = 0.52) at 12, 18 and 24 months respectively. The two types of transcript had almost the same kinetics. Nevertheless, the absolute value of the BCR-ABL1/ABL ratio decrease was faster in the group of patients expressing b3a2, than in those expressing b2a2. At 18 months post IM therapy, patients with a b3a2 transcript have a trend of better MMR that those with b2a2 (77 vs 50%; P = 0.09). The DMR was not significantly different between two groups at 24 months (50 vs 32%; P = 0.20) and 36 months (75 vs 70%; P = 0.54) respectively. The cumulative probability of achieving MRD at 5 years was higher in patients with b3a2 type but not statistically significant; (85 vs. 68%; P = 0.17).

CONCLUSION

Patients with b3a2 transcript may be associated with a better response to Imatinib therapy.

Incidences of Deep Molecular Responses and Treatment-Free Remission in de Novo CP-CML Patients

Simple Summary

Tyrosine kinase inhibitors (TKI) can be safely discontinued in chronic myeloid leukemia patients. Achieving a sustained deep molecular response (DMR) before stop is recommended. Currently, the proportion of patients who achieve a sustained DMR remains to be determined. Based on the follow-up of 398 patients over a ten-years period, we evaluate that 46% of them have achieved a sustained DMR. Gender, BCR-ABL1 transcript type, and disease risk scores were significantly associated with the probability of achieving a DMR. 95/398 (24%) patients stopped TKI with a probability of maintaining molecular reponse without TKI resumption of 47% at 48 months after stop. In this study, TKI duration before stop and second (nilotinib, dasatinib, bosutinib) generation frontline TKI compared to imatinib were significantly associated with a lower risk of molecular relapse after stop in patients who have achieved a sustained DMR.

Abstract

Background: Tyrosine Kinase Inhibitors (TKIs) discontinuation in patients who had achieved a deep molecular response (DMR) offer now the opportunity of prolonged treatment-free remission (TFR). Patients and Methods: Aims of this study were to evaluate the proportion of de novo chronic-phase chronic myeloid leukemia (CP-CML) patients who achieved a sustained DMR and to identify predictive factors of DMR and molecular recurrence-free survival (MRFS) after TKI discontinuation. Results: Over a period of 10 years, 398 CP-CML patients treated with first-line TKIs were included. Median age at diagnosis was 61 years, 291 (73%) and 107 (27%) patients were treated with frontline imatinib (IMA) or second- or third-generation TKIs (2–3G TKI), respectively. With a median follow-up of seven years (range, 0.6 to 13.8 years), 182 (46%) patients achieved a sustained DMR at least 24 months. Gender, BCR-ABL1 transcript type, and Sokal and ELTS risk scores were significantly associated with a higher probability of sustained DMR while TKI first-line (IMA vs. 2–3G TKI) was not. We estimate that 28% of CML-CP would have been an optimal candidate for TKI discontinuation according to recent recommendations. Finally, 95 (24%) patients have entered in a TFR program. MRFS rates at 12 and 48 months were 55.1% (95% CI, 44.3% to 65.9%) and 46.9% (95% CI, 34.9% to 58.9%), respectively. In multivariate analyses, first-line 2–3G TKIs compared to IMA and TKI duration were the most significant factors of MRFS. Conclusions: Our results suggest that frontline TKIs have a significant impact on TFR in patients who fulfill the selection criteria for TKI discontinuation.

Prognostic Significance of Transcript-Type BCR - ABL1 in Chronic Myeloid Leukemia

Chronic myeloid leukemia (CML) is characterized by the presence of the BCR-ABL1 fusion gene. In more than 95% of CML patients, the typical BCR-ABL1 transcript subtypes are e13a2 (b2a2), e14a2 (b3a2), or the simultaneous expression of both. Other less frequent transcript subtypes, such as e1a2, e2a2, e6a2, e19a2, e1a3, e13a3, and e14a3, have been sporadically reported. The main purpose of this review is to assess the possible impact of different transcripts on the response rate to tyrosine kinase inhibitors (TKIs), the achievement of stable deep molecular responses (s-DMR), the potential maintenance of treatment-free remission (TFR), and long-term outcome of CML patients treated with TKIs. According to the majority of published studies, patients with e13a2 transcript treated with imatinib have lower and slower cytogenetic and molecular responses than those with e14a2 transcript. They should be considered a high-risk group that would most benefit from frontline treatment with second-generation TKIs (2GTIKIs). Although few studies have been published, similar significant differences in response rates to 2GTKIs have been not reported. The e14a2 transcript seems to be a favorable prognostic factor for obtaining s-DMR, irrespective of the TKI received, and is also associated with a very high rate of TFR maintenance. Indeed, patients with e13a2 transcript achieve a lower rate of s-DMR and experience a higher probability of TFR failure. According to most reported data in the literature, the type of transcript does not seem to affect long-term outcomes of CML patients treated with TKIs. In TFR, the e14a2 transcript appears to be related to favorable responses. 2GTKIs as frontline therapy might be a convenient approach in patients with e13a2 transcript to achieve optimal long-term outcomes.

Influence of major BCR-ABL1 transcript subtype on outcome in patients with chronic myeloid leukemia in chronic phase treated frontline with nilotinib

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm characterized by the presence of BCR-ABL1 transcript as a result of reciprocal translocation between chromosome 9 and 22. The most common transcripts subtypes are e13a2 (b2a2) and e14a2 (b3a2). The prognostic impact of the type of BCR-ABL1 transcript has been the subject of controversies over time. In the imatinib era, several studies have suggested a deeper and faster response in patients expressing e14a2. However, the impact on response after first line therapy with a second-generation tyrosine kinase inhibitor, nilotinib, is unknown. We retrospectively evaluated 118 patients newly diagnosed with chronic phase CML and treated frontline with nilotinib inside or outside clinical trial in five French centers. Only patients expressing e14a2 or e13a2 transcripts alone were analyzed. At baseline, 55.3% expressed e14a2, 44.7% expressed e13a2. The median age was 51 years and median follow-up was 49 months. Relative risks of CML at diagnosis were similar according to the ELTS score (p = .87). Complete hematological response and complete cytogenetic response rates were similar among groups. Patients expressing e14a2 transcripts compared to e13a2 transcripts had deeper and faster molecular responses, when considering MMR (100% vs 84.1%, p = .007) with a median time of 6.7 and 17.1 months or MR^4.5 (100% vs 59.9%, p = .005) with a median time of 39.7 and 70.9 months, respectively. A sustained treatment free remission was observed in 10/10 patients with e14a2 versus 1/3 with e13a2 transcript (p = .04). In conclusion, even treated with nilotinib first line, patients with chronic phase CML expressing BCR-ABL1 e13a2 transcript have a lower rate of deep molecular responses.

ABL Genomic Editing Sufficiently Abolishes Oncogenesis of Human Chronic Myeloid Leukemia Cells In Vitro and In Vivo

Chronic myelogenous leukemia (CML) is the most common type of leukemia in adults, and more than 90% of CML patients harbor the abnormal Philadelphia chromosome (Ph) that encodes the BCR-ABL oncoprotein. Although the ABL kinase inhibitor (imatinib) has proven to be very effective in achieving high remission rates and improving prognosis, up to 33% of CML patients still cannot achieve an optimal response. Here, we used CRISPR/Cas9 to specifically target the BCR-ABL junction region in K562 cells, resulting in the inhibition of cancer cell growth and oncogenesis. Due to the variety of BCR-ABL junctions in CML patients, we utilized gene editing of the human ABL gene for clinical applications. Using the ABL gene-edited virus in K562 cells, we detected 41.2% indels in ABL sgRNA_2-infected cells. The ABL-edited cells reveled significant suppression of BCR-ABL protein expression and downstream signals, inhibiting cell growth and increasing cell apoptosis. Next, we introduced the ABL gene-edited virus into a systemic K562 leukemia xenograft mouse model, and bioluminescence imaging of the mice showed a significant reduction in the leukemia cell population in ABL-targeted mice, compared to the scramble sgRNA virus-injected mice. In CML cells from clinical samples, infection with the ABL gene-edited virus resulted in more than 30.9% indels and significant cancer cell death. Notably, no off-target effects or bone marrow cell suppression was found using the ABL gene-edited virus, ensuring both user safety and treatment efficacy. This study demonstrated the critical role of the ABL gene in maintaining CML cell survival and tumorigenicity in vitro and in vivo. ABL gene editing-based therapy might provide a potential strategy for imatinib-insensitive or resistant CML patients.

ABL Genomic Editing Sufficiently Abolishes Oncogenesis of Human Chronic Myeloid Leukemia Cells In Vitro and In Vivo

Chronic myelogenous leukemia (CML) is the most common type of leukemia in adults, and more than 90% of CML patients harbor the abnormal Philadelphia chromosome (Ph) that encodes the BCR-ABL oncoprotein. Although the ABL kinase inhibitor (imatinib) has proven to be very effective in achieving high remission rates and improving prognosis, up to 33% of CML patients still cannot achieve an optimal response. Here, we used CRISPR/Cas9 to specifically target the BCR-ABL junction region in K562 cells, resulting in the inhibition of cancer cell growth and oncogenesis. Due to the variety of BCR-ABL junctions in CML patients, we utilized gene editing of the human ABL gene for clinical applications. Using the ABL gene-edited virus in K562 cells, we detected 41.2% indels in ABL sgRNA_2-infected cells. The ABL-edited cells reveled significant suppression of BCR-ABL protein expression and downstream signals, inhibiting cell growth and increasing cell apoptosis. Next, we introduced the ABL gene-edited virus into a systemic K562 leukemia xenograft mouse model, and bioluminescence imaging of the mice showed a significant reduction in the leukemia cell population in ABL-targeted mice, compared to the scramble sgRNA virus-injected mice. In CML cells from clinical samples, infection with the ABL gene-edited virus resulted in more than 30.9% indels and significant cancer cell death. Notably, no off-target effects or bone marrow cell suppression was found using the ABL gene-edited virus, ensuring both user safety and treatment efficacy. This study demonstrated the critical role of the ABL gene in maintaining CML cell survival and tumorigenicity in vitro and in vivo. ABL gene editing-based therapy might provide a potential strategy for imatinib-insensitive or resistant CML patients.

The Q-LAMP Method Represents a Valid and Rapid Alternative for the Detection of the BCR-ABL1 Rearrangement in Philadelphia-Positive Leukemias

Molecular detection of the BCR-ABL1 fusion transcripts is necessary for the genetic confirmation of a chronic myeloid leukemia diagnosis and for the risk classification of acute lymphoblastic leukemia. BCR-ABL1 mRNAs are usually identified using a conventional RT-PCR technique according to the BIOMED-1 method. In this study, we evaluated 122 BCR-ABL1-positive samples with the Q-LAMP assay to establish if this technology may represent a valid alternative to the qualitative BIOMED-1 PCR technique usually employed for the detection and the discrimination of the common BCR-ABL1 transcripts (p190 and p210 isoforms). We found a 100% concordance rate between the two methods. Specifically, the p190- and p210-positive samples were amplified by Q-LAMP with a median threshold time (Tt) of 26.70 min (range: 24.45-31.80 min) and 20.26 min (range: 15.25-34.57 min), respectively. A median time of 19.63 was observed in samples displaying both (e13a2/e14a2) p210 isoforms. Moreover, the Q-LAMP assay allowed recognition of the BCR-ABL1 e13a2 and e14a2 isoforms (median Tts 18.48 for e13a2 vs. 26.08 min for e14a2; p < 0.001). Finally, 20 samples harboring rare BCR-ABL1 isoforms (e1a3, e13a3, e14a3, and e19a2) were correctly identified by the Q-LAMP assay. We conclude that the Q-LAMP assay may represent a faster and valid alternative to the qualitative BIOMED-1 RT-PCR for the diagnosis at BCR-ABL1-positive leukemias, especially when samples are analyzed in centers with restricted resources and/or limited technical expertise.

Early Management of CML

PURPOSE OF REVIEW

The marked improvement in clinical outcomes for patients with chronic myeloid leukaemia (CML) can be solely attributed to the introduction of targeted therapies against the fusion oncoprotein, BCR-ABL1. However, patient responses, although generally positive, remain heterogenous. Careful drug selection, ensuring the optimal TKI, is chosen for each patient and involves a complex decision process which incorporates consideration of numerous factors.

RECENT FINDINGS

For some patients, with disease characteristics that indicate adverse intrinsic disease biology, more potent BCR-ABL1 inhibition is often appropriate, whereas other patients with major co-morbidities will benefit from a less aggressive approach to avoid life-shortening toxicities. For the vast majority of patients, the long-term goal of therapy will be the achievement of a deep molecular response and subsequent treatment-free remission and this consideration will play a large part in the drug selection process. We explore early management of CML, from the first presentation through to frontline therapy selection.

Heterogeneous BCR-ABL1 signal patterns identified by fluorescence in situ hybridization are associated with leukemic clonal evolution and poorer prognosis in BCR-ABL1 positive leukemia

Background

Although extensive use of tyrosine kinase inhibitors has resulted in high and durable response rate and prolonged survival time in patients with BCR-ABL1 positive chronic myeloid leukemia (CML) and acute leukemia, relapse and drug resistance still remain big challenges for clinicians. Monitoring the expression of BCR-ABL1 fusion gene and identifying ABL kinase mutations are effective means to predict disease relapse and resistance. However, the prognostic impact of BCR-ABL1 signal patterns detected by fluorescence in situ hybridization (FISH) remains largely unaddressed.

Methods

BCR-ABL1 signal patterns were analyzed using FISH in 243 CML-chronic phase (CML-CP), 17 CML-blast phase (CML-BP) and 52 BCR-ABL1 positive acute lymphoblastic leukemia (ALL) patients.

Results

The patterns of BCR-ABL1 signals presented complexity and diversity. A total of 12 BCR-ABL1 signals were observed in this cohort, including 1R1G2F, 1R1G1F, 2R1G1F, 1R2G1F, 2R2G1F, 1R2G2F, 1R1G3F, 1G3F, 2G3F, 1G4F, 1R1G4F and 1R4F. Complex BCR-ABL1 signal patterns (≥ two types of signal patterns) were observed in 52.9% (n = 9) of the CML-BP patients, followed by 30.8% (n = 16) of the ALL patients and only 2.1% (n = 5) of the CML-CP patients. More importantly, five clonal evolution patterns related to disease progression and relapse were observed, and patients with complex BCR-ABL1 signal patterns had a poorer overall survival (OS) time compared with those with single patterns (5.0 vs.15.0 months, p = 0.006).

Conclusions

Our data showed that complex BCR-ABL1 signal patterns were associated with leukemic clonal evolution and poorer prognosis in BCR-ABL1 positive leukemia. Monitoring BCR-ABL1 signal patterns might be an effective means to provide prognostic guidance and treatment choices for these patients.