[Show abstract][Hide abstract] ABSTRACT: Clinical trials with SRC family kinases (SFKs) inhibitors used alone or in a combination with anti-CD20 monoclonal antibodies (mAbs) are currently underway in the treatment of B-cell tumors. However, molecular interactions between these therapeutics have not been studied so far. A transcriptional profiling of tumor cells incubated with SFKs inhibitors revealed strong downregulation of MS4A1 gene encoding CD20 antigen. In a panel of primary and established B-cell tumors, we observed that SFKs inhibitors strongly affect CD20 expression at the transcriptional level, leading to inhibition of anti-CD20 mAbs binding and increased resistance of tumor cells to complement-dependent cytotoxicity. Activation of the AKT signaling pathway significantly protected cells from dasatinib-triggered CD20 downregulation. Additionally, SFKs inhibitors suppressed antibody-dependent cellular cytotoxicity by direct inhibition of natural killer cells. Abrogation of antitumor activity of rituximab was also observed in vivo in a mouse model. Noteworthy, the effects of SFKs inhibitors on NK cell function are largely reversible. The results of our studies indicate that development of optimal combinations of novel treatment modalities with anti-CD20 mAbs should be preceded by detailed preclinical evaluation of their effects on target cells.
[Show abstract][Hide abstract] ABSTRACT: A number of single nucleotide polymorphisms have been associated with disease predisposition in chronic lymphocytic leukemia. A single nucleotide polymorphism in the MDM2 promotor region, MDM2SNP309, was shown to soothe the p53 pathway. In the current study, we aimed to clarify the effect of the MDM2SNP309 on chronic lymphocytic leukemia characteristics and outcome. We performed a meta-analysis of data from 2598 individual patients from 10 different cohorts. Patients' data and genetic analysis for MDM2SNP309 genotype, immunoglobulin heavy chain variable region mutation status and fluorescence in situ hybridization results were collected. There were no differences in overall survival based on the polymorphism (log rank test, stratified by study cohort; P=0.76; GG genotype: cohort-adjusted median overall survival of 151 months; TG: 153 months; TT: 149 months). In a multivariable Cox proportional hazards regression analysis, advanced age, male sex and unmutated immunoglobulin heavy chain variable region genes were associated with inferior survival, but not the MDM2 genotype. The MDM2SNP309 is unlikely to influence disease characteristics and prognosis in chronic lymphocytic leukemia. Studies investigating the impact of individual single nucleotide polymorphisms on prognosis are often controversial. This may be due to selection bias and small sample size. A meta-analysis based on individual patient data provides a reasonable strategy for prognostic factor analyses in the case of small individual studies. Individual patient data-based meta-analysis can, therefore, be a powerful tool to assess genetic risk factors in the absence of large studies.
[Show abstract][Hide abstract] ABSTRACT: Mutations in TP53, NOTCH1, and SF3B1 were analyzed in the CLL8 study evaluating first-line therapy with fludarabine and cyclophosphamide (FC) or FC with rituximab (FCR). TP53, NOTCH1, and SF3B1 were mutated in 11.5%, 10.0%, and 18.4% of patients, respectively. While NOTCH1(mut) and SF3B1(mut) virtually showed mutual exclusivity (0.6% concurrence), TP53(mut) was frequently found in NOTCH1(mut) (16.1%) and in SF3B1(mut) (14.0%) patients. There were few significant associations with clinical and laboratory characteristics but genetic markers had strong influence on response and survival. In multivariable analyses, an independent prognostic impact was found for FCR, thymidine kinase (TK) ≥10, unmutated IGHV, 11q deletion, 17p deletion, TP53(mut), and SF3B1(mut) on progression-free survival; and of FCR, age ≥65 years, ECOG performance status ≥0, β2-microglobulin ≥3.5, TK ≥10, unmutated IGHV, 17p deletion, and TP53(mut) on overall survival. Notably, predictive marker analysis identified an interaction of NOTCH1 mutational status and treatment, in that rituximab failed to improve response and survival in patients with NOTCH1(mut). In conclusion, TP53 and SF3B1 mutations appear among the strongest prognostic markers in CLL patients receiving current standard first-line therapy. NOTCH1(mut) was identified as a predictive marker for decreased benefit from the addition of rituximab to FC (FCR). This study is registered at ClinicalTrials.gov, identifier: NCT00281918.
[Show abstract][Hide abstract] ABSTRACT: In a single-center retrospective donor versus no-donor comparison, we investigated if allogeneic stem cell transplantation (alloSCT) can improve the dismal course of poor-risk chronic lymphocytic leukemia (CLL).
All patients with CLL who were referred for evaluation of alloSCT within a 7-year time frame and had a donor search indication according to the EBMT criteria or because of Richter's transformation were included. Patients for whom a matched donor could be found within 3 months (matches) were compared with patients without such a donor (controls). Primary end point was overall survival measured from the 3-month landmark after search initiation.
Of 105 patients with donor search, 97 (matches 83; controls 14) were assessable at the 3-month landmark. Matches and controls were comparable for age, gender, time from diagnosis, number of previous regimens, and remission status. Disregarding if alloSCT was actually carried out or not, survival from the 3-month landmark was significantly better in matches versus controls [hazard ratio 0.38, 95% confidence interval (CI) 0.17-0.85; P = 0.014]. The survival benefit of matches remained significant on multivariate analysis.
This study provides first comparative evidence that alloSCT may have the potential to improve the natural course of poor-risk CLL as defined by the EBMT criteria.
Full-text · Article · Jan 2014 · Annals of Oncology
[Show abstract][Hide abstract] ABSTRACT: Although clonal selection by genetic driver aberrations in cancer is well documented, the ability of epigenetic alterations to promote tumor evolution is undefined. We used 450k arrays and next-generation sequencing to evaluate intra-tumor heterogeneity and evolution of DNA methylation and genetic aberrations in chronic lymphocytic leukemia (CLL). CLL cases exhibit vast inter-patient differences in intra-tumor methylation heterogeneity, with genetically clonal cases maintaining low methylation heterogeneity and up to 10 percent of total CpGs in a monoallelically methylated state. Increasing methylation heterogeneity correlates with advanced genetic subclonal complexity. Selection of novel DNA methylation patterns is observed only in cases that undergo genetic evolution, and independent genetic evolution is uncommon and is restricted to low-risk alterations. These results reveal that although evolution of DNA methylation occurs in high-risk, clinically-progressive cases, positive selection of novel methylation patterns entail co-evolution of genetic alteration(s) in CLL.
No preview · Article · Dec 2013 · Cancer Discovery
[Show abstract][Hide abstract] ABSTRACT: Chronic lymphocytic leukemia (CLL) is an incurable malignancy of mature B cells. One of the major challenges in treatment of CLL is the achievement of a complete remission to prevent relapse of disease originating from cells within lymphoid tissues and subsequent chemoresistance. In search for novel drugs that target CLL cells also in protective microenvironments, we performed a fungal extract screen using cocultures of primary CLL cells with bone marrow-derived stromal cells. A metabolite produced by Penicillium aquamarinium was identified as Chaetoglobosin A, a member of the cytochalasan family that showed preferential induction of apoptosis in CLL cells, even under culture conditions that mimic lymphoid tissues. In vitro testing of 89 CLL cases revealed effective targeting of CLL cells by Chaetoglobosin A, independent of bad prognosis characteristics, like 17p deletion or TP53 mutation. To provide insight into its mechanism of action, we showed that ChA targets filamentous actin in CLL cells and thereby induces cell cycle arrest and inhibits membrane ruffling and cell migration. Our data further revealed that Chaetoglobosin A prevents CLL cell activation and sensitizes them for treatment with PI3K and BTK inhibitors, suggesting this compound as a novel potential drug for CLL.Leukemia accepted article preview online, 27 November 2013. doi:10.1038/leu.2013.360.
Full-text · Article · Nov 2013 · Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K
[Show abstract][Hide abstract] ABSTRACT: Recurrent gene mutations contribute to the pathogenesis of chronic lymphocytic leukaemia (CLL). We developed a next-generation sequencing (NGS) platform to determine the genetic profile, intratumoural heterogeneity, and clonal structure of two independent CLL cohorts. TP53, SF3B1, and NOTCH1 were most frequently mutated (16·3%, 16·9%, 10·7%). We found evidence for subclonal mutations in 67·5% of CLL cases with mutations of cancer consensus genes. We observed selection of subclones and found initial evidence for convergent mutations in CLL. Our data suggest that assessment of (sub)clonal structure may need to be integrated into analysis of the mutational profile in CLL.
No preview · Article · Aug 2013 · British Journal of Haematology
[Show abstract][Hide abstract] ABSTRACT: Aminoferrocene-based prodrugs are activated at cancer specific conditions (high concentration of reactive oxygen species, ROS) with formation of glutathione scavengers (p-quinone methide) and ROS-generating iron complexes. Herein we explored three structural modifications of these prodrugs with an attempt to improve their properties: (a) attachment of a -COOH function to the ferrocene fragment leads to the improvement of water solubility and reactivity in vitro, but also decreases cell membrane permeability and biological activity; (b) alkylation of the N-benzyl residue does not show any significant affect; (c) attachment of the second arylboronic acid fragment improves toxicity (IC50) of the prodrugs towards human promyelocytic leukemia cells (HL-60) from 52 to 12 µM. Finally, we demonstrated that the prodrugs are active against primary chronic lymphotic leukemia (CLL) cells with the best compounds exhibiting IC50 value of 1.5 µM. These most active compounds were found not to affect mononuclear cells and representative bacterial cells.
Full-text · Article · Aug 2013 · Journal of Medicinal Chemistry
[Show abstract][Hide abstract] ABSTRACT: Abstract Extracellular vesicles (EVs) are membrane-enclosed nanoparticles 30 to 1000 nm in size and represent a novel mechanism of cell communication. By transferring RNA and protein from their cell of origin, they can reprogram target cells and thus are involved in changes within the cellular microenvironment - a key player in CLL pathogenesis. In the current study, we were able to isolate EVs of 20 to 300 nm from blood plasma of CLL patients as well as from supernatant of primary CLL cells in culture. Further, proteomic profiling by Coomassie staining of SDS-PAGE gels and by mass spectrometry revealed an EV-specific protein profile. These findings suggest that EVs represent an important mean of CLL cells to interact with other cells, which might contribute to the establishment of a pro-survival microenvironment for CLL cells.
No preview · Article · Aug 2013 · Leukemia & lymphoma
[Show abstract][Hide abstract] ABSTRACT: The ATM–p53 DNA damage response pathway plays a crucial role in chemoresistance in chronic lymphocytic leukemia, as indicated by the adverse prognostic impact of deletions of 17p (locus of TP53) and 11q (locus of ATM) detected by fluorescence in situ hybridization (FISH) analysis. In addition to deletions, mutations in these respective genes are also associated with chemoresistance, and add to the prognostic information provided by FISH. In order to explore the possibility that dysfunction of the ATM–p53 pathway might also result from mechanisms other than ATM/TP53 deletion/mutation, assays have been developed that probe the functional integrity of the ATM–p53 pathway. Currently, four different p53 function assays have been developed that are based on the measurement of p53 and p53-dependent genes at the RNA (real-time polymerase chain reaction [RT-PCR]p21; RT-PCRmiR34a; reverse transcription-multiplex ligation-dependent probe amplification assay [RT-MLPA]p21, bax, puma and CD95) or protein (fluorescence activated cell sorting [FACS]p53-p21) level in untreated cells or following irradiation or drug treatment. Here we provide an overview of these assays based on the available literature.
Full-text · Article · Jul 2013 · Leukemia and Lymphoma
[Show abstract][Hide abstract] ABSTRACT: We studied the incidences, associations and prognostic roles of NOTCH1 and SF3B1 mutations (NOTCH1(mut), SF3B1(mut)) as compared to TP53(mut) in fludarabine-refractory chronic lymphocytic leukemia (CLL) patients treated with alemtuzumab on the CLL2H trial. We found NOTCH1(mut), SF3B1(mut) and TP53(mut) in 13.4%, 17.5% and 37.4% of patients, respectively. NOTCH1(mut) and SF3B1(mut) were mutually exclusive, whereas TP53(mut) were evenly distributed within both subgroups. Apart from correlation of SF3B1(mut) with 11q deletion (p=.029), there were no other significant associations of the mutations with any baseline characteristics or response rates. However, NOTCH1(mut) cases had a significantly longer progression-free survival (PFS) compared to wild type (WT) cases (15.47 vs. 6.74 months; p=.025) while there was no significant difference regarding OS. SF3B1(mut) had no significant impact on PFS and overall survival (OS). In multivariable analyses, NOTCH1(mut) was identified as an independent favorable marker for PFS. This clinical trial is registered at www.clinicaltrials.gov as #NCT00274976.
[Show abstract][Hide abstract] ABSTRACT: Leukemia is one of the leading journals in hematology and oncology. It is published monthly and covers all aspects of the research and treatment of leukemia and allied diseases. Studies of normal hemopoiesis are covered because of their comparative relevance.
Full-text · Article · Jun 2013 · Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K