Evaluation of ZAP-70 expression by flow cytometry in chronic lymphocytic leukemia: A multicentric international harmonization process

Temporal multiomic modeling reveals a B-cell receptor proliferative program in chronic lymphocytic leukemia

B-cell receptor (BCR) signaling is crucial for the pathophysiology of most mature B-cell lymphomas/leukemias and has emerged as a therapeutic target whose effectiveness remains limited by the occurrence of mutations. Therefore, deciphering the cellular program activated downstream this pathway has become of paramount importance for the development of innovative therapies. Using an original ex vivo model of BCR-induced proliferation of chronic lymphocytic leukemia cells, we generated 108 temporal transcriptional and proteomic profiles from 1 h up to 4 days after BCR activation. This dataset revealed a structured temporal response composed of 13,065 transcripts and 4027 proteins, comprising a leukemic proliferative signature consisting of 430 genes and 374 proteins. Mathematical modeling of this complex cellular response further highlighted a transcriptional network driven by 14 early genes linked to proteins involved in cell proliferation. This group includes expected genes (EGR1/2, NF-kB) and genes involved in NF-kB signaling modulation (TANK, ROHF) and immune evasion (KMO, IL4I1) that have not yet been associated with leukemic cells proliferation. Our study unveils the BCR-activated proliferative genetic program in primary leukemic cells. This approach combining temporal measurements with modeling allows identifying new putative targets for innovative therapy of lymphoid malignancies and also cancers dependent on ligand-receptor interactions.

BCR-associated factors driving chronic lymphocytic leukemia cells proliferation ex vivo

A chronic antigenic stimulation is believed to sustain the leukemogenic development of chronic lymphocytic leukemia (CLL) and most of lymphoproliferative malignancies developed from mature B cells. Reproducing a proliferative stimulation ex vivo is critical to decipher the mechanisms of leukemogenesis in these malignancies. However, functional studies of CLL cells remains limited since current ex vivo B cell receptor (BCR) stimulation protocols are not sufficient to induce the proliferation of these cells, pointing out the need of mandatory BCR co-factors in this process. Here, we investigated benefits of several BCR co-stimulatory molecules (IL-2, IL-4, IL-15, IL-21 and CD40 ligand) in multiple culture conditions. Our results demonstrated that BCR engagement (anti-IgM ligation) concomitant to CD40 ligand, IL-4 and IL-21 stimulation allowed CLL cells proliferation ex vivo. In addition, we established a proliferative advantage for ZAP70 positive CLL cells, associated to an increased phosphorylation of ZAP70/SYK and STAT6. Moreover, the use of a tri-dimensional matrix of methylcellulose and the addition of TLR9 agonists further increased this proliferative response. This ex vivo model of BCR stimulation with T-derived cytokines is a relevant and efficient model for functional studies of CLL as well as lymphoproliferative malignancies.

Guidelines for Diagnosis and Treatment of Chronic Lymphocytic Leukemia. Krohem B-Cll 2017

Recent developments in the diagnosis and treatment of chronic lymphocytic leukemia (B-CLL) have led to change of approach in clinical practice. New treatments have been approved based on the results of randomized multicenter trials for first line and for salvage therapy, and the results of numerous ongoing clinical trials are permanently providing new answers and further refining of therapeutic strategies. This is paralleled by substantial increase in understanding the disease genetics due to major advances in the next generation sequencing (NGS) technology. We define current position of the Croatian Cooperative Group for Hematologic Disease on diagnosis and treatment of CLL in the transition from chemo-immunotherapy paradigm into a new one that is based on new diagnostic stratification and unprecedented therapeutic results of B-cell receptor inhibitors (BRI) and Bcl-2 antagonists. This is a rapidly evolving field as a great number of ongoing clinical trials con-stantly accumulate and provide new knowledge. We believe that novel therapy research including genomic diagnosis is likely to offer new options that will eventually lead to time limited therapies without chemotherapy and more effective clinical care for B-CLL based on individualized precision medicine.

Microenvironment-induced CD44v6 promotes early disease progression in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) outgrowth depends on signals from the microenvironment. We have previously found that in vitro reconstitution of this microenvironment induces specific variant isoforms of the adhesion molecule CD44, which confer human CLL with high affinity to hyaluronan (HA). Here, we determined the in vivo contribution of standard CD44 and its variants to leukemic B-cell homing and proliferation in Tcl1 transgenic mice with a B-cell-specific CD44 deficiency. In these mice, leukemia onset was delayed and leukemic infiltration of spleen, liver, and lungs, but not of bone marrow, was decreased. Competitive transplantation revealed that CLL homing to spleen and bone marrow required functional CD44. Notably, enrichment of CD44v6 variants particularly in spleen enhanced CLL engraftment and proliferation, along with increased HA binding. We recapitulated CD44v6 induction in the human disease and revealed the involvement of MAPK and NF-κB signaling upon CD40 ligand and B-cell receptor stimulation by in vitro inhibition experiments and chromatin immunoprecipitation assays. The investigation of downstream signaling after CD44v6-HA engagement uncovered the activation of extracellular signal-regulated kinase and p65. Consequently, anti-CD44v6 treatment reduced leukemic cell proliferation in vitro in human and mouse, confirming the general nature of the findings. In summary, we propose a CD44-NF-κB-CD44v6 circuit in CLL, allowing tumor cells to gain HA binding capacity and supporting their proliferation.

CD49d shows superior performance characteristics for flow cytometric prognostic testing in chronic lymphocytic leukemia/small lymphocytic lymphoma

BACKGROUND

CD49d is emerging as a powerful adverse prognostic marker in chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL). However, flow cytometric testing for CD49d has not yet been widely adopted in the United States, in part due to the lack of establishment of its performance characteristics in the clinical setting, especially in comparison with the more common CLL/SLL prognostic markers CD38 and ZAP-70.

METHODS

CD49d expression levels in 124 CLL/SLL cases were assessed among peripheral blood (PB), bone marrow (BM), and lymph node (LN) specimens and correlated with available CD38 and ZAP-70 expression and cytogenetic findings. For 10 PB/BM specimens, the stability of CD49d, CD38, and ZAP-70 expression was assessed at <24 hours, 48 hours, 72 hours, and 96 hours.

RESULTS

39% (28 of 71) PB, 56% (18 of 32) BM, and 71% (15 of 21) LN involved by CLL/SLL were CD49d+, using a ≥30% threshold. The mean for the CD49d+ cases was 2.8 standard deviations (SD) above the cutoff for positivity, compared with 1.7 SD for CD38 and 1.1 SD for ZAP-70. CD49d demonstrated the lowest mean SD (0.91) and coefficient of variation (CV) (8.0%) compared with CD38 (SD = 2.1, CV = 10.4%) and ZAP-70 (SD = 9.8, CV = 40.5%) in stability studies over a 96-hours time period. CD49d+ CLL/SLL correlated with trisomy 12 (P = 0.025) and lack of isolated deletion (13q) (P = 0.005). CD38+ CLL/SLL correlated with deletion (11q) (P = 0.025). ZAP-70 did not correlate with any underlying cytogenetic abnormality.

CONCLUSIONS

CD49d is a robust adverse prognostic marker in CLL/SLL with superior performance characteristics. © 2016 International Clinical Cytometry Society.

Using the geometric mean fluorescence intensity index method to measure ZAP-70 expression in patients with chronic lymphocytic leukemia

Expression of ζ-chain-associated protein kinase 70 kDa (ZAP-70) in chronic lymphocytic leukemia (CLL) is associated with more aggressive disease and can help differentiate CLL from cases expressing mutated or unmutated immunoglobulin heavy chain variable region (IgHV) genes. However, standardizing ZAP-70 expression by flow cytometric analysis has proved unsatisfactory. The key point is that ZAP-70 is weakly expressed with a continuous expression pattern rather than a clear discrimination between positive and negative CLL cells, which means that the resulting judgment is subjective. Thus, in this study, we aimed at assessing the reliability and repeatability of ZAP-70 expression using the geometric mean fluorescence intensity (geo MFI) index method based on flow cytometry with 256-channel resolution in a series of 402 CLL patients and to compare ZAP-70 with other biological and clinical prognosticators. According to IgHV mutational status, we were able to confirm that the optimal cut-off point for the geo MFI index was 3.5 in the test set. In multivariate analyses that included the major clinical and biological prognostic markers for CLL, the prognostic impact of ZAP-70 expression appeared to have stronger discriminatory power when the geo MFI index method was applied. In addition, we found that ZAP-70-positive patients according to the geo MFI index method had shorter time to first treatment or overall survival (P=0.0002, P=0.0491). This is the first report showing that ZAP-70 expression can be evaluated by a new approach, the geo MFI index, which could be a useful prognostic method as it is more reliable, less subjective, and therefore better associated with improvement of CLL prognostication and prediction of clinical course.

ILK Induction in Lymphoid Organs by a TNFα-NF-κB-Regulated Pathway Promotes the Development of Chronic Lymphocytic Leukemia

The proliferation of chronic lymphocytic leukemia (CLL) cells requires communication with the lymphoid organ microenvironment. Integrin-linked kinase (ILK) is a multifunctional intracellular adaptor protein that transmits extracellular signals to regulate malignant cell motility, metastasis, and cell-cycle progression, but is poorly characterized in hematologic malignancies. In this study, we investigated the role of ILK in the context of CLL and observed high ILK expression in patient samples, particularly in tumor cells harboring prognostic high-risk markers such as unmutated IGHV genes, high Zap70, or CD38 expression, or a signature of recent proliferation. We also found increased numbers of Ki67 (MKI67)-positive cells in regions of enhanced ILK expression in lymph nodes from CLL patients. Using coculture conditions mimicking the proliferative lymph node microenvironment, we detected a parallel induction of ILK and cyclin D1 (CCND1) expression in CLL cells that was dependent on the activation of NF-κB signaling by soluble TNFα. The newly synthesized ILK protein colocalized to centrosomal structures and was required for correct centrosome clustering and mitotic spindle organization. Furthermore, we established a mouse model of CLL in which B-cell-specific genetic ablation of ILK resulted in decelerated leukemia development due to reduced organ infiltration and proliferation of CLL cells. Collectively, our findings describe a TNFα-NF-κB-mediated mechanism by which ILK expression is induced in the lymph node microenvironment and propose that ILK promotes leukemogenesis by enabling CLL cells to cope with centrosomal defects acquired during malignant transformation. Cancer Res; 76(8); 2186-96. ©2016 AACR.

Developing Molecular Signatures for Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a clonal malignancy of mature B cells that displays a great clinical heterogeneity, with many patients having an indolent disease that will not require intervention for many years, while others present an aggressive and symptomatic leukemia requiring immediate treatment. Although there is no cure for CLL, the disease is treatable and current standard chemotherapy regimens have been shown to prolong survival. Recent advances in our understanding of the biology of CLL have led to the identification of numerous cellular and molecular markers with potential diagnostic, prognostic and therapeutic significance. We have used the recently developed digital multiplexed gene-expression technique (DMGE) to analyze a cohort of 30 CLL patients for the presence of specific genes with known diagnostic and prognostic potential. Starting from a set of 290 genes we were able to develop a molecular signature, based on the analysis of 13 genes, which allows distinguishing CLL from normal peripheral blood and from normal B cells, and a second signature based on 24 genes, which distinguishes mutated from unmutated cases (LymphCLL Mut). A third classifier (LymphCLL Diag), based on a 44-gene signature, distinguished CLL cases from a series of other B-cell chronic lymphoproliferative disorders (n = 51). While the methodology presented here has the potential to provide a "ready to use" classification tool in routine diagnostics and clinical trials, application to larger sample numbers are still needed and should provide further insights about its robustness and utility in clinical practice.

Frontline low-dose alemtuzumab with fludarabine and cyclophosphamide prolongs progression-free survival in high-risk CLL

Frontline FCA increases progression-free survival in CLL and, in a post hoc analysis, also survival in younger patients. With the low-dose approach, no increase in treatment related mortality is seen.

Clinical monoclonal B lymphocytosis versus Rai 0 chronic lymphocytic leukemia: A comparison of cellular, cytogenetic, molecular, and clinical features

PURPOSE

To investigate the incidence and clinical relevance of classic and new prognostic markers, IGHV gene mutational status, and chromosomal abnormalities in clinical monoclonal B lymphocytosis (cMBL) compared with Rai stage 0 chronic lymphocytic leukemia (Rai0-CLL).

EXPERIMENTAL DESIGN

A group of 136 patients with cMBL and a group of 216 Rai0-CLL cases were investigated prospectively.

RESULTS

IGHV-mutated cases were significantly more frequent among cMBLs (P = 0.005), whereas the distribution of CD38 and ZAP-70 positive cases, of patients with NOTCH1 and SF3B1 mutations or exhibiting the major CLL cytogenetic abnormalities, was similar in the two groups. Moreover, no significant differences were found either in IGHV/IGHD/IGHJ gene usage or in the overall prevalence of stereotyped IGHV gene sequences. Cells from cMBL and Rai0-CLL exhibited similar gene and microRNA (miRNA) signatures; in addition, when grouped according to the IGHV mutational status, IGHV-unmutated cases showed different transcriptional signatures compared with IGHV-mutated patients, irrespective of the cMBL or Rai0-CLL classification. cMBL diagnosis per se was predictive of longer progression-free survival.

CONCLUSIONS

Our study based on a prospective series of patients indicates that no major differences exist between the circulating cells from cMBL and Rai0-CLL, at least based on a comparison of the markers used in the study. This possibly suggests that the two conditions mainly differ in the initial size of the monoclonal cell population, which may influence the subsequent timing of clonal expansion and clinical manifestations.

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

T/B ratio does not reflect levels of ZAP70 expression in clonal CLL B-cells due to ZAP70 overexpression in patient T-cells

Flow cytometry is the reference technique for assessing ZAP70 expression, a marker of poor prognosis in CLL. One of the most common methods is to assess ZAP70 levels in CLL cells by calculating the ratio between ZAP70 mean fluorescence intensities (MFIs) in residual T-cells and CLL B-cells (ZAP70 T/B ratio). In this study, we developed a new method for ZAP70 labeling. Cells were labeled with a combination of anti ZAP70 phycoerythrin-conjugated SBZAP monoclonal antibody (mAb) and mAbs against CD45, CD19, and CD5. The latter three were used to specifically gate on different lymphocyte subsets. Staining was performed in absence (test) or in presence of excess unconjugated SBZAP mAb (isoclonic control). A so-called ZAP70 isoclonic ratio between SBZAP MFIs in the test and isoclonic control was calculated. A series of 32 patients with CLL and 10 normal controls were studied. Prediction of IGHV mutation status by ZAP70 isoclonic and T/B ratios was similar. By using the ZAP70 isoclonic ratio, we showed that ZAP70 expression was increased in T-cells from CLL patients. Nearly all cases with increased ZAP70 expression in CLL cells were associated with high ZAP70 expression in cognate T-cells. Therefore, the ZAP70 isoclonic ratio was more likely to closely reflect the biology of ZAP70 dysregulation rather than the T/B ratio. These results also explained why ZAP70 T/B ratios were artefactually close to normal in cells from CLL patients with high levels of ZAP70.

Pitfalls and limitations of ZAP-70 detection in chronic lymphocytic leukemia

Zeta-associated protein of 70 kDa (ZAP-70) is a tyrosine kinase that plays a role in signal transduction from the T-cell receptor. ZAP-70 is expressed in normal T-cells and NK-cells. Increased expression of ZAP-70 has been identified in chronic lymphocytic leukemia (CLL). CLL patients with increased ZAP-70 expression have significantly worse prognosis in terms of both progression-free survival and overall survival. There are several methods to quantify ZAP-70: polymerase chain reaction (PCR), immunoblotting, immunohistochemistry, and flow cytometry. Use of flow cytometry for ZAP-70 detection seems to be advantageous as this technique enables us to assess the presence of ZAP-70 separately on CLL clone, T-cells, and NK-cells. On the other hand, detection of ZAP-70 by flow cytometry is substantially influenced by many variables. The principal drawback of flow cytometry is the absence of consensus regarding selection of optimal anti-ZAP-70 antibody, fluorochrome conjugate, the most reliable staining technique, and optimal positivity threshold. This article summarizes pitfalls of flow cytometric analysis of ZAP-70 in CLL.

Prospective study of clinical and biological prognostic factors at diagnosis in patients with early stage B-cell chronic lymphocytic leukemia

Retrospective series have reported many clinical and biological significant prognostic factors in chronic lymphocytic leukemia (CLL). We describe a prospective cohort of 135 patients with CLL homogeneously studied at diagnosis for prognostic factors. Biological variables analyzed were CD38 and ZAP-70 expression, fluorescence in situ hybridization (FISH) for 13q-, +12, 11q-, and 17p-, and conventional cytogenetics. Univariate and multivariate analysis for progression-free survival (PFS) were performed in patients with early stage (Rai 0-1) CLL. CD38 was positive in 42 (31.6%) patients and ZAP-70 in 47 (35.9%). The most frequent FISH finding was isolated 13q- in 50 (38.5%) patients, and 17p- -was found in 11 (8.4%). Among 135 patients, 114 (84.4%) were Rai 0-1 at diagnosis and 39 (28.9%) presented adenopathies. With a median follow-up of 39 months, the presence of lymphadenopathy in patients with Rai 0-1 stage CLL was the only significant variable for predicting PFS in multivariate analysis (odds ratio [OR] 7, 95% confidence interval [CI] 2.2-22, p = 0.001). When only biological factors were analyzed, CD38 expression (OR 3.2, 95% CI 1.1-9.3, p = 0.03) and 17p- (OR 3.5, 95% CI 0.95-13.1, p = 0.05) correlated with worse PFS. A longer follow-up is necessary to analyze the prognostic value of these variables regarding overall survival.

Detection methods of ZAP-70 in chronic lymphocytic leukemia

The clinical course of patients with chronic lymphocytic leukemia (CLL) is highly heterogeneous, with some patients experiencing rapid disease progression and others living for decades without requiring treatment. Immunoglobulin heavy chain variable region (IGHV) mutation status is a powerful prognostic factor in patients with CLL. The presence or absence of IGHV mutation status is currently the gold-standard prognostic factor, but this technique is labor-intensive and costly. The expression of ζ-chain-associated protein kinase 70 kDa (ZAP-70), detected by flow cytometry, has been served as a potential surrogate for the absence of IGHV mutation status since 2003. Given the current problems with the standardization of ZAP-70 assessment by flow cytometry, this chapter reviews the analysis of ZAP-70 expression by flow cytometry and the relative experimental conditions using the associated publications for "ZAP-70" and "detection method" on Medline since 2003. Thus, mean fluorescence intensity (MFI) ratio method yielded a more reproducible and easily adaptable method to routine use in the clinical diagnostic laboratory. In conclusion, though ZAP-70 is a valuable prognostic factor in CLL, detection methods of ZAP-70 remain to be fully standardized.

DNA damage-induced transcriptional program in CLL: biological and diagnostic implications for functional p53 testing

The DNA damage pathway plays a central role in chemoresistance in chronic lymphocytic leukemia (CLL), as indicated by the prognostic impact of TP53 and ATM loss/mutations. We investigated the function of the p53 axis in primary CLL samples by studying p53 and p21 responses to irradiation by FACS and RT-PCR. We observed a distinct response pattern for most cases with a 17p deletion (n = 16) or a sole TP53 mutation (n = 8), but not all cases with a p53 aberration were detected based on a number of different assays used. Samples with a small clone with a TP53 mutation remained undetected in all assays. Only 1 of 123 cases showed high expression of p53, which is suggestive of p53 aberration without proof of mutation of TP53. Samples with an 11q deletion showed a heterogeneous response, with only 13 of 30 showing an abnormal response based on cutoff. Nevertheless, the overall induction of p53 and p21 was impaired, suggesting a gene-dosage effect for ATM in the 11q-deleted samples. The detectability of p53 defects is influenced by clonal heterogeneity and sample purity. Functional assays of p53 defects will detect a small number of cases not detectable by FISH or TP53 mutational analysis. The clinical utility of functional p53 testing will need to be derived from clinical trials.

High expression of the immature laminin receptor protein correlates with mutated IGVH status and predicts a favorable prognosis in chronic lymphocytic leukemia

The immature laminin receptor (iLR) is a tumor-associated antigen. We analyzed the expression of iLR on malignant B cells of 134 unselected patient samples with CLL and hypothesized that iLR expression would have prognostic significance due to a differential expression pattern. High ILR expression (cut-off value 30%) was correlated with mutated IGVH status (p<0.0001). Patients with high iLR-expression had a significantly longer time to progression (p=0.039). Combination of CD38, ZAP-70, and iLR by flow cytometry can be used to construct a diagnostic score identifying patients with a median progression free survival of 80 months, if no adverse marker is present.

Prognosis of Binet stage A chronic lymphocytic leukemia patients: the strength of routine parameters

Recent developments in the management of chronic lymphocytic leukemia (CLL) patients have made necessary the availability of dependable prognostic factors. We have developed a prognostic index derived from the multivariate analysis of 339 stage A patients at diagnosis, exhaustively studied for classical and recent predictive markers. Only 4 biologic parameters were found to be independent predictors of progression-free survival (PFS): serum thymidine kinase (sTK), lymphocytosis, β2-microglobulin, and CD38 expression. Two groups were distinguishable: cases with no or 1 risk factor (among whom 85% did not progress after 7 years), and cases with 2 or more factors showing a median PFS of 20 months. Finally, we propose an easy, fast, cost-effective strategy for a trustworthy prognostication in stage A patients, who currently represent more than 80% of the CLL population, allowing physicians to adapt follow-up individually.

Genome-wide DNA methylation profiling of chronic lymphocytic leukemia allows identification of epigenetically repressed molecular pathways with clinical impact

We performed a genome-wide analysis of aberrant DNA methylation in chronic lymphocytic leukemia (CLL) using methylated CpG island amplification (MCA) coupled with a promoter microarray. We identified 280 potential targets of aberrant DNA methylation in CLL. These genes were located more frequently in chromosomes 19 (16%, p=0.001), 16 (11%, p=0.001), 17 (10%, p=0.02) and 11 (9%, p=0.02) and could be grouped in several functional networks. Methylation status was confirmed for 22 of these genes (SOX11, DLX1, FAM62C, SOX14, RSPO1, ADCY5, HAND2,SPOCK, MLL, ING1, PRIMA1, BCL11B, LTBP2, BNC1, NR2F2, SALL1, GALGT2, LHX1, DLX4, KLK10, TFAP2 and APP) in 78 CLL patients by pyrosequencing. As a proof of principle, we analyzed the expression of 2 genes, PRIMA1 and APP, in primary cells and of GALGT2, TFAP2C and PRIMA1 in leukemia cells. There was an inverse association between methylation and gene expression. This could be reversed by treatment with 5-aza-2'-deoxycytidine in cell lines. Treatment in a clinical trial with 5-azacitidine resulted in decreased methylation of LINE, DLX4 and SALL1 in the peripheral blood B-cells of patients with CLL. IgVH mutational status or ZAP-70 expression were not associated with specific methylation profiles. By multivariate analysis, methylation of LINE and APP was associated with shorter overall survival (p = 0.045 and 0.0035, respectively). This study demonstrates that aberrant DNA methylation is common and has potential prognostic and therapeutic value in CLL.

Targeting CK2 overexpression and hyperactivation as a novel therapeutic tool in chronic lymphocytic leukemia

Expression of protein kinase CK2 is frequently deregulated in cancer and mounting evidence implicates CK2 in tumorigenesis. Here, we show that CK2 is overexpressed and hyperactivated in chronic lymphocytic leukemia (CLL). Inhibition of CK2 induces apoptosis of CLL cells without significantly affecting normal B and T lymphocytes. Importantly, this effect is not reversed by coculture with OP9 stromal cells, which are otherwise capable of rescuing CLL cells from in vitro spontaneous apoptosis. CLL cell death upon CK2 inhibition is mediated by inactivation of PKC, a PI3K downstream target, and correlates with increased PTEN activity, indicating that CK2 promotes CLL cell survival at least in part via PI3K-dependent signaling. Although CK2 antagonists induce significant apoptosis of CLL cells in all patient samples analyzed, sensitivity to CK2 blockade positively correlates with the percentage of CLL cells in the peripheral blood, β2 microglobulin serum levels and clinical stage. These data suggest that subsets of patients with aggressive and advanced stage disease may especially benefit from therapeutic strategies targeting CK2 function. Overall, our study indicates that CK2 plays a critical role in CLL cell survival, laying the groundwork for the inclusion of CK2 inhibitors into future therapeutic strategies.

ZAP-70 expression is associated with increased risk of autoimmune cytopenias in CLL patients

Autoimmune cytopenias (AIC) are frequent in chronic lymphocytic leukemia (CLL) patients, but risk factors and prognostic relevance of these events are controversial. Data about the influence on AIC of biological prognostic markers, as ZAP-70, are scanty. We retrospectively evaluated AIC in 290 CLL patients tested for ZAP-70 expression by immunohistochemistry on bone marrow biopsy at presentation. They were 185 men, median age 63 years, 77.9% Binet stage A, 17.6% B and 4.5% C. AIC occurred in 46 patients (16%): 31 autoimmune hemolytic anemias, 10 autoimmune thrombocytopenias, four Evans syndromes, and one pure red cell aplasia. Of the 46 cases of AIC, 37 (80%) occurred in ZAP-70 positive patients and nine (20%) in ZAP-70 negatives. ZAP-70 expression [Hazard Ratio (HR) = 7.42; 95% confidence interval (CI): 2.49-22.05] and age >65 years (HR = 5.41; 95% CI: 1.67-17.49) resulted independent risk factors for AIC. Among the 136 patients evaluated both for ZAP-70 expression and IGHV status, the occurrence of AIC was higher in ZAP-70 positive/IGHV unmutated cases (35%) than in patients ZAP-70 negative/IGHV mutated (6%) or discordant for the two parameters (4%; P < 0.0001). In ZAP-70 positive patients, occurrence of AIC negatively influenced survival (HR = 1.75; 95% CI: 1.06-2.86). The high risk of developing AIC in ZAP-70 positive CLL, particularly when IGHV unmutated, should be considered in the clinical management.

Clinical utility of molecular and flow cytometric markers in chronic lymphocytic leukaemia

BACKGROUND

Chronic lymphocytic leukaemia (CLL) is a clinically heterogeneous disease. While immunoglobulin variable region heavy chain (IgVH) mutational status remains the 'gold standard' in molecular prognostication, a range of additional markers is increasingly being used in clinical trials. As awareness of trial data increases, requests to determine these prognostic markers for new CLL patients are becoming more prevalent in Australia.

AIM

To explore the clinical utility of currently available prognostic markers for CLL in an Australian cohort.

METHODS

IgVH mutational status and gene usage was determined and compared with other reported immunophenotypic markers, cytogenetics and clinical outcome as defined by treatment-free survival (TFS), lymphocyte doubling time and clinical stage in a cohort of 65 CLL patients.

RESULTS

An unmutated IgVH gene, high expression of CD38, ZAP-70, CD25, CD49d, CD54 or low expression of CD49c was associated with shorter TFS indicating an adverse clinical prognosis in our cohort. High expression of each of CD38, ZAP-70, CD49d and CD54 was significantly associated with an unmutated IgVH gene; however, associations were not absolute. IgVH and CD25 expression retained their significance in multivariate analysis. Concordant CD25(high) /IgVH unmutated CLL patients had the shortest median TFS interval (40 months) in our cohort.

CONCLUSIONS

Molecular and immunophenotypic markers remain useful as adjuncts to clinical prognostication; however, as single parameters they are unable to dictate the timing of therapeutic intervention. The combined use of CD25 and IgVH mutational status may be clinically relevant to CLL prognostication while also providing insight into the biological pathways involved in disease progression.

High expression of lymphocyte-activation gene 3 (LAG3) in chronic lymphocytic leukemia cells is associated with unmutated immunoglobulin variable heavy chain region (IGHV) gene and reduced treatment-free survival

Chronic lymphocytic leukemia (CLL) is characterized by a monoclonal expansion of mature B-lymphocytes. Mutational status of the immunoglobulin variable heavy chain region (IGHV) gene stratifies CLL patients into two prognostic groups. We performed microarray analysis of CLL cells using the Agilent platform to detect the most important gene expression differences regarding IGHV status in CLL cells. We analyzed a cohort of 118 CLL patients with different IGHV mutational status and completely characterized all described prognostic markers using expression microarrays and quantitative real-time RT-PCR (reverse transcription PCR). We detected lymphocyte-activation gene 3 (LAG3) as a novel prognostic marker: LAG3 high expression in CLL cells correlates with unmutated IGHV (P < 0.0001) and reduced treatment-free survival (P = 0.0087). Furthermore, quantitative real-time RT-PCR analysis identified a gene-set (LAG3, LPL, ZAP70) whose overexpression is assigned to unmutated IGHV with 90% specificity (P < 0.0001). Moreover, high expression of tested gene-set and unmutated IGHV equally correlated with reduced treatment-free survival (P = 7.7 * 10(-11) vs. P = 1.8 * 10(-11)). Our results suggest that IGHV status can be precisely assessed using the expression analysis of LAG3, LPL, and ZAP70 genes. Expression data of tested markers provides a similar statistical concordance with treatment-free survival as that of the IGHV status itself. Our findings contribute to the elucidation of CLL pathogenesis and provide novel prognostic markers for possible application in routine diagnostics.

A single tube, four-color flow cytometry assay for evaluation of ZAP-70 and CD38 expression in chronic lymphocytic leukemia

We describe a simple and robust flow cytometry assay for ZAP-70 and CD38 expression. The steps required to validate this assay in a clinical flow cytometry laboratory are described. Two criteria were used to characterize ZAP-70 expression into positive, negative, and indeterminate categories and applied to 111 cases of chronic lymphocytic leukemia (CLL) resulting in 29.7% positive, 56.8% negative, and 13.5% indeterminate cases. A sensitivity-specificity crossover plot between ZAP-70 and CD38 suggested a cutoff of 12.5% for defining CD38 positivity. ZAP-70+ cases were significantly more likely to be at a higher clinical stage and, together with CD38+ cases, were more likely to have unmutated IgV(H). However, for individual patients, the concordance between these markers was not perfect. It may be necessary to evaluate several prognostic markers simultaneously in CLL, and availability of convenient assays for ZAP-70 and CD38 is desirable for optimal clinical decision making.

Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells

BACKGROUND

ZAP-70 is an independent negative prognostic marker in chronic lymphocytic leukemia (CLL). Usually, its expression is investigated by flow cytometric protocols in which the percentage of ZAP-70 positive CLL cells is determined in respect to isotypic control (ISO-method) or residual ZAP-70 positive T cells (T-method). These methods, however, beside suffering of an inherent subjectivity in their application, may give discordant results in some cases. The aim of this study was to assess the prognostic significance of these methods in comparison with another in which ZAP-70 expression was evaluated as a Mean-Fluorescence-Intensity Ratio between gated T and CLL cells (T/B Ratio-method).

METHODS

Cytometric files relative to ZAP-70 determination according to the three readouts were retrospectively reviewed on a cohort of 173 patients (test set), all with complete clinical and biological prognostic assessment and time-to-treatment (TTT) available. Findings were then validated in an independent cohort of 341 cases from a different institution (validation set).

RESULTS

The optimal prognostic cut-offs for ZAP-70 expression were selected at 11% (ISO-method) or 20% of positive cells (T-method), as well as at 3.0 (T/B Ratio-method) in the test set; these cut-offs yielded 66, 60 and 73 ZAP-70+ cases, respectively. Univariate analyses resulted in a better separation of ZAP-70+ vs. ZAP-70- CLL patients utilizing the T/B Ratio, compared to T- or ISO-methods. In multivariate analyses which included the major clinical and biological prognostic markers for CLL, the prognostic impact of ZAP-70 appeared stronger when the T/B-Ratio method was applied. These findings were confirmed in the validation set, in which ZAP-70 expression, evaluated by the T- (cut-off = 20%) or T/B Ratio- (cut-off = 3.0) methods, yielded 180 or 127 ZAP-70+ cases, respectively. ZAP-70+ patients according to the T/B Ratio-method had shorter TTT, both if compared to ZAP-70- CLL, and to cases classified ZAP-70+ by the T-method only.

CONCLUSIONS

We suggest to evaluate ZAP-70 expression in routine settings using the T/B Ratio-method, given the operator and laboratory independent feature of this approach. We propose the 3.0 T/B Ratio value as optimal cut-off to discriminate ZAP-70+ (T/B Ratio less than 3.0) from ZAP-70- (T/B Ratio more/equal than 3.0) cases.

Flow cytometry APC-tandem dyes are degraded through a cell-dependent mechanism

Technological developments of multiparametric flow cytometry come along with the generation of new dyes. The APC-tandem dyes, which combine the fluorophores APC and Cy7/H7, allow the detection of a specific signal in the APC-Cy7/H7 channel along with an unexpected nonspecific signal in the APC channel. Depending on the magnitude of the latter, it may be a handicap for interpreting the data of multicolor labeling experiments. We investigated the alteration of the APC-tandem dyes by labeling peripheral blood cells with antibodies directed toward leukocyte surface proteins and by analyzing cells by flow cytometry. Our results show that the APC-Cy7/H7 tandem fluorochromes degraded over time. Nonspecific APC signal was observed with the various antibodies tested only upon cell attachment but not under bead linkage. Moreover, the percentage of degradation of the APC-Cy7/H7 dyes was dependent on the cell type analyzed. Interestingly, nonspecific APC signal strongly decreased when the metabolic activity of immunolabeled cells was inhibited or when cells were incubated with vitamin C. This study demonstrates that the APC-tandem dyes are the target of cell-dependent degradation, which may be antagonized. These findings will allow cytometer users to optimize their multicolor panels.

Biological prognostic markers in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most frequent leukemic disease of adults in the Western world. It is remarkable by an extraordinary heterogeneity of clinical course with overall survival ranging from several months to more than 15 years. Classical staging sytems by Rai and Binet, while readily available and useful for initial assessment of prognosis, are not able to determine individual patient's ongoing clinical course of CLL at the time of diagnosis, especially in early stages. Therefore, newer biological prognostic parameters are currently being clinically evaluated. Mutational status of variable region of immunoglobulin heavy chain genes (IgVH), cytogenetic aberrations, and both intracellular ZAP-70 and surface CD38 expression are recognized as parameters with established prognostic value. Molecules regulating the process of angiogenesis are also considered as promising markers. The purpose of this review is to summarize in detail the specific role of these prognostic factors in chronic lymphocytic leukemia.

Gene expression factors as predictors of genetic risk and survival in chronic lymphocytic leukemia

BACKGROUND

A variety of surrogate markers for genetic features and outcome have been described in chronic lymphocytic leukemia based on gene expression analyses. Previous studies mostly focused on individual markers and selected disease characteristics, which makes it difficult to estimate the relative value of the novel markers. Therefore, in the present study a comprehensive approach was chosen investigating 18 promising, partly novel expression markers in a well characterized cohort of patients with long clinical follow-up and full genetic information (IGHV status, genomic abnormalities).

DESIGN AND METHODS

Expression markers were evaluated using real-time quantitative reverse transcriptase polymerase chain reaction in CD19(+)-purified samples from 151 patients. Multivariate analyses were performed to test the markers' ability to identify patients at genetic risk and as prognostic markers in the context of established prognostic factors.

RESULTS

For individual markers, ZAP70 expression provided the highest rate (81%) of correct assignment of patients at genetic risk (IGHV unmutated, V3-21 usage, 11q- or 17p-), followed by LPL and TCF7 (76% both). The assignment rate was improved to 88% by information from a four-gene combination (ZAP70, TCF7, DMD, ATM). In multivariate analysis of treatment-free survival, IGHV mutation status and expression of ADAM29 were of independent prognostic value besides disease stage. With regards to overall survival, expression of ATM, ADAM29, TCL1, and SEPT10 provided prognostic information in addition to that derived from clinical and genetic factors.

CONCLUSIONS

Gene expression markers are suitable for screening but not as surrogates for the information from genetic risk factors. While many individual markers may be associated with outcome, only a few are of independent prognostic significance. With regard to prognosis estimation, the genetic prognostic factors cannot be replaced by the expression markers.

Circulating B-cell chronic lymphocytic leukemia cells display impaired migration to lymph nodes and bone marrow

Homing to secondary lymphoid organs and bone marrow (BM) is a central aspect of leukemic pathophysiology. We investigated the roles of the two major lymphocyte integrins LFA-1 and VLA-4 on B-cell chronic lymphocytic leukemia (CLL) cells in these processes. We found that the majority of CLL cells expressed significantly reduced LFA-1 due to low beta2 integrin transcripts. VLA-4 expression was heterogeneous but underwent rapid activation by the BM chemokine CXCL12. CLL cells failed to transmigrate across VCAM-1-expressing, ICAM-1-expressing, and CXCL12-expressing endothelium, whereas when LFA-1 expression was regained in subsets of CLL cells, these lymphocytes rapidly transmigrated the endothelium. Furthermore, when injected into tail veins of immunodeficient mice, normal B cells rapidly homed to lymph nodes (LN) in a LFA-1-dependent manner, whereas CLL cells did not. Nevertheless, only residual CLL subsets could reenter BM, whereas both normal and CLL cells homed to the mice spleen in an LFA-1-independent and VLA-4-independent manner. Our results suggest that CLL cells have a reduced capacity to adhere and transmigrate through multiple vascular endothelial beds and poorly home to lymphoid organs other than spleen. Integrin blocking could thus be an efficient strategy to prevent circulating CLL cells from reaching prosurvival niches in LNs and BM but not in spleen.

Percentage of smudge cells on routine blood smear predicts survival in chronic lymphocytic leukemia

PURPOSE

Smudge cells are ruptured chronic lymphocytic leukemia (CLL) cells appearing on the blood smears of CLL patients. Our recent findings suggest that the number of smudge cells may have important biologic correlations rather than being only an artifact of slide preparation. In this study, we evaluated whether the smudge cell percentage on a blood smear predicted survival of CLL patients.

PATIENTS AND METHODS

We calculated smudge cell percentages (ratio of smudged to intact cells plus smudged lymphocytes) on archived blood smears from a cohort of previously untreated patients with predominantly early-stage CLL enrolled onto a prospective observational study. The relationship between percentage of smudge cells, patient survival, and other prognostic factors was explored.

RESULTS

Between 1994 and 2002, 108 patients were enrolled onto the study and had archived blood smears available for review; 80% of patients had Rai stage 0 or I disease. The median smudge cell percentage was 28% (range, 1% to 75%). The percentage of smudge cells was lower in CD38(+) versus CD38(-) patients (P = .019) and in Zap70-positive versus Zap70-negative patients (P = .028). Smudge cell percentage as a continuous variable was associated with prolonged survival (P = .042). The 10-year survival rate was 50% for patients with 30% or less smudge cells compared with 80% for patients with more than 30% of smudge cells (P = .015). In multivariate analysis, the percentage of smudge cells was an independent predictor of overall survival.

CONCLUSION

Percentage of smudge cells on blood smear is readily available and an independent factor predicting overall survival in CLL.

Predicting clinical outcome in CLL: how and why

The clinical course of patients with chronic lymphocytic leukemia (CLL) is heterogeneous, with some patients experiencing rapid disease progression and others living for decades without requiring treatment. Clinical features and molecular/biologic factors such as ZAP-70, immunoglobulin heavy chain (IGHV) gene mutation status, and cytogenetic abnormalities on fluorescent in situ hybridization (FISH) have been found to be robust predictors of treatment-free survival and overall survival among newly diagnosed patients. Beyond their widely recognized value for providing insight into disease biology and utility for stratifying patient risk in clinical trials, these prognostic tools play an important role in the current counseling and management of patients with CLL. Recent studies have focused on how to combine the results of multiple prognostic assays into an integrated risk stratification system and explored how these characteristics influence response to treatment. This chapter reviews the available tools to stratify patient risk and discusses how these tools can be used in routine clinical practice to individualize patient counseling, guide the frequency of follow-up, and inform treatment selection.

FCRL2 expression predicts IGHV mutation status and clinical progression in chronic lymphocytic leukemia

CD38 and ZAP-70 are both useful prognostic markers for B-cell chronic lymphocytic leukemia (CLL), but are variably discordant with IGHV mutation status. A total of 5 human Fc receptor-like molecules (FCRL1-5) have tyrosine-based immunoregulatory potential and are expressed by B-lineage subpopulations. To determine their prognostic potential in CLL, FCRL expression was compared with IGHV mutation status, CD38 and ZAP-70 expression, and clinical features from 107 patients. FCRL1, FCRL2, FCRL3, and FCRL5 were found at markedly higher levels on CLL cells bearing mutated IGHV genes than on unmutated CLL cells or CD19(+) polyclonal B lymphocytes. Univariate comparisons found that similar to CD38 and ZAP-70, FCRL expression was strongly associated with IGHV mutation status; however, only FCRL2 maintained independent predictive value by multivariate logistic analysis. Strikingly, FCRL2 demonstrated 94.4% concordance with IGHV mutation compared with 76.6% for CD38 and 80.4% for ZAP-70. Compared with other indicators, FCRL2 was also superior at predicting the time to first therapy; the median treatment-free interval was 15.5 years for patients with high FCRL2 expression compared with 3.75 years for FCRL2-low patients. Our studies indicate that FCRL2 has robust predictive value for determining IGHV gene mutation status and clinical progression and thus may further improve prognostic definition in CLL.

Optimization of flow cytometric measurement of ZAP-70 in chronic lymphocytic leukemia

BACKGROUND

The goal of this study was to optimize a cell staining procedure for flow cytometric detection of zeta-chain associated protein-70 (ZAP-70). Our specific objectives were to improve antibody selection criteria, identify a cell permeabilization procedure better tailored to ZAP-70 analysis, as well as to establish objective criteria to control antigen stability.

METHODS

Sequentially titrated 2F3.2-FITC, 1E7.2-FITC, and 1E7.2-Alexa Fluor 488 anti-ZAP-70 antibodies were used to stain normal B and T cells and Scatchard analysis was applied to calculate K(d) and B(max) values from saturation curves of specific binding. ZAP-70 staining was compared in cells permeabilized with two commercially available kits, Triton X-100, and a custom saponin procedure.

RESULTS

Normal B-cells were found to provide an excellent measure of nonspecific staining while varying ZAP-70 antibodies and concentrations. Comparing Scatchard analyses of specific T-cell binding revealed that 1E7.2-Alexa Fluor 488 had the highest binding affinity of the tested anti-ZAP-70 antibodies and was the best choice. The highest levels of ZAP-70 fluorescence occurred when cells were permeabilized using a noncommercial saponin procedure. Decrease of chronic lymphocytic leukemia cell viability correlated with diminished ZAP-70 expression; when viability was lower than 95% the percentage of bright positive samples was significantly decreased, indicating a possibility of false-negative results.

CONCLUSIONS

The efficiency and reliability of flow cytometric detection of ZAP-70 can be optimized by using Scatchard analysis to help select the most effective antibodies and antibody concentrations that maximize specific to nonspecific binding, by using a "custom" ZAP-70 permeabilization procedure, and by better controlling antigen stability by measuring cell viability.

An improved flow cytometric method using FACS Lysing Solution for measurement of ZAP-70 expression in B-cell chronic lymphocytic leukemia

BACKGROUND

B-cell expression of ZAP-70, normally expressed in T and NK cells, correlates with poor prognosis in B-CLL. Poor discrimination between ZAP-70 positive and negative cells hampers routine application of flow cytometry. We examined the usefulness of FACS Lysing Solution.

METHODS

ZAP-70 expression in 65 healthy volunteers was measured by four-color flow cytometry, comparing FACS Lysing Solution for fixation and permeabilization with the Fix & Perm kit. Separation between ZAP-70 positive T cells and negative B cells was based on a ratio of median ZAP-70 staining of T cells to B cells. In 25 B-CLL patients, ZAP-70 expression was estimated using the lower limit of the fluorescence range corresponding with 98% of ZAP-70 positive T cells as threshold marker as well as a ratio of B-CLL cell to internal T-cell median ZAP-70 staining.

RESULTS

Use of FACS Lysing Solution resulted in approximately fourfold increased separation between ZAP-70 positive T cells and negative B cells, when compared with the Fix & Perm kit. In B-CLL samples, ZAP-70 negative and positive B-cell expression could be clearly discerned.

CONCLUSIONS

FACS Lysing Solution is a simple procedure that markedly improves discrimination between ZAP-70 positive and negative cells.

The critical role of histology in an era of genomics and proteomics: a commentary and reflection

The role of histologic examination in lymphoma diagnosis has been called into question by proponents of new technologies, such as genomics and proteomics. We review the history and salient features of morphologic evaluation in lymphoid diseases, and discuss the general and specific limitations of mature ancillary techniques, such as immunohistochemistry, flow cytometry, and molecular studies. We then speculate on the future relationship between morphology and the new genomic and proteomic technologies as they become integrated into clinical practice.

Prognostic markers in chronic lymphocytic leukaemia

Rai and Binet staging of chronic lymphocytic leukaemia (CLL) is being superseded by new prognostic markers. The mutational status of the immunoglobulin variable region heavy-chain genes segregates the disease into more benign and more malignant versions, and has been confirmed as an important prognostic marker in prospective clinical trials. A search for surrogate markers for this difficult-to-perform assay has led to flow cytometric assays for CD38 and ZAP-70 expression, although in both cases there are problems with standardization and interpretation of the assays. A separate pathway of research has revealed two chromosomal aberrations--deletions of 11q and 17p--as important prognostic markers. Fluorescent in-situ hybridization has made their detection readily available. These five markers are in different stages of evaluation, but some of them are ready to be used for risk-adapted therapy in clinical trials. Other assays are in earlier stages of assessment.