11q22.3 deletion in B-chronic lymphocytic leukemia is specifically associated with bulky lymphadenopathy and ZAP-70 expression but not reduced expression of adhesion/cell surface receptor molecules

Elevated FANCA expression determines a worse prognosis in chronic lymphocytic leukemia and interferes with p53 function

Chronic lymphocytic leukemia (CLL) is characterized by a failure in the mechanisms of apoptosis that leads to an accumulation of mature B cells in peripheral blood, bone marrow, and lymphoid organs. The molecular basis of CLL remains unknown. Certain cytogenetic and molecular markers determine a bad prognosis in CLL. Fanconi anemia complementation (FANC) proteins have been related to chromosomal instability and alterations in the mechanisms of p53 activation, control of cell cycle, and apoptosis. We investigated the role of certain FANC proteins in CLL. Our data identified a group of patients with CLL with high expression of FANCA in peripheral B-CLL cells and we established its relationship with the deletion of 11q23 and a worse prognosis. When we investigated the molecular mechanisms of this bad prognosis, we observed a reduction in the expression of 2 p53 target genes, p21 and ∆Np73, in CLL primary cells transfected with FANCA. Functional studies demonstrated an impairment of p53 by FANCA. Moreover, we obtained evidence of a cooperation between FANCA and the NEDD8-interacting protein NUB1L in the destabilization of p53. For the first time, FANCA is reported as a bad prognosis marker by a mechanism other than its role in the Fanconi anemia-breast cancer DNA repair pathway.-Bravo-Navas, S., Yáñez, L., Romón, Í., Pipaón, C. Elevated FANCA expression determines a worse prognosis in chronic lymphocytic leukemia and interferes with p53 function.

Concepts of Chronic Lymphocytic Leukemia Pathogenesis: DNA Damage Response and Tumor Microenvironment

Pathogenesis of chronic lymphocytic leukemia (CLL) is characterized by specific genetic aberrations and alterations of cellular signaling pathways. In particular, a disturbed DNA damage response (DDR) and an activated B-cell receptor signaling pathway play a major role in promoting CLL cell survival. External stimuli are similarly essential for CLL cell survival and lead to activation of the PI3K/AKT and MAPK pathways. Activation of nuclear factor-kappa B (NFkB) influences the disturbed anti-apoptotic balance of CLL cells. Losses or disabling mutations in TP53 and ATM are frequent events in chemotherapy-naïve patients and are further enriched in chemotherapy-resistant patients. As these lesions define key regulatory elements of the DDR pathway, they also determine treatment response to genotoxic therapy. Novel therapeutic strategies therefore try to circumvent defective DDR signaling and to suppress the pro-survival stimuli received from the tumor microenvironment. With increasing knowledge on specific genetic alterations of CLL, we may be able to target CLL cells more efficiently even in the situation of mutated DDR pathways or protection by microenvironmental stimuli.

TLR-9 and IL-15 Synergy Promotes the In Vitro Clonal Expansion of Chronic Lymphocytic Leukemia B Cells

Clinical progression of B cell chronic lymphocytic leukemia (B-CLL) reflects the clone's Ag receptor (BCR) and involves stroma-dependent B-CLL growth within lymphoid tissue. Uniformly elevated expression of TLR-9, occasional MYD88 mutations, and BCR specificity for DNA or Ags physically linked to DNA together suggest that TLR-9 signaling is important in driving B-CLL growth in patients. Nevertheless, reports of apoptosis after B-CLL exposure to CpG oligodeoxynucleotide (ODN) raised questions about a central role for TLR-9. Because normal memory B cells proliferate vigorously to ODN+IL-15, a cytokine found in stromal cells of bone marrow, lymph nodes, and spleen, we examined whether this was true for B-CLL cells. Through a CFSE-based assay for quantitatively monitoring in vitro clonal proliferation/survival, we show that IL-15 precludes TLR-9-induced apoptosis and permits significant B-CLL clonal expansion regardless of the clone's BCR mutation status. A robust response to ODN+IL-15 was positively linked to presence of chromosomal anomalies (trisomy-12 or ataxia telangiectasia mutated anomaly + del13q14) and negatively linked to a very high proportion of CD38(+) cells within the blood-derived B-CLL population. Furthermore, a clone's intrinsic potential for in vitro growth correlated directly with doubling time in blood, in the case of B-CLL with Ig H chain V region-unmutated BCR and <30% CD38(+) cells in blood. Finally, in vitro high-proliferator status was statistically linked to diminished patient survival. These findings, together with immunohistochemical evidence of apoptotic cells and IL-15-producing cells proximal to B-CLL pseudofollicles in patient spleens, suggest that collaborative ODN and IL-15 signaling may promote in vivo B-CLL growth.

High fluorescence in situ hybridization percentage of deletion 11q in patients with chronic lymphocytic leukemia is an independent predictor of adverse outcome

We have analyzed patients with previously untreated chronic lymphocytic leukemia with del11q fluorescence in situ hybridization (FISH) abnormality (n = 196) in this study. Detection of the 11q22.3 used a multicolor FISH technique. Patients with del11q fell into two major FISH subsets-sole del11q (n = 64) and del11q with del13q (n = 132). FISH subsets were compared using the median del11q FISH% (>58%, high vs. ≤58%, low). Overall survival (OS) and time to first treatment (TTFT) were estimated using Kaplan-Meier plots (log rank). Multivariate analysis was performed to assess the association between FISH% of del11q and outcomes. Patients with sole del11q were similar to del11q with del13q in terms of TTFT and OS. Patients with high FISH% of del11q had significantly shorter OS and TTFT as compared with patients with low FISH%, particularly in sole del11q; this negative impact of high FISH% of del11q on OS and TTFT was diminished with coexistent del13q. In multivariate analysis, high FISH% of del11q was a significant predictor for shorter OS and TTFT. A comparison of these del11q subsets with a separate cohort of (n = 673) previously untreated patients with sole del13q showed that the high FISH% del11q cohort had a significantly shorter TTFT and OS. In addition, bulky disease by physical examination or computed tomography imaging was infrequent at presentation in patients with del11q. High FISH% of del11q can reliably discriminate higher risk patients with chronic lymphocytic leukemia. Presence of coexistent del13q should be accounted for while prognosticating patients with del11q.

ATM mutations uniformly lead to ATM dysfunction in chronic lymphocytic leukemia: application of functional test using doxorubicin

ATM abnormalities are frequent in chronic lymphocytic leukemia and represent an important prognostic factor. Sole 11q deletion does not result in ATM inactivation by contrast to biallelic defects involving mutations. Therefore, the analysis of ATM mutations and their functional impact is crucial. In this study, we analyzed ATM mutations in predominantly high-risk patients using: i) resequencing microarray and direct sequencing; ii) Western blot for total ATM level; iii) functional test based on p21 gene induction after parallel treatment of leukemic cells with fludarabine and doxorubicin. ATM dysfunction leads to impaired p21 induction after doxorubicin exposure. We detected ATM mutation in 16% (22 of 140) of patients, and all mutated samples manifested demonstrable ATM defect (impaired p21 upregulation after doxorubicin and/or null protein level). Loss of ATM function in mutated samples was also evidenced through defective p53 pathway activation after ionizing radiation exposure. ATM mutation frequency was 34% in patients with 11q deletion, 4% in the TP53-defected group, and 8% in wild-type patients. Our functional test, convenient for routine use, showed high sensitivity (80%) and specificity (97%) for ATM mutations prediction. Only cells with ATM mutation, but not those with sole 11q deletion, were resistant to doxorubicin. As far as fludarabine is concerned, this difference was not observed. Interestingly, patients from both these groups experienced nearly identical time to first treatment. In conclusion, ATM mutations either alone or in combination with 11q deletion uniformly led to demonstrable ATM dysfunction in patients with chronic lymphocytic leukemia and mutation presence can be predicted by the functional test using doxorubicin.

CD44 regulates the apoptotic response and promotes disease development in chronic lymphocytic leukemia

The cell-surface glycoprotein CD44 is expressed in chronic lymphocytic leukemia (CLL), but its functional role in this disease is poorly characterized. We therefore investigated the contribution of CD44 to CLL in a murine disease model, the Eµ-TCL1 transgenic mouse, and in CLL patients. Surface CD44 increased during murine CLL development. CD44 expression in human CLL was induced by stimulation with interleukin 4/soluble CD40 ligand and by stroma cell contact. Engagement of CD44 by its natural ligands, hyaluronic acid or chondroitin sulfate, protected CLL cells from apoptosis, while anti-CD44 small interfering RNAs impaired tumor cell viability. Deletion of CD44 during TCL1-driven murine leukemogenesis reduced the tumor burden in peripheral blood and spleen and led to a prolonged overall survival. The leukemic cells from these CD44 knockout animals revealed lower levels of antiapoptotic MCL1, a higher propensity to apoptosis, and a diminished B-cell receptor kinase response. The inhibitory anti-CD44 antibodies IM7 and A3D8 impaired the viability of CLL cells in suspension cultures, in stroma contact models, and in vivo via MCL1 reduction and by effector caspase activation. Taken together, CD44 expression in CLL is mediated by the tumor microenvironment. As a coreceptor, CD44 promotes leukemogenesis by regulating stimuli of MCL1 expression. Moreover, CD44 can be addressed therapeutically in CLL by specific antibodies.

Analysis of ZAP70 expression in adult acute lymphoblastic leukaemia by real time quantitative PCR

Background

ZAP70 gene expression is associated with poor prognosis in B-cell lymphoproliferative disorders especially chronic lymphocytic leukaemia (CLL) but its role in adult B-ALL has not been established. On diagnostic samples from 76 patients with adult ALL (65 with B-ALL and 11 with T-ALL) ZAP70 mRNA expression levels were studied by real time-quantitative PCR (RT-qPCR) analysis.

Findings

A broad distribution of ZAP70 expression was observed in ALL, ranging from 0.002 to 5.3 fold that of the ZAP70 positive Jurkat reference cell line. No association was observed between expression levels and the presence of specific cytogenetic abnormalities. Five cases, including one case of T-ALL, had ZAP70 expression above the level of the Jurkat reference cell line.

Conclusions

Our results confirm the frequent expression of ZAP70 in adult ALL. Limited comparisons made did highlight poor-risk patients with high ZAP70 expression, but due to lack of clinical information on patient samples we were unable to directly assess the impact on disease prognosis. ZAP-70 may be an important laboratory assay in adult ALL and further studies are warranted to study a potential correlation with cytogenetic and other genetic markers.

Exploiting biological diversity and genomic aberrations in chronic lymphocytic leukemia

There is remarkable heterogeneity in the clinical course and biological characteristics of patient subgroups with chronic lymphocytic leukemia (CLL). Mutations of key tumor suppressors (ATM, miR-15a/16-1 and TP53) have been identified in CLL, and these aberrations are important "drivers" of the disease and some of its clinical characteristics. While some mutations are associated with poor outcome [particularly del(17p) and TP53 mutation], others are linked to a favorable clinical course [e.g. del(13q) as sole aberration]. In addition to genetic aberrations, antigen drive and microenvironmental interactions contribute to the pathogenesis of CLL. How the genetic aberrations impact on the process of antigen drive or microenvironmental interactions is currently unclear. Our improved understanding of the biology and clinical course of specific genetic subgroups is beginning to be translated into more specific and targeted treatment approaches. As a result, genetic subgroups are treated in distinct protocols. This review summarizes the contribution of the microenvironment and the most important genetic aberrations in CLL and how our improved knowledge of the biology of CLL may translate into improved treatment results.

The basis and rational use of molecular genetic testing in mature B-cell lymphomas

An increasing number of neoplasms are associated with variably specific genetic abnormalities. This is best exemplified by hematological malignancies, in which there is a growing list of entities that are defined by their genetic lesion(s); this is not (yet) the case in mature B-cell lymphomas. However, enhanced insights into the pathogenesis of this large and diverse group of lymphomas have emerged with the ongoing unraveling of a plethora of fascinating genetic abnormalities. The purpose of this review is to synthesize well-recognized data and nascent discoveries in our understanding of the genetic basis of a spectrum of mature B-cell lymphomas, and how this may be applied to contemporary clinical practice. Despite the explosion of new and exciting knowledge in this arena, with the potential for enhanced diagnostic and prognostic strategies, it is essential to remain cognizant of the limitations (and complexity) of genetic investigations, so that assays can be developed and used both judiciously and rationally.

Differential gene expression in murine large cell B-cell lymphoma metastatic variants

Previous studies from this laboratory have characterized RAW117-P murine large cell B-cell lymphoma and its in vivo selected highly malignant and liver metastatic RAW117-H10 subline for their biological and biochemical properties. In this study, to understand the molecular basis of low and high metastatic behavior of these variant sublines, we have investigated the molecular phenotypes of these cells using differential display techniques and cDNA array analysis. Differential display analysis indicated a significant difference in expression of several genes between these two metastatic variant lymphoma cells. Further analyses of these cells using microarray showed an increased expression of several genes including uPAR1, CRE-BP1, Chop-10, IGF, insulin-like growth factor-IA, STAT6, Cyclin-D1, Cyclin-E, ERBB-3, Alpha NGF, Kruppel-like factor LKLF, (P)19INK4 in metastatic RAW117-H10 cells compared to parental RAW117-P cells. On the other hand, MIP1beta, CD14 antigen, Cathepsin B and MOD are expressed more in RAW117-P cells compared to RAW117-H10 cells. Differential expression of the selected genes was confirmed using semiquantitative RT-PCR techniques. The combination of plasminogen activator and its receptor and IGF-like growth factors, cell cycle regulatory molecules and transcription factors might provide an ideal environment for RAW117-H10 cells to metastasize to distant organs and colonize. Thus these results identify certain differentially expressed genes that are involved in the metastatic properties of these lymphoma cells and lay foundation for further in depth analyses to use this information to develop therapy for metastatic lymphoma.

Impact of trisomy 12, del(13q), del(17p), and del(11q) on the immunophenotype, DNA ploidy status, and proliferative rate of leukemic B-cells in chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) is a well-defined clinical entity with heterogeneous molecular and cytogenetic features. Here, we analyze the impact of trisomy 12, del(13q), del(17p), and del(11q) as determined by interphase fluorescence in situ hybridization analysis of purified neoplastic B-CLL cells on their immunophenotype, DNA ploidy status and proliferative rate.Overall, 111 of 180 (62%) B-CLL cases studied displayed one (50%) or more (12%) genetic abnormalities, del(13q) (35%) being more frequently detected than trisomy 12 (23%) followed by del(11q) (9%) and del(17p) (8%). Trisomy 12 was associated with a higher frequency of DNA aneuploidy, stronger expression of CD19, CD20, CD22, CD24, CD27, CD79b, CD38, and sIg and lower reactivity for CD43 with respect to cytogenetically nonaltered cases. In turn, cases with del(13q) displayed greater reactivity for CD20, FMC7, CD27, CD22, CD5, and bcl2, while del(11q) was associated with brighter expression of CD38, FMC7, CD25, and sIg. Hierarchical clustering analysis of the immunophenotype of B-CLL cases with cytogenetic abnormalities allowed the identification of three different groups of patients with increasing frequencies of trisomy 12, del(11q), and del(13q). Remarkably, none of the cytogenetic abnormalities analyzed except coexistence of 13q- and 17p- had a clear impact on the proliferative index of B-CLL cells.

Genetic alteration associated with chronic lymphocytic leukemia

The genetics of B-cell chronic lymphocytic leukemia (B-CLL) differ considerably from most other forms of hematologic malignancy which are usually characterized by chromosome translocations. B-CLL typically contains chromosomal deletions and chromosomes 13q14 and 11q22-->q23 are the most common. These two regions appear to share a common ancestral origin (Auer et al., 2007b). Overall, chromosomal abnormalities can be found in the majority of patients with B-CLL when using sensitive techniques (Dohneret al., 2000) and possibly reflects an underlying predisposition, with a small but significant number of familial cases. Although single and consistent abnormalities are most common, multiple rearrangements can occur, often with disease progression (Feganetal., 1995; Dohner et al., 2000). Regions of recurrent deletion suggest the presence of tumor suppressor genes if following Knudson's theoretical 2-hit model. However, despite extensive sequencing analysis over the last decade and lack of pathogenic mutations identified, there has been a move away from this suggested hypothesis and alternative mechanisms of gene inactivation involving epigenetic silencing or haploinsufficiency may be considered as more likely in this disease. This review focuses on the common genetic abnormalities in B-CLL and relates them to some of the more recent hypotheses on inactivation of genes within these regions of deletion.

Pathology of chronic lymphocytic leukemia: an update

Chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) is a clonal lymphoproliferative disorder characterized by proliferation of morphologically and immunophenotypically mature lymphocytes. CLL/SLL may proceed through different phases: an early phase in which tumor cells are predominantly small in size, with a low proliferation rate and prolonged cell survival, and a transformation phase with the frequent occurrence of extramedullary proliferation and an increase in large, immature cells. Although some patients with CLL have an indolent disease course and die after many years of unrelated causes, others have very rapidly disease progression and die of the disease within a few years of the diagnosis. In the past few years, considerable progress has been made in our ability to diagnose and classify CLL accurately. Through cytogenetics and molecular biology, it has been shown that CLL and variants are associated with a unique genotypic profile and that these genetic lesions often have a direct bearing on the pathogenesis and prognosis of the disease. Similarly, the development of antibodies to new biologic markers has allowed the identification of a unique immunophenotypic profile for CLL and variants. Moreover, accumulating evidence suggests that CLL cells respond to selected microenvironmental signals and that this confers a growth advantage and an extended survival to CLL cells. In this article, we will review the progress in the pathobiology of CLL and give an update on prognostic markers and tools in current pathology practice for risk stratification of CLL.

ATM, CTLA4, MNDA, and HEM1 in High versus Low CD38–Expressing B-Cell Chronic Lymphocytic Leukemia

PURPOSE

In B-cell chronic lymphocytic leukemia (CLL), high CD38 expression has been associated with unfavorable clinical course, advanced disease, resistance to therapy, shorter time to first treatment, and shorter survival. However, the genes associated with CLL patient subgroups with high and low CD38 expression and their potential role in disease progression is not known.

EXPERIMENTAL DESIGN

To identify the genes associated with the clinical disparity in CLL patients with high versus low CD38 expression, transcriptional profiles were obtained from CLL cells from 39 different patients using oligonucleotide microarray. Gene expression was also compared between CLL cells and B cells from healthy individuals.

RESULTS

Gene expression analysis identified 76 differentially expressed genes in CD38 high versus low groups. Out of these genes, HEM1, CTLA4, and MNDA were selected for further studies and their differential expression was confirmed by real-time PCR. HEM1 overexpression was associated with poor outcome, whereas the overexpression of CTLA4 and MNDA was associated with good outcome. Down-regulation of HEM1 expression in patient CLL cells resulted in a significant increase in their susceptibility to fludarabine-mediated killing. In addition, when gene expression patterns in CD38 high and low CLL cells were compared with normal B-cell profiles, ATM expression was found to be significantly lower in CD38 high compared with CD38 low CLL as confirmed by real-time reverse transcription-PCR.

CONCLUSIONS

These results identify the possible genes that may be involved in cell proliferation and survival and, thus, determining the clinical behavior of CLL patients expressing high or low CD38.

Bulky lymphadenopathy with poor clinical outcome is associated with ATM downregulation in B-cell chronic lymphocytic leukemia patients irrespective of 11q23 deletion

B-cell chronic lymphocytic leukemia (B-CLL) is the most common B-cell leukemia among older populations in Western countries. The clinical course of B-CLL is heterogeneous: in some patients the disease course is indolent, in others it is aggressive. The B-CLL subgroups with chromosome 11q23 deletion have been associated with aggressive disease course involving ATM deletion, extensive bulky lymphadenopathy (BLA), and inferior clinical outcome. Using real-time reverse transcriptase-polymerase chain reaction, we found that ATM was consistently underexpressed in B-CLL patients with BLA, irrespective of 11q23 deletion status. In addition, B-CLL patients who presented with BLA had a significantly shorter time to treatment (2 months) than did patients without BLA (74 months). Moreover, gene expression analysis in B-CLL patients with and without BLA revealed differences in expression for genes involved in apoptosis, cell cycle, and cell adhesion. These results indicate an association between BLA and reduced expression of ATM, suggesting a role for ATM in disease progression in B-CLL.