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The salvage of deoxyribonucleosides in the social amoeba Dictyostelium discoideum, which has an extremely A+T-rich genome, was investigated. All native deoxyribonucleosides were phosphorylated by D. discoideum cell extracts and we subcloned three deoxyribonucleoside kinase (dNK) encoding genes. D. discoideum thymidine kinase was similar to the human thymidine kinase 1 and was specific for thymidine with a K(m) of 5.1 microM. The other two cloned kinases were phylogenetically closer to bacterial deoxyribonucleoside kinases than to the eukaryotic enzymes. D. discoideum deoxyadenosine kinase (DddAK) had a K(m) for deoxyadenosine of 22.7 microM and a k(cat) of 3.7 s(-1) and could not efficiently phosphorylate any other native deoxyribonucleoside. D. discoideum deoxyguanosine kinase was also a purine-specific kinase and phosphorylated significantly only deoxyguanosine, with a K(m) of 1.4 microM and a k(cat) of 3 s(-1). The two purine-specific deoxyribonucleoside kinases could represent ancient enzymes present in the common ancestor of bacteria and eukaryotes but remaining only in a few eukaryote lineages. The narrow substrate specificity of the D. discoideum dNKs reflects the biased genome composition and we attempted to explain the strict preference of DddAK for deoxyadenosine by modeling the active center with different substrates. Apart from its native substrate, deoxyadenosine, DddAK efficiently phosphorylated fludarabine. Hence, DddAK could be used in the enzymatic production of fludarabine monophosphate, a drug used in the treatment of chronic lymphocytic leukemia.
J Mol Biol 2007 Jun 08
PMID:Dictyostelium discoideum salvages purine deoxyribonucleosides by highly specific bacterial-like deoxyribonucleoside kinases. 1744 96

To develop a model incorporating relevant prognostic biomarkers for untreated chronic lymphocytic leukemia patients, we re-analyzed the raw data from four published gene expression profiling studies. We selected 88 candidate biomarkers linked to immunoglobulin heavy-chain variable region gene (IgV(H)) mutation status and produced a reliable and reproducible microfluidics quantitative real-time polymerase chain reaction array. We applied this array to a training set of 29 purified samples from previously untreated patients. In an unsupervised analysis, the samples clustered into two groups. Using a cutoff point of 2% homology to the germline IgV(H) sequence, one group contained all 14 IgV(H)-unmutated samples; the other contained all 15 mutated samples. We confirmed the differential expression of 37 of the candidate biomarkers using two-sample t-tests. Next, we constructed 16 different models to predict IgV(H) mutation status and evaluated their performance on an independent test set of 20 new samples. Nine models correctly classified 11 of 11 IgV(H)-mutated cases and eight of nine IgV(H)-unmutated cases, with some models using three to seven genes. Thus, we can classify cases with 95% accuracy based on the expression of as few as three genes.
J Mol Diagn 2007 Sep
PMID:Identification and validation of biomarkers of IgV(H) mutation status in chronic lymphocytic leukemia using microfluidics quantitative real-time polymerase chain reaction technology. 1769 Feb 14

In B-cell chronic lymphocytic leukemia (CLL), Rai stage, immunoglobulin gene mutational status, chromosomal abnormalities, CD38 and ZAP-70 expression were used as prognostic markers. In this study, to understand the molecular basis of chromosomal abnormalities leading to tumor progression, 90 CLL patients were grouped into poor prognosis (with 11q deletion and trisomy 12) and good prognosis (with normal karyotype and 13q deletion) and their clinical outcome was assessed. Gene expression profiles of 35 CLL samples with poor outcome (11q deletion, n=9; trisomy 12, n=5) and good outcome (13q deletion, n=13; normal karyotype, n=8) were analyzed using oligonucleotide microarray. Significance analysis of microarray (SAM) identified 27 differentially expressed genes between these two subgroups with significant overexpression of ATF5 and underexpression of CDC16, PCDH8, SLAM, MNDA and ATF2 in CLL patients with poor outcome. ATF5 gene expression in CLL was further studied because of its role in the regulation of cell cycle progression/differentiation and apoptosis. The overexpression of ATF5 was confirmed by real-time PCR using 39 CLL samples from the poor and good outcome groups. ATF5 was significantly (p<0.001) overexpressed in the poor outcome group. Furthermore, ATF5 expression was significantly higher in the 11q deletion as well as trisomy 12 group alone compared to the 13q deletion and normal karyotype groups. ATF5 overexpression was also associated with significantly (p=0.04) shorter time to treatment. Similarly, expression of five underexpressed genes also correlated with longer time to treatment. Thus, this report demonstrates that ATF5 may be one of the key genes involved in increased proliferation and survival in 11q deletion or trisomy 12, whereas CD16, CD86, SLAM, MNDA and ATF2 may be involved in the decreased proliferation of CLL cells with 13q deletion or normal karyotype.
Int J Mol Med 2007 Oct
PMID:Molecular basis of aggressive disease in chronic lymphocytic leukemia patients with 11q deletion and trisomy 12 chromosomal abnormalities. 1778 76

Zeta-chain (TCR)-associated protein kinase 70 kDa (Zap-70) and CD38 expression may be of prognostic significance in chronic lymphocytic leukemia (CLL). Previous studies indicate that Zap-70 and CD38 are usually positive in cases of CLL with unmutated immunoglobulin variable region genes (IgVH) and may be used to predict IgVH mutation status and prognosis. Usually cases of CLL positive for Zap-70 or CD38 indicate a worse prognosis. In the present investigation, 47 cases of CLL were evaluated for CD38 expression, and 17 cases were evaluated for both Zap-70 and CD38 expression. Of the 47 cases, 19 (40.4%) positively expressed CD38. Of the 17 cases evaluated for Zap-70, 11 (64.7%) were positive for Zap-70, while only 6 (35.3%) were positive for CD38 expression; the remaining cases were negative for CD38. The results of this study show that Zap-70 expression may be a better indicator of the mutational status of IgVH and prognosis of CLL than CD38 expression. In addition, CD38 negativity does not necessarily indicate that IgVH mutation has occurred. These data point to the need for a more extensive study to evaluate the significance of Zap-70 and CD38 expression as indicators of IgVH mutation status and prognosis of CLL patients.
Exp Mol Pathol 2007 Dec
PMID:Zap-70 and CD38 as predictors of IgVH mutation in CLL. 1793 24

Follicular lymphoma (FL) generally expresses immunoglobulin (Ig) with somatically mutated variable (V) region genes. Surprisingly, these almost always carry introduced motifs available for N-glycosylation (Asn-X-Ser/Thr). Introduced motifs are uncommon on normal B cells, but are on other germinal center (GC)-associated B-cell malignancies suggesting a site-specific role. They are not evident in mutated chronic lymphocytic leukemia (CLL) or myeloma. Recently, we found that the glycosylation sites are unusual in containing oligomannose glycans, which are apparently displayed on tumor cell surface IgM. This suggests a potential interaction with a mannose receptor in the GC. However, natural N-glycosylation sites exist in germline (GL) V region genes, particularly the V4-34 gene expressed by normal B cells and by some malignancies, including CLL, potentially undermining the selective importance for FL. To compare oligosaccharide addition at the introduced and natural sites, we expressed V region genes as single chain Fv (scFv) and analyzed the added glycans. In contrast to introduced sites, which were oligomannosylated, the natural GL motif in the V4-34 sequence had no added sugars. The remarkable selective glycosylation within the heavy chain V region gene of FL apparently permits only limited processing to oligomannose at somatically mutated motifs, creating a feature exploitable by GC lymphomas.
Mol Immunol 2008 Mar
PMID:Remarkable selective glycosylation of the immunoglobulin variable region in follicular lymphoma. 1802 32

The somatic hypermutational (SHM) status of the immunoglobulin heavy-chain variable (IgVH) gene is a powerful prognostic factor in patients with chronic lymphocytic leukemia (CLL). However, IgVH SHM analysis is not well-suited to routine use in the clinical diagnostic laboratory. ZAP70 expression is a potential surrogate for the absence of SHM. Given the current problems with the standardization of ZAP70 assessment by flow cytometry, we sought an alternative approach, using immunohistochemistry (IHC). The utility of IHC is largely restricted to tissues, precluding its routine application to most patients with CLL who are typically diagnosed based upon peripheral blood (PB) findings. Accordingly, we developed an IHC assay that can be performed on PB. Enriched PB mononuclear cells from 29 patients with CLL were analyzed for ZAP70 expression by IHC on paraffin-embedded cell blocks, using standard techniques. IgVH SHM analysis was performed on all cases, and clinical features recorded. Seventeen specimens (59%) were negative for ZAP70 expression and 12 (41%) were positive for ZAP70 expression. SHM was evident in 20 specimens (69%), and absent in 9 (31%). Seventy-six percent of the specimens (22/29) displayed "concordant" ZAP70 and SHM results, in that 15 (52%) were SHM-positive/ZAP70 negative, whereas 7 (24%) were SHM-negative/ZAP70 positive. ZAP70 expression in this small cohort correlated with poor clinical outcome. Importantly, IHC analysis of ZAP70 in PB is a simple, reliable, robust assay that may have a valuable role in the routine clinical laboratory assessment of patients with CLL.
Appl Immunohistochem Mol Morphol 2007 Dec
PMID:ZAP70 expression assessed by immunohistochemistry on peripheral blood: a simple prognostic assay for patients with chronic lymphocytic leukemia. 1809 93

In the last decade, arsenic trioxide (As2O3) has been used very successfully to treat acute promyelocytic leukaemia (APL). Much less is known about the effectiveness of As2O3 in other neoplastic disorders. In this paper, we report that after 18 h in vitro treatment with 4 microM As2O3, 75+/-18% of B cell chronic lymphocytic leukaemia (B-CLL) cells (n=52) underwent apoptosis. It is important to note that B-CLL cells harboring a deletion of chromosome 17p13, which predisposes to fludarabine resistance and has been identified as an important negative predictor of clinical outcome, were more susceptible to As2O3 toxicity than cells lacking this aberration. Furthermore, unfavourable risk profiles such as unmutated IgVH status, high CD38 expression and prior treatment were associated with significantly higher sensitivity of B-CLL cells to As2O3. As2O3 also preferentially killed B-CLL cells compared to B cells from healthy age-matched controls. Molecular analysis revealed that basal superoxide dismutase activity was positively correlated with the pro-apoptotic activity of As2O3 pointing to a role of reactive oxygen species in cell death induction. The high activity of As2O3 in B-CLL cells from high-risk patients makes it a promising drug for high-risk and/or fludarabine-refractory B-CLL patients.
J Mol Med (Berl) 2008 May
PMID:Arsenic trioxide induces apoptosis preferentially in B-CLL cells of patients with unfavourable prognostic factors including del17p13. 1829 55

CD38 is an ectoenzyme involved in transmembrane signaling and cell adhesion and is used as a disease marker for leukemias and myeloma. CD38 is a dependable negative prognostic marker for chronic lymphocytic leukemia (CLL). Recent evidence indicates that CD38 is a component of a complex network delivering growth and survival signals to CLL cells. In conjunction with chemokines and their receptors, CD38 also influences cell migratory responses. These considerations are the rationale for devising a CLL therapy that uses CD38 as the target. The use of reagents specifically blocking the molecule might provide a new approach for interfering with deleterious growth circuits, therefore increasing the susceptibility of leukemic cells to conventional chemotherapy.
Trends Mol Med 2008 May
PMID:CD38 at the junction between prognostic marker and therapeutic target. 1840 65

The Dock or CZH proteins are a family of activators for Rho GTPase proteins. The Zizimin subfamily is composed of three members: Dock9, Dock10, and Dock11. We have identified DOCK10 as an interleukin-4 (IL4)-inducible gene in chronic lymphocytic leukemias (CLLs). Subsequently, we have obtained the full-length cDNA sequence, which encodes a 2180 amino acid protein. Dock9 (2069 amino acids) and Dock11 (2073 amino acids) share more identity between them (58%) than with Dock10 (52% and 50%, respectively). Among normal human tissues, DOCK10 and DOCK11 mRNAs were mainly expressed in peripheral blood (PB) leukocytes. Dock10 protein was expressed at similar levels in normal PB-B and PB-T cells. Dock10 protein levels were heterogeneous in CLLs. IL4 consistently increased Dock10 mRNA and protein levels in CLL and normal PB-B cells. In contrast, IL4 did not affect the levels of Dock10 expression in normal PB-T cells. IL4 neither increased DOCK9 or DOCK11 mRNA levels in CLL cells. Dock10 protein distributed in the cytoplasm and nucleus of CLL cells, and IL4 increased its expression in both cellular compartments. The rapid and distinctive induction of Dock10 expression by IL4 in CLL and normal PB-B cells suggests a role for Dock10 in IL4-induced B-cell activation. Dock10 could represent a point of convergence for IL4 signalling and small Rho GTPase function in B cells.
Mol Immunol 2008 Jul
PMID:Dock10, a novel CZH protein selectively induced by interleukin-4 in human B lymphocytes. 1849 58

Genmab A/S and licensee GlaxoSmithKline plc are developing ofatumumab, an anti-CD20 human mAb, for the potential intravenous treatment of non-Hodgkin's lymphoma and autoimmune diseases, such as rheumatoid arthritis (RA) and multiple sclerosis (MS). Phase I and II clinical trials have been completed in patients with chronic lymphocytic leukemia (CLL), rituximab-refractory follicular lymphoma (FL) and RA. At the time of publication ofatumumab was undergoing a phase II clinical trial in patients with diffuse large B-cell lymphoma and phase III clinical trials in patients with B-cell CLL (B-CLL) in which fludarabine and alemtuzumab treatments have failed and in patients with rituximab-refractory FL. Ofatumumab was also undergoing phase II clinical trials as a combination therapy for previously untreated patients with FL in combination with cyclophosphamide, adriamycin, vincristine, and prednisone and in combination with fludarabine and cyclophosphamide for the treatment of B-CLL. In addition, two phase III clinical trials to assess patients who have an inadequate response to methotrexate and TNFalpha therapy were ongoing for patients with RA, and a phase II clinical trial to investigate the effects of repeated doses of ofatumumab was recruiting patients with RA from a previous trial on ofatumumab. A phase I/II clinical trial of ofatumumab in relapsing-remitting MS was expected to commence in 2008.
Curr Opin Mol Ther 2008 Jun
PMID:Ofatumumab, a human monoclonal antibody for lymphoid malignancies and autoimmune disorders. 1853 37


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