Misregulation Of The PRC2 Complex In CML Stem Cells Confers Sensitivity To An EZH2 Inhibitor

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2710-2710
Author(s):  
Mary T Scott ◽  
Koorosh Korfi ◽  
Paolo Gallipoli ◽  
Peter Saffrey ◽  
Heather Jorgensen ◽  
...  
Keyword(s):  
Stem Cells ◽  
Tyrosine Kinase ◽  
Board Of Directors ◽  
Kinase Inhibitors ◽  
Chronic Phase ◽  
Polycomb Group ◽  
Leukemic Cells ◽  
Dependent Manner ◽  
Advisory Committees ◽  
Tki Treatment

Abstract Chronic myeloid leukaemia (CML) is a hematological malignancy resulting from the transformation of a primitive hematopoietic progenitor by the fusion oncogene BCR-ABL, a constitutively active tyrosine kinase. In recent years major advances have been made in the treatment of CML with the development of tyrosine kinase inhibitors (TKIs), resulting in high rates of remission in CML chronic phase (CP) patients. However, relapse is driven by quiescent and self-renewing BCR-ABL+ CML stem cells (LSCs) that are resistant to TKIs. Consequently, identification of novel proteins or pathways which can be drug-targeted to eliminate the LSCs is a primary goal of current CML research. Through comparative analysis between CML and non-leukemic samples, we show that components of the repressive Polycomb group (PcG) complex PRC2 are significantly misregulated in CML samples. By performing genome-wide mRNA and epigenetic screens, we demonstrate that this has led to as many as 3-fold more gene repression events in CML cells being associated with gains in the histone modification H3K27me3. This misregulation results in different biological pathways being targeted by PRC2 than those found in non-leukemic samples. We demonstrate that the majority of this misregulation is present in the LSCs. EZH2 is a key component of the PRC2 complex, responsible for laying down the H3K27me3 mark. To determine the effect of inhibition of the complex on LSC survival we have utilised an inhibitor of EZH2, CPI-625. In the absence and presence of TKI, treatment of CP CML CD34+ cells (n=3) with CPI-625 resulted in decreased cell viability (p<0.001 and p<0.05, -/+ TKI respectively) and increased apoptosis (p<0.05 without TKI) in a dose dependent manner. Significantly, there was also a decrease in the number of cells in the undivided, quiescent ‘TKI resistant’ population relative to controls (p<0.01 and p<0.05 -/+ TKI respectively). This was accompanied by an increase in apoptosis (p<0.05 without TKI). Moreover, treatment with CPI-625 resulted in decreasing Colony Forming Cell (CFC) numbers, both in the absence (p<0.05) and presence (p<0.01) of TKI relative to controls. Similar results were seen with treatment of the more primitive CD34+38- cells. Importantly, these effects were not observed in non-leukemic cells. These results demonstrate that CPI-625 is capable of selective targeting of the LSC population. Our data strongly points to changes in H3K27me3 gene targets in CML as a feature related to misregulation of the PRC2 complex. We have demonstrated that targeting of this complex may have efficacy in the treatment of CML, including eradication of the drug resistant LSCs. Disclosures: Holyoake: Novartis: Membership on an entity’s Board of Directors or advisory committees; Bristol Myers Squibb: Membership on an entity’s Board of Directors or advisory committees; Ariad: Membership on an entity’s Board of Directors or advisory committees.

scholarly journals BCL6-Mediated Repression of p53 Is Critical for Leukemia Stem Cell Survival in Chronic Myeloid Leukemia

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 446-446
Author(s):  
Christian Hurtz ◽  
Katerina Hatzi ◽  
Leandro Cerchietti ◽  
Eugene Park ◽  
Yong-Mi Kim ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Board Of Directors ◽  
Myeloid Leukemia ◽  
Research Funding ◽  
Kinase Inhibitors ◽  
Blast Crisis ◽  
Dominant Negative ◽  
Advisory Committees ◽  
Self Renewal ◽  
Tki Treatment

Abstract Abstract 446 Background: Chronic myeloid leukemia (CML) is induced by the oncogenic BCR-ABL1 tyrosine kinase and can be effectively treated for many years with tyrosine kinase inhibitors (TKI). However, unless CML patients take TKI-treatment life-long, leukemia will eventually recur, which is attributed to the failure of TKI-treatment to eradicate leukemia-initiating cells (LIC; Corbin et al., J Clin Invest 2011). Persistence of LIC in CML can result in acquisition of secondary events eventually leading to TKI-resistant blast crisis, which is fatal within months. Recent work demonstrated that FoxO factors are critical for maintenance of CML-initiating cells (Naka et al., Nature 2010), however the mechanism of FoxO-dependent leukemia-initiation remained elusive. Results: Here we identified the BCL6 protooncogene as a critical effector downstream of FoxO in self-renewal signaling of CML-initiating cells. ChIP-seq analysis demonstrated that BCL6 directly binds to and represses Arf and p53 promoters in human CML cells. Genetic deletion of the BCL6 gene in a mouse model of CML results in progressive depletion of Lin- Sca-1+ c-Kit+ LIC. BCL6-deficient LIC exhibit excessively high expression levels of Arf and p53 and propensity to cellular senescence and apoptosis. As a consequence, BCL-deficient CML cells lack the ability to form colonies and to initiate leukemia in transplant recipient animals. To investigate whether these effects are indeed owing to the role of BCL6 as repressor of Arf/p53, we induced activation of a dominant-negative BCL6-mutant in p53+/+ and p53−/− CML cells. While dominant-negative BCL6 compromised colony formation and self-renewal in p53+/+ CML cells, BCL6 inhibition only had minor effect on p53−/− CML cells. We conclude that BCL6 enables survival of LIC in CML mainly through transcriptional repression of p53. To test potential clinical relevance of these findings, we used a recently developed retro-inverso BCL6 peptide inhibitor (RI-BPI, Cerchietti et al., 2009), which inhibits BCL6 function as transcriptional repressor. RI-BPI is currently under clinical trial for the treatment of BCL6-dependent diffuse large B cell lymphoma (Dr. Ari Melnick, LLS TAP Program). Importantly, peptide inhibition of BCL6 in human CML cells compromises colony formation and leukemia-initiation in transplant recipients and selectively eradicates CD34+ CD38− LIC in patient-derived CML samples. Conclusions: These findings identify pharmacological inhibition of BCL6 as a novel strategy to eradicate LIC in CML. Clinical validation of this concept could limit the duration of TKI-treatment in CML patients, which is currently life-long, and substantially decrease the risk of blast crisis transformation. Based on these findings, we propose a dual targeting strategy, in which (1) tyrosine kinase inhibitors (e.g. Imatinib) to target the transient amplifying pool of CML cells are coupled with (2) BCL6 inhibition that will target quiescent LIC. Disclosures: Hochhaus: Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Honoraria, Membership on an entity's Board of Directors or advisory committees; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding. Shah:Bristol-Myers Squibb: Consultancy, Research Funding; Novartis: Consultancy; Ariad: Consultancy, Research Funding. Druker:Novartis: ; Bristol-Myers Squibb: ; ARIAD Pharmaceuticals: ; OHSU patent #843: Mutated ABL Kinase Domains: Patents & Royalties; MolecularMD: Equity Ownership.

Osteoarticular Pain after Discontinuation of Tyrosine Kinase Inhibitors (TKI): A French Cohort

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 137-137 ◽  
Author(s):  
Marc G Berger ◽  
Bruno Pereira ◽  
Charlotte Oris ◽  
Sandrine Saugues ◽  
Pascale Cony-Makhoul ◽  
...  
Keyword(s):  
Clinical Trials ◽  
Tyrosine Kinase ◽  
Medical History ◽  
Board Of Directors ◽  
Tyrosine Kinase Inhibitors ◽  
Research Funding ◽  
Kinase Inhibitors ◽  
Duration Of Treatment ◽  
Advisory Committees ◽  
History Of

Abstract Context: The Tyrosine Kinase Inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) increasing dramatically the survival of CML patients and leading to a residual disease with a sustained and deep molecular response. In this subset of very good responder patients, the attempts of stopping treatment in different clinical trials were successfully achieved without relapse. The Swedish team in the EURO-SKI protocol already reported cases of musculoskeletal pain occurring after cessation of TKI (Richter et al., JCO, 2014). Since several clinical trials regarding TKI discontinuation have been also run in France, we decided to retrospectively collect data using the pharmacovigilance system of the different Trials collected prospectively. Method: 428 patients from STIM2 (n=204) and EURO-SKI (n=224) trials were systematically analyzed from the case report from each trial. For the EURO-SKI only French patients were included. Statistical analysis was performed using Stata 13 software (StataCorp LP, College Station, TX, US). Comparisons between the independent groups were realized using the Chi-squared or Fisher's exact tests for categorical variables, and using Student t-test or Mann-Whitney test for quantitative. Multivariate analyses were performed to take into account adjustment on covariates fixed according to univariate results and clinically relevance. Results: Among the 428 patients the main characteristics were as follow i,e; 208 (48.6%) men and 220 (51.4%) women, with a median age of 77.5 years (24-93). Sokal scores (n=449) were low in 187 (41.6%) patients, intermediate in 188 (41.9%) patients and high in 74 (16.5%) patients. A withdrawal TKI syndrome (WS) was reported for 102 (23.8%) patients (100 after imatinib and 2 after nilotinib). 2). The WS consists in bone and articular pains and arthritis and affects the upper limbs, shoulders and cervical rachis, with a grade 1 or 2 in most patients and grade 3 in 22% of patients . The prevalence of WS depends on the trials, 34.8% in EURO-SKI group and 13.8% in STIM2 group (p<0.001). The WS was treated by non-steroidal anti-inflammatory drugs, corticosteroids or by local infiltration. The median duration of WS was 7 months (range: 3-30 months, 24 exploitable cases). We did not observe any difference between WS group and the group without painful syndrome in terms of sex ratio (p=0.92), age (p=0.33), sokal score (p=0.15), BCR-ABL transcript (p=0.42) or duration of CML (p=0.24). However the median duration of TKI therapy appeared longer in this subgroup (median: 88.8 months vs 79.8 months (p=0.02). There was no biological inflammatory syndrome and the results of medical imaging were inconclusive. However, a medical history of osteoarticular pains or disease appeared as predisposing to withdrawal syndrome (22.9% in WS group vs 9.8% in control group; p=0.002). Finally the two factors, duration of treatment and medical history were confirmed using multivariate analysis (RR=1.73 and 1.76 respectively). Among 19 exploitable cases suffering CML relapse and requiring further TKI treatment, pain disappeared in 7 patients (37%) within a median period of 3.5 weeks. Conclusion: About 23% of patients who stopped TKIs experienced a TKI WS and all TKI seems to be concerned. The predisposing factors were a medical history of osteoarticular pain or disease, and the duration of treatment. So patients and physicians should be aware and recommendations should be proposed for patients who have treated longtime with a history of arthritis. Disclosures Legros: Novartis: Research Funding, Speakers Bureau; ARIAD: Speakers Bureau; BMS: Speakers Bureau. Nicolini:Ariad Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau. Rousselot:Novartis: Speakers Bureau; Pfizer: Consultancy, Speakers Bureau; ARIAD: Consultancy, Speakers Bureau; BMS: Consultancy, Speakers Bureau. Rea:Novartis: Honoraria; BMS: Honoraria; Ariad: Honoraria; Pfizer: Honoraria. Mahon:Bristol-Myers Squibb: Consultancy, Honoraria; ARIAD: Consultancy; Novartis: Consultancy, Honoraria; Pfizer: Consultancy.

scholarly journals First-Line Second Generation Tyrosine Kinase Inhibitors in Newly Diagnosed Accelerated Phase Chronic Myeloid Leukemia Patients.

Blood ◽  
2018 ◽  
Vol 132 (Supplement 1) ◽  
pp. 48-48 ◽  
Author(s):  
Marie Balsat ◽  
Vincent Alcazer ◽  
Gabriel Etienne ◽  
Gaelle Fossard ◽  
Francoise Huguet ◽  
...  
Keyword(s):  
Chronic Myeloid Leukemia ◽  
Tyrosine Kinase ◽  
Board Of Directors ◽  
Tyrosine Kinase Inhibitors ◽  
Myeloid Leukemia ◽  
Kinase Inhibitors ◽  
Newly Diagnosed ◽  
First Line ◽  
Advisory Committees ◽  
Free Survival

Abstract Introduction Up to 10% of patients (pts) with chronic myeloid leukemia (CML) are already in accelerated phase (AP) at diagnosis and despite treatment advances in the field of tyrosine kinase inhibitors (TKIs), management of these pts is challenging. This study aims to examine the benefit of second generation BCR-ABL tyrosine kinase inhibitors (TKI2) as first-line treatment for newly diagnosed AP-CML. Methods Pts meeting criteria for AP-CML at diagnosis and treated with first-line TKI2 (i. e. Nilotinib or Dasatinib) were included in this retrospective multicenter observational national study. AP-CML were defined according to the ELN (Baccarani, Blood 2013) as hematological acceleration (HEM-AP, any of the following features: blasts in PB or marrow 15-29%, or blasts+promyelocytes in PB or marrow >30% with blasts <30%, basophils in PB ≥20%, or persistent thrombocytopenia <100×109/L (unrelated to therapy) and/or chromosomal abnormalities in addition to the Ph at diagnosis (ACA-AP). Pts initiated nilotinib at 6-800 mg BID or dasatinib at 100-140 mg QD with further dose adaptations according to toxicities or response. Overall survival (OS), progression-free survival (PFS) and failure-free survival [FFS= progression to blast crisis, death, loss of any previous response (CHR, CCyR, or MMR) discontinuation of TKI2 for toxicity], were analysed since TKI2 initiation in intention-to-treat. Results Sixty-six pts were analysed: 45 males (68%) and 21 females (32%) with a median age at diagnosis of 49 (15-78.5) years. The median follow-up of the cohort was 43.5 (1.7-117) months. We segregated the pts in HEM-AP (n=33) and ACA-AP (n=33) for further analyses. Nine pts with HEM-AP harboured ACA and were analysed in the HEM-AP group. Fusion transcripts were of the Major BCR in 57 pts, 6 pts had atypical BCR-ABL transcripts (2 e19a2, and 1 e1a2 in the HEM-AP group and 2 e19a2 and 1 Ma3 in the ACA-AP group), and 3 transcripts unknown. Not surprisingly, spleen enlargement was significantly greater in the HEM-AP group [10 (5-14.75) vs. 3 (0-10)cm, p=0.014]. PB basophils [median 10 (6-16) vs. 3 (2-5)%, p <0.001], PB blasts [median: 12.05 (7.5-15) vs. 1.5 (0-4)%, p<.001], as well as PB blasts+promyelocytes [median 14 (11-20) vs. 4 (1-7)%, p<.001]. Hemoglobin levels were significantly lower in the HEM-AP group [median 93 (6-113.5) vs 120 (100-134) g/L, p<0.001]. Neither WBC counts, platelets counts, nor BCR-ABL/ABL load differed significantly between the 2 groups. In the ACA-AP group, 10 (30%) pts harbored major route ACA and 23 (70%) pts harbored minor route ACA of whom 3 pts with i(17q) and 1 with 7q abnormalities. In the ACA-AP group, Sokal score was low in 42%, intermediate in 32% and high in 26% of pts (2 pts unknown). Dasatinib was initiated in 19/33 pts (57.5%) in the HEM-AP group and in 8/33 pts (24%) in the ACA-AP group. Treatment responses did not significantly differ between ACA-AP and HEM-AP group, regardless of the TKI2 administered, with 33/33 (100%) vs 31/33 (94%) pts achieving a CHR, 2/33 (6%) pts vs 0/33 (0%) pts achieving a MCyR, 5/33 (15%) pts vs 5/33 (15%) pts achieving CCyR, 9/33 (27%) pts vs 4/33 (12%) pts achieving a MMR respectively. However, 11/33 (33%) HEM-AP vs 22/33 (66%) ACA-AP pts achieved a deep molecular response (p=0.013, Fisher test). Median times to CHR and MMR were not significantly different between ACA-AP group and HEM-AP group with 1.05 vs 1.25 months (p=0.088) for CHR and 6 vs 7 months (p=0.156) for MMR, respectively. Overall, the estimated 7-yr FFS rate was 56.92% (95%CI: 40-81), 7-yr PFS was 83.42% (95% CI: 69.6-100%) and 7-yr OS was 87.14% (95%CI: 73.5-100%) (Figure 1.) with no significant differences between ACA-AP vs HEM-AP pts [7-yr FFS: 57.7 vs. 62%, p=0.739; 7-yr PFS: 84.7% vs. 84%, p=0.185; 7-yr OS: 88.9% vs 86.6%, p=0.132] respectively. There was also no difference in FFS, PFS and OS according to the type of TKI2. The only factors influencing negatively OS were the % of BM blasts (HR=1.17, 95%CI: 1.1-1.28, p<0.001) and the % of BM blasts+promyelocytes (HR=1.14, 95%CI: 1.06-1.22, p<0.001). We identified too few significant factors in univariate analysis to perform a multivariate analysis. Conclusion The initiation of a TKI2 in newly diagnosed AP-CML pts induces excellent response and survival rates, probably superior to that of Imatinib first-line, and counterbalances the negative impact of this advanced disease, particularly in HEM AP subgroup. Disclosures Etienne: Pfizer: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Speakers Bureau; BMS: Membership on an entity's Board of Directors or advisory committees, Other: Travel, Speakers Bureau; Novartis: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Incyte: Honoraria, Patents & Royalties, Speakers Bureau. Berger:Sanofi: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Mahon:Incyte: Speakers Bureau; Pfizer: Speakers Bureau; Novartis: Speakers Bureau; BMS: Speakers Bureau. Rea:Bristol-Myers Squibb: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees; Incyte: Honoraria; Pfizer: Honoraria. Nicolini:BMS: Consultancy, Speakers Bureau; Incyte Biosciences: Consultancy, Speakers Bureau; Sun Pharma Ltd: Consultancy.

scholarly journals Combination of tyrosine kinase inhibitors and the MCL1 inhibitor S63845 exerts synergistic antitumorigenic effects on CML cells

2021 ◽  
Vol 12 (10) ◽  
Author(s):  
Alena Malyukova ◽  
Dorina Ujvari ◽  
Elham Yektaei-Karin ◽  
Ana Zovko ◽  
Harsha S. Madapura ◽  
...  
Keyword(s):  
Tyrosine Kinase ◽  
Progenitor Cells ◽  
Kinase Inhibitors ◽  
Kinase Inhibitor ◽  
Residual Disease ◽  
Chronic Phase ◽  
Myeloid Cell ◽  
Hematologic Malignancies ◽  
Hematopoietic Stem ◽  
Tki Treatment

AbstractTyrosine kinase inhibitor (TKI) treatment has dramatically improved the survival of chronic myeloid leukemia (CML) patients, but measurable residual disease typically persists. To more effectively eradicate leukemia cells, simultaneous targeting of BCR-ABL1 and additional CML-related survival proteins has been proposed. Notably, several highly specific myeloid cell leukemia 1 (MCL1) inhibitors have recently entered clinical trials for various hematologic malignancies, although not for CML, reflecting the insensitivity of CML cell lines to single MCL1 inhibition. Here, we show that combining TKI (imatinib, nilotinib, dasatinib, or asciminib) treatment with the small-molecule MCL1 inhibitor S63845 exerted strong synergistic antiviability and proapoptotic effects on CML lines and CD34+ stem/progenitor cells isolated from untreated CML patients in chronic phase. Using wild-type BCR-ABL1-harboring CML lines and their T315I-mutated sublines (generated by CRISPR/Cas9-mediated homologous recombination), we prove that the synergistic proapoptotic effect of the drug combination depended on TKI-mediated BCR-ABL1 inhibition, but not on TKI-related off-target mechanisms. Moreover, we demonstrate that colony formation of CML but not normal hematopoietic stem/progenitor cells became markedly reduced upon combination treatment compared to imatinib monotherapy. Our results suggest that dual targeting of MCL1 and BCR-ABL1 activity may efficiently eradicate residual CML cells without affecting normal hematopoietic stem/progenitors.

Antibody-Targeting of IL-3 Receptor-α Increases the Susceptibility of CD34+ CML Progenitors to Dasatinib-Induced Cell Death,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 3745-3745
Author(s):  
Eva Nievergall ◽  
Deborah L. White ◽  
Hayley Ramshaw ◽  
Angel F. Lopez ◽  
Timothy P. Hughes ◽  
...  
Keyword(s):  
Stem Cells ◽  
Flow Cytometry ◽  
Progenitor Cells ◽  
Board Of Directors ◽  
Myeloid Leukemia ◽  
Research Funding ◽  
Blast Crisis ◽  
Chronic Phase ◽  
Advisory Committees ◽  
Cd34 Cells

Abstract Abstract 3745 Despite the remarkable efficacy of tyrosine kinase inhibitors (TKIs) in the treatment of chronic myeloid leukemia (CML), Ph+ CD34+ progenitor cells remain detectable even in patients with stable complete cytogenetic response. Over 40% of patients in stable complete molecular remission will develop molecular relapse within 6 months of stopping imatinib. While the exact causes are largely unknown, one of the proposed mechanisms is the protection of leukemic stem and early progenitor cells by the paracrine or autocrine production of cytokines, such as IL-3, GM-CSF and G-CSF, which activate survival pathways that bypass TKI-induced cytocidal effects. In acute myeloid leukemia (AML), the IL-3 receptor α chain (CD123) is recognized as a specific marker for CD34+/CD38− stem cells and therefore is attracting increasing interest as a therapeutic target. However, the function of CD123 in CML remains to date mostly unexplored. The aim of this study is to investigate potential synergy between TKIs and CSL362 (a humanized antibody version of 7G3 against CD123) in targeting CML progenitor and stem cells. CD34+ and CD34+/CD38− cells were isolated from mononuclear cells of newly diagnosed CML chronic phase and blast crisis patients. Flow cytometry studies indicated significantly increased CD123 expression on CD34+/CD38− cells of CML patients in both chronic phase and blast crisis when compared to normal hematopoietic stem cells (p<0.01 and p<0.001 for chronic phase and blast crisis, respectively; Figure A). A functional relevance of increased CD123 expression was demonstrated by IL-3-dependent increase in STAT5 phosphorylation (260.5% of baseline with 20 ng/ml IL-3; n=12; p<0.001) in CML CD34+ cells. Dasatinib inhibits STAT5 phosphorylation by blocking BCR-ABL signaling but only in the absence of IL-3 (62.5% of baseline for dasatinib alone vs. 130.8% for dasatinib + IL-3; n=3; p<0.01). In agreement, IL-3 effectively rescues dasatinib-induced cell death, as evaluated by AnnexinV/7-AAD staining (103.3% vs. 72.45%, n=5; p<0.01) and CFU-GM colony forming assays (69.39% vs. 46.13% relative to no treatment control; n=4; p<0.05). CSL362, in turn, revokes IL-3-mediated STAT5 phosphorylation (37.12% vs. 130.8%; n=3; p<0.001) and cytoprotection (45.05% vs. 69.39% CFC; n=4; p<0.01). In order to further elucidate the role of CSL362, CML CD34+ cells were cultured with increasing concentrations of dasatinib in the presence of IL-3 and CSL362 or BM4 isotype-matched control antibody. Even at very low dasatinib concentrations, CSL362 significantly reduces CML CD34+ colony forming cells (p<0.05; Figure B). Together these results substantiate a relevant role for IL-3-mediated resistance in CML progenitor cells and additionally confirming the ability of CSL362 to effectively bind to CD123 and impede IL-3 function. CSL362 furthermore has been optimized to mediate antibody dependent cell cytotoxicity (ADCC). CSL362 causes specific cell lysis of CML CD34+ progenitor cells in co-culture with allogeneic Natural killer cells as determined by increased lactate dehydrogenase release (ADCC activity of 42.4% ± 8.1%; n=3) and a decrease in the number of CFU-GM colonies by 74.1 % ± 12.2% (n=3). Collectively, our results indicate that a combination of dasatinib and CSL362 inhibits CML progenitor cell survival more effectively in vitro. Therefore, targeting IL-3 receptor α with CSL362 in chronic phase and blast crisis CML patients might provide a novel specific treatment approach aiding the elimination of refractory chronic myeloid leukemic stem and progenitor cells. A: Flow cytometry analysis reveals that CD123 expression is significantly higher in CD34+/CD38− cells of CML patients in chronic phase (CML-CP) and blast crisis (BC-CML) as compared to normal patients (NP), as previously documented for AML patients. ** p<0.01, *** p<0.001 by unpaired, two-tailed Student's t-test. B: In the presence of IL-3, CSL362 significantly reduces the number of colony forming cells. CD34+ cells of de novo CML-CP patients were cultured with dasatinib (0 to 10 nM) +IL-3 (1 ng/ml) ± CSL362 or BM4 (isotype control for CSL362). After 72 hours of culture live cells were plated for CFU-GM assay and colonies were counted after 2 weeks. Mean ± SE of three independent experiments is shown, n=4, p<0.05 by two-way ANOVA. Disclosures: Nievergall: CSL: Research Funding. White:CSL: Research Funding. Lopez:CSL: Research Funding. Hughes:Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Ariad: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Hiwase:CSL: Research Funding.

Characterization of the Genomic Landscape of BCR-ABL1 Kinase-Independent Mechanisms of Resistance to ABL1 Tyrosine Kinase Inhibitors in Chronic Myeloid Leukemia

Blood ◽  
2016 ◽  
Vol 128 (22) ◽  
pp. 1119-1119 ◽  
Author(s):  
Christopher A. Eide ◽  
Daniel Bottomly ◽  
Samantha L. Savage ◽  
Libbey White ◽  
Beth Wilmot ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Board Of Directors ◽  
Research Funding ◽  
Kinase Inhibitors ◽  
Chronic Phase ◽  
Kinase Domain ◽  
Advisory Committees ◽  
Dana Farber Cancer Institute ◽  
Kinase Domain Mutation ◽  
Equity Ownership

Abstract Despite the well-established success of ABL1 tyrosine kinase inhibitors (TKIs) in the treatment of patients with chronic myeloid leukemia (CML), approximately 20% of patients treated with frontline imatinib develop resistance by 5 years on therapy. The majority (~60%) of such resistant cases are explained by acquired mutations within the BCR-ABL1 kinase domain that compromise inhibitor binding, and nearly all of these mutations are effectively targeted by one or more of the 2nd and 3rd generation ABL1 kinase inhibitors. In contrast, the remaining ~40% of imatinib-resistant cases harbor no explanatory BCR-ABL1 kinase domain mutation, presumably attributable to BCR-ABL1 kinase-independent mechanisms. We hypothesized that resistance in these patients results from acquired auxiliary molecular aberrations which persistently activate signaling pathways downstream despite inhibition of BCR-ABL1 kinase activity. To identify such mechanisms, we performed whole exome sequencing and RNA sequencing on a cohort of 135 CML patients comprising the following subgroups: newly diagnosed/TKI naïve (n=28), BCR-ABL1 kinase-dependent resistance (n=31), and BCR-ABL1 kinase-independent resistance (n=65), and TKI-induced remission (n=7). Resistant patients were required to have demonstrated clinical resistance to one or more ABL1 kinase inhibitors in the form of suboptimal response or loss of cytogenetic response; the subtype of resistance was defined based on the presence or not of an explanatory BCR-ABL1 kinase domain mutation at the time of resistance. The majority of samples collected were from patients with chronic phase CML (n=97), although smaller cohorts of accelerated phase CML, blast crisis CML, and Ph+ ALL were also profiled (n=20, 19, and 9, respectively). Among the 44,413 protein-altering and 902 splice site variants detected across the 120 WES samples, there were on average 908 missense, 146 truncation and 69 splice variants per sample. Genes with truncation and missense variants were compared between BCR-ABL1 kinase-independent and -dependent resistant chronic phase samples. A total of 44 genes were seen with a frequency difference of at least 10%, including PLEKHG5 and NKD2 (30% and 28% difference, respectively), which are involved in regulation of NF-kB and Wnt signaling. Consistent with previous reports, we also detected EZH2 and TET2 as exclusively mutated in the BCR-ABL1 kinase-independent resistance patients (6% and 3%, respectively). Further analyses stratifying variants among resistant patients according to specific ABL1 kinase inhibitor therapy failed and comparing, where available, serial samples from pre- and post-treatment for clonal expansion are underway. Additionally, sufficient material was available to perform ex vivo small-molecule inhibitor screening for 48 patient specimens, the resultant data of which was used to generate putative effective drug target profiles and integrated with exome sequencing variants to prioritize variants of functional relevance (HitWalker; Bottomly et al., Bioinformatics 2013). Among 23 patient samples exhibiting BCR-ABL1 kinase-independent resistance, the mutated genes most frequently ranked in the top 10 functional-prioritized variants were: ABL1 (which included non-kinase domain variants; 34.7%), MAP3K1, MUC4, FGF20 (each 17.4%), ARHGEF15, MEF2A, EPHA8, TYRO3, BMP2K, and IRS1 (each 13.0%). Notably, the top six candidates are members of the neutrophin (ABL1, MAP3K1, and IRS1), EPHA forward (EPHA8, ARHGEF15), and p38 MAPK signaling pathways (MAP3K1 and MEF2A). Taken together, these findings suggest that several of the same pathogenic molecular abnormalities seen in other myeloid malignancies are also present in CML patients with BCR-ABL1 kinase-independent resistance, including a subset which align to persistent re-activation of signaling pathways involved in CML disease pathogenesis and progression. As such, genetic and/or functional profiling of these patients in the clinic may translate to actionable candidates for combination therapy to maximize disease control and improve patient outcomes. Disclosures Agarwal: CTI BioPharma Corp: Research Funding. Radich:Novartis: Consultancy, Research Funding; BMS: Consultancy; Ariad: Consultancy. Deininger:Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; BMS: Consultancy, Research Funding; Incyte: Consultancy, Membership on an entity's Board of Directors or advisory committees; Gilead: Research Funding; CTI BioPharma Corp.: Membership on an entity's Board of Directors or advisory committees; Celgene: Research Funding; Bristol Myers Squibb: Consultancy, Research Funding; Ariad: Consultancy, Membership on an entity's Board of Directors or advisory committees. Druker:Pfizer: Patents & Royalties; Dana-Farber Cancer Institute: Patents & Royalties: Millipore royalties via Dana-Farber Cancer Institute; Curis: Patents & Royalties; Array: Patents & Royalties; CTI: Consultancy, Equity Ownership; Pfizer: Patents & Royalties; Curis: Patents & Royalties; Array: Patents & Royalties; Dana-Farber Cancer Institute: Patents & Royalties: Millipore royalties via Dana-Farber Cancer Institute; Oncotide Pharmaceuticals: Research Funding; Novartis: Research Funding; BMS: Research Funding; ARIAD: Patents & Royalties: inventor royalties paid by Oregon Health & Science University for licenses, Research Funding; Roche: Consultancy; Gilead Sciences: Consultancy, Other: travel, accommodations, expenses; D3 Oncology Solutions: Consultancy; AstraZeneca: Consultancy; Ambit BioSciences: Consultancy; Agios: Honoraria; MolecularMD: Consultancy, Equity Ownership, Patents & Royalties; Lorus: Consultancy, Equity Ownership; Cylene: Consultancy, Equity Ownership.

scholarly journals Cytogenetically cryptic TNIP1-PDGFRB and PCM1-FGFR1 fusion leading to myeloid/lymphoid neoplasms with eosinophilia (MLN-eo) in children

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 4638-4638
Author(s):  
Ann-Cathrine Berking ◽  
Tim Flaadt ◽  
Yvonne Lisa Behrens ◽  
Andreas Reiter ◽  
Ayami Yoshimi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Tyrosine Kinase ◽  
Board Of Directors ◽  
Rna Sequencing ◽  
Kinase Inhibitors ◽  
Array Cgh ◽  
Genetic Diagnosis ◽  
Fusion Transcript ◽  
Chromosome 8 ◽  
Advisory Committees

Abstract Introduction: MLN-eo associated with gene rearrangements of PDGFRA, PDGFRB, FGFR1, or PCM1-JAK2 are rare haematological neoplasms primarily affecting adults. Eosinophilia commonly occurs but may also be absent. The heterogeneous clinical picture and the rarity of the disease, especially in children, may delay an early diagnosis. MLN-eo are characterized by constitutive tyrosine kinase activity due to gene fusions. It is thus of prognostic importance to obtain a prompt genetic diagnosis to start a specific therapy. Here we report two female paediatric cases of MLN-eo (6 months and 13 years old at initial diagnosis). Methods: In both cases, bone marrow morphology, karyotyping, fluorescence in-situ hybridization analysis (FISH) via break apart probes (PDGFRB (5q32), FGFR1 (8p12), JAK2 (9p24), FIP1L1/CHIC2/PDGFRA (4q12)), targeted RNA sequencing and in one case array CGH were performed. Results: The 6 months old girl was admitted to hospital with a 3-month history of rash and leukocytosis with eosinophilia. The skin showed multiple purpuric lesions (Fig 1 A/B). Mild splenomegaly was noted. White blood count (WBC) was 48000/µl with 38% eosinophils. Bone marrow trephine showed hypercellular marrow with mild fibrosis and eosinophilia without increase in blasts. Biopsy of a skin nodule displayed a histological pattern of interface dermatitis with eosinophilic infiltrate. (Fig 1 C/D). Fluorescence R-banding showed a normal karyotype (46,XX) (Fig. 2 A). However, FISH and array CGH detected an interstitial deletion of 5` PDGFRB (5q32) in 61 % of interphase nuclei (Fig. 2 B-D). Targeted RNA sequencing (RNA-seq) confirmed, as the array CGH suggested, the suspected TNIP1/PDGFRB fusion. According to the WHO criteria, diagnosis of a myeloid neoplasia with PDGFRB rearrangement due to an interstitial deletion in 5q was made. Because of the PDGFRB rearrangement, imatinib (250 mg/m²/d) therapy was started. Leukocyte and eosinophil counts normalized within 4 days without signs of tumour lysis. Skin lesions disappeared within 2 weeks. After 4 weeks, the dose was reduced to 100 mg/m² 3 x/week. Now at 14 months of age, peripheral counts continue to be normal and the fusion transcript is not detectable in the peripheral blood. The 13 years old girl was admitted with severe tachypnoea due to pleural effusions, hepatosplenomegaly and lymphadenopathy. Echocardiography showed endocarditis, left ventricular fibrosis and mitral insufficiency. WBC was 112170 /µL with 39% eosinophils. Bone marrow aspirate and trephine showed a feature of myeloproliferative neoplasia (MPN) with eosinophilia. The karyotype was normal. A rearrangement involving the FGFR1 locus was detected by FISH (Fig. 3 B/C). Splitting of the probe signals indicated an inversion on chromosome 8. Targeted RNA sequencing revealed a PCM1-FGFR1 fusion transcript. Diagnosis of a MLN-eo with FGFR1 rearrangement and evidence of a PCM1-FGFR1 fusion, most likely caused by an inversion on chromosome 8, was made. The girl stabilized after therapy with prednisone, vincristine, hydroxycarbamide and anti-IL-5 antibody. Peripheral blood counts normalized within 2 weeks. Eight weeks after initial diagnosis she presented with signs of a transient ischemic attack, respiratory distress and arterial hypotension. At that time WBC was 139000/µl with 53% myeloid blasts and 5% eosinophils. Trisomy 8 was detected in all metaphases and 88% of cells in FISH (Fig.3 A-C). Diagnosis of a progression to a myeloid blast phase was made. Induction chemotherapy (cytarabine, idarubicin, etoposidphosphate) was administered. On day +22 bone marrow aspirates showed the persisting picture of MPN. Preparations for hematopoietic stem cell transplantation (HSCT) and ponatinib therapy were begun, but cardiac and respiratory insufficiency that developed during chemotherapy were fatal. Conclusion: As these two cases have shown, standard cytogenetic and molecular methods may not be sufficient to diagnose MLN-eo due to cytogenetically cryptic aberrations. Thus, genetic diagnosis must be precise and quick (e.g. break apart FISH, targeted RNA-seq) in order to initiate adequate therapies with tyrosine kinase inhibitors or HSCT. Patients with rearrangements of PDGFRA or PDGFRB usually respond well to imatinib, whereas patients with FGFR1 and JAK2 gene fusions exhibit more aggressive diseases with variable sensitivity to tyrosine kinase inhibitors and have an early indication for HSCT. Figure 1 Figure 1. Disclosures Reiter: Novartis: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses, Research Funding; Blueprint Medicines: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; Incyte: Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; AOP Orphan Pharmaceuticals: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support; Deciphera: Membership on an entity's Board of Directors or advisory committees, Other: Travel expenses; Abbvie: Membership on an entity's Board of Directors or advisory committees; Celgene/BMS: Honoraria, Membership on an entity's Board of Directors or advisory committees, Other: travel support.

Proteomic Signature of CD34+ Cells From Chronic Myeloid Leukemia Patients

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3733-3733
Author(s):  
Maria Rosaria Ricciardi ◽  
Valentina Salvestrini ◽  
Roberto Licchetta ◽  
Simone Mirabilii ◽  
Maria Teresa Petrucci ◽  
...  
Keyword(s):  
Chronic Myeloid Leukemia ◽  
Board Of Directors ◽  
Myeloid Leukemia ◽  
Kinase Inhibitors ◽  
Chronic Phase ◽  
Molecular Therapy ◽  
Antibody Array ◽  
Proteomic Profile ◽  
Advisory Committees ◽  
Cd34 Cells

Abstract Abstract 3733 The tyrosine kinase inhibitors (TKIs) represent the successful molecular therapy for patients with chronic myeloid leukemia (CML), targeting the Bcr-Abl oncogenic product. However, this disease may remain not curable for the presence of residual refractory cells, persisting during the history of the disease treatment. Several mechanisms have been associated with resistance to TKIs, including the presence of rare quiescent leukemic stem cells, less susceptible to TKIs. Moreover, Bcr-Abl activates additional downstream pathways involved in the apoptotic and proliferation control of CML cells, such as RAS/MEK/ERK, PI3K/Akt, Wnt and STAT5 pathways, potentially contributing to CML TKIs drug resistance. Therefore, in this study we aimed to investigate, at the protein level, proliferative and apoptotic signal transduction pathways (STP) in CML CD34+ cells, as compared to normal CD34+ cells, in order to identify additional aberrant signals, potentially therapeutic targetable. CD34+ cells were purified from peripheral blood (PB) of five newly diagnosed, chronic phase (CP) CML patients, three normal cord blood (CB) and one leukapheretic product of a normal volunteer (PBSC). The phosphorylation status of 46 proteins from various STP and the expression of 32 proteins of the apoptotic machinery were assessed by using a customized direct phase proteome profiler antibody array. The resulting dots were visualised using ECL and quantified by densitometric analysis. CML samples were collected from patient in CP, with a WBC count ranging between 41900–135400 per microliter. The Sokal risk category was low (1/5) and intermediate (4/5). The comparison between normal CD34+ cells obtained from CB and PBSC showed that the first cells were characterized by a lower expression of STAT, Tyrosine-protein kinase and MAPK protein families. The phospho-proteomic profile of CD34+ cells from CML samples showed remarkably similarity when compared to normal CB CD34+ cells, while only two proteins resulted differently expressed in CP CD34+ cell vs. PBSC: CREB-S133, involved in the pro-survival/anti-apoptotic gene control (p=0.025) and p70S6K-T389, along the PI3k/Atk pathway and involved in the cell proliferation (p=0.049). The analysis of the 32 apoptotic proteins revealed that 10 of them were statistically significant lower in CML CD34+ cells compared to PBSC. Most of them were related to the Bcl-2 family and caspase inhibitors family, such as cIAP-1 (p=0.025), cIAP-2 (p=0.0003) and livin (p=0.016). The expression of the cyclin-dependent kinase inhibitors (CKI) was found significantly lower in CML CD34+ (p=0.05 and p=0.02 for p21/CIP1 and p27/Kip1, respectively). In conclusion, we have reported in this study that proteins and/or phosphoproteins controlling apoptosis and proliferation STP, such as Bcl-2, IAP, MAPK, PI3K/Akt, STATs and CKI families, are differentially expressed in CD34+ from CML CP, compared to PBSC. The understanding of these differences in the proteomic profile may confirm that additional multiple aberrant STP are involved in the CML and therefore must be taken into account for targeted therapies, especially of resistant cases. Disclosures: Petrucci: Jansse-Cilag, Celgene: Honoraria. Castagnetti:Novartis Pharma: Consultancy, Honoraria, Speakers Bureau; Bristol Myers Squibb: Consultancy, Honoraria, Speakers Bureau. Rosti:Bristol Myers Squibb: Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Novartis Pharma: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Roche: Speakers Bureau; Pfizer: Speakers Bureau.

Human MICL Is An Early Marker In Myeloid Differentiation and Identifies a Subgroup Of CML Patients With Expanded Granulocyte-Macrophage Progenitor Populations At Diagnosis

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 2704-2704
Author(s):  
Peter Buur van Kooten Niekerk ◽  
Anne Stidsholt Roug ◽  
Charlotte Christie Petersen ◽  
Line Nederby ◽  
Charlotte Guldborg Nyvold ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Board Of Directors ◽  
Research Funding ◽  
Mononuclear Cells ◽  
Chronic Phase ◽  
Colony Growth ◽  
Advisory Committees ◽  
Fraction Size ◽  
Tki Treatment ◽  
Progenitor Compartment

Abstract Although chronic myeloid leukemia (CML) originates from a primitive hematopoietic stem cell (HSC), it is the more differentiated progenitor cells that drive the expansion of the malignant clone. In addition, previous studies of chronic phase CML have shown that, despite the marked leukocytosis observed here, megakaryocyte-erythroid progenitors dominate the progenitor fraction. We sought to elucidate this by employing the new marker for leukemic stem cells, the human myeloid inhibitory C-type lectin-like receptor (hMICL), in the study of progenitor cell expansion in CML. Bone marrow or peripheral blood stem cells were acquired from 11 normal donors and 31 CML patients at diagnosis in chronic phase and/or after 3-119 months of tyrosine kinase inhibitor (TKI) treatment. Cells were stained with fluorescent monoclonal antibodies and FACS sorted into HSCs (CD34+CD38-), hMICL+ progenitors (MpP; CD34+CD38+hMICL+), and hMICL- progenitors (MnP; CD34+CD38+hMICL-). Sorted cell subsets were subjected to growth in a 14-day methylcellulose assay and analyzed quantitatively for expression of the BCR-ABL fusion transcript. In normal donors, hMICL expression reproducibly identified a well-defined subpopulation of the CD34+CD38+ cells (fig 1A). The MpPs were highly enriched for cells of granulocyte-macrophage progenitors (GMP) phenotype compared to the MnPs (p=0.012) (fig 1B). Sorted MpPs produced almost exclusively granulocyte and/or macrophage (CFU-GM) colonies (median: 92% of colonies), while colonies from MnPs were dominated by BFU-Es (91%) and, as opposed to the MpPs, also contained CFU-GEMM colonies (0.64%) (fig 1C). Thus, hMICL seems to be a useful marker for the GMP population.Figure 1Immunological and functional properties of MpPs in normal donors. (A) Identification of MpPs, MnPs, and HSCs within the CD34+ compartment. (B) Cells with GMP phenotype (CD34+CD38+CD123lowCD45RA+) in MpP and MnP subsets. (C) Colony growth of bone marrow mononuclear cells (MNC) and sorted MpPs and MnPs in a 14-day methylcellulose assay. Error bars denote SDs.Figure 1. Immunological and functional properties of MpPs in normal donors. (A) Identification of MpPs, MnPs, and HSCs within the CD34+ compartment. (B) Cells with GMP phenotype (CD34+CD38+CD123lowCD45RA+) in MpP and MnP subsets. (C) Colony growth of bone marrow mononuclear cells (MNC) and sorted MpPs and MnPs in a 14-day methylcellulose assay. Error bars denote SDs. In CML at diagnosis we found decreased numbers of MpPs (mean 23% of CD34+CD38+ cells (range: 6.3-48%)), compared to the normal donors (33% (18-48%), p=0.030) (fig 2A). Extraordinarily, the MpP fraction varied considerably in size among CML patients, and 12/23 patients had MpP fractions within the 90% reference range (RR) of normal donors (MpPHIGH patients) and thus distinctly higher than the remaining patients (MpPLOW patients) (fig 2B-C). High MpP fractions significantly correlated with high WBC (Spearman's r = 0.47, p=0.049) (fig 2D), high neutrophil counts (r = 0.55, p=0.043), large spleen size (r = 0.66, p=0.0069), and low hemoglobin at the time of diagnosis (r = -0.58, p=0.014). Within the progenitor compartment, high ratio of BCR-ABL in the MpP to BCR-ABL in the MnP significantly correlated with large MpP fractions (r = 0.54, p=0.021).Figure 2Human MICL expression in chronic phase CML patients. (A) Fraction of MpPs in normal donors and CML patients at diagnosis. (B) Typical immunological profiles of MpPLOW patients and (C) MpPHIGH patients. (D) Correlation between MpP fraction size and total white blood cell count at the time of diagnosis. (E) Development of MpP fraction size in individual patients after 3-6 months (solid lines) and after 12-119 months (dotted lines) of TKI treatment in MpPLOW patients and (F) MpPHIGH patients.Figure 2. Human MICL expression in chronic phase CML patients. (A) Fraction of MpPs in normal donors and CML patients at diagnosis. (B) Typical immunological profiles of MpPLOW patients and (C) MpPHIGH patients. (D) Correlation between MpP fraction size and total white blood cell count at the time of diagnosis. (E) Development of MpP fraction size in individual patients after 3-6 months (solid lines) and after 12-119 months (dotted lines) of TKI treatment in MpPLOW patients and (F) MpPHIGH patients. During the first 6 months of TKI treatment differing developments in MpP fraction size were observed for MpPLOW and MpPHIGH patients. While MpPLOW patients showed increasing MpP fractions during the first 6 months of treatment (fig 2E), 4/4 and 2/4 MpPHIGH patients displayed a decrease in MpPs at 3 and 6 months, respectively (fig 2F). Thus, in these patients, the majority of the Ph+ progenitor cells being cleared seemed to be GMPs. In conclusion, our data demonstrate that hMICL is an early marker of granulocyte-macrophage differentiation, and provides a readily accessible approach to assessing the GMP population during TKI therapy in CML. Using the present approach we have uncovered a higher degree of variability in the composition of the progenitor compartment at diagnosis than previously reported, and shown that a significant proportion of the patients have expanded GMP populations. Ongoing studies are aimed at determining whether these patients may represent patients with a more advanced form of disease at the time of diagnosis. Disclosures: Stentoft: Novartis: Consultancy, Financial support for relevant congress participation Other, Membership on an entity’s Board of Directors or advisory committees, Research Funding; Bristol-Myers-Squibb: Membership on an entity’s Board of Directors or advisory committees, Research Funding; Danish Regions: Membership on an entity’s Board of Directors or advisory committees. Hokland:Novartis: Research Funding.

Cooperative Targeting of Bcl-2 Family Proteins By ABT-199 (GDC-0199) and Tyrosine Kinase Inhibitors to Eradicate Blast Crisis CML and CML Stem/Progenitor Cells

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 512-512 ◽  
Author(s):  
Bing Z Carter ◽  
Po Yee Mak ◽  
Hong Mu ◽  
Hongsheng Zhou ◽  
Duncan H Mak ◽  
...  
Keyword(s):  
Stem Cells ◽  
Tyrosine Kinase ◽  
Progenitor Cells ◽  
Tyrosine Kinase Inhibitors ◽  
Kinase Inhibitors ◽  
Blast Crisis ◽  
Single Agent ◽  
Specific Inhibitor ◽  
Chronic Phase

Abstract Bcr-Abl tyrosine kinase supports CML cell survival in part by regulating antiapoptotic Bcl-2 proteins such as Bcl-xL and Mcl-1. Tyrosine kinase inhibition, the front-line therapy for patients with chronic phase CML, is less effective in blast crisis (BC) patients and inactive against quiescent CML stem/progenitor cells. We reported that ABT-737, a dual Bcl-2/Bcl-xL inhibitor, induces apoptosis in BC CML cells including CD34+quiescent CML cells. ABT-199, a potent Bcl-2 specific inhibitor, has entered clinical trials for various hematological malignancies. We hypothesized that cooperative targeting of antiapoptotic Bcl-2 proteins using a combination of ABT-199 and tyrosine kinase inhibitors (TKIs) would exert enhanced activity against BC CML and CML stem/progenitor cells. Cells from patients (n=4) with TKI-resistant BC CML were treated with ABT-199, TKIs, and combinations. Although exerting low activity by itself, ABT-199 in combination with TKIs synergistically induced apoptosis (CI<0.1) in bulk and CD34+38- cells from these patients regardless of their previous clinical responses to TKIs. The combinations had minimal activity against normal CD34+cells (n=3). Mechanistic studies demonstrated that nilotinib inhibited the expression of Bcl-xL and Mcl-1 mRNA and protein, even in cells from TKI (including nilotinib) resistant patients. Individual inhibition of Bcl-xL or Mcl-1, and even more so inhibition of both, by siRNAs increased the sensitivity of cells to ABT-199, suggesting that cooperative inhibition of Bcl-2 by ABT-199 and Bcl-xL/Mcl-1 by TKIs contributes to the synergy. To evaluate the effect of these combinations on TKI-insensitive quiescent stem/progenitor CML cells, BC CML patient cells were stained with the cell division-tracking dye carboxyfluorescein succinimidyl ester (CFSE) and then co-cultured with human bone marrow (BM)-derived mesenchymal stromal cells (MSCs). Once proliferating and quiescent cells were distinguishable by flow cytometry, cells were treated with ABT-199, TKIs, and their combinations for 48 hours with or without MSC co-culture. Apoptosis was measured in proliferating and quiescent progenitor cells, defined as the percentage of annexin V positivity in CD34+CFSEdim and CD34+CFSEbright cells, respectively. ABT-199 as a single agent decreased viability of CML cells cultured alone or co-cultured with MSCs in both proliferating (IC50=191±103nM and 194±64nM, respectively) and quiescent (IC50=221±75nM and 205±123nM, respectively) CD34+ CML cells. Combinations of ABT-199 with TKIs, including imatinib, nilotinib, dasatinib, or ponatinib, synergistically induced death (CI<0.2) and decreased the number of viable cells in proliferating as well as quiescent CD34+progenitor cell populations (n=6). All 6 patients were resistant to TKIs, and 4 had mutations in the BCR-ABL gene, including three with the T315I mutation. To further test the ability of ABT-199 and TKI combinations to eradicate CML stem cells, we used an inducible transgenic CML mouse model in which the BCR-ABL gene is expressed under control of a tet-regulated enhancer of the murine stem cell leukemia (Scl) gene, allowing targeted BCR-ABL expression in stem/progenitor cells. Once BM cells from transgenic Scl-tTa-BCR-ABL/GFP mice were engrafted in wild type recipient mice, the mice were treated with ABT-199, nilotinib, or both. At the end of a 3-week treatment period, each single agent alone, and even more so with the combinations, significantly decreased blood total GFP+ WBC (12.9±1.4, 5.2±0.3, 6.1±0.4, and 1.6±0.3 x106/ml in controls, ABT-199, nilotinib, and combination, respectively) and neutrophils (1.43±0.03, 0.49±0.06, 0.32±0.03, and 0.25±0.05 x106/ml in the respective groups). ABT-199 (P=0.02), and more so with the combination (P<0.01) but not nilotinib alone (P=0.29), significantly decreased BM GFP+ LSK cells (12.0±1.2, 6.8±0.6, 9.5±1.6, and 2.2±0.2 x103 cells in the respective groups). The in vivo experiments are ongoing. Conclusions: ABT-199 and TKIs cooperatively target antiapoptotic Bcl-2 family proteins. This combination is highly effective in killing bulk and CD34+38- CML cells and quiescent CD34+ CML stem/progenitor cells from BC CML patients in vitro and in suppressing leukemia and leukemia stem cells in vivo. This strategy has the potential to eradicate BC CML cells and CML stem/progenitor cells, neither of which are effectively targeted by TKIs alone. Disclosures Carter: AbbVie, Inc.: Research Funding. Leverson:AbbVie, Inc.: Employment. Konopleva:AbbVie, Inc: clinic trial Other.

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