Primary del 17 chronic lymphocytic leukaemia lymphocytes are hypersensitive to dasatinib in vitro

Combined chronic myeloid leukaemia and chronic lymphocytic leukaemia in five patients, including one with 17p deletion

We report a series of five Australian cases of chronic lymphocytic leukaemia (CLL) occurring concurrently with chronic myeloid leukaemia (CML). Patient management including therapies and response together with clinical progress was obtained from medical records and laboratory information systems. Prior to CML diagnosis, all five had a preceding diagnosis of CLL. Three had received prior fludarabine. All received tyrosine kinase inhibitors (TKI). None required subsequent therapy for CLL. One patient had 17p deletion CLL and another patient had normal CLL cytogenetics. All currently have satisfactory blood counts with quantitative polymerase chain reaction for CML showing molecular response. All remain alive. Thus, such cases can be successfully managed by treating each haematological disorder in the usual manner. The control achieved in CML with the TKI enables satisfactory marrow function to recover in patients with concomitant CLL. The role for allograft in patients with dual malignancies is uncertain and needs to be individualised depending on control of each malignancy.

Metabolic rewiring beyond Warburg in chronic lymphocytic leukemia: How much do we actually know?

Chronic Lymphocytic Leukemia (CLL) is the most common adult leukemia in the western world. CLL consists of the accumulation of malignant B-cells in the blood stream and homing tissues. Although treatable, this disease is not curable, and resistance or relapse is often present. In many cancers, the study of metabolic reprograming has uncovered novel targets that are already being exploited in the clinic. However, CLL metabolism is still poorly understood. The ability of CLL lymphocytes to adapt to diverse microenvironments is accompanied by modifications in cell metabolism, revealing the challenge of targeting the CLL lymphocytes present in all different compartments. Despite this, the study of CLL metabolism led to an ongoing clinical trial using glucose uptake and mitochondrial respiration inhibitors. In contrast, glutamine and fatty acid metabolism remain to be further exploited in CLL. Here, we summarize the present knowledge of CLL metabolism, as well as the metabolic influence of Myc, ATM and p53 on CLL lymphocytes.

Ibrutinib Resistance Is Reduced by an Inhibitor of Fatty Acid Oxidation in Primary CLL Lymphocytes

Chronic Lymphocytic Leukemia (CLL) is an incurable disease, characterized by the accumulation of malignant B-lymphocytes in the blood stream (quiescent state) and homing tissues (where they can proliferate). In CLL, the targeting of B-cell receptor signaling through a Burton's tyrosine kinase inhibitor (ibrutinib) has rendered outstanding clinical results. However, complete remission is not guaranteed due to drug resistance or relapse, revealing the need for novel approaches for CLL treatment. The characterization of metabolic rewiring in proliferative cancer cells is already being applied for diagnostic and therapeutic purposes, but our knowledge of quiescent cell metabolism—relevant for CLL cells—is still fragmentary. Recently, we reported that glutamine metabolism in primary CLL cells bearing the del11q deletion is different from their del11q negative counterparts, making del11q cells especially sensitive to glutaminase and glycolysis inhibitors. In this work, we used our primary CLL lymphocyte bank and compounds interfering with central carbon metabolism to define metabolic traits associated with ibrutinib resistance. We observe a differential basal metabolite uptake linked to ibrutinib resistance, favoring glutamine uptake and catabolism. Upon ibrutinib treatment, the redox balance in ibrutinib resistant cells is shifted toward NADPH accumulation, without an increase in glutamine uptake, suggesting alternative metabolic rewiring such as the activation of fatty acid oxidation. In accordance to this idea, the curtailing of fatty acid oxidation by CPT1 inhibition (etomoxir) re-sensitized resistant cells to ibrutinib. Our results suggest that fatty acid oxidation could be explored as a target to overcome ibrutinib resistance.

The phosphatidylinositol-3 kinase I inhibitor BKM120 induces cell death in B-chronic lymphocytic leukemia cells in vitro

BKM120, a pan class I PI3K inhibitor, was cytotoxic in the majority of primary B-chronic lymphocytic leukemia (CLL) lymphocytes, including samples from patients who have a high-risk for poor response to treatment (patient with del11 and del17) at clinically obtainable concentrations. The PI3Kδ inhibitor Cal-101 is cytotoxic in B-CLL lymphocytes in vitro and is active in the treatment of CLL in vivo. Interestingly, we demonstrated that BKM120 is 3.6 fold more toxic than Cal-101 in malignant B-CLL lymphocytes in vitro. BKM120 cytotoxicity correlated with the basal expression of proteins involved in the PI3K/Akt pathway. A protein signature of PI3K pathway proteins predicts the response to BKM120 treatment. In the primary B-CLL lymphocytes tested in vitro, BKM120 decreased the phosphorylation status of molecular biomarkers used as indicators of PI3K pathway inhibition in vivo. Also, BKM120 induced apoptosis in primary B-CLL cells culture in the presence and absence of stromal cell support. Our findings suggest that BKM120 should be tested clinically in CLL.

Protein kinases: emerging therapeutic targets in chronic lymphocytic leukemia

INTRODUCTION

Although protein kinases are primary targets for inhibition in hematological malignancies, until recently their contribution to chronic lymphocytic leukemia (CLL) was poorly understood. Insights into B-cell receptor signaling and its role in regulating key cellular functions have shed light on candidate protein kinases that are aberrantly activated in CLL. In this regard, protein kinases are now considered as potential drug targets in CLL.

AREA COVERED

This review has covered signaling pathways and associated protein kinases in CLL and the kinase inhibitors currently available in preclinical and clinical investigations. Individual protein kinases that are abnormally active in CLL and the functional consequences of their inhibition are discussed.

EXPERT OPINION

A growing body of evidence suggests that protein kinases are druggable targets for patients with CLL. The emergence of novel and bio-available kinase inhibitors and their promising clinical activity in CLL underscore the oncogenic role of kinases in leukemogenesis. Further investigations directed towards their role as single agents or in combinations may provide insight into understanding the substantial role of kinase-mediated signal transduction pathways and their inhibition in B- CLL.

Dasatinib plus Nutlin-3 shows synergistic antileukemic activity in both p53 wild-type and p53 mutated B chronic lymphocytic leukemias by inhibiting the Akt pathway

PURPOSE

To analyze the effect of the combination of Dasatinib, a multikinase inhibitor, plus Nutlin-3, a nongenotoxic activator of the p53 pathway, in primary B chronic lymphocytic leukemia (B-CLL) patient samples and B leukemic cell line models.

EXPERIMENTAL DESIGN

The induction of cytotoxicity was evaluated in both primary B-CLL cell samples (n = 20) and in p53(wild-type) (EHEB, JVM-2) and p53(deleted/mutated) (MEC-2, BJAB) B leukemic cell lines. The role of Akt in modulating leukemic cell survival/apoptosis in response to Dasatinib or Dasatinib + Nutlin-3 was documented by functional experiments carried out using specific pharmacological inhibitors and by overexpression of membrane-targeted constitutively active form of Akt.

RESULTS

The combination of Dasatinib + Nutlin-3 exhibited a synergistic cytotoxicity in the majority (19 out of 20) of B-CLL samples, including patients carrying 17p- (n = 4), and in both p53(wild-type) and p53(deleted/mutated) B leukemic cell lines. At the molecular level, Dasatinib significantly counteracted the Nutlin-3-mediated induction of the p53 transcriptional targets MDM2 and p21 observed in p53(wild-type) leukemic cells. Conversely, Nutlin-3 did not interfere with the ability of Dasatinib to decrease the phosphorylation levels of ERK1/2, p38/MAPK, and Akt in both p53(wild-type) and p53(deleted/mutated) B leukemic cell lines. A critical role of Akt downregulation in mediating the antileukemic activity of Dasatinib and Dasatinib + Nutlin-3 was demonstrated in experiments carried out by specifically modulating the Akt pathway.

CONCLUSIONS

These findings suggest that Dasatinib + Nutlin-3 might represent an innovative therapeutic combination for both p53(wild-type) and p53(deleted/mutated) B-CLL.

p53 and autophagy contribute to dasatinib resistance in primary CLL lymphocytes

B-cell chronic lymphocytic leukemia (CLL) is the most common leukemia in adults and there is no cure for the disease. Although dasatinib is cytotoxic to primary CLL lymphocytes in vitro, the drug has been shown to be active in a small percent of CLL patients. Our previous results suggest that dasatinib targets del17 CLL lymphocytes which are the CLL patients with the worst prognosis. Here we present mechanistic evidence that dasatinib induces endoplasmic reticulum stress and autophagy in CLL lymphocytes. Furthermore we provide evidence suggesting that autophagy mediates resistance to the drugs, process that is modulated by p53.