Predictive nonlinear modeling of malignant myelopoiesis and tyrosine kinase inhibitor therapy

Chronic myeloid leukemia (CML) is a blood cancer characterized by dysregulated production of maturing myeloid cells driven by the product of the Philadelphia chromosome, the BCR-ABL1 tyrosine kinase. Tyrosine kinase inhibitors (TKIs) have proved effective in treating CML, but there is still a cohort of patients who do not respond to TKI therapy even in the absence of mutations in the BCR-ABL1 kinase domain that mediate drug resistance. To discover novel strategies to improve TKI therapy in CML, we developed a nonlinear mathematical model of CML hematopoiesis that incorporates feedback control and lineage branching. Cell-cell interactions were constrained using an automated model selection method together with previous observations and new in vivo data from a chimeric BCR-ABL1 transgenic mouse model of CML. The resulting quantitative model captures the dynamics of normal and CML cells at various stages of the disease and exhibits variable responses to TKI treatment, consistent with those of CML patients. The model predicts that an increase in the proportion of CML stem cells in the bone marrow would decrease the tendency of the disease to respond to TKI therapy, in concordance with clinical data and confirmed experimentally in mice. The model further suggests that, under our assumed similarities between normal and leukemic cells, a key predictor of refractory response to TKI treatment is an increased maximum probability of self-renewal of normal hematopoietic stem cells. We use these insights to develop a clinical prognostic criterion to predict the efficacy of TKI treatment and design strategies to improve treatment response. The model predicts that stimulating the differentiation of leukemic stem cells while applying TKI therapy can significantly improve treatment outcomes.

A prospective clinical trial to evaluate the performance of a multi-analyte blood test for early detection of hepatocellular carcinoma among at-risk patients with liver cirrhosis: The CLiMB study

TPS617

Background: Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death in patients with cirrhosis in the U.S. HCC surveillance is associated with significant improvements in early tumor detection, receipt of curative therapy and overall survival in patients with cirrhosis. However, current surveillance strategies suffer from poor adherence and suboptimal sensitivity. The multi-analyte HelioLiver test is a novel blood test for the early detection of HCC. The test provides a qualitative result based on a multiparametric algorithm that incorporates information from cell-free DNA (cfDNA) methylation markers, protein tumor markers (AFP, AFP-L3%, DCP) and patient demographic characteristics (sex, and age). Here, we describe the protocol for a prospective, multicenter clinical trial designed to investigate the performance of this multi-analyte blood test in cirrhosis patients at risk for HCC. Methods: The Prospective Clinical Trial to Detect Liver Cancer through Quantification of cfDNA Methylation in Blood Samples (CLiMB) is a longitudinal, multicenter, prospective study with a targeted enrollment of 1,600 participants. The main inclusion and exclusion criteria are described in the table. Within the Initial Surveillance Visit (t=0 months), all enrolled subjects will provide blood specimens for the multi-analyte blood test and undergo conventional ultrasound to examine the liver. Every subject will then undergo diagnostic imaging by multiphasic MRI to determine the clinical truth. The results of diagnostic imaging will be scored by a Liver Reporting and Data System (LI-RADS) score and the number and size of any malignant lesions identified will be recorded. After the Initial Surveillance Visit (t=0 months), subjects with an indeterminant HCC finding by MRI (LI-RADS 3) will be recommended to have up to three Follow-Up Visits (t=6 months, t=12 months, and t=18 months) to attempt to resolve the clinical truth for these subjects. The primary endpoints of the trial are to demonstrate the superiority for sensitivity and non-inferiority for specificity of the multi-analyte blood test over ultrasound for the detection of HCC. The data of all diagnostic imaging by MRI will be saved and uploaded for evaluation by a blinded, centralized team of radiologists, which will be used as the basis of the clinical truth for all subjects. All participants are currently enrolled across the U.S. from over 40 clinical sites. Clinical trial information: NCT03694600 . [Table: see text]

1668. The SAFER Lines Project: A Mobile-App Strategy for Prevention of Outpatient Central Line Associated Bloodstream Infection (CLABSI)

Background

Outpatient peripherally inserted central catheters (PICC) use has grown without standardized protocols for their management. We assessed the impact of a mobile app strategy for outpatient CLABSI prevention using photo-monitoring, assessment, and response to lines with local inflammation/infection in a cohort of cancer clinic patients.

Methods

This prospective cohort study evaluated adults with PICCs at an academic cancer clinic at baseline (7/2015–12/2016) and after implementing the SAFER (Standardizing Assessment For Effective Response) Lines program (intervention 5/2017–11/2018). This included a mobile app enabling (1) clinic assessment of localized inflammation or infection defined as Central Line Insertion Site Assessment (CLISA) score 2 or 3, respectively (Table 1), (2) photo-documentation, and (3) score-based automated physician alerts for remote response. We assessed demographics, malignancy type, and line characteristics. Generalized linear mixed effects model assessed program impact on frequency of CLISA 2 or 3 lines, clustered by patient. Cox proportional hazards and Kaplan Meier models assessed days to line removal after CLISA 2 or 3 were identified.

Results

Among 4,894 assessments of 528 PICCs in 380 outpatients, there were 272 lines (199 patients) at baseline and 256 lines (181 patients) after SAFER program implementation. Mean age, gender, PICC dwell time, and history of prior PICC were similar at baseline and intervention. The proportion of inflamed (CLISA 2) and infected (CLISA 3) lines decreased 40% (from 26% to 16%, and 19% to 11%, respectively) during intervention compared to baseline. Lines with peeling dressings decreased 80% (from 46% to 9%). Mean days to removal of inflamed lines decreased 59% (from 19 to 8 days); removal of infected lines decreased 85% (from 11 to < 2 days). Intervention was associated with 46% lower risk of local inflammation/infection (OR 0.46, CI=0.26–0.83, p< 0.01, Table 2) and faster line removal when such lines were identified (HR 0.18, CI=0.12–0.27, p< 0.01).

Conclusion

The SAFER Lines mobile app and program decreased the frequency of locally inflamed or infected PICC insertion sites and increased the speed of removal when local inflammation/infection was found in cancer clinic patients.

Disclosures

Raheeb Saavedra, AS, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products Raveena D. Singh, MA, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products Susan S. Huang, MD, MPH, Medline: Conducted studies in which hospitals and nursing homes received contributed antiseptic and/or environmental cleaning products|Molnlyke: Conducted clinical studies in which hospitals received contributed antiseptic product|Stryker: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic products|Xttrium Laboratories: Conducted clinical studies in which hospitals and nursing homes received contributed antiseptic product.

Perspective: Pivotal translational hematology and therapeutic insights in chronic myeloid hematopoietic stem cell malignancies

Despite much of the past 2 years being engulfed by the devastating consequences of the SAR-CoV-2 pandemic, significant progress, even breathtaking, occurred in the field of chronic myeloid malignancies. Some of this was show-cased at the 15th Post-American Society of Hematology (ASH) and the 25th John Goldman workshops on myeloproliferative neoplasms (MPN) held on 9th-10th December 2020 and 7th-10th October 2021, respectively. The inaugural Post-ASH MPN workshop was set out in 2006 by John Goldman (deceased) and Tariq Mughal to answer emerging translational hematology and therapeutics of patients with these malignancies. Rather than present a resume of the discussions, this perspective focuses on some of the pivotal translational hematology and therapeutic insights in these diseases.

A multi-analyte cell-free DNA-based blood test for early detection of hepatocellular carcinoma

The limited performance of guideline-recommended abdominal ultrasound and serum alpha-fetoprotein (AFP) highlights the urgent, unmet need for new biomarkers for more accurate detection of early hepatocellular carcinoma (HCC). To this end, we have conducted a prospective clinical validation study to evaluate the performance of the HelioLiver Test, a multi-analyte blood test combining cell-free DNA methylation patterns, clinical variables, and protein tumor markers. A blinded, multicenter validation study was performed with 247 subjects, including 122 subjects with HCC and 125 control subjects with chronic liver disease. The performance of the HelioLiver Test was compared with AFP and the GALAD score as established HCC surveillance blood tests. The performance of the HelioLiver Test (area under the receiver operating characteristic curve [AUROC] = 0.944) was superior to both AFP (AUROC = 0.851; p < 0.0001) and GALAD (AUROC = 0.899; p < 0.0001). Using a prespecified diagnostic algorithm, the HelioLiver Test showed sensitivities of 85% (95% confidence interval [CI], 78%-90%) for HCC of any stage and 76% (95% CI, 60%-87%) for early stage (American Joint Committee on Cancer [AJCC] I and II) HCC. In contrast, AFP (≥20 ng/mL) alone and the GALAD score (≥-0.63) showed lower sensitivities of 62% (95% CI, 54%-70%) and 75% (95% CI, 67%-82%) for HCC overall, and 57% (95% CI, 40%-71%) and 65% (95% CI, 49%-79%) for early stage (AJCC I and II) HCC, respectively. The specificities of the HelioLiver Test (91%; 95% CI, 85%-95%), AFP (97%; 95% CI, 92%-99%), and the GALAD score (94%; 95% CI, 88%-97%) were similar for control subjects. The HelioLiver Test showed superior performance for HCC detection compared to with both AFP and the GALAD score and warrants further evaluation in HCC surveillance settings.

The impact of Rhodiola rosea on biomarkers of diabetes, inflammation, and microbiota in a leptin receptor-knockout mouse model

Type 2 diabetes is the most prevalent endocrine disease in the world, and recently the gut microbiota have become a potential target for its management. Recent studies have illustrated that this disease may predispose individuals to certain microbiome compositions, and treatments like metformin have been shown to change gut microbiota and their associated metabolic pathways. However, given the limitations and side effects associated with pharmaceuticals currently being used for therapy of diabetes, there is a significant need for alternative treatments. In this study, we investigated the effects of a root extract from Rhodiola rosea in a Leptin receptor knockout (db/db) mouse model of type 2 diabetes. Our previous work showed that Rhodiola rosea had anti-inflammatory and gut microbiome-modulating properties, while extending lifespan in several animal models. In this study, treatment with Rhodiola rosea improved fasting blood glucose levels, altered the response to exogenous insulin, and decreased circulating lipopolysaccharide and hepatic C-reactive protein transcript levels. We hypothesize that these changes may in part reflect the modulation of the microbiota, resulting in improved gut barrier integrity and decreasing the translocation of inflammatory biomolecules into the bloodstream. These findings indicate that Rhodiola rosea is an attractive candidate for further research in the management of type 2 diabetes.

Specific, targetable interactions with the microenvironment influence imatinib-resistant chronic myeloid leukemia

Therapy resistance in leukemia may be due to cancer cell-intrinsic and/or -extrinsic mechanisms. Mutations within BCR-ABL1, the oncogene giving rise to chronic myeloid leukemia (CML), lead to resistance to tyrosine kinase inhibitors (TKI), and some are associated with clinically more aggressive disease and worse outcome. Using the retroviral transduction/transplantation model of CML and human cell lines we faithfully recapitulate accelerated disease course in TKI resistance. We show in various models, that murine and human imatinib-resistant leukemia cells positive for the oncogene BCR-ABL1T315I differ from BCR-ABL1 native (BCR-ABL1) cells with regards to niche location and specific niche interactions. We implicate a pathway via integrin β3, integrin-linked kinase (ILK) and its role in deposition of the extracellular matrix (ECM) protein fibronectin as causative of these differences. We demonstrate a trend towards a reduced BCR-ABL1T315I+ tumor burden and significantly prolonged survival of mice with BCR-ABL1T315I+ CML treated with fibronectin or an ILK inhibitor in xenogeneic and syngeneic murine transplantation models, respectively. These data suggest that interactions with ECM proteins via the integrin β3/ILK-mediated signaling pathway in BCR-ABL1T315I+ cells differentially and specifically influence leukemia progression. Niche targeting via modulation of the ECM may be a feasible therapeutic approach to consider in this setting.

Emerging translational science discoveries, clonal approaches, and treatment trends in chronic myeloproliferative neoplasms

The 60th American Society of Hematology (ASH) held in San Diego in December 2018 was followed by the 13th Post-ASH chronic myeloproliferative neoplasms (MPNs) workshop on December 4 and 5, 2018. This closed annual workshop, first introduced in 2006 by Goldman and Mughal, was organized in collaboration with Alpine Oncology Foundation and allowed experts in preclinical and clinical research in the chronic MPNs to discuss the current scenario, including relevant presentations at ASH, and address pivotal open questions that impact translational research and clinical management. This review is based on the presentations and deliberations at this workshop, and rather than provide a resume of the proceedings, we have selected some of the important translational science and treatment issues that require clarity. We discuss the experimental and observational evidence to support the intimate interaction between aging, inflammation, and clonal evolution of MPNs, the clinical impact of the unfolding mutational landscape on the emerging targets and treatment of MPNs, new methods to detect clonal heterogeneity, the challenges in managing childhood and adolescent MPN, and reflect on the treatment of systemic mastocytosis (SM) following the licensing of midostaurin.

Cell-free DNA methylation markers for noninvasive early detection of nasopharyngeal carcinoma

e14537

Background: Nasopharyngeal carcinoma (NPC) is one of the most prevalent malignancies among populations native to Southeast Asia, the Mediterranean Basin and the Arctic. Early diagnosis of NPC is predicted to improve survival. The identification of cancer-specific DNA methylation patterns of cell-free DNA (cfDNA) isolated from blood samples is an established approach for detecting various cancers. In the present study, we evaluated the performance characteristics of a previously identified NPC methylation marker panel for the diagnosis of nasopharyngeal carcinoma. Methods: Retrospective samples were obtained for 168 subjects, including: 59 subjects diagnosed with NPC (Stage I to IV), 14 subjects diagnosed with benign nasopharyngeal disease and 43 healthy subjects. In addition, sample were obtained for 52 subjects diagnosed with breast, colorectal, liver or lung cancer. Samples were provided to the laboratory blinded for DNA methylation analysis by using the IvyGene Platform. Results: A total of 57 of the 59 samples drawn from subjects with NPC were correctly identified for an overall sensitivity of 97%, with little difference between the sensitivity of detecting Stage I to Stage IV nasopharyngeal carcinoma (range 92% to 100%). For subjects diagnosed with other cancers, 85% of colorectal cancer samples, 82% of lung cancer samples, 93% of both breast cancer and liver cancer samples, were correctly identified as negative for NPC, for a total calculated analytical specificity of 86%. Additionally, all 43 samples drawn from healthy donors and 14 samples drawn from subjects diagnosed with benign nasopharyngeal disease were correctly identified as negative for nasopharyngeal carcinoma for a combined specificity of 100%. Conclusions: The NPC methylation panel was demonstrated to be both sensitive and specific for the detection of nasopharyngeal carcinoma. The potential of cfDNA methylation markers for the early detection of nasopharyngeal carcinoma is predicted to improve patient outcomes through earlier detection of the disease.

Epigenetic biomarkers for noninvasive detection of colorectal cancer

45

Background: Aberrant DNA hypermethylation is known to be a major mechanism for inactivation of cancer-associated genes, including tumor suppressor genes, in colorectal cancer (CRC) and in other human cancers. Cancer-specific DNA methylation patterns of cell-free DNA (cfDNA) isolated from blood samples is a non-invasive method to obtain representative epigenetic information from solid tumors. In the present study, we identified and validated colorectal cancer-specific methylation markers for diagnosis of the disease with high sensitivity and specificity. We also compared the relative amount of DNA methylation at these target sites in relation to colorectal cancer stage. Methods: For marker validation, a total of 154 samples drawn from 68 subjects diagnosed with colorectal cancer (Stage I to IV), 42 healthy donors, 14 subjects with benign colorectal diseases, and 30 subjects diagnosed with other cancer types (breast, liver and lung cancer: 10 cases each) were obtained for a randomized, blinded study. Cell-free DNA was then extracted from the samples, bisulfite converted, and DNA methylation was quantified by using the IvyGene Platform. Results: By quantifying DNA methylation at the target sites, colorectal cancer samples were differentiated from samples drawn from healthy subjects or subjects with benign disease with an overall sensitivity of 93% (95% CI: 86-99) and specificity of 100% (95% CI: 85-100). All stages (I to IV) of colorectal cancer were identified with sensitivities ranging from 67% to 100%. None of the 30 samples drawn from subjects diagnosed with breast, liver or lung cancers were incorrectly identified as a colorectal cancer by the assay, for a calculated analytical specificity of 100%. Conclusions: These results demonstrate the high diagnostic potential of cfDNA methylation markers isolated from blood for the detection of colorectal cancer. Taken together, these findings establish the utility of methylation biomarkers for the detection of colorectal cancers as early as Stage I. In addition, a quantitative analysis of cfDNA provides an opportunity for non-invasive detection and monitoring of disease.

Precision immunotherapy, mutational landscape, and emerging tools to optimize clinical outcomes in patients with classical myeloproliferative neoplasms

Following the 47th American Society of Hematology Meeting in 2005, the late John Goldman and Tariq Mughal commenced a conference, the 1st Post-ASH Workshop, which brought together clinicians and scientists, to accelerate the adoption of new therapies for patients with myeloproliferative neoplasms (MPNs). The concept began with recognition of the CML success story following imatinib therapy, the discovery of JAK2^V617F , and the demonstration that BCR-ABL1-negative MPNs are driven by abnormal JAK2 activation. This review is based on the presentations and deliberations at the XIIth Post-ASH Workshop on BCR-ABL1 positive and negative MPNs that took place on December 12 to 13, 2017, in Atlanta, Georgia, immediately following the 59th American Society of Hematology Meeting. We have selected some of the translational research and clinical topics, rather than an account of the proceedings. We discuss the role of immunotherapy in MPNs and the impact of the mutational landscape on TKI treatment in CML. We also consider how we might reduce TKI cardiovascular side effects, the potential role of nutrition as adjunctive nonpharmacologic intervention to reduce chronic inflammation in MPNs, and novel investigational therapies for MPNs.

Recent advances in the genomics and therapy of BCR/ABL1-positive and -negative chronic myeloproliferative neoplasms

This review is based on the presentations and deliberations at the 7th John Goldman Chronic Myeloid Leukemia (CML) and Myeloproliferative Neoplasms (MPN) Colloquium which took place in Estoril, Portugal on the 15th October 2017, and the 11th post-ASH International Workshop on CML and MPN which took place on the 6th-7th December 2016, immediately after the 58th American Society of Hematology Annual Meeting. Rather than present a resume of the proceedings, we have elected to address some of the topical translational research and clinically relevant topics in greater detail. We address recent updates in the genetics and epigenetics of MPN, the mechanisms of transformation by mutant calreticulin, advances in the biology and therapy of systemic mastocytosis, clinical updates on JAK2 inhibitors and other therapeutic approaches for patients with MPNs, cardiovascular toxicity related to tyrosine kinase inhibitors and the concept of treatment-free remission for patients with CML.

Superenhancer reprogramming drives a B-cell-epithelial transition and high-risk leukemia

Here, Hu et al. investigated the mechanisms by which IKAROS promotes B-cell differentiation and prevents leukemogenesis. By using chromatin, transcription, and gene inactivation studies in primary wild-type and IKAROS-deficient B-cell precursors, they show that a dual mechanism of IKAROS regulation promotes differentiation while safeguarding against a hybrid stem–epithelial–B-cell phenotype that underlies high-risk B-ALL.

IKAROS is required for the differentiation of highly proliferative pre-B-cell precursors, and loss of IKAROS function indicates poor prognosis in precursor B-cell acute lymphoblastic leukemia (B-ALL). Here we show that IKAROS regulates this developmental stage by positive and negative regulation of superenhancers with distinct lineage affiliations. IKAROS defines superenhancers at pre-B-cell differentiation genes together with B-cell master regulators such as PAX5, EBF1, and IRF4 but is required for a highly permissive chromatin environment, a function that cannot be compensated for by the other transcription factors. IKAROS is also highly enriched at inactive enhancers of genes normally expressed in stem–epithelial cells. Upon IKAROS loss, expression of pre-B-cell differentiation genes is attenuated, while a group of extralineage transcription factors that are directly repressed by IKAROS and depend on EBF1 relocalization at their enhancers for expression is induced. LHX2, LMO2, and TEAD–YAP1, normally kept separate from native B-cell transcription regulators by IKAROS, now cooperate directly with them in a de novo superenhancer network with its own feed-forward transcriptional reinforcement. Induction of de novo superenhancers antagonizes Polycomb repression and superimposes aberrant stem–epithelial cell properties in a B-cell precursor. This dual mechanism of IKAROS regulation promotes differentiation while safeguarding against a hybrid stem–epithelial–B-cell phenotype that underlies high-risk B-ALL.

Phase 1 dose-finding study of rebastinib (DCC-2036) in patients with relapsed chronic myeloid leukemia and acute myeloid leukemia

A vailable tyrosine kinase inhibitors for chronic myeloid leukemia bind in an adenosine 5′-triphosphate-binding pocket and are affected by evolving mutations that confer resistance. Rebastinib was identified as a switch control inhibitor of BCR-ABL1 and FLT3 and may be active against resistant mutations. A Phase 1, first-in-human, single-agent study investigated rebastinib in relapsed or refractory chronic or acute myeloid leukemia. The primary objectives were to investigate the safety of rebastinib and establish the maximum tolerated dose and recommended Phase 2 dose. Fifty-seven patients received treatment with rebastinib. Sixteen patients were treated using powder-in-capsule preparations at doses from 57 mg to 1200 mg daily, and 41 received tablet preparations at doses of 100 mg to 400 mg daily. Dose-limiting toxicities were dysarthria, muscle weakness, and peripheral neuropathy. The maximum tolerated dose was 150 mg tablets administered twice daily. Rebastinib was rapidly absorbed. Bioavailability was 3- to 4-fold greater with formulated tablets compared to unformulated capsules. Eight complete hematologic responses were achieved in 40 evaluable chronic myeloid leukemia patients, 4 of which had a T315I mutation. None of the 5 patients with acute myeloid leukemia responded. Pharmacodynamic analysis showed inhibition of phosphorylation of substrates of BCR-ABL1 or FLT3 by rebastinib. Although clinical activity was observed, clinical benefit was insufficient to justify continued development in chronic or acute myeloid leukemia. Pharmacodynamic analyses suggest that other kinases inhibited by rebastinib, such as TIE2, may be more relevant targets for the clinical development of rebastinib (clinicaltrials.gov Identifier:00827138).

Contemporary insights into the pathogenesis and treatment of chronic myeloproliferative neoplasms

This review is based on the deliberations at the 5th John Goldman Colloquium held in Estoril on 2nd October 2015 and the 9th post-ASH International Workshop on chronic myeloid leukemia (CML) and BCR-ABL1-negative myeloproliferative neoplasms (MPN) which took place on the 10th-11th December 2014, immediately following the 56th American Society of Hematology Annual Meeting. It has been updated since and summarizes the most recent advances in the biology and therapy of these diseases, in particular updates of genetics of MPN, novel insights from mouse MPN models, targeting CML stem cells and its niche; clinical advances include updates on JAK2 inhibitors and other therapeutic approaches to BCR-ABL1-negative MPNs, the use of alpha interferons, updates on tyrosine kinase inhibitors (TKI) randomized trials in CML, TKI cessation studies, and optimal monitoring strategies.

Abstract 4202: Targeting focal adhesion kinase is a novel approach to therapy of high-risk, Ikaros-mutant acute B-cell lymphoblastic leukemia

Deletions and dominant-negative mutations in IKZF1, the gene encoding Ikaros transcription factor, are found in ∼85% of Ph+ B-ALL and in some cases of Ph− B-ALL, and are associated with poor prognosis. Genomic studies of high-risk Ph− or “Ph-like” B-ALLs have revealed frequent mutation and activation of TK genes and signaling pathways. While ABL1 tyrosine kinase inhibitors (TKIs) such as dasatinib and ponatinib have been incorporated into chemotherapy regimens for Ph+ B-ALL, the majority of patients still relapse, which correlates with residual bone marrow disease following induction therapy. New therapeutic strategies are needed for patients with Ikaros-mutant, high-risk Ph+ and Ph− B-ALL.

Using mice with a conditional Ikzf1 mutation (Ike5fl) that mimics the dominant-negative Ik6 mutant found in human B-ALL, we demonstrated that loss of Ikaros DNA-binding function arrests B-lymphoid development at a large pre-B cell stage that can give rise to B-ALL. Survival and proliferation of Ikaros mutant pre-B cells is dependent on increased integrin-mediated stromal adhesion and activation of focal adhesion kinase (FAK). FAK is a non-receptor TK downstream of integrins and growth factor receptors that plays important roles in cancer stem cell biology and the tumor microenvironment.

Here, we show that dysregulated tyrosine kinases, including BCR-ABL1, cooperate with Ikaros mutation to accelerate the development of B-lymphoblastic leukemia in mice, correlated with a striking (∼30-fold) increase in the frequency of engrafting leukemia-initiating or leukemic stem cells (LSCs). Ikzf1-mutant BCR-ABL1+ lymphoblasts exhibit relative resistance to ABL1 TKIs including dasatinib that is dependent on the presence of stroma. VS-4718 is a potent, orally bioavailable FAK inhibitor that inhibits tumor growth and metastasis in preclinical models, and is currently under evaluation in clinical trials in patients with various solid tumors. VS-4718 treatment abolished stromal adhesion and induced apoptosis of Ikzf1-mutant B-ALL and synergized with dasatinib, but had little effect on Ikzf1 WT B-ALL cells. Primary human Ph+ B-ALL samples showed a correlation between IKZF1 mutation status, stromal adherence, and sensitivity to FAK and ABL inhibitors in vitro, and BM tropism in vivo in xenografted NSG mice. Results from ongoing in vivo therapy experiments will be presented.

Together, these results suggest a new model for the pathogenesis of high-risk B-ALL and its resistance to conventional therapy. B-ALLs with IKZF1 mutations may be resistant to TKIs and to chemotherapy by virtue of their stromal adhesion phenotype, resulting in failure to eliminate BM leukemic stem cells. Inhibition of FAK signaling in Ph+ or Ph− IKZF1-mutant B-ALL may reverse the stromal-mediated resistance to ABL1 TKIs and/or chemotherapy. FAK inhibitors represent a promising new approach for the treatment of high-risk IKZF1-mutant B-ALL patients.

Citation Format: Nilamani Jena, Ila Joshi, Toshimi Yoshida, Zhihong Zhang, Zhong-Ying Liu, Prasanthi Tata, Irina M. Shapiro, Jonathan A. Pachter, David T. Weaver, Katia Georgopoulos, Richard A. Van Etten. Targeting focal adhesion kinase is a novel approach to therapy of high-risk, Ikaros-mutant acute B-cell lymphoblastic leukemia. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4202. doi:10.1158/1538-7445.AM2015-4202

Novel insights into the biology and treatment of chronic myeloproliferative neoplasms

Myeloproliferative neoplasms (MPNs) are clonal disorders of hematopoiesis characterized by a high frequency of genetic alterations, and include chronic myeloid leukemia (CML) and the BCR-ABL1-negative MPNs. Herein we summarize recent advances and controversies in our understanding of the biology and therapy of these disorders, as discussed at the 8th post-American Society of Hematology CML-MPN workshop. The principal areas addressed include the breakthrough discovery of CALR mutations in patients with JAK2/MPL wild type MPN, candidate therapies based on novel genetic findings in leukemic transformation and new therapeutic targets in MPNs, and an appraisal of bone marrow histopathology in MPNs with a focus on the potential new clinical entity of "masked" polycythemia vera. An update on clinical trials of Janus kinase (JAK) inhibitors is presented as well as current understanding regarding the definitions and mechanisms of resistance to JAK inhibitors, and updated information on the safety and efficacy of discontinuation of tyrosine kinase inhibitors in patients with CML.

IKK-dependent activation of NF-κB contributes to myeloid and lymphoid leukemogenesis by BCR-ABL1

The product of the Ph chromosome, the BCR-ABL1 tyrosine kinase activates diverse signaling pathways in leukemic cells from patients with chronic myeloid leukemia (CML) and Ph(+) B-cell acute lymphoblastic leukemia (B-ALL). Previous studies showed that nuclear factor κB (NF-κB) is activated in BCR-ABL1-expressing cells, but the mechanism of activation and importance of NF-κB to the pathogenesis of BCR-ABL1-positive myeloid and lymphoid leukemias are unknown. Coexpression of BCR-ABL1 and a superrepressor mutant of inhibitory NF-κB α (IκBαSR) blocked nuclear p65/RelA expression and inhibited the proliferation of Ba/F3 cells and primary BCR-ABL1-transformed B lymphoblasts without affecting cell survival. In retroviral mouse models of CML and B-ALL, coexpression of IκBαSR attenuated leukemogenesis, prolonged survival, and reduced myeloid leukemic stem cells. Coexpression of dominant-negative mutants of IκB kinase α (IKKα)/IKK1 or IKKβ/IKK2 also inhibited lymphoid and myeloid leukemogenesis by BCR-ABL1. Blockade of NF-κB decreased expression of the NF-κB targets c-MYC and BCL-X and increased the sensitivity of BCR-ABL1-transformed lymphoblasts to ABL1 kinase inhibitors. These results demonstrate that NF-κB is activated through the canonical IKK pathway and plays distinct roles in the pathogenesis of myeloid and lymphoid leukemias induced by BCR-ABL1, validating NF-κB and IKKs as targets for therapy of Ph(+) leukemias.

Emerging therapeutic paradigms to target the dysregulated Janus kinase/signal transducer and activator of transcription pathway in hematological malignancies

Over the past decade, there has been increasing biochemical evidence that the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway is aberrantly activated in malignant cells from patients with a wide spectrum of cancers of the blood and immune systems. The emerging availability of small molecule inhibitors of JAK and other signaling molecules in the JAK/STAT pathway has allowed preclinical studies validating an important role of this pathway in the pathogenesis of many hematologic malignancies, and provided motivation for new strategies for treatment of these diseases. Here, a round-table panel of experts review the current preclinical and clinical landscape of the JAK/STAT pathway in acute lymphoid and myeloid leukemias, lymphomas and myeloma, and chronic myeloid neoplasms.

Differential regulation of myeloid leukemias by the bone marrow microenvironment

Like their normal hematopoietic stem cell counterparts, leukemia stem cells (LSC) in chronic myelogenous leukemia (CML) and acute myeloid leukemia (AML) are presumed to reside in specific niches in the bone marrow microenvironment (BMM)¹, and may be the cause of relapse following chemotherapy.² Targeting the niche is a novel strategy to eliminate persistent and drug-resistant LSC. CD44^3,4 and IL-6⁵ have been implicated previously in the LSC niche. Transforming growth factor (TGF)-β1 is released during bone remodeling⁶ and plays a role in maintenance of CML LSCs⁷, but a role for TGF-β1 from the BMM has not been defined. Here, we show that alteration of the BMM by osteoblastic cell-specific activation of the parathyroid hormone (PTH) receptor^8,9 attenuates BCR-ABL1-induced CML-like myeloproliferative neoplasia (MPN)¹⁰ but enhances MLL-AF9-induced AML¹¹ in mouse transplantation models, possibly through opposing effects of increased TGF-β1 on the respective LSC. PTH treatment caused a 15-fold decrease in LSCs in wildtype mice with CML-like MPN, and reduced engraftment of immune deficient mice with primary human CML cells. These results demonstrate that LSC niches in chronic and acute myeloid leukemias are distinct, and suggest that modulation of the BMM by PTH may be a feasible strategy to reduce LSC, a prerequisite for the cure of CML.

Retargeting NK-92 cells by means of CD19- and CD20-specific chimeric antigen receptors compares favorably with antibody-dependent cellular cytotoxicity

Multiple natural killer (NK) cell-based anticancer therapies are currently under development. Here, we compare the efficiency of genetically modified NK-92 cells expressing chimeric antigen receptors (CARs) at killing NK cell-resistant B-lymphoid leukemia cells to the antibody-dependent cell-mediated cytotoxicity (ADCC) of NK-92 cells expressing a high affinity variant of the IgG Fc receptor (FcγRIII). First, we compared in vitro the abilities of NK-92 cells expressing CD20-targeting CARs to kill primary chronic lymphocytic leukemia (CLL) cells derived from 9 patients with active, untreated disease to the cytotoxicity of NK-92 cells expressing FcγRIII combined with either of the anti-CD20 monoclonal antibodies (mAbs) rituximab or ofatumumab. We found that CAR-expressing NK-92 cells effectively kill NK cell-resistant primary CLL cells and that such a cytotoxic response is significantly stronger than that resulting from ADCC. For studying CAR-expressing NK cell-based immunotherapy in vivo, we established xenograft mouse models of residual leukemia using the human BCR-ABL1+ cell lines SUP-B15 (CD19+CD20-) and TMD-5 (CD19+CD20+), two acute lymphoblastic leukemia (ALL) lines that are resistant to parental NK-92 cells. Intravenous injection of NK-92 cells expressing CD19-targeting CARs eliminated SUP-B15 cells, whereas they had no such effect on TMD-5 cells. However, the intrafemoral injection of NK-92 cells expressing CD19-targeting CAR resulted in the depletion of TMD-5 cells from the bone marrow environment. Comparative studies in which NK-92 cells expressing either CD19- or CD20-targeting CARs were directly injected into subcutaneous CD19+CD20+ Daudi lymphoma xenografts revealed that CD20-targeting CAR is superior to its CD19-specific counterpart in controlling local tumor growth. In summary, we show here that CAR-expressing NK-92 cells can be functionally superior to ADCC (as mediated by anti-CD20 mAbs) in the elimination of primary CLL cells. Moreover, we provide data demonstrating that the systemic administration of CAR-expressing NK-92 cells can control lymphoblastic leukemia in immunocompromised mice. Our results also suggest that the direct injection of CAR-expressing NK-92 cells to neoplastic lesions could be an effective treatment modality against lymphoma.

Signal transduction in the chronic leukemias: implications for targeted therapies

The chronic leukemias, including chronic myeloid leukemia (CML), the Philadelphia-negative myeloproliferative neoplasms (MPNs), and chronic lymphocytic leukemia (CLL), have been characterized extensively for abnormalities of cellular signaling pathways. This effort has led to the elucidation of the central role of dysregulated tyrosine kinase signaling in the chronic myeloid neoplasms and of constitutive B-cell receptor signaling in CLL. This, in turn, has stimulated the development of small molecule inhibitors of these signaling pathways for therapy of chronic leukemia. Although the field is still in its infancy, the clinical results with these agents have ranged from encouraging (CLL) to spectacular (CML). In this review, we summarize recent studies that have helped to define the signaling pathways critical to the pathogenesis of the chronic leukemias. We also discuss correlative studies emerging from clinical trials of drugs targeting these pathways.

Advances in the biology and therapy of chronic myeloid leukemia: proceedings from the 6th Post-ASH International Chronic Myeloid Leukemia and Myeloproliferative Neoplasms Workshop

Following the 53rd annual meeting of the American Society of Hematology (ASH) in San Diego in December 2011, a group of clinical and laboratory investigators convened for the 6th Post-ASH International Workshop on Chronic Myeloid Leukemia (CML) and Myeloproliferative Neoplasms (MPN). The Workshop took place on 13-14 December at the Estancia, La Jolla, California, USA. This report summarizes the most recent advances in the biology and therapy of CML that were presented at the ASH meeting and discussed at the Workshop. Preclinical studies focused on the CML stem cell and its niche, and on early results of deep sequencing of CML genomes. Clinical advances include updates on second- and third-generation tyrosine kinase inhibitors (TKIs), molecular monitoring, TKI discontinuation studies and new therapeutic agents. A report summarizing the pertinent advances in MPN has been published separately.

Alternative approaches to eradicating the malignant clone in chronic myeloid leukemia: tyrosine-kinase inhibitor combinations and beyond

In patients with chronic myeloid leukemia (CML) in chronic phase who have achieved complete molecular remission on imatinib therapy, clinical trials from France and Australia have demonstrated that the majority experience prompt molecular relapse of their leukemia upon discontinuation of the drug, showing that long-term monotherapy with tyrosine kinase inhibitors is not curative in the majority of patients with CML. This has focused attention on strategies to eradicate residual disease in CML that is presumed to arise from malignant Ph+ stem cells, which should result in permanent cure and long-term leukemia-free survival. Here, we review the evidence that targeting CML stem cells will be of clinical benefit and discuss pharmacological and immunological approaches to accomplish this goal. Where possible, we link preclinical studies of CML stem cell biology to emerging results from clinical trials of agents that may target these cells.

Autologous stem cell transplant recipients tolerate haploidentical related-donor natural killer cell-enriched infusions

BACKGROUND

In the setting of allogeneic stem cell transplantation (SCT), infusing natural killer (NK) cells from a major histocompatibility complex (MHC)-mismatched donor can mediate an antileukemic effect. The graft-versus-tumor effect after autologous stem cell transplantation (ASCT) may result in less disease relapse.

STUDY DESIGN AND METHODS

We performed a Phase I clinical trial to assess the safety and feasibility of infusing distantly processed donor NK-enriched mononuclear cell (NK-MNC) infusions from a MHC haplotype-mismatched (haploidentical) donor to patients who recently underwent ASCT for a hematologic malignancy. On Day 1, peripheral blood MNCs were obtained by steady-state leukapheresis and sent from Boston to the Production Assistance for Cellular Therapies (PACT) facility at the University of Minnesota, where immunomagnetic depletion of CD3 cells was performed on Day 2. NK-MNC products were then returned to Boston on Day 2 for infusion on Day 3. Toxicity, cellular product characteristics, and logistic events were monitored.

RESULTS

At a median of 90 days (range, 49-191 days) after ASCT, 13 patients were treated with escalating doses of NK-MNCs per kilogram from 10(5) to 2 × 10(7) . Adverse effects included Grade 2 rigors and muscle aches, but no Grade 3 or 4 events and no graft-versus-host disease or marrow suppression. One air courier delay occurred. NK-MNC products were viable with cytotoxic activity after transport.

CONCLUSION

CD3-depleted, MHC-mismatched allogeneic NK-MNC infusions can be safely and feasibly administered to patients after ASCT after distant processing and transport, justifying further development of this approach.

Unraveling the genetic underpinnings of myeloproliferative neoplasms and understanding their effect on disease course and response to therapy: proceedings from the 6th International Post-ASH Symposium

Immediately after the annual scientific meeting of the American Society of Hematology (ASH), a select group of clinical and laboratory investigators in myeloproliferative neoplasms (MPN) is summoned to a post-ASH conference on chronic myeloid leukemia and the BCR-ABL1-negative MPN. The 6th such meeting occurred on December 13–14,2011, in La Jolla, California, USA, under the direction of its founder,Dr. Tariq Mughal. The current document is the first of two reports on this post-ASH event and summarizes the most recent preclinical and clinical advances in polycythemia vera, essential thrombocythemia,and primary myelofibrosis.

Murine retroviral bone marrow transplantation models for the study of human myeloproliferative disorders

Human myeloproliferative diseases are common hematologic disorders characterized by clonal overproduction of maturing myeloid or erythroid cells, often caused by expression of a mutant, dysregulated tyrosine kinase (TK). These diseases can be accurately modeled in laboratory mice by the retroviral transfer of a mutant TK gene into murine hematopoietic stem and progenitor cells, followed by transplantation of these cells into irradiated recipient mice. This yields a model system for analyzing the molecular pathophysiology of these conditions and provides a platform for testing therapies, particularly molecularly targeted new chemical entities (NCEs). The Basic Protocol in this unit describes the preparation of mouse bone marrow cells to express the relevant human oncogene before transplanting them into irradiated recipient mice. An alternate protocol describes a similar technique that allows specific induction of lymphoproliferative disease by some TKs. Support protocols for generating and titering retroviral stocks are also included.

Comparison of mRNA and lentiviral based transfection of natural killer cells with chimeric antigen receptors recognizing lymphoid antigens

Natural killer (NK) cells can be engineered to kill resistant B-lymphoid cell lines and primary B-cell chronic lymphocytic leukemia (B-CLL) cells after transfection with chimeric antigen receptors (CARs) recognizing CD19 or CD20. Here we compared mRNA electroporation with lentiviral vector (LV) transduction for both CARs. Transfection efficiency and cytotoxicity of previously NK-92 resistant CLL cells were significantly higher after mRNA electroporation than after LV transduction. Further cell sorting of LV-transduced NK-92 cells resulted in a highly enriched population of transduced cells with significant target cell lysis. Compared to NK-92 cells, peripheral blood and cord blood cells consistently showed < 10% transfection efficiency with mRNA, while LV transduction varied between 8 and 16% for peripheral blood and 12 and 73% for cord blood. These results suggest that LV should be used to achieve sufficient transgene expression if blood NK cells are considered for CAR transduction. Transfection with mRNA results in clinically relevant levels of transfection only in NK-92 cells.

Chronic myeloid leukemia 2011: successes, challenges, and strategies--proceedings of the 5th annual BCR-ABL1 positive and BCR-ABL1 negative myeloproliferative neoplasms workshop

This report is based on the presentations and discussions at the 5th annual BCR-ABL1 positive and BCR-ABL1 negative myeloproliferative neoplasms (MPN) workshop, which took place immediately following the 52nd American Society of Hematology (ASH) meeting in Orlando, Florida on December 7th-8th, 2011. Relevant data which was presented at the ASH meeting as well as all other recent publications were presented and discussed at the workshop. This report covers front-line therapies of BCR-ABL1-positive leukemias, in addition to addressing some topical biological, pre-clinical and clinical issues, such as new insights into genomic instability and resistance to tyrosine kinase inhibitors (TKIs), risk stratification and optimizing molecular monitoring. A report pertaining to the new therapies and other pertinent preclinical and clinical issues in the BCR-ABL1 negative MPNs is published separately.

BCL6: a novel target for therapy of Ph+ B cell acute lymphoblastic leukemia

BCL6 is a zinc-finger transcriptional repressor known for its oncogenic role in B cell lymphoma. In a recent issue of Nature, Duy et al. describe a novel role for BCL6 at the center of a transcriptional network in Ph(+) acute lymphoblastic leukemia cells that modulates their leukemogenicity and response to kinase inhibitors.

Conformational control inhibition of the BCR-ABL1 tyrosine kinase, including the gatekeeper T315I mutant, by the switch-control inhibitor DCC-2036

Acquired resistance to ABL1 tyrosine kinase inhibitors (TKIs) through ABL1 kinase domain mutations, particularly the gatekeeper mutant T315I, is a significant problem for patients with chronic myeloid leukemia (CML). Using structure-based drug design, we developed compounds that bind to residues (Arg386/Glu282) ABL1 uses to switch between inactive and active conformations. The lead "switch-control" inhibitor, DCC-2036, potently inhibits both unphosphorylated and phosphorylated ABL1 by inducing a type II inactive conformation, and retains efficacy against the majority of clinically relevant CML-resistance mutants, including T315I. DCC-2036 inhibits BCR-ABL1(T315I)-expressing cell lines, prolongs survival in mouse models of T315I mutant CML and B-lymphoblastic leukemia, and inhibits primary patient leukemia cells expressing T315I in vitro and in vivo, supporting its clinical development in TKI-resistant Ph(+) leukemia.

Navigating the road toward optimal initial therapy for chronic myeloid leukemia

PURPOSE OF REVIEW

Tyrosine kinase inhibitors (TKIs) have revolutionized the treatment of chronic myeloid leukemia (CML) and are now widely accepted as the initial therapy of choice in this disease, supplanting interferon and allogeneic stem cell transplantation. There are currently three drugs approved by the US Food and Drug Administration (FDA) for front-line treatment of CML: imatinib, nilotinib, and dasatinib. A fourth drug, bosutinib, may also win FDA approval in 2011. The goal of this review is to summarize the most recent information on initial treatment of CML and to aid clinicians in managing newly diagnosed CML patients.

RECENT FINDINGS

Phase III studies comparing imatinib with nilotinib or dasatinib in newly diagnosed CML were published in June 2010, leading to accelerated FDA approval for both of these 'second-generation' TKIs for initial therapy of CML. There are significant differences between the agents in terms of frequency and rate of responses, progression-free survival, and side-effects. However, the follow-up period on these trials is short, and there are as yet no significant differences in overall survival. Guidelines for monitoring CML patients on TKI therapy have been recently revised.

SUMMARY

Management of newly diagnosed CML patients in the coming decade will begin to resemble antibiotic treatment of infection, with therapy individualized based on patient risk factors, co-morbidities, and tolerability. In addition, the cost of therapy will emerge as an important consideration as generic imatinib becomes available in 2015. In this context, clinical trials to guide decision-making in newly diagnosed CML patients are needed.

The Ph-positive and Ph-negative myeloproliferative neoplasms: some topical pre-clinical and clinical issues

This review focuses on topical issues in the biology and treatment of the myeloproliferative neoplasms (MPNs). Studies in transgenic mice suggest that BCR-ABL1 reduces the fraction of self-renewing 'leukemic' stem cells in the bone marrow but that some of these cells survive treatment with imatinib. This also seems to operate in humans. Data from models also strongly support the notion that JAK2(V617F) can initiate and sustain MPNs in mice; relevance to disease in humans is less clear. These data also support the hypothesis that level of JAK2(V617F) expression influences the MPN phenotype: higher levels favor erythrocytosis whereas lower levels favor thrombocytosis. Although TET2-mutations were thought to precede JAK2(V617F) in some persons with MPNs, it now appears that TET2 mutations may occur after JAK2(V617F). Further understanding of signal-transduction pathways activated in chronic myeloid leukemia suggests various possible targets for new therapies including the WNT/beta catenin, notch and hedgehog pathways. Finally, the clinical role of the new JAK2- and BCR-ABL1-inhibitors is considered. Much further progress is likely in several of these areas soon.

Targeting autophagy potentiates tyrosine kinase inhibitor-induced cell death in Philadelphia chromosome-positive cells, including primary CML stem cells

Imatinib mesylate (IM), a potent inhibitor of the BCR/ABL tyrosine kinase, has become standard first-line therapy for patients with chronic myeloid leukemia (CML), but the frequency of resistance increases in advancing stages of disease. Elimination of BCR/ABL-dependent intracellular signals triggers apoptosis, but it is unclear whether this activates additional cell survival and/or death pathways. We have shown here that IM induces autophagy in CML blast crisis cell lines, CML primary cells, and p210BCR/ABL-expressing myeloid precursor cells. IM-induced autophagy did not involve c-Abl or Bcl-2 activity but was associated with ER stress and was suppressed by depletion of intracellular Ca2+, suggesting it is mechanistically nonoverlapping with IM-induced apoptosis. We further demonstrated that suppression of autophagy using either pharmacological inhibitors or RNA interference of essential autophagy genes enhanced cell death induced by IM in cell lines and primary CML cells. Critically, the combination of a tyrosine kinase inhibitor (TKI), i.e., IM, nilotinib, or dasatinib, with inhibitors of autophagy resulted in near complete elimination of phenotypically and functionally defined CML stem cells. Together, these findings suggest that autophagy inhibitors may enhance the therapeutic effects of TKIs in the treatment of CML.

GCK is essential to systemic inflammation and pattern recognition receptor signaling to JNK and p38

Systemic inflammation arising from the organismal distribution of pathogen-associated molecular patterns is a major cause of clinical morbidity and mortality. Herein we report a critical and previously unrecognized in vivo role for germinal center kinase (GCK, genome nomenclature: map4k2), a mammalian Sterile 20 (STE20) orthologue, in PAMP signaling, and systemic inflammation. We find that disruption of gck in mice strongly impairs PAMP-stimulated macrophage cytokine and chemokine release and renders mice resistant to endotoxin-mediated lethality. Bone marrow transplantation studies show that hematopoietic cell GCK signaling is essential to systemic inflammation. Disruption of gck substantially reduces PAMP activation of macrophage Jun-N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs) via reduced activation of the MAPK-kinase-kinases (MAP3Ks) mixed lineage kinases (MLKs)-2 and -3. Extracellular signal-regulated kinase (ERK) and nuclear factor-kappaB (NF-kappaB) activation are largely unaffected. Thus, GCK is an essential PAMP effector coupling JNK and p38, but not ERK or NF-kappaB to systemic inflammation.

Suppression of E-protein activity interferes with the development of BCR-ABL-mediated myeloproliferative disease

E-proteins are a class of helix-loop-helix (HLH) proteins, which play multiple roles throughout lymphoid development. The DNA binding activities of the E-proteins are regulated by a distinct class of antagonistic HLH proteins, named Id1-4. Here we demonstrate that Id2 deficient mice in a C57BL/6 genetic background exhibit increased cellularity in the granulocyte/myeloid progenitor compartment and show significantly higher numbers of maturing neutrophils. Within 6 months of age, Id2 deficient mice succumbed from overwhelming granulocytosis. The disease closely mimicked the distinctive features of human chronic myeloid leukemia: leukocytosis with maturing neutrophils, splenomegaly, hepatomegaly, and myeloid infiltration into peripheral tissues, including spleen, liver, and lungs. Strikingly, forced Id2 expression in murine bone marrow cells substantially delayed the onset of myeloproliferative disease (MPD). Collectively, these studies show that suppression of E-protein activity interferes with the development of BCR-ABL-mediated MPD.

Peroxiredoxin1 prevents excessive endothelial activation and early atherosclerosis

The peroxiredoxin (Prdx) family of antioxidant enzymes uses redox-active cysteines to reduce peroxides, lipid hydroperoxides, and peroxynitrites. Prdx1 is known to be important to protect red blood cells against reactive oxygen species and in tumor prevention. In this study, the role of Prdx1 in inflammation, thrombosis, and atherosclerosis was investigated. Using intravital microscopy, we showed that the number of leukocytes rolling per minute in unstimulated veins was increased by 2.5-fold in Prdx1(-/-) compared to Prdx1(+/+) mice. In Prdx1(-/-) mice, 50% of leukocytes rolled at a velocity <10 mum/sec compared with 10% in Prdx1(+/+) mice, suggesting that adhesion molecule density on the endothelium may have been increased by Prdx1 deficiency. Indeed, endothelial P-selectin, soluble P-selectin, and von Willebrand factor in plasma were increased in Prdx1(-/-) mice compared to Prdx1(+/+) mice, indicating elevated Weibel-Palade body release. In contrast to this excessive endothelial activation, Prdx1(-/-) platelets showed no sign of hyperreactivity, and their aggregation both in vitro and in vivo was normal. We also examined the role of Prdx1 in the apoE(-/-) murine spontaneous model of atherosclerosis. Prdx1(-/-)/apoE(-/-) mice fed normal chow developed larger, more macrophage-rich aortic sinus lesions than Prdx1(+/+)/apoE(-/-) mice, despite similar amounts and size distributions of cholesterol in their plasma lipoproteins. Thus, Prdx1 protects against excessive endothelial activation and atherosclerosis, and the Prdx1(-/-) mice could serve as an animal model susceptible to chronic inflammation.

Comparison of mutated ABL1 and JAK2 as oncogenes and drug targets in myeloproliferative disorders

Constitutively activated mutants of the non-receptor tyrosine kinases (TK) ABL1 (Abelson murine leukemia viral (v-abl) homolog (1) protein) and JAK2 (JAnus Kinase 2 or Just Another Kinase 2) play a central role in the pathogenesis of clinically and morphologically distinct chronic myeloproliferative disorders but are also found in some cases of de novo acute leukemia and lymphoma. Ligand-independent activation occurs as a consequence of point mutations or insertions/deletions within functionally relevant regulatory domains (JAK2) or the creation of TK fusion proteins by balanced reciprocal translocations, insertions or episomal amplification (ABL1 and JAK2). Specific abnormalities are correlated with clinical phenotype, although some are broad and encompass several World Health Organization-defined entities. TKs are excellent drug targets as exemplified by the activity of imatinib in BCR-ABL1-positive disease, particularly chronic myeloid leukemia. Resistance to imatinib is seen in a minority of cases and is often associated with the appearance of secondary point mutations within the TK domain of BCR-ABL1. These mutations are highly variable in their sensitivity to increased doses of imatinib or alternative TK inhibitors such as nilotinib or dasatinib. Selective and non-selective inhibitors of JAK2 are currently being developed, and encouraging data from pre-clinical experiments and initial phase-I studies regarding efficacy and potential toxicity of these compounds have already been reported.

Production of replication-defective retrovirus by transient transfection of 293T cells

Our lab studies human myeloproliferative diseases induced by such oncogenes as Bcr-Abl or growth factor receptor-derived oncogenes (ZNF198-FGFR1, Bcr-PDGFRalpha, etc.). We are able to model and study a human-like disease in our mouse model, by transplanting bone marrow cells previously infected with a retrovirus expressing the oncogene of interest. Replication-defective retrovirus encoding a human oncogene and a marker (GFP, RFP, antibiotic resistance gene, etc.) is produced by a transient transfection protocol using 293T cells, a human renal epithelial cell line transformed by the adenovirus E1A gene product. 293 cells have the unusual property of being highly transfectable by calcium phosphate (CaPO4), with up to 50-80% transfection efficiency readily attainable. Here, we co-transfect 293 cells with a retroviral vector expressing the oncogene of interest and a plasmid that expresses the gag-pol-env packaging functions, such as the single-genome packaging constructs kat or pCL, in this case the EcoPak plasmid. The initial transfection is further improved by use of chloroquine. Stocks of ecotropic virus, collected as culture supernatant 48 hrs. post-transfection, can be stored at -80 degrees C and used for infection of cell-lines in view of transformation and in vitro studies, or primary cells such as mouse bone marrow cells, that can then be used for transplant in our mouse model.

Right on target: eradicating leukemic stem cells

Less than a third of adults with acute myeloid leukemia (AML) are cured by current treatments, emphasizing the need for new approaches to therapy. The discovery over a decade ago that myeloid leukemias originate from rare stem-like cells that can transfer the disease to immunodeficient mice suggested that these 'leukemia stem cells' (LSCs) are responsible for relapse of leukemia following conventional or targeted cancer therapy and that eradication of LSCs might be necessary to cure the disease permanently. Several recent studies have provided insight into the signaling pathways underlying the LSC phenotype and have also described approaches to eliminate LSCs with antibodies. Here, we review recent advances in LSC research and discuss novel therapeutic strategies to specifically target LSCs.

Molecular mechanisms of cardiotoxicity of tyrosine kinase inhibition

Cancer therapy has progressed remarkably in recent years. In no area has this been more apparent than in the development of "targeted therapies", particularly those using drugs that inhibit the activity of certain tyrosine kinases, activating mutations or amplifications of which are causal, or strongly contributory, to tumorigenesis. However, some of these therapies have been associated with toxicity to the heart. Here we summarize what is known about the cardiotoxicity of cancer drugs that target tyrosine kinases. We focus on basic mechanisms through which interruption of specific signalling pathways leads to cardiomyocyte dysfunction and/or death, and contrast this with therapeutic responses in cancer cells.