Versha Banerji

The intersection of genetic and chemical genomic screens identifies GSK-3α as a target in human acute myeloid leukemia

Acute myeloid leukemia (AML) is the most common form of acute leukemia in adults. Long-term survival of patients with AML has changed little over the past decade, necessitating the identification and validation of new AML targets. Integration of genomic approaches with small-molecule and genetically based high-throughput screening holds the promise of improved discovery of candidate targets for cancer therapy. Here, we identified a role for glycogen synthase kinase 3α (GSK-3α) in AML by performing 2 independent small-molecule library screens and an shRNA screen for perturbations that induced a differentiation expression signature in AML cells. GSK-3 is a serine-threonine kinase involved in diverse cellular processes, including differentiation, signal transduction, cell cycle regulation, and proliferation. We demonstrated that specific loss of GSK-3α induced differentiation in AML by multiple measurements, including induction of gene expression signatures, morphological changes, and cell surface markers consistent with myeloid maturation. GSK-3α-specific suppression also led to impaired growth and proliferation in vitro, induction of apoptosis, loss of colony formation in methylcellulose, and anti-AML activity in vivo. Although the role of GSK-3β has been well studied in cancer development, these studies support a role for GSK-3α in AML.

High incidence of chronic lymphocytic leukemia (CLL) diagnosed by immunophenotyping: A population-based Canadian cohort

Incidence and outcomes of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) are not well established at the population level, especially since the widespread use of immunophenotyping. We studied the epidemiology of CLL in Manitoba (Canada) by combining data from a centralized flow cytometry facility and the provincial cancer registry for the period 1998-2003. Of 616 cases identified, 27% of patients identified by flow cytometry were not on the cancer registry. The age-adjusted incidence of 7.99/100,000 is substantially higher than the reported incidence in registry reports. We also noted differences in relative survival based on age and gender.

SYK regulates mTOR signaling in AML

Spleen tyrosine kinase (SYK) was recently identified as a new target in acute myeloid leukemia (AML); however, its mechanistic role in this disease is poorly understood. Based on the known interaction between SYK and mammalian target of rapamycin (mTOR) signaling in lymphoma, we hypothesized that SYK may regulate mTOR signaling in AML. Both small-molecule inhibition of SYK and SYK-directed shRNA suppressed mTOR and its downstream signaling effectors, as well as its upstream activator, AKT. Moreover, the inhibition of multiple nodes of the phosphatidylinositol 3′-kinase (PI3K) signaling pathway enhanced the effects of SYK suppression on AML cell viability and differentiation. Evaluation of the collateral mitogen-activated protein kinase (MAPK) pathway revealed a heterogeneous response to SYK inhibition in AML with downregulation of MEK and extracellular signal–regulated kinase (ERK) phosphorylation in some AML cell lines but a paradoxical increase in MEK/ERK phosphorylation in RAS-mutated AML. These studies reveal SYK as a regulator of mTOR and MAPK signaling in AML and demonstrate that inhibition of PI3K pathway activity enhances the effects of SYK inhibition on AML cell viability and differentiation.

On-Target Effect of FK866, a Nicotinamide Phosphoribosyl Transferase Inhibitor, by Apoptosis-Mediated Death in Chronic Lymphocytic Leukemia Cells

Purpose: Chronic lymphocytic leukemia (CLL) remains incurable despite advances in therapy. In this study, we characterize the effect of nicotinamide phosphoribosyltransferase (NAMPT) inhibition by FK866 in primary CLL cells from patients with various clinical prognostic markers. Experimental Design: CLL cells were treated with FK866 to assess viability by Annexin V/PI staining. Functional analysis of FK866 included time- and concentration-dependent evaluation of cellular NAD, ATP, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), and apoptotic signaling. Chemosensitization potential by FK866 to fludarabine was also assessed. Prognostic markers were correlated with drug response. Results: FK866 induced CLL cell death by depleting cellular NAD content by day 1, followed by a drop in ATP on day 2. We observed loss of MMP, ROS increase, and induction of apoptotic signaling at day 3. On-target activity of FK866 was confirmed by NAD-mediated rescue of NAD and ATP loss, apoptotic signaling, and viability. The response to FK866 was independent of most prognostic markers. Higher doses were required with short lymphocyte doubling time and positive CD38 status, whereas CLL cells resistant to fludarabine in vitro and from patients with del17p13.1 were equally sensitive to FK866. FK866 did not upregulate the p53-target p21, nor did the p53 activator Nutlin improve FK866-mediated cell death. Furthermore, fludarabine and FK866 were synergistic at clinically relevant concentrations. Conclusions: NAMPT inhibition by FK866 may be a potential treatment for CLL, including patients with del17p13.1 or other high-risk features. FK866 may complement standard agents to enhance their efficacy and/or allow dose reduction for improved tolerability. Clin Cancer Res; 20(18); 4861–72. ©2014 AACR.

Ventricular arrhythmias and sudden death in patients taking ibrutinib

To the editor: Ibrutinib, approved by the US Food and Drug Administration (FDA), is an inhibitor of Bruton tyrosine kinase (BTK).[1][1][⇓][2][⇓][3][⇓][4]-[5][5] Ibrutinib use is associated with atrial fibrillation (AF), with an incidence of 5% to 6% after 18 months on therapy[4][4][⇓][5]-[6

Lysophosphatidic acid (LPA) induces the expression of VEGF leading to protection against apoptosis in B-cell derived malignancies

Vascular endothelial growth factor (VEGF) is a survival and angiogenesis factor that is a target for therapy in a variety of cancers. In many hematological malignancies, VEGF production is increased leading to cell survival responses. Herein, we demonstrate that lysophosphatidic acid (LPA) induces mRNA expression of VEGF in the multiple myeloma cell line, U266, the Burkitts lymphoma cell line, BJAB, and the chronic lymphocytic leukemia (CLL)-like cell line, I-83. This increase in mRNA levels of VEGF corresponded with increased luciferase activity of the VEGF promoter in BJAB and I-83 cells and increased protein levels in I-83 cells. Secretion of VEGF was also increased in these cells following LPA treatment. LPA treatment also caused the activation of both VEGFR1 and VEGFR2. The increase in VEGF expression by LPA is mediated by the activation of c-Jun N-terminal Kinase (JNK) and transcription factor NFkappaB since blocking JNK or NFkappaB activation inhibited LPA induced VEGF expression. Furthermore, we have demonstrated that LPA protects cells from apoptosis and blocking activation of both VEGFR1 and VEGFR2 using a VEGF receptor kinase inhibitor prevented LPA survival responses. Knocking down expression of VEGFR1 and inhibiting activation of NFkappaB and JNK also blocked LPA induced protection against apoptosis. Taken together, this indicates that LPA contributes to VEGF production in B cell malignancies leading to cell survival.

Consensus guidelines for the diagnosis and management of patients with classic hairy cell leukemia

Hairy cell leukemia is an uncommon hematologic malignancy characterized by pancytopenia and marked susceptibility to infection. Tremendous progress in the management of patients with this disease has resulted in high response rates and improved survival, yet relapse and an appropriate approach to re-treatment present continuing areas for research. The disease and its effective treatment are associated with immunosuppression. Because more patients are being treated with alternative programs, comparison of results will require general agreement on definitions of response, relapse, and methods of determining minimal residual disease. The development of internationally accepted, reproducible criteria is of paramount importance in evaluating and comparing clinical trials to provide optimal care. Despite the success achieved in managing these patients, continued participation in available clinical trials in the first-line and particularly in the relapse setting is highly recommended. The Hairy Cell Leukemia Foundation convened an international conference to provide common definitions and structure to guide current management. There is substantial opportunity for continued research in this disease. In addition to the importance of optimizing the prevention and management of the serious risk of infection, organized evaluations of minimal residual disease and treatment at relapse offer ample opportunities for clinical research. Finally, a scholarly evaluation of quality of life in the increasing number of survivors of this now manageable chronic illness merits further study. The development of consensus guidelines for this disease offers a framework for continued enhancement of the outcome for patients.

Increased risk of second malignancies in chronic lymphocytic leukaemia patients as compared with follicular lymphoma patients: a Canadian population-based study

Background:Chronic lymphocytic leukaemia (CLL) patients have an increased risk of other malignancies. This may be due to surveillance bias, treatment or immunosuppression.Methods:Cohort study of 612 consecutively diagnosed CLL patients in a Canadian province, with comparisons to follicular lymphoma (FL) patients.Results:Treated CLL patients had a 1.7-fold increased risk of second cancers compared with untreated CLL patients. As compared with untreated FL patients, untreated CLL patients had a two-fold increased incidence of second malignancies.Conclusion:Chronic lymphocytic leukaemia patients have an inherent predisposition to second cancers and the incidence is further increased by treatment.

Targeting MTHFD2 in acute myeloid leukemia

Pikman et al. demonstrate that the mitochondrial enzyme MTHFD2 is a potential therapeutic target in acute myeloid leukemia.

Targeting Metabolism and Autophagy in the Context of Haematologic Malignancies

Autophagy is a cellular process that maintains the homeostasis of the normal cell. It not only allows for cell survival in times of metabolic stress with nutrient recycling but also is able to lead to cell death when required. During malignant transformation the cell is able to proliferate and survive. This is due to altered cell metabolism and the presence of altered genetic changes that maintain the cell survival. Metabolism was considered an innocent bystander that was a consequence of the increased nutrient requirement for the survival and proliferation of haematological malignancies. The interdependency of metabolism and cellular mechanisms such as autophagy are becoming more evident and important. This interdependence contributes to increased cancer progression and drug resistance. In this paper we aim to discuss autophagy, how it pertains to metabolism in the context of hematologic malignancies, and the implications for therapy.