The BCL2 inhibitor ABT-199 significantly enhances imatinib-induced cell death in chronic myeloid leukemia progenitors

Chronic myeloid leukemia: 2025 update on diagnosis, therapy, and monitoring

DISEASE OVERVIEW

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with an annual incidence of two cases/100 000. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults.

DIAGNOSIS

CML is characterized by a balanced genetic translocation, t(9;22) (q34;q11.2), involving a fusion of the Abelson murine leukemia (ABL1) gene from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR::ABL1 fusion oncogene, which in turn translates into a BCR::ABL1 oncoprotein.

FRONTLINE THERAPY

Four tyrosine kinase inhibitors (TKIs), imatinib, dasatinib, bosutinib, and nilotinib, are approved by the United States Food and Drug Administration (FDA) for first-line treatment of newly diagnosed CML in the chronic phase (CML-CP). Clinical trials with second and third-generation TKIs in frontline CML-CP therapy reported significantly deeper and faster responses but had no impact on survival prolongation, likely because of their potent efficacy and the availability of effective TKIs salvage therapies for patients who have a cytogenetic relapse with frontline TKI therapy. All four TKIs are equivalent if the aim of therapy is to improve survival. In younger patients with high-risk disease and in whom the aim of therapy is to induce a treatment-free remission status, second-generation TKIs may be favored.

SALVAGE THERAPY

For CML post-failure on frontline therapy, second-line options include second and third-generation TKIs. Although potent and selective, these TKIs exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities and financial status, disease stage, and BCR::ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib, asciminib, and olverembatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP and failure (due to resistance) of at least two TKIs and for all patients in advanced-phase disease. Older patients who have a cytogenetic relapse post-failure on all TKIs can maintain long-term survival if they continue a daily most effective/least toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, and others).

How to improve treatment-free remission eligibility in chronic myeloid leukaemia?

The achievement of treatment-free remission (TFR) has become a significant clinical end-point in the management of patients with chronic myeloid leukaemia (CML), providing an opportunity to discontinue therapy with tyrosine kinase inhibitors (TKIs) while maintaining deep molecular response (DMR). Early studies, such as the French STIM trial, have demonstrated that a portion of patients can maintain DMR after treatment cessation, with rates ranging from 40% to 50%, and most relapses occurring within the first 6 months. Key prognostic factors for successful TFR, including treatment duration, duration of DMR, risk scores, and transcript type, have been identified. Optimal patient selection for TFR remains a challenge, but recent research provides insights into potential strategies to increase TFR eligibility. Evidence suggests that early intervention switching to achieve optimal response, treatment combinations, proactive switch in the case of absence of DMR, dose-optimization and induction-maintenance approach can improve molecular responses and, consequently, enhance TFR eligibility. In this review, we report and discuss all the potential therapeutic strategies that may enhance eligibility for a first attempt at TFR, with a particular emphasis on potential future approaches.

Pharmacotherapeutic advances for chronic myelogenous leukemia: beyond tyrosine kinase inhibitors

INTRODUCTION

Despite the notable success of tyrosine kinase inhibitors (TKIs) in treating chronic myeloid leukemia (CML), a subset of patients experiences resistance, or relapse after discontinuation. This challenge is attributed to the Ph+ leukemia stem cells (LSCs) pool not fully involved in the inhibition process due to the current therapeutic approach.

AREAS COVERED

Current pharmacological advancements in CML therapy focus on targeting LSCs, intervening in self-renewal pathways, and exploiting biological vulnerabilities. Beyond BCR::ABL1 inhibition, innovative approaches include immunotherapy, epigenetic modulation, and interference with microenvironmental mechanisms.

EXPERT OPINION

Diverse therapeutic strategies beyond TKIs are under investigation. Immunotherapy with interferon-α (IFN-α) shows some biological effects, although further research is needed for optimal application in enhancing discontinuation rates. Other compounds were able to mobilize Ph+ LSCs from the bone marrow niche (DPP-IV inhibitor vildagliptin or PAI-1 inhibitor TM5614) increasing the LSC clearance or target the CD26, a Ph+ specific surface receptor. It is noteworthy that the majority of these alternative strategies still incorporate TKIs. In conclusion, novel therapeutic perspectives are emerging for CML, holding the potential for substantial advancements in disease treatment.

Profiling of miRNAs and their interfering targets in peripheral blood mononuclear cells from patients with chronic myeloid leukaemia

Introduction

MicroRNAs may be implicated in the acquisition of drug resistance in chronic myeloid leukemia as they regulate the expression of not only BCR-ABL1 but also genes associated with the activation of drug transfer proteins or essential signaling pathways.

Methods

To understand the impact of specifically expressed miRNAs in chronic myeloid leukemia and their target genes, we collected peripheral blood mononuclear cells (PBMC) from patients diagnosed with chronic myeloid leukemia (CML) and healthy donors to determine whole miRNA expression by small RNA sequencing and screened out 31 differentially expressed microRNAs (DE-miRNAs) with high expression. With the utilization of miRNA set enrichment analysis tools, we present here a comprehensive analysis of the relevance of DE-miRNAs to disease and biological function. Furthermore, the literature-based miRNA-target gene database was used to analyze the overall target genes of the DE-miRNAs and to define their associated biological responses. We further integrated DE-miRNA target genes to identify CML miRNA targeted gene signature singscore (CMTGSS) and used gene-set enrichment analysis (GSEA) to analyze the correlation between CMTGSS and Hallmark gene-sets in PBMC samples from clinical CML patients. Finally, the association of CMTGSS stratification with multiple CML cell lineage gene sets was validated in PBMC samples from CML patients using GSEA.

Results

Although individual miRNAs have been reported to have varying degrees of impact on CML, overall, our results show that abnormally upregulated miRNAs are associated with apoptosis and aberrantly downregulated miRNAs are associated with cell cycle. The clinical database shows that our defined DE-miRNAs are associated with the prognosis of CML patients. CMTGSS-based stratification analysis presented a tendency for miRNAs to affect cell differentiation in the blood microenvironment.

Conclusion

Collectively, this study defined differentially expressed miRNAs by miRNA sequencing from clinical samples and comprehensively analyzed the biological functions of the differential miRNAs in association with the target genes. The analysis of the enrichment of specific myeloid differentiated cells and immune cells also suggests the magnitude and potential targets of differentially expressed miRNAs in the clinical setting. It helps us to make links between the different results obtained from the multi-faceted studies to provide more potential research directions.

Modulating retinoid-X-receptor alpha (RXRA) expression sensitizes chronic myeloid leukemia cells to imatinib in vitro and reduces disease burden in vivo

Introduction: The ligand-activated transcription factors, nuclear hormone receptors (NHRs), remain unexplored in hematological malignancies except for retinoic acid receptor alpha (RARA). Methods: Here we profiled the expression of various NHRs and their coregulators in Chronic myeloid leukemia (CML) cell lines and identified a significant differential expression pattern between inherently imatinib mesylate (IM)-sensitive and resistant cell lines. Results: Retinoid-X-receptor alpha (RXRA) was downregulated in CML cell lines inherently resistant to IM and in primary CML CD34⁺ cells. Pre-treatment with clinically relevant RXRA ligands improved sensitivity to IM in-vitro in both CML cell lines and primary CML cells. This combination effectively reduced the viability and colony-forming capacity of CML CD34⁺ cells in-vitro. In-vivo, this combination reduced leukemic burden and prolonged survival. Overexpression (OE) of RXRA inhibited proliferation and improved sensitivity to IM in-vitro. In-vivo, RXRA OE cells showed reduced engraftment of cells in the bone marrow, improved sensitivity to IM, and prolonged survival. Both RXRA OE and ligand treatment markedly reduced BCR::ABL1 downstream kinase activation, activating apoptotic cascades and improving sensitivity to IM. Importantly, RXRA OE also led to the disruption of the oxidative capacity of these cells. Conclusion: Combining IM with clinically available RXRA ligands could form an alternative treatment strategy in CML patients with suboptimal response to IM.

The miR-106b-25 cluster mediates drug resistance in myeloid leukaemias by inactivating multiple apoptotic genes

Drug resistance is a major obstacle to the successful treatment of cancer. The role of the miR-106b-25 cluster in drug resistance of haematologic malignancies has not yet been elucidated. Here, we show that the miR-106b-25 cluster mediates resistance to therapeutic agents with structural and mechanistic dissimilarity in vitro and in vivo. RNA sequencing data revealed that overexpression of the miR-106b-25 cluster or its individual miRNAs resulted in downregulation of multiple key regulators of apoptotic pathways. Luciferase reporter assay identified TP73 as a direct target of miR-93 and miR-106b, BAK1 as a direct target of miR-25 and CASP7 as a direct target of all three miRNAs. We also showed that inhibitors of the miR-106b-25 cluster and BCL-2 exert synergistic effects on apoptosis induction in primary myeloid leukaemic cells. Thus, the members of the miR-106b-25 cluster may jointly contribute to myeloid leukaemia drug resistance by inactivating multiple apoptotic genes. Targeting this cluster could be a promising combination strategy in patients resistant to therapeutic agents that induce apoptosis.

Concomitant Venetoclax and Imatinib for Comanaging Chronic Lymphocytic Leukemia and Chronic Myeloid Leukemia: A Case Report

Patients with synchronous malignancies can be problematic to diagnose and manage because workup and therapeutic targeting for each individual malignancy must be coordinated carefully. This report presents a patient with concurrent chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) managed with concomitant venetoclax and imatinib. Because imatinib is a moderate cytochrome P450 3A4 inhibitor, close monitoring is required when using with a substrate of 3A4 such as venetoclax. Although the target dose of venetoclax is 400 mg, it was capped at 100 mg due to the interaction. Despite the interaction and possible enhancement of toxicities, the patient has tolerated therapy well, and both diseases have responded to this novel approach. In addition, because aberrant BCL-2 activity has been implicated in CML, the use of venetoclax may contribute to success in the management of this patient's CML. This case report represents the safe concomitant use of venetoclax and imatinib in a patient with synchronous CML and CLL.

Chronic Myeloid Leukemia: 2022 Update on Diagnosis, Therapy and Monitoring

DISEASE OVERVIEW

Chronic Myeloid Leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100,000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults DIAGNOSIS: CML is characterized by a balanced genetic translocation, t (9;22) (q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR::ABL1 fusion oncogene, which in turn translates into a BCR::ABL1 oncoprotein.

FRONTLINE THERAPY

Four tyrosine kinase inhibitors (TKIs), imatinib, dasatinib, bosutinib, and nilotinib are approved by the United States Food and Drug Administration for first-line treatment of newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses but had no impact on survival prolongation, likely because of the availability of effective TKIs salvage therapies for patients who have a cytogenetic relapse with frontline TKI therapy.

SALVAGE THERAPY

For CML post failure on frontline therapy, second-line options include second and third generation TKIs. Although potent and selective, these TKIs exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR::ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib, asciminib, and olverembatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP and failure (due to resistance) of at least 2 TKIs, and for all patients in advanced phase disease. Older patients who have a cytogenetic relapse post failure on all TKIs can maintain long-term survival if they continue a daily most effective/least toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, busulfan, others). This article is protected by copyright. All rights reserved.

BCR-ABL1 Tyrosine Kinase Complex Signaling Transduction: Challenges to Overcome Resistance in Chronic Myeloid Leukemia

The constitutively active BCR-ABL1 tyrosine kinase, found in t(9;22)(q34;q11) chromosomal translocation-derived leukemia, initiates an extremely complex signaling transduction cascade that induces a strong state of resistance to chemotherapy. Targeted therapies based on tyrosine kinase inhibitors (TKIs), such as imatinib, dasatinib, nilotinib, bosutinib, and ponatinib, have revolutionized the treatment of BCR-ABL1-driven leukemia, particularly chronic myeloid leukemia (CML). However, TKIs do not cure CML patients, as some develop TKI resistance and the majority relapse upon withdrawal from treatment. Importantly, although BCR-ABL1 tyrosine kinase is necessary to initiate and establish the malignant phenotype of Ph-related leukemia, in the later advanced phase of the disease, BCR-ABL1-independent mechanisms are also in place. Here, we present an overview of the signaling pathways initiated by BCR-ABL1 and discuss the major challenges regarding immunologic/pharmacologic combined therapies.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

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.

BH3-mimetics: recent developments in cancer therapy

The hopeful outcomes from 30 years of research in BH3-mimetics have indeed served a number of solid paradigms for targeting intermediates from the apoptosis pathway in a variety of diseased states. Not only have such rational approaches in drug design yielded several key therapeutics, such outputs have also offered insights into the integrated mechanistic aspects of basic and clinical research at the genetics level for the future. In no other area of medical research have the effects of such work been felt, than in cancer research, through targeting the BAX-Bcl-2 protein-protein interactions. With these promising outputs in mind, several mimetics, and their potential therapeutic applications, have also been developed for several other pathological conditions, such as cardiovascular disease and tissue fibrosis, thus highlighting the universal importance of the intrinsic arm of the apoptosis pathway and its input to general tissue homeostasis. Considering such recent developments, and in a field that has generated so much scientific interest, we take stock of how the broadening area of BH3-mimetics has developed and diversified, with a focus on their uses in single and combined cancer treatment regimens and recently explored therapeutic delivery methods that may aid the development of future therapeutics of this nature.

Combination Therapies in Chronic Myeloid Leukemia for Potential Treatment-Free Remission: Focus on Leukemia Stem Cells and Immune Modulation

Although tyrosine Kinase Inhibitors (TKI) has revolutionized the treatment of chronic myeloid leukemia (CML), patients are not cured with the current therapy modalities. Also, the more recent goal of CML treatment is to induce successful treatment-free remission (TFR) among patients achieving durable deep molecular response (DMR). Together, it is necessary to develop novel, curative treatment strategies. With advancements in understanding the biology of CML, such as dormant Leukemic Stem Cells (LSCs) and impaired immune modulation, a number of agents are now under investigation. This review updates such agents that target LSCs, and together with TKIs, have the potential to eradicate CML. Moreover, we describe the developing immunotherapy for controlling CML.

Targeting Chronic Myeloid Leukemia Stem/Progenitor Cells Using Venetoclax-Loaded Immunoliposome

CML is a hematopoietic stem-cell disorder emanating from breakpoint cluster region/Abelson murine leukemia 1 (BCR/ABL) translocation. Introduction of different TKIs revolutionized treatment outcome in CML patients, but CML LSCs seem insensitive to TKIs and are detectable in newly diagnosed and resistant CML patients and in patients who discontinued therapy. It has been reported that CML LSCs aberrantly express some CD markers such as CD26 that can be used for the diagnosis and for targeting. In this study, we confirmed the presence of CD26+ CML LSCs in newly diagnosed and resistant CML patients. To selectively target CML LSCs/progenitor cells that express CD26 and to spare normal HSCs/progenitor cells, we designed a venetoclax-loaded immunoliposome (IL-VX). Our results showed that by using this system we could selectively target CD26+ cells while sparing CD26- cells. The efficiency of venetoclax in targeting CML LSCs has been reported and our system demonstrated a higher potency in cell death induction in comparison to free venetoclax. Meanwhile, treatment of patient samples with IL-VX significantly reduced CD26+ cells in both stem cells and progenitor cells population. In conclusion, this approach showed that selective elimination of CD26+ CML LSCs/progenitor cells can be obtained in vitro, which might allow in vivo reduction of side effects and attainment of treatment-free, long-lasting remission in CML patients.

The application of BH3 mimetics in myeloid leukemias

Execution of the intrinsic apoptotic pathway is controlled by the BCL-2 proteins at the level of the mitochondrial outer membrane (MOM). This family of proteins consists of prosurvival (e.g., BCL-2, MCL-1) and proapoptotic (e.g., BIM, BAD, HRK) members, the functional balance of which dictates the activation of BAX and BAK. Once activated, BAX/BAK form pores in the MOM, resulting in cytochrome c release from the mitochondrial intermembrane space, leading to apoptosome formation, caspase activation, and cleavage of intracellular targets. This pathway is induced by cellular stress including DNA damage, cytokine and growth factor withdrawal, and chemotherapy/drug treatment. A well-documented defense of leukemia cells is to shift the balance of the BCL-2 family in favor of the prosurvival proteins to protect against such intra- and extracellular stimuli. Small molecule inhibitors targeting the prosurvival proteins, named 'BH3 mimetics', have come to the fore in recent years to treat hematological malignancies, both as single agents and in combination with standard-of-care therapies. The most significant example of these is the BCL-2-specific inhibitor venetoclax, given in combination with standard-of-care therapies with great success in AML in clinical trials. As the number and variety of available BH3 mimetics increases, and investigations into applying these novel inhibitors to treat myeloid leukemias continue apace the need to evaluate where we currently stand in this rapidly expanding field is clear.

Targeting BCL-2 as a Therapeutic Strategy for Primary p210BCR-ABL1-positive B-ALL Cells

BACKGROUND/AIM

Philadelphia-positive acute lymphoblastic leukemia (Ph⁺ B-ALL) is caused by the malignant transformation of lymphoid cells induced by BCR-ABL1 constitutive catalytic activity. BCR-ABL1 tyrosine kinase inhibitors (TKIs) are effective against chronic myeloid leukemia (CML) cells, inducing durable hematological, cytogenetic and molecular responses. However, in Ph⁺ B-ALL - as in CML progressing to blast crisis - TKIs fail to maintain disease remission. We, therefore, wanted to investigate if dual targeting of BCL-2 and BCR-ABL1 would be more effective in killing Ph⁺ B-ALL cells.

MATERIALS AND METHODS

p210-B-ALL CD34-positive cells were used to evaluate the BCR-ABL expression and pharmacological targeting of BCL-2, by venetoclax, alone or in combination with BCR-ABL1 inhibition.

RESULTS

We demonstrated the cytotoxic effect of BCL-2 inhibition and that dual targeting of BCL-2 and BCR-ABL1 with venetoclax and nilotinib further increases this cytotoxicity.

CONCLUSION

BCL-2 is a key survival factor for primary Ph⁺ B-ALL cells and its inhibition - alone or in combination with a BCR-ABL1 TKI - should be further investigated as a potential therapeutic strategy for these patients.

Bcl-2/Bcl-xL inhibitor navitoclax increases the antitumor effect of Chk1 inhibitor prexasertib by inducing apoptosis in pancreatic cancer cells via inhibition of Bcl-xL but not Bcl-2

In our previous study, we showed that prexasertib, a checkpoint kinase 1 (Chk1) inhibitor, enhances the effects of standard drugs for pancreatic cancer, including gemcitabine (GEM), S-1, and the combination of GEM and S-1 (GS). The combination of prexasertib and GS has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating anti-apoptotic protein Bcl-2. In the present study, we investigated the combined effect of GEM, S-1, and prexasertib with a selective Bcl-2 inhibitor (venetoclax) and a non-selective Bcl-2 inhibitor (navitoclax) in SUIT-2 pancreatic cancer cells. An MTT assay revealed that the combination of prexasertib with navitoclax showed a synergistic effect but the combination with venetoclax did not. Investigation of the pancreatic cancer cell lines SUIT-2, MIA PaCa-2, and BxPC-3 revealed that BxPC-3 also showed a high synergistic effect when combined with prexasertib and navitoclax but not venetoclax. Mechanistic analysis of the combined effect showed that apoptosis was induced. Bcl-2 knockdown with siRNA and prexasertib treatment did not induce apoptosis, whereas Bcl-xL knockdown with siRNA and prexasertib treatment resulted in strong induction of apoptosis. In addition, among the three cell lines, the combined effect of prexasertib and navitoclax resulted in increased apoptotic cell death because the protein expression levels of Bcl-xL and Chk1 were higher. Our results demonstrate that the combination of prexasertib and navitoclax has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating Bcl-xL. Simultaneous inhibition of Chk1 and Bcl-xL could be a new strategy for treating pancreatic cancer.

Chronic myeloid leukemia: 2020 update on diagnosis, therapy and monitoring

DISEASE OVERVIEW

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100 000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults.

DIAGNOSIS

CML is characterized by a balanced genetic translocation, t(9;22)(q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR-ABL1 fusion oncogene, which in turn translates into a BCR-ABL oncoprotein.

FRONTLINE THERAPY

Four tyrosine kinase inhibitors (TKIs), imatinib, nilotinib, dasatinib, and bosutinib are approved by the United States Food and Drug Administration for first-line treatment of newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses, but they had no impact on survival prolongation, likely because of the existence of highly effective salvage therapies for patients who have a cytogenetic relapse with frontline TKI.

SALVAGE THERAPY

For CML post failure on frontline therapy, second-line options include second and third generation TKIs. Although potent and selective, these exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR-ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP who have failed at least 2 TKIs, and for all patients in advanced phase disease. Even among older patients who have a cytogenetic relapse post failure on all TKIs, they can maintain long-term survival if they continue on a daily most effective/less toxic TKI, with or without the addition of non-TKI anti-CML agents (hydroxyurea, omacetaxine, azacitidine, decitabine, cytarabine, busulfan, others).

Inhibition of EGFR pathway promotes the cytotoxicity of ABT-263 in human leukemia K562 cells by blocking MCL1 upregulation

ABT-263 induces MCL1 upregulation in cancer cells, which confers resistance to the drug. An increased understanding of the mechanism underlying ABT-263-induced MCL1 expression may provide a strategy to improve its tumor-suppression activity. The present study revealed that ABT-263 reduced the turnover of MCL1 mRNA, thereby upregulating MCL1 expression in human K562 leukemia cells. Furthermore, ABT-263-induced EGFR activation promoted AGO2 phosphorylation at Y393 and reduced miR-125b maturation. Treatment with EGFR inhibitors mitigated MCL1 upregulation induced by ABT-263. Additionally, lithium chloride (LiCl) alleviated ABT-263-induced MCL1 upregulation through EGFR-AGO2 axis-modulated miR-125b suppression. Ectopic expression of dominant negative AGO2(Y393F) or transfection with miR-125b abolished ABT-263-induced upregulation of MCL1 mRNA and protein levels. Co-treatment with either EGFR inhibitors or LiCl collaboratively enhanced ABT-263 cytotoxicity, while MCL1 overexpression eliminated this synergistic effect. Collectively, our data reveal that ABT-263 increases EGFR-mediated AGO2 phosphorylation, which in turn suppresses miR-125b-mediated MCL1 mRNA degradation in K562 cells. The suppression of this signaling pathway results in the synergistic cytotoxic effect of EGFR inhibitors or LiCl and ABT-263.

Venetoclax: A Review in Relapsed/Refractory Chronic Lymphocytic Leukemia

Venetoclax (Venclyxto^®; Venclexta^®) is a first-in-class, oral, selective B cell lymphoma-2 (BCL-2) inhibitor. The drug is approved in numerous countries, including those of the EU and in the USA, for the treatment of adults with relapsed or refractory (RR) chronic lymphocytic leukemia (CLL); the specific indication(s) for venetoclax may vary between individual countries. Venetoclax monotherapy or combination therapy with rituximab was an effective treatment, provided durable responses, and had a manageable safety profile in pivotal clinical trials in adults with RR CLL, including in patients with adverse prognostic factors. In combination with 6 cycles of rituximab, venetoclax (fixed 24 months' treatment) was more effective than bendamustine plus rituximab (6 cycles) in prolonging progression-free survival (PFS) and inducing undetectable minimal residual disease (uMRD) in peripheral blood (PB) and bone marrow (BM), with these benefits sustained during 36 months' follow-up. Hence, with its novel mechanism of action and convenient oral once-daily regimen, venetoclax monotherapy or fixed 24-month combination therapy with rituximab represents an important option for treating RR CLL, including in patients with del(17p) or TP53 mutation and those failing a B cell receptor (BCR) inhibitor and/or chemotherapy.

The leukaemia stem cell: similarities, differences and clinical prospects in CML and AML

For two decades, leukaemia stem cells (LSCs) in chronic myeloid leukaemia (CML) and acute myeloid leukaemia (AML) have been advanced paradigms for the cancer stem cell field. In CML, the acquisition of the fusion tyrosine kinase BCR-ABL1 in a haematopoietic stem cell drives its transformation to become a LSC. In AML, LSCs can arise from multiple cell types through the activity of a number of oncogenic drivers and pre-leukaemic events, adding further layers of context and genetic and cellular heterogeneity to AML LSCs not observed in most cases of CML. Furthermore, LSCs from both AML and CML can be refractory to standard-of-care therapies and persist in patients, diversify clonally and serve as reservoirs to drive relapse, recurrence or progression to more aggressive forms. Despite these complexities, LSCs in both diseases share biological features, making them distinct from other CML or AML progenitor cells and from normal haematopoietic stem cells. These features may represent Achilles' heels against which novel therapies can be developed. Here, we review many of the similarities and differences that exist between LSCs in CML and AML and examine the therapeutic strategies that could be used to eradicate them.

Druggable Biochemical Pathways and Potential Therapeutic Alternatives to Target Leukemic Stem Cells and Eliminate the Residual Disease in Chronic Myeloid Leukemia

Chronic Myeloid Leukemia (CML) is a disease arising in stem cells expressing the BCR-ABL oncogenic tyrosine kinase that transforms one Hematopoietic stem/progenitor Cell into a Leukemic Stem Cell (LSC) at the origin of differentiated and proliferating leukemic cells in the bone marrow (BM). CML-LSCs are recognized as being responsible for resistances and relapses that occur despite the advent of BCR-ABL-targeting therapies with Tyrosine Kinase Inhibitors (TKIs). LSCs share a lot of functional properties with Hematopoietic Stem Cells (HSCs) although some phenotypical and functional differences have been described during the last two decades. Subverted mechanisms affecting epigenetic processes, apoptosis, autophagy and more recently metabolism and immunology in the bone marrow microenvironment (BMM) have been reported. The aim of this review is to bring together the modifications and molecular mechanisms that are known to account for TKI resistance in primary CML-LSCs and to focus on the potential solutions that can circumvent these resistances, in particular those that have been, or will be tested in clinical trials.

Management of Chronic Myeloid Leukemia in Advanced Phase

Management of chronic myeloid leukemia (CML) in advanced phases remains a challenge also in the era of tyrosine kinase inhibitors (TKIs) treatment. Cytogenetic clonal evolution and development of resistant mutations represent crucial events that limit the benefit of subsequent therapies in these patients. CML is diagnosed in accelerated (AP) or blast phase (BP) in <5% of patients, and the availability of effective treatments for chronic phase (CP) has dramatically reduced progressions on therapy. Due to smaller number of patients, few randomized studies are available in this setting and evidences are limited. Nevertheless, three main scenarios may be drawn: (a) patients diagnosed in AP are at higher risk of failure as compared to CP patients, but if they achieve optimal responses with frontline TKI treatment their outcome may be similarly favorable; (b) patients diagnosed in BP may be treated with TKI alone or with TKI together with conventional chemotherapy regimens, and subsequent transplant decisions should rely on kinetics of response and individual transplant risk; (c) patients in CP progressing under TKI treatment represent the most challenging population and they should be treated with alternative TKI according to the mutational profile, optional chemotherapy in BP patients, and transplant should be considered in suitable cases after return to second CP. Due to lack of validated and reliable markers to predict blast crisis and the still unsatisfactory results of treatments in this setting, prevention of progression by careful selection of frontline treatment in CP and early treatment intensification in non-optimal responders remains the main goal. Personalized evaluation of response kinetics could help in identifying patients at risk for progression.

Long-term follow-up of lower dose dasatinib (50 mg daily) as frontline therapy in newly diagnosed chronic-phase chronic myeloid leukemia

BACKGROUND

Dasatinib, a potent Bcr-Abl tyrosine kinase inhibitor, is approved for the treatment of chronic-phase chronic myeloid leukemia (CML-CP) in the frontline and salvage settings. Notable side effects include pleural effusions and myelosuppression. Dasatinib at 50 mg daily has previously been reported to be active and better tolerated than the approved 100-mg daily dose. The aim of this study was to update the long-term follow-up results of dasatinib at 50 mg daily as frontline therapy for CML-CP.

METHODS

Eighty-three patients with newly diagnosed CML-CP received dasatinib at 50 mg daily. Eligibility and response criteria were standards used in previous protocols.

RESULTS

After a minimum follow-up of 12 months, 81 patients were evaluable. Two patients came off the study in less than 3 months. The rates of BCR-ABL1 transcript levels (International Standard) at ≤10% and ≤1% at 3 months were 96% and 77%, respectively. The cumulative rates for a complete cytogenetic response by 6 and 12 months were 77% and 95%, respectively. The cumulative rates for a major molecular response, a molecular response with a 4.0-log reduction, and a molecular response with a 4.5-log reduction by 12 months were 81%, 55%, and 49%, respectively. Twenty-one patients (25%) had treatment interruptions for a median of 13 days (range, 4-64 days). Five patients (6%) developed pleural effusions; 4 of these patients (80%) required a dose reduction. Two patients (2%) failed to achieve any cytogenetic or molecular response and were taken off the study. At a median follow-up of 24 months, none of the patients had disease transformation to an accelerated or blastic phase. The 2-year event-free and overall survival rates were 100%.

CONCLUSIONS

These updated results continue to support 50 mg of dasatinib daily as an effective and safe dose for early CML-CP.

Chronic myelogenous leukemia, a still unsolved problem: pitfalls and new therapeutic possibilities

Chronic myeloid leukemia (CML) is a clonal myeloproliferative disorder of hematopoietic stem cells. At the molecular level, the disorder results from t(9;22)(q34;q11) reciprocal translocation between chromosomes, which leads to the formation of an oncogenic BCR–ABL gene fusion. Instead of progress in the understanding of the molecular etiology of CML and the development of novel therapeutic strategies, clinicians still face many challenges in the effective treatment of patients. In this review, we discuss the pathways of diagnosis and treatment of patients, as well as the problems appearing in the course of disease development. We also briefly refer to several aspects regarding the current knowledge on the molecular basis of CML and new potential therapeutic targets.

Current perspectives for the treatment of chronic myeloid leukemia

With an annual incidence of 1–2 in a million, Ph*(+) chronic myeloid leukemia (CML) is a clonal hematopoietic stem cell disease that makes myeloid neoplastic cells breed out of control. This BCR-ABL(+) myeloproliferative disease makes up about 15%–20% of all leukemia cases in adults. CML is seen more in males than females, with a rate of three to two. However, it does not show differences in prevalence in terms of age. CML consists of three clinical phases. The first one is the chronic phase, defined by rising white blood cell levels and also by myeloid proliferation and bone marrow maturation. While this phase does not exhibit complications, in diagnosis, it comprises most of the patients. The second phase is the accelerated phase, which the disease progresses to if it is not treated or does not respond to treatment. This usually takes about 3 years. The third phase is the blastic phase. The chronic phase can still progress to the next two phases within the first 2 years, with a rate of 10%. In the following years, the possibility increases by 15%–20% each year. Tyrosine kinase inhibitors (TKIs) are revolutionary drugs for the management of disease course in CML. The aim of this review is to assess current approaches to CML patients’ follow-up and treatment with TKIs. A literature search on CML and TKIs was made in PubMed, Web of Science, and Scopus with particular focus on randomized clinical trials, recommendations, guidelines, and expert opinions. In managing CML, various treatment methods have been utilized for many decades. Prior to the development of TKIs, interferon alpha was the primary tool, which was then complemented by allogeneic hematopoietic stem cell transplantation (HSCT). HSCT was successful in slowing the disease down in the long term and curing up to 50% of patients. Then the coming of the imatinib era opened up different treatment perspectives. For the patients resistant or intolerant to imatinib, second- and third-generation TKIs are successfully used in distinct CML disease states. The survival benefits of TKIs including imatinib, nilotinib, dasatinib, bosutinib, and ponatinib for CML patients are outstanding. TKI-related adverse events could impact the clinical course, especially in long-term drug administrations. The current aim for CML disease management in the TKI era is to provide age- and sex-matched normal life duration to CML patients.

BCL2 inhibitor ABT-199 and JNK inhibitor SP600125 exhibit synergistic cytotoxicity against imatinib-resistant Ph+ ALL cells

Imatinib (IMT), a specific tyrosine kinase inhibitor (TKI), has drastically changed the treatment strategy for Ph+ ALL (Philadelphia chromosome-positive acute lymphoblastic leukemia). However, TKI resistance remains a serious problem for patient prognosis. Here, a Ph+ ALL cell line NphA2 and the IMT-resistant subline NphA2/STIR were analyzed to identify a potential novel treatment strategy. We also examined other Ph+ ALL cells, MR87 and its IMT-resistant subline, MR87/STIR. IMT induced apoptosis of NphA2 and MR87 but had no effect on resistant sublines. Increased phosphorylated ERK and BCL2, but not BCL-XL, were observed in NphA2/STIR compared with NphA2. NphA2/STIR but not NphA2 was moderately sensitive to U0126, an ERK inhibitor. Interestingly, SP600125, a JNK inhibitor, was potent in cell growth inhibition and apoptosis induction of both parental and IMT-resistant NphA2 and MR87 cells. Moreover, NphA2 and MR87 and their IMT-resistant sublines were sensitive to ABT-199, a specific BCL2 inhibitor. The combination of SP600125 and ABT-199 synergistically suppressed both parental and IMT-resistant cells, including one with T315I mutation, suggesting that Ph+ ALL exhibits high sensitivity to ABT-199 and SP600125 regardless of TKI resistance. This combination might be a possible therapeutic strategy for Ph+ ALL in the future.

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SP600125 JNK inhibitor is cytotoxic against imatinib-resistant Ph+ ALL cells.

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BCl2 inhibitor ABT 199 exhibits cytotoxicity against imatinib-resistant Ph+ ALL.

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SP600125 and ABT199 are synergistic in imatinib-resistant Ph+ ALL with T315I.

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Some leukemia cells are sensitive to MCL1 inhibitor maritoclax but not to ABT-199.

Early results of lower dose dasatinib (50 mg daily) as frontline therapy for newly diagnosed chronic-phase chronic myeloid leukemia

BACKGROUND

Dasatinib is a potent BCR-ABL1 and Src family tyrosine kinase inhibitor. It is approved at a dose of 100 mg orally daily for the treatment of chronic myeloid leukemia in chronic phase (CML-CP). This dose schedule is associated with myelosuppression and pleural effusions. Anecdotal data suggest that lower doses may be as effective and less toxic. The aim of this study was to assess the efficacy and safety of a lower dose of dasatinib (50 mg daily) in patients with newly diagnosed CML-CP.

METHODS

Seventy-five patients with newly diagnosed CML-CP received dasatinib 50 mg daily. The eligibility and response criteria were standards used in previous protocols.

RESULTS

At a median follow-up of 9 months, 60 patients were evaluable for a response at 3 months. The rates of patients achieving BCR-ABL1 transcript levels ≤ 10% and ≤ 1% at 3 months by the International Standard were 93% and 72%, respectively. The rates of complete cytogenetic response by conventional cytogenetics or fluorescence in situ hybridization at 6 and 12 months were 86% and 88%, respectively. At 12 months, 79%, 71%, and 46% of the patients had achieved a major molecular response, a molecular response with a 4.0-log reduction, and a molecular response with a 4.5-log reduction, respectively. Nine patients had a dose interruption for ≤14 days. Only 1 patient developed a pleural effusion requiring a dose reduction to 20 mg. All patients remained alive and with no transformation so far.

CONCLUSION

Dasatinib 50 mg daily is active and well tolerated in patients with newly diagnosed CML-CP. It should be further explored as a new potential standard-of-care option for chronic myeloid leukemia. Cancer 2018;124:2740-2747. © 2018 American Cancer Society.

Chronic myeloid leukemia: 2018 update on diagnosis, therapy and monitoring

DISEASE OVERVIEW

Chronic myeloid leukemia (CML) is a myeloproliferative neoplasm with an incidence of 1-2 cases per 100 000 adults. It accounts for approximately 15% of newly diagnosed cases of leukemia in adults.

DIAGNOSIS

CML is characterized by a balanced genetic translocation, t(9;22)(q34;q11.2), involving a fusion of the Abelson gene (ABL1) from chromosome 9q34 with the breakpoint cluster region (BCR) gene on chromosome 22q11.2. This rearrangement is known as the Philadelphia chromosome. The molecular consequence of this translocation is the generation of a BCR-ABL1 fusion oncogene, which in turn translates into a BCR-ABL1 oncoprotein. Frontline therapy: Four tyrosine kinase inhibitors (TKIs), imatinib, nilotinib, dasatinib, and bosutinib are approved by the United States Food and Drug Administration for first-line treatment of patients with newly diagnosed CML in chronic phase (CML-CP). Clinical trials with second generation TKIs reported significantly deeper and faster responses; this has not translated into improved long-term survival, because of the availability of effective salvage therapies. Salvage therapy: For patients who fail frontline therapy, second-line options include second and third generation TKIs. Second and third generation TKIs, although potent and selective, exhibit unique pharmacological profiles and response patterns relative to different patient and disease characteristics, such as patients' comorbidities, disease stage, and BCR-ABL1 mutational status. Patients who develop the T315I "gatekeeper" mutation display resistance to all currently available TKIs except ponatinib. Allogeneic stem cell transplantation remains an important therapeutic option for patients with CML-CP who have failed at least 2 TKIs, and for all patients in CML advanced phases.

Non ABL-directed inhibitors as alternative treatment strategies for chronic myeloid leukemia

The introduction of ABL Tyrosine Kinase Inhibitors (TKIs) has significantly improved the outcome of Chronic Myeloid Leukemia (CML) patients that, in large part, achieve satisfactory hematological, cytogenetic and molecular remissions. However, approximately 15-20% fail to obtain optimal responses according to the current European Leukemia Network recommendation because of drug intolerance or resistance.Moreover, a plethora of evidence suggests that Leukemic Stem Cells (LSCs) show BCR-ABL1-independent survival. Hence, they are unresponsive to TKIs, leading to disease relapse if pharmacological treatment is discontinued.All together, these biological events generate a subpopulation of CML patients in need of alternative therapeutic strategies to overcome TKI resistance or to eradicate LSCs in order to allow cure of the disease.In this review we update the role of "non ABL-directed inhibitors" targeting signaling pathways downstream of the BCR-ABL1 oncoprotein and describe immunological approaches activating specific T cell responses against CML cells.

Therapeutic synergy between tigecycline and venetoclax in a preclinical model of MYC/BCL2 double-hit B cell lymphoma

High-grade B cell lymphomas with concurrent activation of the MYC and BCL2 oncogenes, also known as double-hit lymphomas (DHL), show dismal prognosis with current therapies. MYC activation sensitizes cells to inhibition of mitochondrial translation by the antibiotic tigecycline, and treatment with this compound provides a therapeutic window in a mouse model of MYC-driven lymphoma. We now addressed the utility of this antibiotic for treatment of DHL. BCL2 activation in mouse Eμ-myc lymphomas antagonized tigecycline-induced cell death, which was specifically restored by combined treatment with the BCL2 inhibitor venetoclax. In line with these findings, tigecycline and two related antibiotics, tetracycline and doxycycline, synergized with venetoclax in killing human MYC/BCL2 DHL cells. Treatment of mice engrafted with either DHL cell lines or a patient-derived xenograft revealed strong antitumoral effects of the tigecycline/venetoclax combination, including long-term tumor eradication with one of the cell lines. This drug combination also had the potential to cooperate with rituximab, a component of current front-line regimens. Venetoclax and tigecycline are currently in the clinic with distinct indications: Our preclinical results warrant the repurposing of these drugs for combinatorial treatment of DHL.

Bax Activation Blocks Self-Renewal and Induces Apoptosis of Human Glioblastoma Stem Cells

Glioblastoma (GBM) is characterized by a poor response to conventional chemotherapeutic agents, attributed to the insurgence of drug resistance mechanisms and to the presence of a subpopulation of glioma stem cells (GSCs). GBM cells and GSCs present, among others, an overexpression of antiapoptotic proteins and an inhibition of pro-apoptotic ones, which help to escape apoptosis. Among pro-apoptotic inducers, the Bcl-2 family protein Bax has recently emerged as a promising new target in cancer therapy along with first BAX activators (BAM7, Compound 106, and SMBA1). Herein, a derivative of BAM-7, named BTC-8, was employed to explore the effects of Bax activation in different human GBM cells and in their stem cell subpopulation. BTC-8 inhibited GBM cell proliferation, arrested the cell cycle, and induced apoptosis through the induction of mitochondrial membrane permeabilization. Most importantly, BTC-8 blocked proliferation and self-renewal of GSCs and induced their apoptosis. Notably, BTC-8 was demonstrated to sensitize both GBM cells and GSCs to the alkylating agent Temozolomide. Overall, our findings shed light on the effects and the relative molecular mechanisms related to Bax activation in GBM, and they suggest Bax-targeting compounds as promising therapeutic tools against the GSC reservoir.

Inhibitor of Apoptosis Proteins (IAPs) are commonly dysregulated in GIST and can be pharmacologically targeted to enhance the pro-apoptotic activity of imatinib

Gastrointestinal stromal tumors (GIST) exhibit a strong oncogenic dependency on KIT and KIT inhibitors confer long lasting disease stabilization in the majority of patients. Nonetheless, KIT inhibition alone does not cure GIST as a subset of GIST cells evade apoptosis and eventually develop resistance. Inhibitors of Apoptosis Proteins (IAPs) may confer resistance to drug-induced apoptosis. We observed that the mRNA and protein of IAPs XIAP (BIRC4) and survivin (BIRC5) were highly expressed in primary GIST tumors and cell line models. Amplification of the respective gene loci (BIRC2, BIRC3, BIRC4, BIRC5) was detected in 47% of GIST studied by SNP arrays. Whole exome analyses revealed a mutation of SMAC(DIABLO) in a heavily pretreated patient. Both, survivin (rank 62-92/11.194 tested proteins) and XIAP (rank 106-557/11.194) were found to be essential proteins for survival in a synthetic lethality screen. Expression of XIAP and survivin decreased upon KIT inhibition and may play a role in KIT-regulated pro-survival signaling. SMAC-mimetic treatment with LCL161 and TL32711 reduced cIAP1 and XIAP expression. Survivin inhibitor YM155 lead to transcriptional repression of BIRC5/survivin (YM155) and induced apoptosis. Combinational treatment with KIT inhibitors (imatinib, regorafenib) enhanced the proapoptotic effect. These findings support the combination of KIT inhibition with IAP antagonists in GIST.

Reduction of microRNA-184 by E6 oncoprotein confers cisplatin resistance in lung cancer via increasing Bcl-2

MicroRNA-184 suppresses cell growth and survival via targeting c-Myc and Bcl- 2. We recently reported that miR-184 promotes tumor progression in non-small cell lung cancer via targeting CDC25A and c-Myc. We here hypothesized that miR-184 could be down-regulated by E6 oncoprotein to confer cisplatin resistance in NSCLC. Human papillomavirus (HPV) 16-positive lung cancer TL-1 and cervical cancer SiHa cells compared with HPV16-negative TL-10 and C33A cells were enrolled for E6 manipulation. MiR-184 expression levels were increased by E6-knockdown in TL-1 and SiHa cells, but decreased by E6-overexpression in TL-10 and C33A cells. The MTT assay showed that the inhibition concentration of cisplatin yielding for 50% cell viability was dependent on miR-184 levels. Bcl-2 de-targeted by E6-mediated miR- 184 reduction was responsible for cisplatin resistance. Luciferase reporter assay and real- time PCR analysis indicated that the miR-184 promoter activity and its expression were modulated by E6 and/or p53 manipulation. Chromatin immunoprecipitation (ChIP) assay confirmed that p53 was bound onto the miR-184 promoter and its binding activity was modulated by E6 and/or p53 manipulation. Among patients, high miR184 and high Bcl-2 mRNA expression was more commonly occurred in E6- positive tumors than in E6-negative tumors. Fifty-nine out of 136 patients receiving cisplatin-based chemotherapy were available for the retrospective study. Patients with low-mR-184, E6-positive, high-Bcl-2 tumors, and both combinations were more prevalently occurred unfavorable response to cisplatin-based chemotherapy than their counterparts. In conclusion, a decrease in miR-184 level by E6 oncoprotein may predict unfavorable response to cisplatin-based chemotherapy in HPV-infected NSCLC patients via increasing Bcl-2 expression.

Combined targeting of BCL-2 and BCR-ABL tyrosine kinase eradicates chronic myeloid leukemia stem cells

BCR-ABL tyrosine kinase inhibitors (TKIs) are effective against chronic myeloid leukemia (CML), but they rarely eliminate CML stem cells. Disease relapse is common upon therapy cessation, even in patients with complete molecular responses. Furthermore, once CML progresses to blast crisis (BC), treatment outcomes are dismal. We hypothesized that concomitant targeting of BCL-2 and BCR-ABL tyrosine kinase could overcome these limitations. We demonstrate increased BCL-2 expression at the protein level in bone marrow cells, particularly in Lin(-)Sca-1(+)cKit(+) cells of inducible CML in mice, as determined by CyTOF mass cytometry. Further, selective inhibition of BCL-2, aided by TKI-mediated MCL-1 and BCL-XL inhibition, markedly decreased leukemic Lin(-)Sca-1(+)cKit(+) cell numbers and long-term stem cell frequency and prolonged survival in a murine CML model. Additionally, this combination effectively eradicated CD34(+)CD38(-), CD34(+)CD38(+), and quiescent stem/progenitor CD34(+) cells from BC CML patient samples. Our results suggest that BCL-2 is a key survival factor for CML stem/progenitor cells and that combined inhibition of BCL-2 and BCR-ABL tyrosine kinase has the potential to significantly improve depth of response and cure rates of chronic-phase and BC CML.

Found in Translation: How Preclinical Research Is Guiding the Clinical Development of the BCL2-Selective Inhibitor Venetoclax

Since the discovery of apoptosis as a form of programmed cell death, targeting the apoptosis pathway to induce cancer cell death has been a high-priority goal for cancer therapy. After decades of effort, drug-discovery scientists have succeeded in generating small-molecule inhibitors of antiapoptotic BCL2 family proteins. Innovative medicinal chemistry and structure-based drug design, coupled with a strong fundamental understanding of BCL2 biology, were essential to the development of BH3 mimetics such as the BCL2-selective inhibitor venetoclax. We review a number of preclinical studies that have deepened our understanding of BCL2 biology and facilitated the clinical development of venetoclax.Significance: Basic research into the pathways governing programmed cell death have paved the way for the discovery of apoptosis-inducing agents such as venetoclax, a BCL2-selective inhibitor that was recently approved by the FDA and the European Medicines Agency. Preclinical studies aimed at identifying BCL2-dependent tumor types have translated well into the clinic thus far and will likely continue to inform the clinical development of venetoclax and other BCL2 family inhibitors. Cancer Discov; 7(12); 1376-93. ©2017 AACR.

Targeting the Akt, GSK-3, Bcl-2 axis in acute myeloid leukemia

Over the last few decades, there has been significant progress in the understanding of the pathogenetic mechanisms of the Acute Myeloid Leukemia (AML). However, despite important advances in elucidating molecular mechanisms, the treatment of AML has not improved significantly, remaining anchored at the standard chemotherapy regimen "3 + 7", with the prognosis of patients remaining severe, especially for the elderly and for those not eligible for transplant procedures. The biological and clinical heterogeneity of AML represents the major obstacle that hinders the improvement of prognosis and the identification of new effective therapeutic approaches. To date, abundant information has been collected on the genetic and molecular alterations of AML carrying prognostic significance. However, not enough is known on how AML progenitors regulate proliferation and survival by redundant and cross-talking signal transduction pathways (STP). Furthermore, it remains unclear how such complicated network affects prognosis and therapeutic treatment options, although many of these molecular determinants are potentially attractive for their druggable characteristics. In this review, some of the key STP frequently deregulated in AML, such as PI3k/Akt/mTOR pathway, GSK3 and components of Bcl-2 family of proteins, are summarized, highlighting in addition their interplay. Based on this information, we reviewed new targeted therapeutic approaches, focusing on the aberrant networks that sustain the AML blast proliferation, survival and drug resistance, aiming to improve disease treatment. Finally, we reported the approaches aimed at disrupting key signaling cross-talk overcoming resistances based on the combination of different targeting therapeutic strategies.

Phosphorylation of Bcl-2 plays an important role in glycochenodeoxycholate-induced survival and chemoresistance in HCC

Hepatocellular carcinoma (HCC) is a highly malignant tumor and can evolve rapidly to resistance to chemotherapies. Glycochenodeoxycholate (GCDA), which is toxic and hydrophobic, is the main ingredient in the bile and associated with carcinogenesis of gastrointenstinal tumors. Bcl-2 is the most important anti-apoptotic protein and overexpressed in various human tumors. In the present study, we found that GCDA can induce the chemoresistance of human liver cancer cells and specific depletion of Bcl-2 by RNA interference blocks GCDA-stimulated chemoresistance, which indicate the pivotal role of Bcl-2 in such process. Mechanistically, GCDA simultaneously stimulates phosphorylation of Bcl-2 at Ser70 site and activates extracellular signal-regulated kinase 1/2 (ERK1/2), and inhibition of ERK1/2 by PD98059 (MAPK/ERK1/2 inhibitor) or siRNA (targeting ERK1/2) suppresses GCDA-stimulated phosphorylation of Bcl-2 and significantly attenuates the survival and chemoresistance induced by GCDA in liver cancer cells. Thus, GCDA-induced survival and chemoresistance of liver cancer cells may occur through activation of Bcl-2 by phosphorylation at Ser70 site through MAPK/ERK1/2 pathway, which may contribute to the development of human liver cancer and chemoresistance.

Synergistic drug combinations for cancer identified in a CRISPR screen for pairwise genetic interactions

Identification of effective combination therapies is critical to address the emergence of drug-resistant cancers, but direct screening of all possible drug combinations is infeasible. Here we introduce a CRISPR-based double knockout (CDKO) system that improves the efficiency of combinatorial genetic screening using an effective strategy for cloning and sequencing paired single guide RNA (sgRNA) libraries and a robust statistical scoring method for calculating genetic interactions (GIs) from CRISPR-deleted gene pairs. We applied CDKO to generate a large-scale human GI map, comprising 490,000 double-sgRNAs directed against 21,321 pairs of drug targets in K562 leukemia cells and identified synthetic lethal drug target pairs for which corresponding drugs exhibit synergistic killing. These included the BCL2L1 and MCL1 combination, which was also effective in imatinib-resistant cells. We further validated this system by identifying known and previously unidentified GIs between modifiers of ricin toxicity. This work provides an effective strategy to screen synergistic drug combinations in high-throughput and a CRISPR-based tool to dissect functional GI networks.

Beyond tyrosine kinase inhibitors: Combinations and other agents

The modern therapeutic strategy for patients with chronic myeloid leukemia (CML) has been successfully altered by first and subsequently second generation tyrosine kinase inhibitors. However, despite high rate of molecular response, minimal residual disease persists in the majority of patients. Thus other approaches are warranted in order to eliminate the leukemia stem cells. Targeting CML stem cells could be of clinical benefit and a number of new agents are currently tested in phase I/II trials. Also immunological approaches with vaccination strategies and combination of tyrosine kinase inhibitors with various form of interferons are actively ongoing.

BCL-2 inhibition impairs mitochondrial function and targets oral tongue squamous cell carcinoma

Purpose

To understand the role of Bcl-2 overexpression in oral tongue squamous cell carcinoma (OTSCC) patients and investigate the efficacy of targeting Bcl-2 in OTSCC.

Methods

The expression level of Bcl-2 on normal tongue cells and OTSCC cells were measured by real-time PCR and western blotting. The functional roles of Bcl-2 were examined by MTS, flow cytometry and xenograft cancer mouse model. Mechanism studies were performed by analyzing mitochondrial functions in a panel of OTSCC cell lines.

Results

Bcl-2 is up-regulated at mRNA and protein levels in a panel of OTSCC cell lines compared to normal tongue epithelial cells (NTEC). Importantly, overexpression of Bcl-2 confers resistance of OTSCC cells to chemotherapeutic drug cisplatin treatment. Overexpression of Bcl-2 in NTEC significantly increased cell growth. In contrast, inhibition of Bcl-2 by genetic and pharmacological approaches inhibits proliferation and induces apoptosis in OTSCC cells. Mechanistically, Bcl-2 inhibitor ABT-199 impairs mitochondrial functions as shown by the decreased levels of mitochondrial membrane potential, mitochondrial respiration and ATP, and the increased levels of ROS in OTSCC cells. In addition, ABT-199 inhibits proliferation and induces apoptosis and mitochondrial dysfunctions in NTEC cells, but to a less extent than in OTSCC cells. We further show that ABT-199 augments the effects of cisplatin in eliminating OTSCC cells in in vitro tongue cancer cellular system and in vivo tongue cancer xenograft mouse model.

Conclusions

Inhibition of Bcl-2 effectively targets OTSCC cells through inhibiting proliferation and inducing apoptosis. Inhibition of Bcl-2 also augments the inhibitory effects of cisplatin in vitro and in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-016-3310-2) contains supplementary material, which is available to authorized users.

RBP2 Promotes Adult Acute Lymphoblastic Leukemia by Upregulating BCL2

Despite recent increases in the cure rate of acute lymphoblastic leukemia (ALL), adult ALL remains a high-risk disease that exhibits a high relapse rate. In this study, we found that the histone demethylase retinoblastoma binding protein-2 (RBP2) was overexpressed in both on-going and relapse cases of adult ALL, which revealed that RBP2 overexpression was not only involved in the pathogenesis of ALL but that its overexpression might also be related to relapse of the disease. RBP2 knockdown induced apoptosis and attenuated leukemic cell viability. Our results demonstrated that BCL2 is a novel target of RBP2 and supported the notion of RBP2 being a regulator of BCL2 expression via directly binding to its promoter. As the role of RBP2 in regulating apoptosis was confirmed, RBP2 overexpression and activation of BCL2 might play important roles in ALL development and progression.

High CIP2A levels correlate with an antiapoptotic phenotype that can be overcome by targeting BCL-XL in chronic myeloid leukemia

Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a predictive biomarker of disease progression in many malignancies, including imatinib-treated chronic myeloid leukemia (CML). Although high CIP2A levels correlate with disease progression in CML, the underlying molecular mechanisms remain elusive. In a screen of diagnostic chronic phase samples from patients with high and low CIP2A protein levels, high CIP2A levels correlate with an antiapoptotic phenotype, characterized by downregulation of proapoptotic BCL-2 family members, including BIM, PUMA and HRK, and upregulation of the antiapoptotic protein BCL-XL. These results suggest that the poor prognosis of patients with high CIP2A levels is due to an antiapoptotic phenotype. Disrupting this antiapoptotic phenotype by inhibition of BCL-XL via RNA interference or A-1331852, a novel, potent and BCL-XL-selective inhibitor, resulted in extensive apoptosis either alone or in combination with imatinib, dasatinib or nilotinib, both in cell lines and in primary CD34(+) cells from patients with high levels of CIP2A. These results demonstrate that BCL-XL is the major antiapoptotic survival protein and may be a novel therapeutic target in CML.

A link between the driver mutations and dysregulated apoptosis in BCR-ABL1 negative myeloproliferative neoplasms

The current understanding of BCR-ABL1 negative myeloproliferative neoplasms pathogenesis is centred on the phenotypic driver mutations in JAK2, MPL, or CALR genes, and the constitutive activation of JAK-STAT pathway. Nonetheless, there is still a need to better characterize the cellular processes that are triggered by these genetic alterations, such as apoptosis that might play a role in the pathological expansion of the myeloid lineages and, especially, in the morphological anomalies of the bone marrow megakaryocytes. In this article we will explore the connection between the driver mutations in MPN and the abnormal apoptosis that might be translated in new therapeutic strategies.