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Recent studies show that redox-active small molecules are selectively cytotoxic to chronic lymphocytic leukemia (CLL). Although elevated leveis of reactive oxygen species in CLL cells have been implicated, the molecular mechanism underlying this selectivity is unclear. In other cell types, the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway regulates the oxidative stress response. We found elevated Nrf2 signaling in untreated CLL cells compared with normal lymphocytes. Therefore, we tested 27 known electrophilic and antioxidant compounds with drug-like properties and determined their CLLoselective cytotoxicity and effect on Nrf2 signaling. The selected compounds were from five distinct structural classes; [alpha]-[beta] unsaturated carbonyls, isothiocyanates, sulfhydryl reactive metals, flavones, and polyphenols. Our results show that compounds containing [alpha]-[beta] unsaturated carbonyls, sulfhydryl reactive metals, and isothiocyanates are strong activators of Nrf2 in a reporter assay system and in primary human CLL based on increased expression of the Nrf2 target heme oxygenase-1. [alpha]-[beta] Unsaturated carbonylcontaining compounds were selectively cytotoxic to CLL, and Ioss of the [alpha]-[beta] unsaturation abrogated Nrf2 activity and CLL toxicity. The [alpha]-[beta] unsaturated carbonyl containing compounds ethacrynic acid and parthenolide activated Nrf2 in normal peripheral blood mononuclear cells, but had a less potent effect in CLL cells. Furthermore, ethacrynic acid bound directly to the Nrf2-negative regulator Kelch-like ECH-associated protein 1 (Keapl) in CLL cells. These experiments clocument the presence of Nrf2 signaling in human CLL and suggest that altered Nrf2 responses may contribute to the observed selective cytotoxicity of electrophilic compounds in this disease. antioxidant response | electrophilic stress response activators | natural product | dietary component doi/ 10.1073/pnas.1002890107

Chronic lymphocytic leukemia (CLL) is a malignant disease of small mature lymphocytes. Previous studies have shown that CLL B lymphocytes express relatively large amounts of CD74 mRNA relative to normal B cells. In the present study, we analyzed the molecular mechanism regulated by CD74 in B-CLL cells. The results presented here show that activation of cell-surface CD74, expressed at high levels from an early stage of the disease by its natural ligand, macrophage migration-inhibition factor (MIF), initiates a signaling cascade that contributes to tumor progression. This pathway induces NF-[kappa]B activation, resulting in the secretion of IL-8 which, in turn, promotes cell survival. Inhibition of this pathway leads to decreased cell survival. These findings could form the basis of unique therapeutic strategies aimed at blocking the CD74-induced, IL-8- dependent survival pathway. apoptosis | invariant chain

The amount of ZAP-70 protein in leukemia cells from patients with chronic lymphocytic leukemia can be used to determine their prognosis. If at least 20% of the leukemia cells produce ZAP-70, the patient will have a poor prognosis. If less than 20% of the leukemia cells produce ZAP-70, the patient will have a good prognosis. This was the conclusion of a study of 56 patients.

Chronic lymphocytic leukemia (CLL) is the most common form of adult leukemia in Western countries, and there is significant variability in survival within CLL clinical stages. Earlier studies showed that CLL cells produce and are usually growth inhibited by transforming growth factor [Beta] type 1 (TGF-[Beta]1), suggesting a mechanism for the clinically indolent course of most CLL. Here we studied the mechanism by which CLL cells from about one-third of the patients are insensitive to TGF-[Beta]1. Of the 13 patients studied, CLL cells isolated from the peripheral blood of 8 patients were sensitive to growth inhibition by TGF-[Beta]1, as determined by incorporation of tritiated thymidine, whereas those from 5 patients were completely resistant to TGF-[Beta]1. As judged by binding of radiolabeled TGF-[Beta]1 followed by cross-linking and immunoprecipitation with anti-receptor antisera, CLL cells sensitive to TGF-[Beta]1 exhibited normal cell surface expression of both types 1 and 2 TGF-[Beta] receptors. In contrast, all CLL cells resistant to TGF-[Beta]1 exhibited no detectable surface type I receptors able to bind TGF-[Beta]1, but normal expression of type II receptors. Both TGF-[Beta]1-sensitive and TGF-[Beta]1-resistant CLL cells contained normal amounts of both type 1 and type 2 receptor mRNAs. Specific loss of type 1 receptor expression represents a new mechanism by which cells acquire resistance to TGF-[Beta]1-mediated growth inhibition in the development and progression of human lymphoproliferative malignancies.

Background Chronic lymphocytic leukemia (CLL), the most common adulthood leukemia, is characterized by the accumulation of abnormal [CD5.sup.+] B lymphocytes, which results in a progressive failure of the immune system. Despite intense research efforts, drug resistance remains a major cause of treatment failure in CLL, particularly in patients with dysfunctional TP53. The objective of our work was to identify potential approaches that might overcome CLL drug refractoriness by examining the pro-apoptotic potential of targeting the cell surface receptor CD47 with serum-stable agonist peptides. Methods and Findings In peripheral blood samples collected from 80 patients with CLL with positive and adverse prognostic features, we performed in vitro genetic and molecular analyses that demonstrate that the targeting of CD47 with peptides derived from the C-terminal domain of thrombospondin-1 efficiently kills the malignant CLL B cells, including those from high-risk individuals with a dysfunctional TP53 gene, while sparing the normal T and B lymphocytes from the CLL patients. Further studies reveal that the differential response of normal B lymphocytes, collected from 20 healthy donors, and leukemic B cells to CD47 peptide targeting results from the sustained activation in CLL B cells of phospholipase C gamma-1 (PLC[gamma]1), a protein that is significantly over-expressed in CLL. Once phosphorylated at tyrosine 783, PLC[gamma]1 enables a [Ca.sup.2+]-mediated, caspase-independent programmed cell death (PCD) pathway that is not down-modulated by the lymphocyte microenvironment. Accordingly, down-regulation of PLC[gamma]1 or pharmacological inhibition of PLC[gamma]1 phosphorylation abolishes CD47-mediated killing. Additionally, in a CLL-xenograft model developed in NOD/scid gamma mice, we demonstrate that the injection of CD47 agonist peptides reduces tumor burden without inducing anemia or toxicity in blood, liver, or kidney. The limitations of our study are mainly linked to the affinity of the peptides targeting CD47, which might be improved to reach the standard requirements in drug development, and the lack of a CLL animal model that fully mimics the human disease. Conclusions Our work provides substantial progress in (i) the development of serum-stable CD47 agonist peptides that are highly effective at inducing PCD in CLL, (ii) the understanding of the molecular events regulating a novel PCD pathway that overcomes CLL apoptotic avoidance, (iii) the identification of PLC[gamma]1 as an over-expressed protein in CLL B cells, and (iv) the description of a novel peptide-based strategy against CLL., Introduction Chronic lymphocytic leukemia (CLL), a human malignancy caused by an imbalance between proliferation and programmed cell death (PCD) [1], is the most common form of leukemia in adults. CLL [...]

Patients with chronic lymphocytic leukemia (CLL) can develop anemia (decreased levels of hemoglobin in the blood, which carries oxygen to other cells in the body). Some patients, in the end stages of disease, have low levels of cells in their blood. Approximately 6 percent of CLL patients have red cell aplasia (failure to generate red blood cells). A certain subtype of T lymphocytes, T-gamma cells, contain receptors for immunoglobulin G molecules. These cells may inhibit the growth of precursor red blood cells in the bone marrow. Treatment with cyclosporin-A, an immune-suppressing agent, and antibody molecules which react specifically with T-gamma cells can stop the inhibition of the growth of red blood cells. A case study is reported on a patient with B-cell CLL whose numbers of blood cells were reduced because of the lack of all types of precursor cells in the bone marrow. This is the first time depletion of all precursor cells has been reported in patients with CLL. The patient was treated with corticosteroids and immunoglobulin with no success. However, when given antibodies to thymocytes, the levels of blood cells returned to normal. This indicates that T lymphocytes were responsible for the suppression of the growth of the cells in the bone marrow. (Consumer Summary produced by Reliance Medical Information, Inc.)