The role of interferon-alpha in the treatment of chronic myeloid leukemia

Biological agents have long been used in the treatment of cancer, and interferon-alpha was the first human cytokine to be widely studied in this setting. Chronic myeloid leukemia (CML) is a hematopoietic stem cell disorder for which interferon-alpha has demonstrated substantial activity. In the 1980s interferon-alpha became first-line therapy for patients with chronic-phase CML, not eligible for allogeneic stem cell transplantation. Following the discovery of the leukemic oncogene BCR/ABL and its causal association with CML, the potent BCR/ABL tyrosine kinase inhibitor imatinib mesylate was developed. Imatinib proved to be superior to interferon-alpha in all outcome measures, making imatinib the new standard of care for patients with CML. There is both clinical and laboratory evidence suggesting imatinib therapy alone is not curative in CML, whereas IFN has induced a low but reproducible curative effect in some patients. This unique activity may be the basis for the reincorporation of IFN into the management of CML. These observations may be best explained by imatinib's negligible activity against the leukemic stem cell (LSC) population. This review discusses the history of interferon-alpha in the treatment of CML, the evolution of molecularly targeted therapies, and some of the lessons we have learned from years of informative research in CML. It also explores the new challenge of managing minimal residual disease in the imatinib era, and addresses the promising role for LSC-directed therapies in the future treatment of CML.     

Methylenetetrahydrofolate reductase gene polymorphisms contribute to acute myeloid leukemia and chronic myeloid leukemia susceptibilities: Evidence from meta-analyses

PurposeThe expression of methylenetetrahydrofolate reductase (MTHFR) is associated with acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Most studies have linked the common functional C677T and A1298C polymorphisms of the MTHFR gene and susceptibility to AML and CML, but the results were not consistent. The aim of the present study was to derive a more precise estimation of the relationship.MethodsMeta-analyses assessing the association of MTHFR C677T and A1298C variations with AML and CML were conducted. Eligible articles were identified from the PubMed and EMBASE databases. All statistical analyses were conducted using Review Manager Software.Results10 and 10 studies were included in the meta-analysis about the role of C677T polymorphism on the AML and CML risks, respectively; 6 and 4 studies were included about the role of A1298C polymorphism on the AML and CML risks, respectively. Overall, both the C677T and A1298C polymorphisms were significantly associated with CML risk under the recessive model (P = 0.04, OR = 1.35, 95% CI = 1.02–1.79 for C677T and P = 0.003, OR = 2.17, 95% CI = 1.29–3.63 for A1298C). In addition, the risk of CML was higher in 1298CC genotype carriers than in 1298AA genotype carriers (P = 0.004, OR = 2.17, 95% = 1.28–3.69). Conversely, the overall data failed to indicate a significant association of C677T or A1298C polymorphisms with AML risk under any model.ConclusionsThe findings provide evidence that C677T and A1298C polymorphisms are risk factors for CML risk.     

Risk of adult acute and chronic myeloid leukemia with cigarette smoking and cessation

BackgroundCigarette smoking is an established risk factor for adult myeloid leukemia, particularly acute myeloid leukemia (AML), but less is known about the nature of this association and effects of smoking cessation on risk.MethodsIn a large population-based case–control study of myeloid leukemia that included 414 AML and 185 chronic myeloid leukemia (CML) cases and 692 controls ages 20–79 years, we evaluated risk associated with cigarette smoking and smoking cessation using unconditional logistic regression methods and cubic spline modeling.ResultsAML and CML risk increased with increasing cigarette smoking intensity in men and women. A monotonic decrease in AML risk was observed with increasing time since quitting, whereas for CML, the risk reduction was more gradual. For both AML and CML, among long-term quitters (≥30 years), risk was comparable to non-smokers.ConclusionsOur study confirms the increased risk of myeloid leukemia with cigarette smoking and provides encouraging evidence of risk attenuation following cessation.     

Aberrant expressions of leptin and adiponectin receptor isoforms in chronic myeloid leukemia patients

Background

Leptin and adiponectin receptors mediate the role of leptin in stimulating the growth of leukemic cells and the protective function of adiponectin undertaken in several malignancies such as leukemia. In this study, we investigated the involvement of the expression of leptin and adiponectin receptors in chronic myeloid leukemia (CML) pathogenesis.

Methods

The expression of leptin receptor isoforms, OB-Rt, OB-Ra, and OB-Rb, and the expression of adiponectin receptors, AdipoR1 and AdipoR2, were measured as mRNA levels in two CML cell lines (K562 and Meg-01) and 20 CML patients and 24 healthy controls by using RT-PCR.

Results

OB-Rt and OB-Ra isoforms expression of the leptin receptors were found to be significantly lower in Meg-01 cell lines than K562 cells. All leptin receptors were downregulated in CML patients and more particularly OB-Rb level was found to be undetectably low in normal PBMC as well as in CML patients. AdipoR1 expression level was higher in Meg-01 than in K562, whereas AdipoR2 level was found to be unchanged in both cell lines. Interestingly, while AdipoR1 expression increased in CML patients, AdipoR2 decreased. Moreover, imatinib therapy did not affect both leptin and adiponectin isoform expressions.

Conclusion

While the decrease in leptin receptor levels in CML patients was confirmed, the increase in AdipoR1 levels and relevant decrease in AdipoR2 levels depicted their possible involvement in CML pathogenesis. This suggests different functions of adiponectin receptors in CML development.     

Karyotypic findings in chronic myeloid leukemia cases undergoing treatment

BACKGROUND:

Chronic myeloid leukemia (CML) is a clonal myeloproliferative expansion of primitive hematopoietic progenitor cells.

MATERIALS AND METHODS:

In the present study, CML samples were collected from various hospitals in Amritsar, Jalandhar and Ludhiana.

RESULTS:

Chromosomal alterations seen in peripheral blood lymphocytes of these treated and untreated cases of CML were satellite associations, double minutes, random loss, gain of C group chromosomes and presence of marker chromosome. No aberrations were observed in control samples. Karyotypic abnormalities have also been noted in the Ph-negative cells of some patients in disease remission.

CONCLUSION:

This is a novel phenomenon whose prognostic implications require thorough and systematic evaluation.     

Exosomes derived from imatinib-resistant chronic myeloid leukemia cells mediate a horizontal transfer of drug-resistant trait by delivering miR-365

Chronic myeloid leukemia (CML) is a malignant disorder of hematopoietic stem/progenitor cells. Majority of patients can be effectively treated with tyrosine kinase inhibitors (TKIs) such as imatinib, but a portion of patients will develop drug resistance. Accumulated evidences have identified exosomes in cancer as promoters of tumor progression. Herein, we found that exosomes derived from imatinib resistant CML cells can be internalized into sensitive CML cells and confer drug-resistance traits. We also demonstrated a significant higher level of miR-365 in exosomes derived from drug-resistant CML cells compared with those from sensitive ones using microarray and qRT-PCR. The imatinib sensitive CML cells transfected with pre-miR-365 displayed lower chemosensitivity and apoptosis rate compared with controls. We further confirmed that exosomal transfer of miR-365 induced drug resistance by inhibiting expression of pro-apoptosis protein in sensitive CML cells. In conclusion, our study reveals that exosomes mediate a horizontal transfer of drug-resistant trait in chronic myeloid leukemia cell by delivering miR-365.     

The use of isobaric tag peptide labeling (iTRAQ) and mass spectrometry to examine rare,primitive hematopoietic cells from patients with chronic myeloid leukemia

Chronic Myeloid Leukemia (CML) is a hematopoietic stem cell disease, associated with a t(9, 22) chromosomal translocation leading to formation of the BCR/ABL chimeric protein, which has an intrinsic tyrosine kinase activity. Recently, the BCR/ABL tyrosine kinase inhibitor imatinib mesylate (imatinib) has been successfully used clinically, although, disease relapse can still occur. The precise detail of the mechanism by which CML cells respond to imatinib is still unclear. We therefore systematically examined the effects of imatinib on the primitive CML cell proteome, having first established that the drug inhibits proliferation and induces increased apoptosis and differentiation. To define imatinib-induced effects on the CML proteome, we employed isobaric tag peptide labeling (iTRAQ) coupled to two-dimensional liquid chromatography/tandem mass spectrometry. Given the limited clinical material available, the isobaric tag approach identified a large population of proteins and provided relative quantification on four samples at once. Novel consequences of the action of imatinib were identified using this mass spectrometric approach. DEAD-box protein 3, heat shock protein 105 kDa, and peroxiredoxin-3 were identified as potential protein markers for response to imatinib. Electronic Supplementary Material The online version of this article (doi: ) contains supplementary material, which is available to authorized users. Stephen D. Griffiths and John Burthem contributed equally to this publication. This work is supported by The Leukaemia Research Fund (UK).     

Spred2 is involved in imatinib-induced cytotoxicity in chronic myeloid leukemia cells

Spreds, a recently established class of negative regulators of the Ras-ERK (extracellular signal-regulated kinase) pathway, are involved in hematogenesises, allergic disorders and tumourigenesis. However, their role in hematologic neoplasms is largely unknown. Possible effects of Spreds on other signal pathways closely related to Ras-ERK have been poorly investigated. In this study, we investigated the in vitro effects of Spred2 on chronic myeloid leukemia (CML) cells. In addition to inhibiting the well-established Ras-ERK cascade, adenovirus-mediated Spred2 over-expression inhibits constitutive and stem cell factor (SCF)-stimulated sphingosine kinase-1 (SPHK1) and Mcl-1 expression, as well as inhibiting proliferation and inducing apoptosis in CML cells. In K562 cells and primary CML cells, imatinib induces endogenous Spred2 expression. Spred2 silencing by stable RNA interference partly protects K562 cells against imatinib-induced apoptosis. Together, these data implicate Spred2 in imatinib-induced cytotoxicity in CML cells, possibly by inhibiting the Ras-ERK cascade and the pro-survival signaling molecules SPHK1 and Mcl-1. These findings reveal potential targets for selective therapy of CML.     

Metoclopramide treatment blocks CD93-signaling-mediated self-renewal of chronic myeloid leukemia stem cells

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Comparative analysis of cell surface proteins in chronic and acute leukemia cell lines

This study was designed to identify the cell surface protein markers that can differentiate between chronic myeloid leukemia (CML) and acute promyelocytic leukemia cells (APL). The differentially expressed plasma membrane proteins were analyzed between CML cell line (K562) and APL cell line (NB4) using the comparative proteomic approach. The cell membrane proteins were enriched by labeling with a membrane-impermeable biotinylation reagent, sulfo-NHS-SS-Biotin, and subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS). By comparative proteomic analysis of K562 and NB4 cells, we identified 25 membrane and 14 membrane-associated proteins. The result of LC-MS/MS combined with chemical tagging method was validated by confirming the expression and localization of one of the differentially expressed plasma membrane proteins, CD43, by FACS and confocal microscopy. Our results indicate that CD43 could be a potential candidate for differentiating CML from APL.     

Use of moving optical gradient fields for analysis of apoptotic cellular responses in a chronic myeloid leukemia cell model

To facilitate quantitation of cellular apoptotic responses to various antineoplastic agents, a laser-based technology, Optophoresis, has been developed to provide analysis of cells without any need for labeling or cell processing. Optophoresis is defined as the analysis of the motion of cells, where the motion is either induced or modified by a moving optical gradient field, which produces radiation pressure forces on the cells in an aqueous suspension. Quantitation of the induced motion provides a basis for distinguishing one population of cells from another. One Optophoretic technique, Fast Scan, measures the distribution of distances traversed by a population of cells when exposed to a fast-moving optical gradient. Fast Scan was validated using a cell-based model of chronic myeloid leukemia treated with Gleevec, a specific inhibitor of aberrant Bcr-Abl protein kinase. The Optophoretic measurements were quantitatively comparable to reference assays with regard to drug selectivity and potency and to target specificity, demonstrating the suitability of this technology for pharmaceutical and clinical applications.     

Foetal liver infusion in a chronic myeloid leukemia patient with busulphan toxicity

A 36-year-old man suffering from chronic myeloid leukemia (in chronic phase) was initially treated with busulphan. At the end of 6 months of follow-up he developed bone marrow aplasia. He was given single foetal liver infusion therapy. The patient recovered fully from aplasia. He continued in chronic phase for more than 7 years with intermittent busulphan therapy.     

Betanin a betacyanin pigment purified from fruits of Opuntia ficus-indica induces apoptosis in human chronic myeloid leukemia Cell line-K562

Betalains are water-soluble nitrogenous vacuolar pigments present in flowers and fruits of many caryophyllales with potent antioxidant properties. In the present study the antiproliferative effects of betanin, a principle betacyanin pigment, isolated from the fruits of Opuntia ficus-indica, was evaluated on human chronic myeloid leukemia cell line (K562). The results show dose and time dependent decrease in the proliferation of K562 cells treated with betanin with an IC(50) of 40 microM. Further studies involving scanning and transmission electron microscopy revealed the apoptotic characteristics such as chromatin condensation, cell shrinkage and membrane blebbing. Agarose electrophoresis of genomic DNA of cells treated with betanin showed fragmentation pattern typical for apoptotic cells. Flow cytometric analysis of cells treated with 40 microM betanin showed 28.4% of cells in sub G0/G1 phase. Betanin treatment to the cells also induced the release of cytochrome c into the cytosol, poly (ADP) ribose polymerase (PARP) cleavage, down regulation Bcl-2, and reduction in the membrane potentials. Confocal microscopic studies on the cells treated with betanin suggest the entry of betanin into the cells. These studies thus demonstrate that betanin induces apoptosis in K562 cells through the intrinsic pathway and is mediated by the release of cytochrome c from mitochondria into the cytosol, and PARP cleavage. The antiproliferative effects of betanin add further value to the nutritional characteristics of the fruits of O. ficus-indica.     

The molecular signature of oncofusion proteins in acute myeloid leukemia

Acute myeloid leukemia (AML) associated translocations often cause gene fusions that encode oncofusion proteins. Although many of the breakpoints involved in chromosomal translocations have been cloned, in most cases the role of the chimeric proteins in tumorigenesis is not elucidated. Here we will discuss the fusion proteins of the 4 most common translocations associated with AML as well as the common molecular mechanisms that these four and other fusion proteins utilize to transform progenitor cells. Intriguingly, although the individual partners within the fusion proteins represent a wide variety of cellular functions, at the molecular level many commodities can be found.     

Characterization of p87C3G, a novel, truncated C3G isoform that is overexpressed in chronic myeloid leukemia and interacts with Bcr-Abl

A novel C3G isoform, designated p87C3G, lacking the most amino terminal region of the cognate protein has been found to be overexpressed in two CML cell lines, K562 and Boff 210, both expressing Bcr-Abl p210. p87C3G expression is also highly augmented in patients diagnosed with chronic myeloid leukemia (CML) Ph+, in comparison with healthy individuals, and returns to basal levels after treatment with STI571. p87C3G co-immunoprecipitates with both CrkL and Bcr-Abl in CML cell lines and co-immunoprecipitation between p87C3G and Bcr-Abl was also detected in primary cells from CML patients. These interactions have been confirmed by in vitro pull down experiments. The interaction between p87C3G and Bcr-Abl involves the SH3-binding domain of p87C3G and the SH3 domain of Abl and depends mostly on the first polyproline region of p87C3G. Furthermore, we also demonstrated that p87C3G is phosphorylated in vitro by a Bcr-Abl-dependent mechanism. These results indicate that p87C3G overexpression is linked to CML phenotype and that p87C3G may exert productive functional interactions with Bcr-Abl signaling components suggesting the implication of this C3G isoform in the pathogenesis of chronic myeloid leukemia.     

Role of P-glycoprotein in evolution of populations of chronic myeloid leukemia cells treated with imatinib

Imatinib mesylate (imatinib) is a new generation preparation that is now successfully used for treatment of cancer, particularly for chemotherapy of chronic myeloid leukemia (CML). Imatinib inhibits the activity of chimeric kinase BCR-ABL, which is responsible for the development of CML. The goal of this study was to investigate the role of a multidrug resistance protein, P-glycoprotein (Pgp), in the evolution of CML treated with imatinib. We demonstrate here that although imatinib is a substrate for Pgp, cultured CML cells (strain K562/i-S9), overexpressing active Pgp, do not exhibit imatinib resistance. Studies of CML patients in the accelerated phase have shown variations in the number of Pgp-positive cells (Pgp+) among individual patients treated with imatinib. During treatment of patients with imatinib for 6-12 months, the number of Pgp-positive cells significantly increased in most patients. The high number of Pgp+ cells remained in patients at least for 4.5 years and correlated with active Rhodamine 123 (Rh123) efflux. Such correlation was not found in the group of imatinib-resistant patients examined 35-60 months after onset of imatinib therapy: cells from the imatinib-resistant patients exhibited efficient Rh123 efflux irrespectively of Pgp expression. We also compared the mode of Rh123 efflux by cells from CML patients who underwent imatinib treatment for 6-24 months and the responsiveness of patients to this therapy. There were significant differences in survival of patients depending on the absence or the presence of Rh123 efflux. In addition to Pgp, patients' cells expressed other transport proteins of the ABC family. Our data suggest that treatment with imatinib causes selection of leukemic stem cells characterized by expression of Pgp and other ABC transporters.     

Targeting leukemia stem cells: The new goal of therapy in adult acute myeloid leukemia

The most popular view of hematopoietic cell lineage organization is that of complex reactive or adaptative systems. Leukemia contains a subpopulation of cells that display characteristics of stem cells. These cells maintain tumor growth. The properties of leukemia stem cells indicate that current conventional chemotherapy, directed against the bulk of the tumor, will not be effective. Leukemia stem cells are quiescent and do not respond to cell cycle-specific cytotoxic agents used to treat leukemia and thus contribute to treatment failure. New strategies are required that specifically target this malignant stem cell population.