Efficacy of Dasatinib in a CML Patient in Blast Crisis with F317L Mutation: A Case Report and Literature Review

Overcoming flumatinib resistance in chronic myeloid leukaemia: Insights into cellular mechanisms and ivermectin's therapeutic potential

Chronic myeloid leukaemia (CML) is a haematological malignancy characterized by the constitutive tyrosine kinase activity of the BCR-ABL1 fusion protein. Flumatinib, a second-generation tyrosine kinase inhibitor, has exhibited superior clinical efficacy compared to its precursor, imatinib. However, with increased clinical use, resistance to flumatinib has emerged as a significant challenge. To investigate the mechanisms of flumatinib resistance in CML, we induced the human CML cell line K562 using a flumatinib concentration gradient method in vitro, successfully establishing a flumatinib-resistant K562/FLM cell line. This cell line exhibited cross-resistance to imatinib and doxorubicin, but remained sensitive to the antiparasitic agent ivermectin, which possesses antitumoural effects. Through cellular experimentation, we explored the resistance mechanisms, which indicated that K562/FLM cells evade flumatinib cytotoxicity by enhancing autophagy, increasing the expression of membrane transport proteins, particularly P-glycoprotein, ABCC1 and ABCC4, as well as enhancing phosphorylation of p-EGFR, p-ERK and p-STAT3 proteins. Moreover, it was found that ivermectin effectively suppressed the expression of autophagy and transport proteins in K562/FLM cells, reduced the activity of the aforementioned phosphoproteins, and promoted apoptotic cell death. Collectively, the increased autophagy, higher expression of drug-efflux proteins and hyperactivation of the EGFR/ERK/STAT3 signalling pathway were identified as pivotal elements promoting resistance to flumatinib. The significant effects of ivermectin might offer a novel therapeutic strategy to overcome flumatinib resistance and optimize the treatment outcomes of CML.

Which Second-Line Tyrosine Kinase Inhibitor(s) for Chronic Myeloid Leukemia?

OPINION STATEMENT

In patients with chronic myeloid leukemia who require second-line tyrosine kinase inhibitor therapy, many options exist. These treatments include alternate generation tyrosine kinase inhibitors and in some cases consideration of allogeneic transplant. Although efficacious, each tyrosine kinase inhibitor possesses distinct side effects and pharmacological profiles that prevent a generalizable treatment approach. Furthermore, there is limited head-to-head trial data that would suggest the superiority of one tyrosine kinase inhibitor over another to help guide treatment decisions in specific clinical settings. Therefore, we treat each patient independently. A patient's treatment plan must be personalized by a variety of clinical factors to optimize response and tolerability. Our general approach is to first examine the reason for treatment failure, which may be due to either intolerance or relapse. Second, we consider the age and patient's comorbidities such as lung disease, diabetes, or cardiovascular disease. In patients who have inadequate responses, we analyze the patient's BCR-ABL1 mutational profile, which is beneficial if that patient harbors a specific tyrosine kinase inhibitor responsive mutation, such as T315I. Using these steps, we can provide a generalizable approach to choosing the appropriate second-line tyrosine inhibitor for chronic myeloid leukemia.

From bench to bedside: bridging the gaps in best practices for real-world chronic myeloid leukemia care

INTRODUCTION

Although tyrosine kinase inhibitors (TKIs) determined an improvement of responses and overall survival (OS) in chronic phase chronic myeloid leukemia (CP-CML) patients, some patients still fail the achievement of important milestones.

AREAS COVERED

In this review, we focus on the need of appropriate molecular and mutational monitoring during TKI treatment with new laboratory tools and on new compounds developed to counteract the unmet clinical need in CP-CML.

EXPERT OPINION

The appropriate identification of BCR::ABL1 dependent and independent mechanisms of resistance with Next Generation Sequencing (NGS) and digital droplet PCR (ddPCR) can allow to improve the therapeutic strategies and prevent the onset of a failure to treatment. New compounds have been recently approved or are still in investigational trials to improve the response in some critical forms of resistance and/or intolerance to available TKIs.

Differences in Variants in the Structural Domain of BCR-ABL1 Kinase between Chinese Han and Minority Patients with Chronic Myeloid Leukemia by Sanger Sequencing and Next-Generation Sequencing

This study aimed to detect differences in BCR-ABL1 kinase domain (KD) variants in patients with chronic myeloid leukemia (CML) who have been warned and failed in tyrosine kinase inhibitor (TKI) treatment among Chinese Han and ethnic minorities through Sanger sequencing (SS) and next-generation sequencing (NGS), and analyze the difference between SS and NGS detection. Peripheral blood samples from 51 CML patients with warning and failure of TKI therapy were analyzed using SS and NGS, and the detection differences between both sequencing types were compared. BCR-ABL1 KD variants were found in 23.53% of the cohort, including 7 Han Chinese (58.33%) and 5 ethnic minority cases (41.67%). Y253H, F317L, M244V, D276G, F359I, L387F, E459K, E255K, T315I, M351V, and heterozygous insertional mutated genes (ABL1 c.1068_1070dup) were detected. Comparison of the two sequencing assays revealed that NGS could detect compound variants and low frequency variants that were not detected by SS. More compound variants were detected in Han patients than in ethnic minority patients. In conclusion, there is no significant difference in BCR-ABL1 KD mutations between Han and ethnic minority patients. NGS has a higher mutation detection rate than SS, and can detect compound variants and genes with lower mutation frequency that are not detected by SS.

Resistance to Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia-From Molecular Mechanisms to Clinical Relevance

Simple Summary

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasia associated with a molecular alteration, the fusion gene BCR-ABL1, that encodes the tyrosine kinase oncoprotein BCR-ABL1. This led to the development of tyrosine kinase inhibitors (TKI), with Imatinib being the first TKI approved. Although the vast majority of CML patients respond to Imatinib, resistance to this targeted therapy contributes to therapeutic failure and relapse. Here we review the molecular mechanisms and other factors (e.g., patient adherence) involved in TKI resistance, the methodologies to access these mechanisms, and the possible therapeutic approaches to circumvent TKI resistance in CML.

Abstract

Resistance to targeted therapies is a complex and multifactorial process that culminates in the selection of a cancer clone with the ability to evade treatment. Chronic myeloid leukemia (CML) was the first malignancy recognized to be associated with a genetic alteration, the t(9;22)(q34;q11). This translocation originates the BCR-ABL1 fusion gene, encoding the cytoplasmic chimeric BCR-ABL1 protein that displays an abnormally high tyrosine kinase activity. Although the vast majority of patients with CML respond to Imatinib, a tyrosine kinase inhibitor (TKI), resistance might occur either de novo or during treatment. In CML, the TKI resistance mechanisms are usually subdivided into BCR-ABL1-dependent and independent mechanisms. Furthermore, patients’ compliance/adherence to therapy is critical to CML management. Techniques with enhanced sensitivity like NGS and dPCR, the use of artificial intelligence (AI) techniques, and the development of mathematical modeling and computational prediction methods could reveal the underlying mechanisms of drug resistance and facilitate the design of more effective treatment strategies for improving drug efficacy in CML patients. Here we review the molecular mechanisms and other factors involved in resistance to TKIs in CML and the new methodologies to access these mechanisms, and the therapeutic approaches to circumvent TKI resistance.

Mutations in the BCR-ABL1 kinase domain in patients with chronic myeloid leukaemia treated with TKIs or at diagnosis

The aim of the present study was to analyse the incidence of mutations in the BCR-ABL1 kinase region in patients with newly diagnosed or treated chronic myeloid leukaemia (CML), and the association between mutations clinicopathological characteristics. Samples were collected for mutation analysis from patients who exhibited tyrosine kinase inhibitor resistance following treatment or were in the accelerated or blast phase at diagnosis. The mutations in the breakpoint cluster region (BCR)-ABL proto-oncogene 1 (ABL1) kinase domain were evaluated using conventional sequencing or ultra-deep sequencing (UDS) of peripheral blood samples. Sanger sequencing and UDS of the cDNA region corresponding to the BCR-ABL1 kinase domain was performed. χ² test was used to assess the association of categorical variables between the mutated and non-mutated groups. In addition, the Kaplan-Meier method was applied to generate the survival curves. Sequencing detected 28 different mutations in 54 of the 175 (30.86%) patients with CML. A total of 14 (8.0%) patients presented with the T315I mutation, accounting for the largest proportion in the mutated group. Eight patients (4.6%) presented with more than one mutation, three (37.5%) of whom harboured T315I coexisting with other mutations, and for nine (5.1%) patients, the results differed between conventional sequencing and UDS, with the mutations being missed by conventional sequencing. The results form this study suggested that programing mutation analysis in patients with chronic myeloid leukaemia timely may guide the choice of TKIs.

Down regulation of G protein-coupled receptor 137 expression inhibits proliferation and promotes apoptosis in leukemia cells

Background

G protein-coupled receptors (GPR) are involved in a wide range of physiological processes, some of which, however, can be hijacked by tumor cells. Over-expression of G protein-coupled receptors 137 (GPR137) are associated with the growth of tumor cells, but under-expression of GPR137 has shown to inhibit cell proliferation in several different types of cancers. Currently, the role of GPR137 in leukemia is still unclear. In this study, the effect of under-expression of GPR137 on inhibiting the proliferation of leukemia cells is explored, to identify a novel target for leukemia treatment.

Materials and methods

In this study, lentivirus-mediated RNA interference (RNAi) was employed to investigate the role of GPR137 in two leukemia cell lines K562 and HL60. The gene expression of GPR137 was analyzed by RT-PCR and its protein expression was determined by Western blot. Flow cytometry and Annexin V/7-AAD Apoptosis Detection Kit was used respectively in cell cycle and apoptosis analysis. The protein expression of CyclinD1, CDK4, BCL-2 and caspase-3 were also determined.

Results

There was high level of constitutive expression of GPR137 in leukemia cancer cell lines K562 and HL60. Lentivirus-mediated RNAi could significantly down-regulate gene and protein expression of GPR137 in both cell lines. Down regulation of GPR137 was associated with the reduction in proliferation rate and colony forming capacity. In addition, down regulation of GPR137 arrested cells in the G0/G1 phase of cell cycle and induced apoptosis in both leukemia cell lines K562 and HL60.

Conclusions

The expression of GPR137 is associated with the proliferation of leukemia cell lines. Down regulation of GPR137 could inhibit proliferation and promote apoptosis in leukemia cells, which makes it a promising bio-marker and therapeutic target to treat patients with leukemia.