Advanced Chronic Myelogenous Leukemia Research Articles

Spred1 Insufficiency in the Hematopoietic and/or Vascular Compartments of the Bone Marrow (BM) Niche Promotes Aggressive Leukemogenesis in Chronic Myelogenous Leukemia (CML)

Spred1, a member of the Sprouty family of proteins and a negative regulator of RAS-MAPK signaling, is highly expressed in normal hematopoietic stem cells (HSCs) where it negatively regulates self-renewal activity. Lack of Spred1 function has been associated with aberrant hematopoiesis (Tadokoro, 2018). Spred1 knocked-out (KO) mice fed with high-fat diet develop a myeloproliferative phenotype (Tadokoro, 2018), and lower SPRED1 expression in acute myeloid leukemia associates with a poor outcome (Li, 2015; Olsson, 2014; Pasmant, 2015), suggesting a potential role of this gene as a tumor suppressor in myeloid malignancies. In CML, however, the role of Spred1 has not been fully dissected. Thus, we generated Spred1 KO CML (i.e., Spred1-/-SCLtTA/BCR-ABL) mice by crossing Spred1 KO (a gift from Dr. Yoshimura, Japan) with inducible SCLtTA/BCR-ABL CML mice. Spred1 KO mice showed increased cell cycling of BM long-term HSCs (LTHSCs; Lin-Sca-1+c-kit+Flt3-CD150+CD48-; G0: 62% vs 76%), and increased white blood cell (WBC) counts [14 vs 5.9 k/ul at 12 weeks (w) old, n=15 per group, p<0.0001], as compared to wt mice. Upon B/A induction by tetracycline withdrawal, Spred1-/-SCLtTA/BCR-ABL mice had higher WBC (102.5 vs 12 k/ul at 4 w, n=15 per group, p<0.0001), more pronounced splenomegaly (spleen weight: 0.28g vs 0.19g, n=4 per group, p=0.06) and a significantly shorter survival (median: 39 vs 83 days, n=23 per group, p<0.0001) than Spred1 wt CML mice. In Spred1-/-SCLtTA/BCR-ABL mice, we observed a more rapid expansion of circulating mature myeloid cells (CD11b+Gr-1+ cells: 63% vs 25%, n=8 per group, p<0.01) and a deeper decrease of BM LTHSCs (1,385 vs 2,164 per femur, n=5 per group, p<0.01) and increase of spleen LTHSCs (27330 vs 18546, n=5 per group, p<0.01) at 4 w after B/A induction compared with Spred1 wt CML mice. Further, we found a higher fraction of Spred-/-SCLtTA/BCR-ABL mice (33% vs 10%) developed lymph node enlargement, with infiltration with pro-B lymphoblastic cells (B220+CD43+CD19+IgM−) compared with Spred1 wt CML mice. Altogether these features suggested that Spred1 insufficiency accelerates CML development and evolution to more aggressive phases of the disease. Since upregulation of Spred1 reportedly disrupts vascular integrity (Fish, 2008; Wang 2008), a finding that we have also confirmed in the BM niche, in order to evaluate separately the leukemogenic effect of Spred1 expression on different compartments of the BM niche, we generated the following conditional Spred1 KO strains: Spred1flox(f)/fMxl-cre+ (Spred1 KO in HSCs, hereafter called Spred1HSCΔ/Δ), Spred1f/fTie2-cre+ [Spred1 KO in endothelial cells (ECs), hereafter called Spred1ECΔ/Δ], Spred1HSCΔ/ΔSCLtTA/BCR-ABL and Spred1ECΔ/ΔSCLtTA/BCR-ABL by crossing SCLtTA/BCR-ABL with the above Spred1 KO mice. LTHSCs from Spred1HSCΔ/ΔSCLtTA/BCR-ABL mice showed an increase in cell cycling, RAS/MAPK/ERK activity and Bcl-2 levels, and higher engraftment in recipient mice (blood: 9.7% vs 26.5% at 6w, 14.8% vs 42% at 8w, 14.7% vs 48% at 12w, n=10 per group, p<0.01), compared to Spred1 wt CML LTHSCs. Spred1HSCΔ/ΔSCLtTA/BCR-ABL mice (n=15) showed enhanced leukemia progression (WBC: 19 vs 12 k/ul, p=0.004; CD11b+Gr-1+ in blood: 36% vs 25%, p=0.04 at 4 w after B/A induction) and a significantly shorter survival (median: 49.5 vs 83 days, p=0.01) compared to Spred1 wt CML mice (n=20). However, the disease in these mice appeared to be overall less aggressive than global Spred1 KO CML (i.e., Spred1-/-SCLtTA/BCR-ABL) mice (WBC: 19 vs 102 k/ul; CD11b+Gr-1+ in blood: 36 vs 63%; Survival: 49.5 vs 39 days), suggesting that Spred1 depletion in other non-hematopoietic cell compartments may also be important for leukemogenesis. In fact, Spred1ECΔ/ΔSCLtTA/BCR-ABL mice (n=8) showed enhanced leukemia progression (WBC: 26 vs 9.8 k/ul at 4 w after B/A induction, p=0.02), a trend for a reduced survival (median: 56 vs 83 days, p=0.09), and increased arteriolar vascularization, compared to Spred1 wt CML mice (n=20). Mechanistic studies on how endothelial Spred1 insufficiency co-participates in leukemogenesis are ongoing. Altogether our results support a role of Spred1 insufficiency in distinct BM niche compartments to produce a more aggressive CML phenotype, likely through different, but complementary mechanisms. Spred1 may therefore emerge as a novel target for advanced CML. Disclosures No relevant conflicts of interest to declare.

Outcomes Following Bone Marrow Transplantation in Children With Accelerated Phase or Blast Crisis Chronic Myelogenous Leukemia in the Era of Tyrosine Kinase Inhibitors.

The management of chronic myelogenous leukemia (CML) in children changed dramatically with the introduction of tyrosine kinase inhibitors (TKIs). Unfortunately, outcomes for patients presenting in an advanced stage-accelerated phase or blast crisis CML-continues to be poor, requiring chemotherapy and allogeneic hematopoietic stem cell transplant (HSCT) to attempt cure. Integration of TKIs in the therapy of advanced CML is still an area of active investigation. There are little published data on TKI use in children with advanced stage CML. We performed a retrospective review of all children treated at our institution between January 1, 2010 and June 30, 2013, and identified 5 children, age 12 to 18 years, with advanced stage CML. All patients were treated with a TKI before HSCT and TKIs were restarted post-HSCT in 4/5 with a goal of continuing until 2 years posttransplant. At time of HSCT all were in a morphologic and cytogenetic remission; 1 patient had also achieved molecular remission. All patients are alive and in molecular remission at an average of 38 months (range, 14 to 51 mo) following transplant. Our experience indicates that TKIs are safe and well tolerated in children both pretransplant and posttransplant and may improve outcomes in this aggressive disease.

Identification of ILK as a novel therapeutic target for acute and chronic myeloid leukemia

Current treatment options as well as clinical efficacy are limited for chronic myelogenous leukemia (CML), Ph+ acute lymphoblastic leukemia (ALL), and acute myeloid leukemia (AML). In response to the pressing need for more efficacious treatment approaches and strategies to override drug resistance in advanced stage CML, Ph+ ALL, and AML, we investigated the effects of inhibition of ILK as a potentially novel and effective approach to treatment of these challenging malignancies. Using the small molecule ILK inhibitor, Cpd22, and ILK knockdown, we investigated the importance of ILK in the growth and viability of leukemia. Our results suggest that the ILK inhibition may be an effective treatment for CML, Ph+ ALL, and AML as a single therapy, with ILK expression levels positively correlating with the efficacy of ILK inhibition. The identification of ILK as a novel target for leukemia therapy warrants further investigation as a therapeutic approach that could be of potential clinical benefit in both acute and chronic myeloid leukemias.

Photochemical internalisation for the local delivery of chemotherapy

Current treatment options as well as clinical efficacy are limited for chronic myelogenous leukemia (CML), Ph+ acute lymphoblastic leukemia (ALL), and acute myeloid leukemia (AML). In response to the pressing need for more efficacious treatment approaches and strategies to override drug resistance in advanced stage CML, Ph+ ALL, and AML, we investigated the effects of inhibition of ILK as a potentially novel and effective approach to treatment of these challenging malignancies. Using the small molecule ILK inhibitor, Cpd22, and ILK knockdown, we investigated the importance of ILK in the growth and viability of leukemia. Our results suggest that the ILK inhibition may be an effective treatment for CML, Ph+ ALL, and AML as a single therapy, with ILK expression levels positively correlating with the efficacy of ILK inhibition. The identification of ILK as a novel target for leukemia therapy warrants further investigation as a therapeutic approach that could be of potential clinical benefit in both acute and chronic myeloid leukemias.

MiR-300 Acts As a Tumor Supressor in Ph+ Progenitors By Modulating the JAK2-SET/PP2A/β-Catenin Interplay

The persistence of tyrosine kinase inhibitor (TKI)-resistant malignant Philadelphia-positive (Ph+) hematopoietic stem cells (HSC) in chronic myelogenous leukemia (CML) TKI-treated patients in complete molecular remission, and the dismal prognosis of blast crisis CML indicate that the molecular mechanisms underlying its emergence, maintenance and progression are not totally dependent on the unrestrained kinase activity of BCR-ABL1 and might rely on other cell autonomous and/or microenvironmental signal capable of sustaining survival and self-renewal of the chronic phase and blast crisis Ph+ HSC compartment(s).We recently demonstrated that the Jak2/SET-PP2A/β-catenin pathway is essential for survival and self-renewal of quiescent TKI-resistant CD34+CD38- Ph+ HSC and that activation of such oncogenic signals requires the expression but not the activity of BCR-ABL1. Because microRNAs (miRNAs) are likely to control in a canonical and/or decoy manner the expression of different components of the Jak2 signalosome, this makes them an attractive target for further understanding the mechanisms of leukemogenesis and, perhaps, for developing new alternative therapies that selectively eradicate quiescent leukemic HSCs.In silico analysis revealed that a specific miR subset shares multiple targets of the BCR-ABL1/Jak2/SET-PP2A signalosome. Nanostring Array analysis performed on primary bone marrow cells from normal individuals and chronic phase or blast crisis CML patients revealed that expression of some of these miRNA is altered in CML. For example, expression of miR-300 and miR-101, which are predicted to simultaneously modulate directly Jak2, hnRNP-A1 and β-catenin and, indirectly, other molecules of the BCR-ABL1/Jak2/SET-PP2A/β-catenin pathway, is significantly inhibited in chronic phase CML and further decreases in advanced CML samples. Additionally, miR-300 expression is several folds lower in dividing (div. 1) compared to quiescent (CFSEMAX) CD34+ CML cells.Lentiviral-transduction of miR-300 in human BCR-ABL+ cell lines resulted in marked downmodulation of JAK2, β-Catenin hnRNPA1 and SET and, as expected, in increased PP2A activity. Moreover, ectopic miR-300 expression decreased reduced clonogenic potential and proliferation, and increased susceptibility to TKI (e.g. Imatinib) induced apoptosis. Interestingly, it appears that forced BCR-ABL1 expression in TF-1 leukemic cells decreases miR-300, consistent with the reported activation in these cells of the Jak2-SET-PP2A-β-catenin pathway.Altogether our results suggest that miR-300 expression and, potentially, that of other deregulated non-coding RNAs might be dispensable or deleterious for the phenotype of Ph+ progenitors and/or indispensable for that of Ph+ HSCs. Thus, experiments in BCR-ABL1 cell lines as well as primary stem and progenitor cell fractions are currently ongoing to assess the role of this and other miRNAs in survival, self-renewal/proliferation of CML stem and progenitor cells. DisclosuresNo relevant conflicts of interest to declare.

Chronic myelogenous leukemia, version 1.2015.

Chronic myelogenous leukemia (CML) is usually diagnosed in the chronic phase. Untreated chronic phase CML will eventually progress to advanced phase (accelerated or blast phase) CML. Tyrosine kinase inhibitors (TKIs) have been shown to induce favorable response rates in patients with accelerated and blast phase CML. The addition of TKIs to chemotherapy has also been associated with improved outcomes in patients with blast phase CML. Allogeneic hematopoietic stem cell transplant remains a potentially curative option for patients with advanced phase CML, although treatment with a course of TKIs will be beneficial as a bridge to transplant. This manuscript discusses the recommendations outlined in the NCCN Guidelines for the diagnosis and management of patients with advanced phase CML.

Origins of Cancer Symposium Report

Origins of Cancer Symposium Report

Enhanced SH3/Linker Interaction Overcomes Abl Kinase Activation by Gatekeeper and Myristic Acid Binding Pocket Mutations and Increases Sensitivity to Small Molecule Inhibitors*

Multidomain kinases such as c-Src and c-Abl are regulated by complex allosteric interactions involving their noncatalytic SH3 and SH2 domains. Here we show that enhancing natural allosteric control of kinase activity by SH3/linker engagement has long-range suppressive effects on the kinase activity of the c-Abl core. Surprisingly, enhanced SH3/linker interaction also dramatically sensitized the Bcr-Abl tyrosine kinase associated with chronic myelogenous leukemia to small molecule inhibitors that target either the active site or the myristic acid binding pocket in the kinase domain C-lobe. Dynamics analyses using hydrogen exchange mass spectrometry revealed a remarkable allosteric network linking the SH3 domain, the myristic acid binding pocket, and the active site of the c-Abl core, providing a structural basis for the biological observations. These results suggest a rational strategy for enhanced drug targeting of Bcr-Abl and other multidomain kinase systems that use multiple small molecules to exploit natural mechanisms of kinase control.

Assessment of the Effect of Nilotinib (Tasigna) Maintenance Therapy After Allogeneic Stem Cell Transplantation in Patients with Advanced CML and Ph+ ALL On Immune Reconstitution and Lymphocyte Function

Abstract Abstract 4478 Allogeneic stem cell transplantation (AlloSCT) is the treatment of choice in advanced chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). However, post transplant relapse rate is high and outcome is often poor in this setting. Reduction of tumor mass pre-transplant and maintenance therapy post alloSCT, may improve response rate and reduce relapse rate. We speculated that the second-generation tyrosine-kinase inhibitor (TKI) Nilotinib (Tasigna, Novartis Pharmaceuticals) would be effective in achieving these goals. In the current study Nilotinib, was administered as maintenance therapy post alloSCT in patients (pts) with advanced CML and Ph+ ALL (study CAMN107AIL03T). However, TKIs have been demonstrated in previously published literature to affect T cells proliferation and signal transduction and to potentiate LGL and NK cell activity. Furthermore, in recent studies TKIs have also been demonstrated to ameliorate chronic GVHD. We therefore assessed immunological reconstitution and function including flow analysis of lymphocyte subsets, T-mitogenic response to αCD3 and PHA, thymic activity as determined by the quantification of the T cell receptor excision circles (TREC), TCR repertoire and NK cells cytotoxic activity against K562 cell line. In all, the study included 24 pts. Patients engrafted in a median day +15 (range, 10–38) with 100% donor chimerism. Acute GVHD grade 3/4 was reported in 3 pts (14%) and the rate of extensive chronic GVHD at last follow up was 50%. At 6 months after alloSCT, 11 of 15 pts with advanced CML had attained CCyR, 11 of 15 pts with advanced CML had attained a MMR or better, and 5 of 7 pts with Ph+ ALL attained a CR. The median OS was 16 months, with predicted 1- and 2- year rates of 55% (95% CI, 32% – 72%) and 50% (95% CI, 28% – 68%), respectively. The median PFS was 11 months, with predicted 1- and 2- year rates of 50% (95% CI, 28% – 68%) and 38% (95% CI, 17% – 59%), respectively. Immunological testing was performed pre- and post Nilotinib maintenance therapy in 12 pts (advanced CML-8, Ph+ ALL-4) who received Nilotinib for at least 90 days following alloSCT. The median age was 34.5 years (range, 21–57) and 75% were males. Six pts underwent alloSCT from an HLA-matched sibling donor, 4 from matched unrelated and 2 from an alternative donor (cord blood-1, haploidentical-1). All had myeloablative conditioning. GVHD prophylaxis included CSA and MMF. The relative percentage of T- lymphocyte subsets (assessed by FACS) and total lymphocytes number were stable during Nilotinib maintenance administration after alloSCT, while a 7.8±2.5 fold increase in B cells was noted. T cell mitogenic response with αCD3 and PHA (stimulation index ratio) was sustained (2.5±1.0, vs. 2.8±1.05 and 3.3±1.3 vs. 5.3±2.9 stimulation, pre- and post Nilotinib therapy, respectively). Mean thymic output determined by TREC quantification pre-, during and post Nilotinib administration was 81.8±108, 81.2±90.3 and 142.8±197.4 copies per 0.5ug DNA indicating continuous thymopoiesis. Similarly, no significant change of the TCR repertoire was observed during Nilotinib treatment. Specifically, normal expression of the TCR repertoire was detected in 15.1±5.5 and 15.3±5.6 of the examined TCRs, clonal expression was detected in 2.5±2.2 and 2.9±3 of the examined receptors, while reduced expression was detected only in 6.4±4.3 and 5.8±4.5 of the examined receptors pre-and post Nilotinib treatment, respectively. NK cytotoxic activity against K562 expressed as fold of change from baseline, also remained stable during Nilotinib treatment (2.8±1.1 and 2.3±0.8, respectively). In summary, Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL did not interfere or jeopardized immune reconstitution and function including the number of immune cell subsets, T cell mitogenic response, TCR repertoire, thymic output and NK cytolytic activity post alloSCT. Based on this immunological data we would further recommend Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL. Disclosures: Nagler: Novartis: Honoraria, Research Funding.

Assessment of the Effect of Nilotinib (Tasigna) Maintenance Therapy After Allogeneic Stem Cell Transplantation in Patients with Advanced CML and Ph+ ALL On Immune Reconstitution and Lymphocyte Function

AbstractAbstract 4478Allogeneic stem cell transplantation (AlloSCT) is the treatment of choice in advanced chronic myelogenous leukemia (CML) and Ph+ acute lymphoblastic leukemia (ALL). However, post transplant relapse rate is high and outcome is often poor in this setting. Reduction of tumor mass pre-transplant and maintenance therapy post alloSCT, may improve response rate and reduce relapse rate. We speculated that the second-generation tyrosine-kinase inhibitor (TKI) Nilotinib (Tasigna, Novartis Pharmaceuticals) would be effective in achieving these goals. In the current study Nilotinib, was administered as maintenance therapy post alloSCT in patients (pts) with advanced CML and Ph+ ALL (study CAMN107AIL03T). However, TKIs have been demonstrated in previously published literature to affect T cells proliferation and signal transduction and to potentiate LGL and NK cell activity. Furthermore, in recent studies TKIs have also been demonstrated to ameliorate chronic GVHD. We therefore assessed immunological reconstitution and function including flow analysis of lymphocyte subsets, T-mitogenic response to αCD3 and PHA, thymic activity as determined by the quantification of the T cell receptor excision circles (TREC), TCR repertoire and NK cells cytotoxic activity against K562 cell line. In all, the study included 24 pts. Patients engrafted in a median day +15 (range, 10–38) with 100% donor chimerism. Acute GVHD grade 3/4 was reported in 3 pts (14%) and the rate of extensive chronic GVHD at last follow up was 50%. At 6 months after alloSCT, 11 of 15 pts with advanced CML had attained CCyR, 11 of 15 pts with advanced CML had attained a MMR or better, and 5 of 7 pts with Ph+ ALL attained a CR. The median OS was 16 months, with predicted 1- and 2- year rates of 55% (95% CI, 32% – 72%) and 50% (95% CI, 28% – 68%), respectively. The median PFS was 11 months, with predicted 1- and 2- year rates of 50% (95% CI, 28% – 68%) and 38% (95% CI, 17% – 59%), respectively. Immunological testing was performed pre- and post Nilotinib maintenance therapy in 12 pts (advanced CML-8, Ph+ ALL-4) who received Nilotinib for at least 90 days following alloSCT. The median age was 34.5 years (range, 21–57) and 75% were males. Six pts underwent alloSCT from an HLA-matched sibling donor, 4 from matched unrelated and 2 from an alternative donor (cord blood-1, haploidentical-1). All had myeloablative conditioning. GVHD prophylaxis included CSA and MMF. The relative percentage of T- lymphocyte subsets (assessed by FACS) and total lymphocytes number were stable during Nilotinib maintenance administration after alloSCT, while a 7.8±2.5 fold increase in B cells was noted. T cell mitogenic response with αCD3 and PHA (stimulation index ratio) was sustained (2.5±1.0, vs. 2.8±1.05 and 3.3±1.3 vs. 5.3±2.9 stimulation, pre- and post Nilotinib therapy, respectively). Mean thymic output determined by TREC quantification pre-, during and post Nilotinib administration was 81.8±108, 81.2±90.3 and 142.8±197.4 copies per 0.5ug DNA indicating continuous thymopoiesis. Similarly, no significant change of the TCR repertoire was observed during Nilotinib treatment. Specifically, normal expression of the TCR repertoire was detected in 15.1±5.5 and 15.3±5.6 of the examined TCRs, clonal expression was detected in 2.5±2.2 and 2.9±3 of the examined receptors, while reduced expression was detected only in 6.4±4.3 and 5.8±4.5 of the examined receptors pre-and post Nilotinib treatment, respectively. NK cytotoxic activity against K562 expressed as fold of change from baseline, also remained stable during Nilotinib treatment (2.8±1.1 and 2.3±0.8, respectively). In summary, Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL did not interfere or jeopardized immune reconstitution and function including the number of immune cell subsets, T cell mitogenic response, TCR repertoire, thymic output and NK cytolytic activity post alloSCT. Based on this immunological data we would further recommend Nilotinib maintenance therapy post alloSCT in pts with advanced CML and Ph+ALL. Disclosures:Nagler:Novartis: Honoraria, Research Funding.

Chronic Myelogenous Leukemia Patients with Highly Nilotinib-Resistant BCR-ABL Mutations Demonstrate Similar Efficacy to Dasatinib, but Have a Higher Likelihood of Developing New Mutations in the Event of Clinical Resistance

AbstractAbstract 3755 Objective:Assess the outcome of imatinib- and/or nilotinib-failure chronic myelogenous leukemia (CML) patients with pre-existing, highly nilotinib-resistant mutations (Y253H, E255K/V and F359V/C), during dasatinib therapy. Methods:Sixty-one CML patients who failed imatinib (n=44) or imatinib and nilotinib (n=17), including 20 in chronic phase (CP), 16 in accelerated phase (AP) and 25 in blast phase (BP), were switched to dasatinib, except for patients with highly dasatinib-resistant mutations (T315I/A, F317L/V/I/C and V299L). Patients were grouped into 3 cohorts: no mutation (n=22), no-specific mutation (any mutation except highly nilotinib-resistant mutations; n=15), or specific mutation (Y253H, E255K/V or F359V/C; n=24), according to baseline BCR-ABL mutation status. Cumulative incidence frequencies of hematological response (HR), complete hematological response (CHR), major cytogenetic response (MCR), complete cytogenetic response (CCR) and major molecular response (MMR) were compared. Probabilities of clinical resistance to dasatinib (according to European LeukemiaNet recommendations), progression-free survival (PFS) and overall survival (OS), and dynamics of BCR-ABL mutations during dasatinib therapy were also assessed. Results:Prior nilotinib was associated with a higher proportion of specific mutation versus no mutation (50.0% vs 13.6%, P=0.001) and non-specific mutation (50.0% vs 13.3%, P=0.02). Patients harboring specific mutation also had a higher frequency of advanced phase CML before dasatinib treatment than patients with no mutation (83.3% vs 50.0%, P=0.008), and a similar frequency to those with non-specific mutation (83.3% vs 66.7%, P=0.266). Response, PFS and OS rates, and follow-up duration were similar among the 3 cohorts by baseline mutation status, as shown in Table. Probability of clinical resistance to dasatinib in patients with specific mutation was not significantly different to those with no mutation (54.2% vs 77.3%, P=0.100) or non-specific mutation (54.2% vs 33.3%, P=0.204) despite that there was a significant difference between the cohort with no mutation and non-specific mutation (77.3% vs 33.3%, P=0.008). Among 32 patients who developed clinical resistance to dasatinib and were assessed for BCR-ABL mutation status, newly detectable mutations were identified in 14 patients and most frequently occurred in those already harboring specific mutation versus those with no mutation (76.9% vs 26.7%, P=0.008) and non-specific mutation (76.9% vs 0%, P=0.015) at baseline. T315I (9/14, 64.3%) was the most common newly acquired BCR-ABL mutation. Harboring specific mutation compared with other mutation states at baseline (76.9% vs 16.7%, P=0.001), and developing hematological resistance rather than cytogenetic resistance during dasatinib therapy (65.0% vs 8.1%, P=0.002), were identified as risk factors associated with the development of new mutations. Conclusions:Imatinib- and/or nilotinib-failure patients with highly nilotinib-resistant BCR-ABL mutations demonstrate similar efficacy to dasatinib as those with no or any other mutation. However, patients with highly nilotinib-resistant mutations had a higher likelihood of developing new mutations at the time of clinical resistance. More extensive studies are needed to assess the significance of various BCR-ABL mutations prior to and during tyrosine kinase inhibitor therapy for CML.Table:Response, survival and clinical resistance to dasatinib by baseline BCR-ABL mutation statusMutation statusP valueNo mutation n=22Non-specific mutation n=15Specific mutation n=24HR, n (%)16 (72.7)14 (93.3)21 (87.5)0.202CHR, n (%)16 (72.7)12 (80.0)19 (79.2)0.832MCR, n (%)a9 (69.2)8 (80.0)12 (70.6)0.826CCR, n (%)a8 (61.5)8 (80.0)10 (58.8)0.511MMR, n (%)a3 (23.1)5 (50.0)4 (23.5)0.2813-year PFS, %84.673.765.20.4693-year OS, %75.680.854.00.798Clinical resistance to dasatinib, n (%)17 (77.3)5 (33.3)13 (54.2)0.027Follow-up (months), median (range)31 (2..C48)24 (2..C48)7 (1..C48)0.277a40 patients were evaluated including 13 with no mutation,10 with non-specific mutation and 17 with specific mutation Disclosures:No relevant conflicts of interest to declare.

Abstract 1127: Bcr-Abl inhibition in leukemia cells creates metabolic addictions

Abstract Bcr-Abl kinase inhibitors are the standard therapy for chronic myelogenous leukemia (CML). While effective in controlling disease in chronic phase, these inhibitors often fail to completely eliminate Bcr-Abl+ CML cells and also fail to achieve durable remissions for advanced CML and Bcr-Abl+ acute lymphoblastic leukemias (ALL). Our lab employed a large-scale synthetic lethal shRNA screen to identify genes involved in CML survival upon treatment with the Bcr-Abl kinase inhibitor imatinib (IM) [Cancer Cell. 2010;18(1):74-87]. This screen identified several genes involved in energy utilization including a component of pyruvate dehydrogenase, dihydrolipoyllysine-residue acetyltransferase. CML proliferation depends on Bcr-Abl-driven glycolysis for energy production. Upon IM treatment, we hypothesized that these cells are forced to rely on other sources of energy including the TCA cycle and the electron transport chain, and that targeting alternative energy production pathways will enhance IM-mediated elimination of CML cells. Thus, we predicted that inhibition of mitochondrial respiration by knockdown or pharmacologic inhibition would cooperate with tyrosine kinase inhibitors (TKI) to eliminate Bcr-Abl+ leukemia. Indeed, our experiments have shown that knocking down pyruvate dehydrogenase in human blast crisis Bcr-Abl+ CML cells (K562) greatly sensitized cells to IM in vitro. Conversely, supplementing the cell culture media with increasing concentrations of methyl-pyruvate protected K562 cells from IM treatment. Moreover, we found that the mitochondrial ATP-synthase inhibitor Oligomycin A (OA) also synergized with IM to kill CML cells in vitro. Interestingly, the doses of OA are far below the IC50 and do not affect the oxygen consumption rates, indicating that mitochondrial respiration is not inhibited. These OA doses alter mitochondrial transmembrane potential and increasing superoxide levels. In addition, OA enhanced elimination of Bcr-Abl+ cells by a Bcr-Abl TKI in vivo and prolonged disease-free survival in a mouse model of Bcr-Abl+ B-ALL. Notably, drug doses of OA used had no apparent adverse effects on these mice. Targeting mitochondrial metabolism as an adjuvant drug therapy may prevent the survival of residual Bcr-Abl+ CML cells upon tyrosine kinase inhibitor treatment. This project is supported by pre-doctoral fellowship number F31CA157166 from the National Cancer Institute, and Leukemia and Lymphoma Society Grant Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1127. doi:1538-7445.AM2012-1127

Efficacy and safety of nilotinib in Japanese patients with imatinib-resistant or -intolerant Ph+ CML or relapsed/refractory Ph+ ALL: a 36-month analysis of a phase I and II study

Although the tyrosine kinase inhibitor (TKI) imatinib is often used as first-line therapy for newly diagnosed chronic myelogenous leukemia (CML), some patients fail to respond, or become intolerant to imatinib. Nilotinib is a potent and selective second-generation TKI, with confirmed efficacy and tolerability in patients with imatinib-resistant or -intolerant CML. A phase I/II study was conducted in Japanese patients with imatinib-resistant or -intolerant CML or relapsed/refractory Ph+ acute lymphoblastic leukemia. Thirty-four patients were treated with nilotinib for up to 36 months. Major cytogenetic response was achieved in 15/16 patients (93.8%) with chronic-phase CML within a median of approximately 3 months. Major molecular response was achieved in 13/16 patients (81.3%). These responses were sustained at the time of the most recent evaluation in 13 patients and 11 patients, respectively. Hematologic and cytogenetic responses were also observed in patients with advanced CML. The BCR-ABL mutation associated with the most resistance to available TKIs, T315I, was observed in three patients. Common adverse events included rash, nasopharyngitis, leukopenia, neutropenia, thrombocytopenia, nausea, headache and vomiting. Most adverse events resolved following nilotinib dose interruptions/reductions. These results support the favorable long-term efficacy and tolerability of nilotinib in Japanese patients with imatinib-resistant or -intolerant chronic-phase chronic myeloid leukemia.

Older Adults with Chronic Myelogenous Leukemia (CML), During the Tyrosine Kinase Inhibitor (TKI) Era, Can Be Successfully Treated with Reduced Intensity Conditioning (RIC) Hematopoietic Cell Transplant (HCT) Using Sibling or Unrelated Donors: A Center for International Blood and Marrow Transplant Research (CIBMTR) Analysis

Abstract 494The introduction of tyrosine kinase inhibitors (TKI) and advent of RIC and non-myeloablative (NMA) conditioning hematopoietic cell transplants (HCT) have changed and the therapeutic strategy for patients with CML. We analyzed the post HCT outcomes of CML patients aged 40 and older undergoing RIC/NMA HCT in 2001–2007. Detailed information regarding pre HCT TKI use or rationale for timing of transplant was not available; however, the analysis time period captures the entry of TKIs into clinical practice. Outcomes were compared between age cohorts of 40–49, 50–59, and ≥ 60 years. Overall survival (OS), Day +100 acute graft versus host disease (aGVHD) grades II-IV, chronic (cGVHD), transplant-related mortality (TRM), relapse, and disease-free survival (DFS) were analyzed with multivariate analysis testing the impact of age, gender, disease status at HCT (CP1vs. CP2/accelerated phase (AP) vs. blast phase (BP), sex match, HLA match, GVHD prophylaxis, and conditioning intensity (RIC versus NMA as described by Bacigalupo et all 2009) on outcomes. A total of 306 CML patients underwent HCT at 125 centers: 117 (38%) aged 40–49; 119 (39%) aged 50–59; and 70 (23%) aged ≥ 60. At HCT most patients in the 40–49 age cohort were in CP1 (72%), while only 44% of patients aged 50–59 and 31% aged ≤ 60 were in CP1. Interval from diagnosis to HCT for CP1 patients was similar across age groups with a large percentage of each age cohort undergoing HCT ≥ 2 years (32%, 40%, and 45%, respectively). Sibling donors were the stem cell source for 56% of those aged 40–49; older cohorts had a higher percentage of unrelated donors (58 and 60%, respectively). Primarily peripheral blood grafts (78%, 80% and 90%) and RIC (78%, 76% and 70%) were used across age groups, respectively. GVHD prophylaxis was similar. Three year OS and cGVHD, Day +100 grade II-IV acute GVHD, and 1 year TRM were similar in all age cohorts. Three year relapse incidence increased and DFS decreased with age. Importantly in analysis of CP1 patients only, relapse and DFS were similar in each age cohort.Table 1:Univariate AnalysisOutcomeAge 40–49 Probability (95% CI)Age 50–59 Probability (95% CI)Age ≥ 60 Probability (95% CI)P-valueEntire CohortOSA54% (44–64)52% (42–61)41% (30–54)0.26aGVHDB II-IV26% (18–34)32% (24–40)32% (21–43)0.53cGVHDA58% (47–68)51% (41–61)43% (33–55)0.19TRMC18% (11–26)20% (13–27)13% (6–22)0.43RelapseA36% (27–46)43% (34–52)66% (53–77)0.001DFSA35% (26–45)32% (24–41)16% (7–27)0.01CP1 OnlyRelapseA34% (23–46)42% (28–56)51% (29–72)0.40DFSA43% (31–55)36% (23–51)39% (19–61)0.81A=3 year; B=Day +100; C=1 yearMultivariate analysis confirmed the significant adverse impact of advanced CML (AP/CP2+ and BP) at HCT, NMA conditioning intensity, male gender, and older age on relapse and DFS. Overall survival was not impacted by age, but was significantly worse with advanced CML at HCT. (Table 2)Table 2:Multivariate AnalysisOutcomeRR95% CIP valueRelapse:Age:10.69–1.6420.000340–491.0641.441–3.60750–592.28≥60Disease Status:10.1319–0.9170.01CP11.3350.0036–1.403AP/CP2+2.823BPConditioning Intensity10.222–0.469<0.0001NMA0.323RICGender10.397–0.830.0032Male0.574FemaleOverall SurvivalAge:10.55–1.2260.4240–490.8210.683–1.61850–591.051≥60Disease Status:11.206–2.47<0.0001CP11.7263.199–10.0740.42AP/CP2+5.677BPGender:10.0189–0.4810.019Male0.671FemaleThese data indicate that HCT is safe in older patients with CML with equivalent acute and chronic GVHD, TRM, and OS across age cohorts. Relapse increased in patients receiving NMA conditioning and in those aged 60 and above; most of whom had advanced disease. However, for HCT during CP1 relapse risks and DFS were similar, regardless of age. Allogeneic HCT using RIC conditioning for older patients with CP1 CML can control relapse with acceptable toxicity and survival. Comparison of outcomes with second line TKI versus HCT are as yet unreported but these favorable findings indicate appropriate consideration of HCT for older patients with CML. Disclosures:Gupta:Incyte: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Honoraria, Membership on an entity's Board of Directors or advisory committees.

CBL, CBLB, TET2, ASXL1, and IDH1/2 mutations and additional chromosomal aberrations constitute molecular events in chronic myelogenous leukemia

AbstractProgression of chronic myelogenous leukemia (CML) to accelerated (AP) and blast phase (BP) is because of secondary molecular events, as well as additional cytogenetic abnormalities. On the basis of the detection of JAK2, CBL, CBLB, TET2, ASXL1, and IDH1/2 mutations in myelodysplastic/myeloproliferative neoplasms, we hypothesized that they may also contribute to progression in CML. We screened these genes for mutations in 54 cases with CML (14 with chronic phase, 14 with AP, 20 with myeloid, and 6 with nonmyeloid BP). We identified 1 CBLB and 2 TET2 mutations in AP, and 1 CBL, 1 CBLB, 4 TET2, 2 ASXL1, and 2 IDH family mutations in myeloid BP. However, none of these mutations were found in chronic phase. No cases with JAK2V617F mutations were found. In 2 cases, TET2 mutations were found concomitant with CBLB mutations. By single nucleotide polymorphism arrays, uniparental disomy on chromosome 5q, 8q, 11p, and 17p was found in AP and BP but not involving 4q24 (TET2) or 11q23 (CBL). Microdeletions on chromosomes 17q11.2 and 21q22.12 involved tumor associated genes NF1 and RUNX1, respectively. Our results indicate that CBL family, TET2, ASXL1, and IDH family mutations and additional cryptic karyotypic abnormalities can occur in advanced phase CML.

Abstract 3796: Inhibition of mitochondrial respiration synergizes with tyrosine kinase inhibitors to eliminate Bcr-Abl+ leukemia

Abstract Bcr-Abl kinase inhibitors are the standard therapy for chronic myelogenous leukemia (CML). While effective in controlling disease in chronic phase, these inhibitors often fail to completely eliminate Bcr-Abl+ CML cells and also fail to achieve durable remissions for advanced CML and Bcr-Abl+ acute lymphoblastic leukemias (ALL). Our lab employed a large-scale synthetic lethal shRNA screen to identify genes involved in CML survival upon treatment with the Bcr-Abl kinase inhibitor imatinib (IM) [Cancer Cell. 2010;18(1):74-87]. This screen identified several genes involved in energy utilization including a component of pyruvate dehydrogenase, dihydrolipoyllysine-residue acetyltransferase. This target was identified by two independent shRNAs, each underrepresented over 22 fold in treated cells compared to untreated. CML proliferation depends on Bcr-Abl-driven glycolysis for energy production. Upon IM treatment, I hypothesized that these cells are forced to rely on other sources of energy including the TCA cycle and mitochondrial respiration, and that targeting alternative energy production pathways will enhance IM-mediated elimination of CML cells. Thus, I predicted that inhibition of mitochondrial respiration by knockdown or pharmacologic inhibition would cooperate with tyrosine kinase inhibitors to eliminate Bcr-Abl+ leukemias. My experiments have shown that knocking down pyruvate dehydrogenase in human blast crisis Bcr-Abl+ CML cells (K562) greatly sensitizes cells to IM in vitro. Conversely, supplementing the cell culture media with increasing concentrations of methyl-pyruvate protects K562 cells from IM treatment. Moreover, I find that the mitochondrial ATP-synthase inhibitor Oligomycin A also synergizes with IM to kill CML cells in vitro. In addition, inhibition of mitochondrial respiration with Oligomycin A enhances elimination of Bcr-Abl+ cells by a Bcr-Abl tyrosine kinase inhibitor in vivo and prolongs disease-free survival in a mouse model of Bcr-Abl+ B-ALL. The drug doses of Oligomycin A used are over 100-fold below the LD50, and have no apparent adverse effects on these mice. Targeting mitochondrial metabolism as an adjuvant drug therapy may prevent the survival of residual Bcr-Abl+ CML cells upon tyrosine kinase inhibitor treatment. *This project is supported in part by pre-doctoral fellowship number F31CA157166 from the National Cancer Institute. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3796. doi:10.1158/1538-7445.AM2011-3796

The BCR-ABL1-Regulated hnRNP A1, hnRNP E2, and hnRNP K Are Differentially Expressed Between CD34+ and CD34+/CD38- Ph+ Cells, and After Blastic Transformation of CML.

AbstractAbstract 1222The molecular mechanism leading to disease progression of chronic myelogenous leukemia (CML) still remains to be identified although enhanced BCR/ABL expression and activity seems to play an important role in controlling genomic stability, differentiation, and self renewal of the leukemic cell clone undergoing blastic tranformation by affecting expression and function of RNA binding proteins (RBPs) like hnRNP A1, hnRNP E2, and hnRNP K (Perrotti D. et al. J. Clin Invest. 2010).We previously reported (Harb J. et al., ASH 2009) that a BCR-ABL1 dosage-dependence and hierarchical organization exists for the expression of hnRNP A1, hnRNP E2, and hnRNP K in cell line models of CML. In fact, as BCR/ABL levels increase, upregulated expression of hnRNP A1 is observed, followed by increased expression of hnRNP E2 and hnRNP K. HnRNP A1 and hnRNP K were also temporally expressed within Lineage- Sca-1+ c-kit+ (LSK), common myeloid progenitors (CMP), and granulocyte macrophage progenitors (GMP) in a mouse model (SCLtTA TRE-BCR/ABL) of chronic myeloid leukemia. Interestingly, hnRNP A1 and hnRNP K levels in BCR/ABL+ mouse progenitors correlated with disease severity as mice with higher levels of these RBPs presented a more progressed phenotype characterized by increased mixed lineage B220+/Mac-1+ progenitors in bone marrow and spleen when compared with mice that developed a CML-CP-like phenotype.Here we show that hnRNP A1, hnRNP E2, and hnRNP K expression levels, as well as BCR/ABL activity are different in HSC (CD34+/CD38-), CMP (CD34+/CD38+/CD45+/IL-3Ra-), and GMP (CD34+/CD38+/CD45+/IL-3Ra+) isolated from peripheral blood of patients in chronic phase (CML-CP) at diagnosis, untreated accelerated phase (CML-AP), and blast crisis (CML-BC). Interestingly, in CML-CP, the highest expression of hnRNP A1 was found in the CD34+/CD38- stem cell fraction and it gradually decreased in the more mature CMP and GMP progenitors (55% and 65% lower, respectively). By contrast, consistent with the role of hnRNP A1 as regulator of progenitor cell proliferation and survival, hnRNP A1 expression progressively increased in the HSC, CMP and GMP fractions isolated from patients in CML-AP and CML-BC. Unlike hnRNP A1, hnRNP E2 and hnRNP K were barely detected in the CD34+/CD38- from CML-CP patients but their expression was markedly pronounced in the HSC fraction of progressed CML patients. In agreement with our cell line data, expression of hnRNP A1 and hnRNP E2 in advanced CML (CML-AP and CML-BC) increases when CD34+/CD38- stem cells undergo maturation toward CMP. Conversely, it appears that hnRNP K expression is the last to increase in CML-BC, suggesting a hierarchical regulation of RBP expression during differentiation and lineage commitment. Expectedly, levels of hnRNP A1 in CMPs increase during disease progression (CP<AP<BC). Because of the highest expression of hnRNP A1 in the CD34+/CD38- fraction in CML-CP, and its previously described role in regulating survival and proliferation of Ph+ CD34+ cells (Iervolino et al., Mol Cell Biol 2002; Neviani et al. Cancer Cell 2005), we lentivirally transduced a hnRNP A1 shRNA into the CD34+/CD38- and CD34+/CD38+ cell fractions in CML-CP and assessed the role played by this RBP in survival of primitive and committed CML-CP progenitors. Western blot analysis demonstrated that hnRNP A1 was efficiently knockdown (≥ 80% reduction) in both compartments. Due to its ability to regulate BCR-ABL1 expression/function through the SET-PP2A axis, downregulation of hnRNP A1 led to reduced BCR/ABL activity in both stem and progenitor cells. However, cell survival and cytokine-dependent proliferation were severely compromised in committed progenitors transduced with the hnRNP A1 shRNA but not in the shRNA hnRNP A1-expressing CD34+/CD38- cells, consistent with the notion that progenitors but not stem cells are BCR-ABL1 oncogene addicted. Colony forming assays performed with empty vector- and hnRNP A1 shRNA-transduced CD34+/CD38- cells showed a 50% reduction in the number of CFCs upon hnRNP A1 downregulation. Accordingly, levels of the hnRNP A1-regulated anti-apoptotic Bcl-xL were substantially reduced in CD34+/CD38- cells.Taken together, these data further implicate RBPs hnRNP A1, hnRNP E2, and hnRNP K in CML disease progression and suggest their possible role in the control of survival of stem and primitive CML-CP progenitors. Disclosures:No relevant conflicts of interest to declare.

Weekend Drug Holiday of Dasatinib in CML Patients Not Tolerating Standard Dosing Regimens. Reducing Toxicity with Maintained Disease Control.

Abstract 1119Poster Board I-141Dasatinib (DA) is a multitargeted tyrosine kinase inhibitor (TKI) approved for 2nd line treatment of chronic myelogenous leukemia (CML) patients after imatinib failure. DA-related toxicity mandates dose reduction in selected patients beyond the labelled reduced continuous dosing. In chronic phase (CP) patients, intermittent targeting of BCR-ABL by a once daily regimen reduces side effects with equal efficacy compared to the initially explored twice daily regimen. Thus, considering the short half-life of DA (3-5 hours) additional treatment interruptions to reduce the total weekly dose may not negatively affect treatment outcome while allowing continued treatment with an effective drug. In a retrospective analysis 33 CML patients (pts; 20 m, 13 f, median age 66 years, range 39-81) with intolerance (n=11) or resistance (n=22) to imatinib were investigated. Pts were selected based on the toxicity-guided administration of a dose reduced dasatinib regimen and were treated with an on/off regimen (3 to 5 days on, 4 to 2 days off) expecting a reduction of DA dependent off-target toxicity. Pts were followed by routine hematologic and cytogenetic assessment, and molecular monitoring (quantitative reverse transcriptase polymerase chain reaction, PCR) to safeguard clinical response to the altered drug schedule. Further, resistant pts were regularly screened for BCR-ABL mutations. Median time since CML diagnosis until start of DA treatment was 38 mo (range, 6-189). The median number of preceding treatment modalities was 3 (range, 1-5). The median follow up of interval treatment was 23 mo (range, 3-41). 30 patients were in CP, 2 in accelerated phase, and one in blast phase CML. 13/33 patients carried mutant BCR-ABL prior to onset of DA-treatment. Non-exclusive reasons for dose reduction were hematologic toxicity (17/33; 51%), and fluid retention (18/33, 55%), including 17 patients with pleural effusions. 27 patients (82%) suffered from grade III/IV (CTC) side effects. The median weekly dose of the DA weekend holiday schedule was 500mg (range, 320-500). During interval treatment, mean CTC grade for hematologic toxicity improved from grade 3.2 to 1.5 (p<0.001), and for fluid retention from grade 2.9 to 1.6 (p<0.001). All but 2 pts (89%) affected by fluid retention, and all but one patient suffering from hematologic toxicity (94%) achieved a lower CTC toxicity level by allowing drug holiday. In 6/33 pts, resistance mutations (T315I x 2, F317L x 3, L248V) were recovered. For response analysis, 2 pts were excluded due to early stem cell transplantation or loss of follow up. 13/31 (42%) did either show transient improved molecular response or remained on stable BCR-ABL load over time. 3/31 progressed to advanced phase CML. 18/31 (58%) pts showed the desired disease control according to established criteria despite reduced total weekly DA doses either demonstrated by achieving an improved response level (12/31), or keeping the response level achieved by continuous dosing (6/31). Fourteen of the 18 pts achieved or maintained major molecular response (MMR) with 5 pts repeatedly tested negative by PCR. The remainder four pts demonstrated response by achieving complete cytogenetic remission (CCyR, 2x) or reduced BCR-ABL load <1% according to the international scale. Of note, 10/12 pts with improved response have been treated for a minimum of 6 mo with continuous dosing DA regimens without having achieved the response level observed after allowing drug holiday. We conclude that weekend treatment interruption allows continuation of DA treatment for pts suffering from side effects. This retrospective analysis in pts resistant or intolerant to imatinib with up to 5 preceding treatment modalities suggests good and in many cases even improved efficacy of interval treatment compared to continuous dosing. These data mandate the initiation of clinical trials to investigate alternative intermittent targeting regimens. DisclosuresOff Label Use: Dasatinib, a multikinase tyrosine kinase inhibitor, has been used in a lower than labeled total weekly dose to reduce off target toxicity for CML patients.. Hochhaus:Bristol Myers Squibb: Research Funding.

Extended kinase profile and properties of the protein kinase inhibitor nilotinib

As a drug used to treat imatinib-resistant and -intolerant, chronic and advanced phase chronic myelogenous leukaemia, nilotinib is well characterised as a potent inhibitor of the Abl tyrosine kinase activity of wild-type and imatinib-resistant mutant forms of BCR-Abl. Here we review the profile of nilotinib as a protein kinase inhibitor. Although an ATP-competitive inhibitor of Abl, nilotinib binds to a catalytically inactive conformation (DFG-out) of the activation loop. As a consequence of this, nilotinib exhibits time-dependent inhibition of Abl kinase in enzymatic assays, which can be extrapolated to other targets to explain differences between biochemical activity and cellular assays. Although these differences confound assessment of kinase selectivity, as assessed using a combination of protein binding and transphosphorylation assays, together with cellular autophosporylation and proliferation assays, well established kinase targets of nilotinib in rank order of inhibitory potency are DDR-1>DDR-2>BCR-Abl (Abl)>PDGFRα/β>KIT>CSF-1R. In addition nilotinib has now been found to bind to both MAPK11 (p38β) and MAPK12 (p38α), as well as with very high affinity to ZAK kinase. Although neither enzymatic nor cellular data are yet available to substantiate the drug as an inhibitor of ZAK phosphorylation, modeling predicts that it binds in an ATP-competitive fashion.

Downregulation of JUNB mRNA expression in advanced phase chronic myelogenous leukemia

JUNB inactivation in transgenic mice results in a myeloproliferative disorder that closely resembles human chronic myelogenous leukemia (CML). It has been reported that downregulation of JUNB expression is a universal phenomenon in patients with CML due aberrant DNA methylation of its promoter. Based on this, we studied methylation and gene expression levels of JUNB in CML. We analyzed the methylation status of the JUNB gene in 6 cell lines and in 102 patients with CML using several bisulfite PCR assays. JUNB expression was analyzed using real-time PCR and gene expression profiling. JUNB methylation was not observed in any of the cell lines studied, and only in 3% of patients with CML. Despite the lack of JUNB methylation, JUNB was expressed at low levels both in CML cell lines (median dCT −6.86; range −5.87 to −9.61), and in patients with CML in blastic phase (BP) (median dCT −3.95; range −1.48 to −6.29) ( p = 0.002). Finally, we evaluated JUNB expression in 82 additional patients with CML by gene expression arrays. We found that JUNB was significantly downregulated in advanced phase CML in contrast to chronic phase CML (median log ratio difference in expression = 0.53). Overall, our results indicate that JUNB expression is downregulated in advanced phase CML through a mechanism independent from DNA methylation.