Prognostic usage of V(H) gene mutation status and its surrogate markers and the role of antigen selection in chronic lymphocytic leukemia

A novel diagnostic biosensor for distinguishing immunoglobulin mutated and unmutated types of chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), the immunoglobulin heavy-chain variable (IgVH) region may be mutated (Ig-mutated CLL) or unmutated (Ig-unmutated CLL); and the presence or absence of mutations in this region of CLL cells distinguishes two clinically distinct forms. It is important for physicians to distinguish between patients with Ig-unmutated CLL, where typically have more indolent disease with median survivals close to 25 years, and Ig-mutated CLL, where have more aggressive disease with median survivals around eight years. In this work, a biosensor capable of diagnosis and distinguishing between these two types of CLL was reported. The biosensor was fabricated by modifying a gold electrode with gold nanoparticles (AuNPS) followed by coating of ZAP70 oligonucleotide probe on the surface to detect specific sequence of ZAP70 gene. ZAP70 could predict the IgVH mutation status and is a good marker for differentiating Ig-mutated and Ig-unmutated CLL and serve as prognostic marker. First, we focused on achieving hybridization between probe and its complementary sequence. Hybridization between probe and target was determined with electrochemical impedance spectroscopy (EIS). Then, our efforts turned to optimize the conditions for the detection of any point mutation and also to maximize the selectivity. Under optimal conditions, the biosensor has a good calibration range between 2.0 × 10(-14) and 1.0 × 10(-9)molL(-1), with ZAP70 DNA sequence detection limit of 4.0 × 10(-15)molL(-1). We successfully detect hybridization first in synthetic samples, and ultimately in blood samples from patients. Experimental results illustrated that the nanostructured biosensor clearly discriminates between mutated and non-mutated CLL and predict the IgVH mutation status, which it has been considered as the single most informative stage independent prognostic factor in CLL.

Molecular diagnosis of hematopoietic neoplasms

Cytogenetic abnormalities are considered to be common events in hematologic malignancies. These abnormalities generally consist of structural chromosomal abnormalities or gene mutations, which often are integral to the pathogenesis and subsequent evolution of an individual malignancy. Improvements made in identifying and interpreting these molecular alterations have resulted in advances in the diagnosis, prognosis, monitoring, and therapy for cancer. As a consequence of the increasingly important role of molecular testing in hematologic malignancy management, this article presents an update on the importance and use of molecular tests, detailing the advantages and disadvantages of each test when applicable.

Large-scale analysis of DNA methylation in chronic lymphocytic leukemia

AIMS

B-cell chronic lymphocytic leukemia (CLL) is a heterogeneous malignancy that clinically ranges from indolent to rapidly progressive. CLL, like other cancers, can be affected by epigenetic alterations.

MATERIALS & METHODS

A microarray discovery-based study was initiated to determine DNA methylation in CLL cases with a range of CD38 expression (1–92%).

RESULTS

Many loci were either methylated or unmethylated across all CD38 levels, but differential methylation was also observed for some genes. Genomic sequencing of DLEU7 confirmed extensive cytosine methylation preferentially in patient samples with low CD38 expression, whereas NRP2, SFRP2 and ADAM12 were more commonly methylated in those with high CD38 expression.

CONCLUSION

This study demonstrates that CLL is affected by CpG island methylation in some genes that segregate with CD38 expression levels, while most others show similar methylation patterns across all levels. The CpG island methylation in certain functional gene groups and pathway-associated genes that are known to be deregulated in CLL provides additional insights into the CLL methylome and epigenetic contribution to cellular dysfunction. It will now be useful to investigate the effectiveness of epigenetic therapeutic reversal of these alterations to develop effective treatments for the disease.

Quantification of ZAP-70 mRNA by real-time PCR is a prognostic factor in chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) is heterogeneous with respect to prognosis and clinical outcome. Mutational status of immunoglobulin heavy chain variable region (IGHV) appears to be a particularly strong prognostic marker, but it is difficult to perform in a routine clinical laboratory. ζ-chain-associated protein kinase 70 kDa (ZAP-70) protein detected by flow cytometry is a strong surrogate marker of IGHV mutational status; however, it suffers from the lack of standardization.

METHODS

We investigated whether ZAP-70 mRNA expression level can be a prognostic factor in CLL. Real-time quantitative polymerase chain reaction was used to analyze ZAP-70 mRNA expression from 102 CLL patients.

RESULTS

The expression of ZAP-70 mRNA was significantly associated with Binet stage (P < 0.001), lactate dehydrogenase (P = 0.003), ZAP-70 protein (P = 0.018), IGHV mutational status (P = 0.038), and cytogenetic abnormality of del(17p13) or del(11q22.3) (P = 0.037) in CLL patients. According to receiver operating characteristic curve analysis for ZAP-70 mRNA and ZAP-70 protein, positive ZAP-70 mRNA (P = 0.006) was an adverse factor in determining the treatment free survival (TFS). In a multivariate Cox analysis of TFS, ZAP-70 mRNA is not ideal as an independent prognostic factor. However, ZAP-70 mRNA was statistically significant in predicting treatment response.

CONCLUSION

This study demonstrated the value of determination of ZAP-70 mRNA in providing useful prognostic information in CLL patients. However, ZAP-70 mRNA is not an independent prognostic factor.

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.

IGHV gene rearrangements as outcome predictors for CLL patients: experience of Ukrainian group

Important characteristics of chronic lymphocytic leukaemia (CLL) cells are biased immunoglobulin variable heavy chain (IGHV) gene repertoire and expression of stereotyped B-cell receptors (BCRs); however, their prognostic value (in contrast to the impact of IGHV gene mutational status) is less clear. To evaluate the impact of separate IGHV gene usage and expression of stereotyped BCRs in CLL prognosis. Clinical data and IGHV gene configuration were analysed in 319 consecutive patients with CLL. We found that the majority of clinical parameters of patients were defined by IGHV mutational status. Our data also provided new evidence supporting the prognostic relevance of separate IGHV genes or stereotyped BCR in CLL, namely: (a) a restricted non-mutated (UM) IGHV gene repertoire in CLL patients with autoimmune haemolytic anaemia (AIHA) (more frequent expression of UM IGHV1-69, IGHV3-11 and IGHV4-59 genes, P = 0.001), a shorter period of AIHA development for expressors of these genes (P = 0.001) and a tendency towards expression of a stereotypic HCDR3 (P = 0.029), (b) a high incidence of second solid tumour development in IGHV3-21-expressing patients (P = 0.005) and (c) differences in overall survival (OS) of UM CLL patients depending on the BCR structure. Further research of specific IGHV gene usage and subsets of stereotyped BCRs in CLL may be helpful in more precise prediction of CLL prognosis in individual patients.

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.

Chronic lymphocytic leukemia: new concepts and emerging therapies

OPINION STATEMENT

Remarkable progress in elucidating the biology of chronic lymphocytic leukemia (CLL) has been made over the last two decades. Improved understanding of CLL has lead to new prognostic tools and therapeutic options, and holds promise for eventually finding a cure for this disease. Challenges lie in incorporating the various treatment modalities, including chemotherapy, monoclonal antibodies, immunotherapeutic strategies and novel small molecules, into a comprehensive treatment strategy guided by the biological complexity of CLL.

Regulated expression of BAFF-binding receptors during human B cell differentiation

BAFF plays a central role in B-lineage cell biology; however, the regulation of BAFF-binding receptor (BBR) expression during B cell activation and differentiation is not completely understood. In this study, we provide a comprehensive ex vivo analysis of BBRs in human B-lineage cells at various stages of maturation, as well as describe the events that drive and regulate receptor expression. Our data reveal that B-lineage cells ranging from naive to plasma cells (PCs), excluding bone marrow PCs, express BAFF-R uniformly. In contrast, only tonsillar memory B cells (MB) and PCs, from both tonsil and bone marrow tissues, express BCMA. Furthermore, we show that TACI is expressed by MB cells and PCs, as well as a subpopulation of activated CD27(neg) B cells. In this regard, we demonstrate that TACI is inducible early upon B cell activation and this is independent of B cell turnover. In addition, we found that TACI expression requires activation of the ERK1/2 pathway, since its expression was blocked by ERK1/2-specific inhibitors. Expression of BAFF-R and B cell maturation Ag (BCMA) is also highly regulated and we demonstrate that BCMA expression is only acquired in MB cells and in a manner accompanied by loss of BAFF-R expression. This inverse expression coincides with MB cell differentiation into Ig-secreting cells (ISC), since blocking differentiation inhibited both induction of BCMA expression and loss of BAFF-R. Collectively, our data suggest that the BBR profile may serve as a footprint of the activation history and stage of differentiation of normal human B cells.

Use of IGHJ and IGHD gene mutations in analysis of immunoglobulin sequences for the prognosis of chronic lymphocytic leukemia

The level of somatic point mutation in immunoglobulin genes is an important prognostic indicator for patients with chronic lymphocytic leukemia (CLL). Mutation analysis presently focuses solely upon the heavy chain IGHV gene, however mutation is a stochastic process that also targets IGHD and IGHJ genes. Here, we evaluate the completeness and reliability of the reported IGHJ gene repertoire, and demonstrate the likely consequences of the inclusion of IGHD and IGHJ mutations in CLL analysis, using a dataset of 607 sequences. Inclusion of these mutations would lead to the re-classification of many sequences, which should significantly improve the prognostic value of mutation analysis.

Serum TK levels in CLL identify Binet stage A patients within biologically defined prognostic subgroups most likely to undergo disease progression

OBJECTIVE

Serum thymidine kinase (TK) levels have been shown to be correlated with survival in many malignancies, including chronic lymphocytic leukaemia (CLL). This study was designed to investigate associations between TK levels and other prognostic markers, in newly and previously diagnosed Binet stage A patients. Furthermore, the use of serum TK measurement to identify subcategories of disease within those defined by IgV(H) mutational status, gene usage and chromosomal aberrations was investigated.

METHODS

Ninety-one CLL patients were enrolled. Serum TK levels were measured using a radioenzyme assay. IgV(H) mutational status and V(H) gene usage were determined using BIOMED-2 primers and protocol. Recurring chromosomal abnormalities were detected by interphase fluorescent in situ hybridisation (FISH). Flow cytometry and reverse transcriptase polymerase chain reaction (RT-PCR) determined CD38 and Zap-70 expression, respectively.

RESULTS

Significantly higher serum TK levels were found in IgV(H) unmutated, compared with IgV(H) mutated, patients (P < 0.001). Elevated TK levels were also found in patients with CD38 and Zap-70 positivity (P = 0.004, P < 0.001, respectively), short lymphocyte doubling time (LDT) (P = 0.044) and poor or intermediate prognosis chromosomal aberrations (P < 0.001).

CONCLUSION

A TK level of >8.5 U/L best identified patients with progressive disease. Elevated TK levels could identify patients categorised, at diagnosis, into good prognosis subgroups by the various biological markers (mutated IgV(H), good prognosis chromosomal aberrations, Zap-70(-) and CD38(-)) who subsequently showed disease progression. Additionally, patients with V(H)3-21 gene usage showed high TK levels, irrespective of mutational status, and serum TK measurement retained predictive power as disease progressed in all subcategories studied.

New Prognostic Markers in CLL

The individual prognosis of patients with chronic lymphocytic leukemia (CLL) is extremely variable. Although clinical stages remain the basis for assessing prognosis in CLL, a number of biological markers, particularly serum markers, cytogenetic abnormalities, IgVH mutations, CD38 and ZAP-70 expression in leukemic cells offer important, independent prognostic information. Before being incorporated into daily practice, however, these markers require standardization and validation in large, prospective trials. Meanwhile, treatment of patients with CLL not included in clinical studies should be decided on the basis of classical NCI/CLL Working Group criteria. An important area of research in CLL prognostication is the identification of markers useful for predicting response to therapy and its duration. Among them, del(17p), reflecting P53 abnormalities, is particularly important. Also relevant is del(11q), which points to ATM defects. There is also some correlation between IgVH mutational status, ZAP-70 and CD38 expression and response to therapy and its duration, although these relationships need further investigation. Finally, there is increasing evidence that response to therapy, particularly in those cases in which minimal residual disease is eradicated, is associated with longer survival.