CLLU1 expression levels predict time to initiation of therapy and overall survival in chronic lymphocytic leukemia

CLLU1 as an emerging biomarker in chronic lymphoid leukemia

CLLU1, a disease-specific gene associated with chronic lymphoid leukemia (CLL), is located on chromosome 12q22. Previous studies considered CLLU1 to be a non-coding RNA; however, recent research has discovered that its coding sequence region possesses the potential to encode a short peptide similar to interleukin-4. Remarkably, abnormally elevated expression of CLLU1 has only been detected in chronic lymphoid leukemia among all hematological cancers. High CLLU1 expression often indicates more malignant pathological features and an unfavorable prognosis for patients. Importantly, the expression level of CLLU1 remains unaffected by the passage of time or therapeutic interventions, thus rendering it a novel prognostic marker. This article provides a comprehensive summary of relevant research findings on CLLU1 in the context of CLL prognosis and clinical applications, aiming to guide subsequent theoretical and clinical investigations in this field.

The Role of Methylation in Chronic Lymphocytic Leukemia and Its Prognostic and Therapeutic Impacts in the Disease: A Systematic Review

Epigenetic regulation has been thoroughly investigated in recent years and has emerged as an important aspect of chronic lymphocytic leukemia (CLL) biology. Characteristic aberrant features such as methylation patterns and global DNA hypomethylation were the early findings of the research during the last decades. The investigation in this field led to the identification of a large number of genes where methylation features correlated with important clinical and laboratory parameters. Gene-specific analyses investigated methylation in the gene body enhancer regions as well as promoter regions. The findings included genes and proteins involved in key pathways that play central roles in the pathophysiology of the disease. Τhe application of these findings beyond the theoretical understanding can not only lead to the creation of prognostic and predictive models and scores but also to the design of novel therapeutic agents. The following is a review focusing on the present knowledge about single gene/gene promoter methylation or mRNA expression in CLL cases as well as records of older data that have been published in past papers.

Meta-analysis of genome-wide DNA methylation identifies shared associations across neurodegenerative disorders

BACKGROUND

People with neurodegenerative disorders show diverse clinical syndromes, genetic heterogeneity, and distinct brain pathological changes, but studies report overlap between these features. DNA methylation (DNAm) provides a way to explore this overlap and heterogeneity as it is determined by the combined effects of genetic variation and the environment. In this study, we aim to identify shared blood DNAm differences between controls and people with Alzheimer's disease, amyotrophic lateral sclerosis, and Parkinson's disease.

RESULTS

We use a mixed-linear model method (MOMENT) that accounts for the effect of (un)known confounders, to test for the association of each DNAm site with each disorder. While only three probes are found to be genome-wide significant in each MOMENT association analysis of amyotrophic lateral sclerosis and Parkinson's disease (and none with Alzheimer's disease), a fixed-effects meta-analysis of the three disorders results in 12 genome-wide significant differentially methylated positions. Predicted immune cell-type proportions are disrupted across all neurodegenerative disorders. Protein inflammatory markers are correlated with profile sum-scores derived from disease-associated immune cell-type proportions in a healthy aging cohort. In contrast, they are not correlated with MOMENT DNAm-derived profile sum-scores, calculated using effect sizes of the 12 differentially methylated positions as weights.

CONCLUSIONS

We identify shared differentially methylated positions in whole blood between neurodegenerative disorders that point to shared pathogenic mechanisms. These shared differentially methylated positions may reflect causes or consequences of disease, but they are unlikely to reflect cell-type proportion differences.

The Impact and Prognostic Significance of Chronic Lymphocytic Leukemia Upregulated 1 (CLLU1) Gene Expression in Patients with Chronic Lymphocytic Leukemia: A Single Center Experience

OBJECTIVES

To determine CLLU1 gene levels and the relationship of that gene among other prognostic parameters in patients with chronic lymphocytic leukemia.

METHODS

Bone-marrow infiltration pattern, β2-microglobulin (β 2-M), cluster of differentiation (CD)38, and ZAP-70 status were recorded. CLLU1 levels were assessed by real-time polymerase chain reaction (RT-PCR) and expressed as folds. The relationship between CLLU1 and other known prognostic parameters was evaluated.

RESULTS

CLLU1 expression was positive in 81 patients and negative in 3 patients. The median (interquartile range [IQR]) CLLU1 level was 6.45 folds (3.75-16.57 folds) in patients with β 2-M normal values and 16.22 folds (3.91-62.00 folds) in patients with increased β 2-M (P = .15). Patients with a higher CD38 value than the median level had 3 times higher CLLU1 levels than the other group (P = .07). The median (IQR) CLLU1 level was 4.25 folds (2.75-13.71 folds) in patients with CLL who tested negative on ZAP-70, whereas it was 49.52 folds (15.06-446.36 folds) in those who tested positive via ZAP-70 (P = .005).

CONCLUSIONS

CLLU1 is a specific parameter to CLL, and its level corresponds well with the ZAP-70 level.

Construction and Comprehensive Analyses of a Competing Endogenous RNA Network in Tumor-Node-Metastasis Stage I Hepatocellular Carcinoma

Background

Long noncoding RNAs (lncRNAs) can function as competing endogenous RNAs (ceRNAs) and interact with microRNAs (miRNAs) to regulate target gene expression, which can greatly influence tumor development and progression. Different tumor-node-metastasis (TNM) stages of hepatocellular carcinoma (HCC) defined by the American Joint Committee on Cancer (AJCC) have different clinical results. Our purpose was to comprehensively analyze differentially expressed (DE) lncRNAs, miRNAs, and mRNAs in stage I HCC and identify prognosis-associated RNAs.

Methods

RNA-seq data were obtained from The Cancer Genome Atlas (TCGA) database. A stage I HCC-associated miRNA-lncRNA-mRNA network was constructed. Next, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment pathway analyses of ceRNA-associated DEmRNAs were performed using Database for Annotation, Visualization, and Integrated Discovery (DAVID) 6.8 and Clusterprofile in the R package. The protein-protein interaction (PPI) network of the above mRNAs was then constructed using STRING. Finally, the association between lncRNAs and mRNAs in the ceRNA network and prognosis of patients was further analyzed. Linear regression analysis of the above lncRNAs and mRNAs associated with overall survival was performed.

Results

After a comparison between HCC and adjacent nontumor tissues, 778 lncRNAs, 1608 mRNAs, and 102 miRNAs that were abnormally expressed were identified. The ceRNA network was composed of 56 DElncRNAs, 14 DEmiRNAs, and 30 DEmRNAs. Functional analysis results showed that 30 DEmRNAs were enriched in 14 GO biological process categories and 6 KEGG categories (false discovery rate (FDR) < 0.05). A PPI network was composed of 22 nodes and 58 edges. We detected 4 DElncRNAs (BPESC1, AC061975.6, AC079341.1, and CLLU1) and 6 DEmRNAs (CEP55, E2F1, E2F7, EZH2, G6PD, and SLC7A11) that had significant influences on the overall survival (OS) of stage I HCC patients (P < 0.05). lncRNA BPESC1 was positively correlated with mRNA CEP55 via miR-424, and lncRNA AC061975.6 was positively correlated with mRNA E2F1 via miR-519d.

Conclusion

Our study identified novel lncRNAs and mRNAs that were associated with the progression and prognosis of stage I HCC and further investigated the regulatory mechanism of lncRNA-mediated ceRNAs in the development of stage I HCC.

Impact of Fluorescent In Situ Hybridization Aberrations and CLLU1 Expression on the Prognosis of Chronic Lymphocytic Leukemia: Presentation of 156 Patients from Turkey

OBJECTIVE

This study evaluates the impact of CLLU1 expression and fluorescent in situ hybridization (FISH) analysis of a group of Turkish chronic lymphocytic leukemia (CLL) patients.

MATERIALS AND METHODS

A total of 156 CLL patients were analyzed by FISH method; 47 of them were also evaluated for CLLU1 expression. Results were correlated with clinical parameters.

RESULTS

FISH aberrations were found in 62% of patients. These aberrations were del13q14 (67%), trisomy 12 (27%), del11q22 (19%), del17p (8%), and 14q32 rearrangements (20%). Overall del11q22 and del17p were associated with the highest mortality rates, shortest overall survival (OS), and highest need for medication. Homozygous del13q14, 14q32 rearrangements, and higher CLLU1 expression correlated with shorter OS.

CONCLUSION

Cytogenetics/FISH analysis is still indicated for routine evaluation of CLL. Special consideration is needed for the poor prognostic implications of del11q22, del17p, 14q32 rearrangements, and homozygous del13q14. The impact of CLLU1 expression is not yet clear and it requires more data before becoming routine in genetic testing in CLL patients.

Expression of evolutionarily novel genes in tumors

The evolutionarily novel genes originated through different molecular mechanisms are expressed in tumors. Sometimes the expression of evolutionarily novel genes in tumors is highly specific. Moreover positive selection of many human tumor-related genes in primate lineage suggests their involvement in the origin of new functions beneficial to organisms. It is suggested to consider the expression of evolutionarily young or novel genes in tumors as a new biological phenomenon, a phenomenon of TSEEN (tumor specifically expressed, evolutionarily novel) genes.

Chronic lymphocytic leukemia patients have a preserved cytomegalovirus-specific antibody response despite progressive hypogammaglobulinemia

Chronic lymphocytic leukemia (CLL) is characterized by progressive hypogammaglobulinemia predisposing affected patients to a variety of infectious diseases but paradoxically not to cytomegalovirus (CMV) disease. Moreover, we found reactivity of a panel of CLL recombinant antibodies (CLL-rAbs) encoded by a germ-line allele with a single CMV protein, pUL32, despite differing antibody binding motifs. To put these findings into perspective, we studied prospectively relative frequency of viremia, kinetics of total and virus-specific IgG over time, and UL32 genetic variation in a cohort of therapy-naive patients (n=200). CMV-DNA was detected in 3% (6/200) of patients. The decay of total IgG was uniform (mean, 0.03; SD, 0.03) and correlated with that of IgG subclasses 1-4 in the paired samples available (n=64; p<0.001). Total CMV-specific IgG kinetics were more variable (mean, 0,02; SD, 0,06) and mean decay values differed significantly from those of total IgG (p=0.034). Boosts of CMV-specific antibody levels were observed in 49% (22/45) of CMV-seropositive patients. In contrast, VZV- and EBV-specific IgG levels decayed in parallel with total IgG levels (p=0.003 and p=0.001, respectively). VZV-specific IgG even became undetectable in 18% (9/50) of patients whereas CMV-specific ones remained detectable in all seropositive patients. The observed CMV-specific IgG kinetics were predicated upon the highly divergent kinetics of IgG specific for individual antigens - glycoprotein B-specific IgG were boosted in 51% and pUL32-specific IgG in 32% of patients. In conclusion, CLL patients have a preserved CMV-specific antibody response despite progressive decay of total IgG and IgG subclasses. CMV-specific IgG levels are frequently boosted in contrast to that of other herpesviruses indicative of a higher rate of CMV reactivation and antigen-presentation. In contrast to the reactivity of multiple different CLL-rAbs with pUL32, boosts of humoral immunity are triggered apparently by other CMV antigens than pUL32, like glycoprotein B.

Prognostic markers and their clinical applicability in chronic lymphocytic leukemia: where do we stand?

Chronic lymphocytic leukemia (CLL) is a clinically and biologically heterogeneous disease where the majority of patients have an indolent disease course, while others may experience a far more aggressive disease, treatment failure and poor overall survival. During the last two decades, there has been an intense search to find novel biomarkers that can predict prognosis as well as guide treatment decisions. Two of the most reliable molecular prognostic markers, both of which are offered in routine diagnostics, are the immunoglobulin heavy chain variable (IGHV) gene mutational status and fluorescence in situ hybridization (FISH) detection of prognostically relevant genomic aberrations (e.g. 11q-, 13q-, +12 and 17p-). In addition to these markers, a myriad of additional biomarkers have been postulated as potential prognosticators in CLL, on the protein (e.g. CD38, ZAP70, TCL1), the RNA (e.g. LPL, CLLU1, micro-RNAs) and the genomic (e.g. TP53, NOTCH1, SF3B1 and BIRC3 mutations) level. Efforts are now being made to test these novel markers in larger patient cohorts as well as in prospective trials, with the ultimate goal to combine the "best" markers in a "CLL prognostic index" applicable for the individual patient. Although it is clear that these studies have significantly improved our knowledge regarding both prognostication and the biology of the disease, there is still an immediate need for recognizing biomarkers that can predict therapy response, and efforts should now focus on addressing this pertinent issue. In the present article, we review the extensive literature in the field of prognostic markers in CLL, focus on the most clinically relevant markers and discuss future directions regarding biomarkers in CLL.

Molecular characterization of neoplastic and normal "sister" lymphoblastoid B-cell lines from chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) B-cells resemble self-renewing CD5 + B-cells carrying auto/xeno-antigen-reactive B-cell receptors (BCRs) and multiple innate pattern-recognition receptors, such as Toll-like receptors and scavenger receptors. Integration of signals from BCRs with multiple surface membrane receptors determines whether the cells will be proliferating, anergic or apoptotic. To better understand the role of antigen in leukemogenesis, CLL cell lines producing monoclonal antibodies (mAbs) will facilitate structural analysis of antigens and supply DNA for genetic studies. We present here a comprehensive genotypic and phenotypic characterization of available CLL and normal B-cell-derived lymphoblastoid cell lines (LCLs) from the same individuals (n = 17). Authenticity and verification studies of CLL-patient origin were done by IGHV sequencing, fluorescence in situ hybridization (FISH) and DNA/short tandem repeat (STR) fingerprinting. Innate B-cell features, i.e. natural Ab production and CD5 receptors, were present in most CLL cell lines, but in none of the normal LCLs. This panel of immortalized CLL-derived cell lines is a valuable reference representing a renewable source of authentic Abs and DNA.

CLLU1 expression has prognostic value in chronic lymphocytic leukemia after first-line therapy in younger patients and in those with mutated IGHV genes

CLLU1, located at chromosome 12q22, encodes a transcript specific to chronic lymphocytic leukemia and has potential prognostic value. We assessed the value of CLLU1 expression in the LRF CLL4 randomized trial. Samples from 515 patients with chronic lymphocytic leukemia were collected immediately before the start of treatment. After RNA extraction and cDNA synthesis, CLLU1 expression was assessed by quantitative polymerase chain reaction. In total, 247 and 268 samples were identified as having low and high CLLU1 expression, respectively. The median follow-up was 88 months. High CLLU1 expression was significantly correlated with unmutated IGHV genes, ZAP-70 and CD38 positivity, and absence of 13q deletion (all r>0.2, P<0.0001). At 6 years, patients with high CLLU1 expression had significantly worse progression-free survival (9% versus 17%; P=0.03) and overall survival (42% versus 57%; P=0.0003) than patients with low CLLU1 expression. Among patients with mutated IGHV genes, overall survival at 6 years was 50% in those with high CLLU1 expression and 76% in those with low CLLU1 expression (P=0.005). However, CLLU1 expression was not an independent predictor of overall survival in a multivariate model including TP53 aberrations, beta-2 microglobulin level, age and IGHV mutation status. Nor did it predict response to treatment. CLLU1 expression analysis helps to refine the prognosis of patients with chronic lymphocytic leukemia who have mutated IGHV genes.

Uncovering the DNA methylome in chronic lymphocytic leukemia

Over the past two decades, aberrant DNA methylation has emerged as a key player in the pathogenesis of chronic lymphocytic leukemia (CLL), and knowledge regarding its biological and clinical consequences in this disease has evolved rapidly. Since the initial studies relating DNA hypomethylation to genomic instability in CLL, a plethora of reports have followed showing the impact of DNA hypermethylation in silencing vital single gene promoters and the reversible nature of DNA methylation through inhibitor drugs. With the recognition that DNA hypermethylation events could potentially act as novel prognostic and treatment targets in CLL, the search for aberrantly methylated genes, gene families and pathways has ensued. Subsequently, the advent of microarray and next-generation sequencing technologies has supported the hunt for such targets, allowing exploration of the methylation landscape in CLL at an unprecedented scale. In light of these analyses, we now understand that different CLL prognostic subgroups are characterized by differential methylation profiles; we recognize DNA methylation of a number of signaling pathways genes to be altered in CLL, and acknowledge the role of DNA methylation outside of traditional CpG island promoters as fundamental players in the regulation of gene expression. Today, the significance and timing of altered DNA methylation within the complex epigenetic network of concomitant epigenetic messengers such as histones and miRNAs is an intensive area of research. In CLL, it appears that DNA methylation is a rather stable epigenetic mark occurring rather early in the disease pathogenesis. However, other consequences, such as how and why aberrant methylation marks occur, are less explored. In this review, we will not only provide a comprehensive summary of the current literature within the epigenetics field of CLL, but also highlight some of the novel findings relating to when, where, why and how altered DNA methylation materializes in CLL.

Analysis of CLLU1 expression levels before and after therapy in patients with chronic lymphocytic leukemia

OBJECTIVE

  Chronic lymphocytic leukemia (CLL) is incurable, but therapy leading to eradication of minimal residual disease (MRD) in CLL is associated with improved clinical outcomes. CLL upregulated gene 1 (CLLU1) is solely upregulated in CLL patient samples. We hypothesized that CLLU1 could be used to monitor for residual disease in CLL patient samples after therapy.

METHODS

  We examined whether the CLLU1 real-time quantitative PCR (RQ-PCR) could detect small numbers of CLL cells in mixtures of normal peripheral blood mononuclear (PBMC) cells. We then performed a retrospective analysis on time-matched cryo-preserved specimens from patients who achieved MRD-negative remissions that underwent serial marrow biopsies for evaluation of residual disease by 4-color flow cytometry. RNA from PBMC samples collected at the time of the marrow assessments was analyzed for CLLU1. Nine patients underwent a total of 46 paired blood and marrow evaluations (median 5 assessments per patient).

RESULTS

  CLLU1 RQ-PCR on PBMCs of healthy donors reconstituted with varying amounts of CLL cells demonstrated leukemia cells could be reliably detected with high sensitivities depending on the CLLU1 expression level. Analysis of time-matched samples assessed for CLLU1 levels in the blood by RQ-PCR and residual disease of the marrow determined by 4-color flow cytometry revealed a correlation coefficient of 0.96 (P < 0.0001).

CONCLUSION

  The CLLU1 RQ-PCR is a sensitive and specific assay for detecting residual CLL cells after therapy. Assessment of blood CLLU1 levels can be used as a reliable marker of tumor burden and has the potential to complement currently used techniques for MRD monitoring in patients with CLL.

TOSO is overexpressed and correlated with disease progression in Chinese patients with chronic lymphocytic leukemia

Recently, a gene named TOSO was identified as being overexpressed and associated with the anti-apoptotic characteristic of chronic lymphocytic leukemia (CLL). However, the association of TOSO expression with clinical features of CLL has not been fully described, especially in Chinese patients. TOSO expression was detected by quantitative RT-PCR in CD19+ sorted cells in a cohort of 81 untreated patients with CLL. The results showed that the expression of TOSO in CLL was significantly higher than that in healthy controls (p = 0.027) and other B-cell lymphoproliferative diseases (p = 0.033). The expression level of TOSO was significantly correlated with Binet staging, IGVH mutation status, age, and time to treatment in CLL. A negative correlation was observed between age and TOSO expression (Spearman's, p = 0.025). No correlation was observed between the expression of TOSO and CD38 or ZAP-70. Cox regression analysis indicated that high expression of TOSO (more than 8.4) was an independent indicator for shorter treatment-free survival in CLL. We conclude that TOSO is specifically overexpressed and associated with progressive disease, and might be an important prognostic factor in CLL.

A molecular score by quantitative PCR as a new prognostic tool at diagnosis for chronic lymphocytic leukemia patients

BACKGROUND

Several markers have been proposed to predict the outcome of chronic lymphocytic leukemia (CLL) patients. However, discordances exist between the current prognostic factors, indicating that none of these factors are totally perfect.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we compared the prognostic power of new RNA-based markers in order to construct a quantitative PCR (qPCR) score composed of the most powerful factors. ZAP70, LPL, CLLU1, microRNA-29c and microRNA-223 were measured by real time PCR in a cohort of 170 patients with a median follow-up of 64 months (range3-330). For each patient, cells were obtained at diagnosis and RNA was extracted from purified CD19 cells. The best markers were included in a qPCR score, which was thereafter compared to each individual factor. Statistical analysis showed that all five RNA-based markers can predict treatment-free survival (TFS), but only ZAP70, LPL and microRNA-29c could significantly predict overall survival (OS). These three markers were thus included in a simple qPCR score that was able to significantly predict TFS and OS by dividing patients into three groups (0/3, 1-2/3 and 3/3). Median TFS were >210, 61 and 24 months (P<0.0001) and median OS were >330, 242 and 137 months (P<0.0001), respectively. Interestingly, TFS results were also confirmed in Binet stage A patients (P<0.0001). When compared to other classical factors, this score displays the highest univariate Cox hazard ratio (TFS: HR=9.45 and OS: HR=13.88) but also provides additional prognostic information.

CONCLUSIONS

In our hands, this score is the most powerful tool for CLL risk stratification at the time of diagnosis.

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.

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.

The prognostic evaluation of CLLU1 expression levels in 50 Chinese patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by the relentless accumulation of monoclonal B cells with the appearance of small mature lymphocytes and a characteristic CD5 and CD19 co-expression immunophenotype. The incidence of CLL is lower in Asian countries than in Western countries, where CLL is the most common leukemia. To investigate CLLU1 expression in CLL and explore the relationship between CLLU1 expression and alternative prognostic markers, we measured CLLU1 expression levels by semiquantitative RT-PCR in a cohort of 50 Chinese patients with CLL. Analyses of IgVH somatic mutational status, ZAP-70 expression, CD38 expression, and chromosomal aberrations were also performed. The expression of CLLU1 mRNA was determined in 26 of the 50 cases (52%), among which 7 at Binet A (7/21, 33.33%) and 19 at Binet B + C (19/29, 65.52%). The expression levels of CLLU1 were significantly increased in B + C CLL patients at Binet stage compared with those at Binet stage A (P = 0.005). Data for the IgVH somatic mutational status were available for 20 patients with known CLLU1 expression. Five (25%) patients, all expressed CLLU1 mRNA, displayed unmutated IgVH gene usage. While in 15 patients (15/20, 75%) with mutated IgVH gene, only 6 were CLLU1 positive. Patients with unmutated IgVH genes expressed higher levels of CLLU1 than did those with IgVH mutations (P < 0.05). Among 24 CD38(+)-CLL cases, 17 (70.83%) were CLLU1 positive, whereas only 9 (34.62%) positive cases were identified in 26 CD38(-)-CLL patients. Thus, the expression of CLLU1 in CD38(+)-CLL was significantly higher than that in CD38(-)-CLL. However, no significant difference of CLLU1 expression was found between ZAP-70(+) (14/22, 63.64%) and ZAP-70(-) (12/28, 42.86%) patients (P > 0.05). We conclude that CLLU1 expression was significantly associated with clinical stages, IgVH somatic mutational status and CD38 expression, and might be an important prognostic factor in CLL patients.

CLLU1 expression analysis adds prognostic information to risk prediction in chronic lymphocytic leukemia

We recently identified a disease-specific gene CLLU1 in chronic lymphocytic leukemia (CLL) and also demonstrated that high CLLU1 expression levels predict poor clinical outcome. To validate this finding, we measured CLLU1 mRNA expression levels by real-time reverse transcriptase–polymerase chain reaction (RT-PCR) in 175 patients with CLL. Analyses of IgVH mutational status, ZAP-70 expression, CD38 expression, and chromosomal aberrations were also performed. High levels of CLLU1 expression were associated with shorter overall survival (P < .001), with a 7% increase in risk of early death by each doubling of the CLLU1 expression level. Stratification for age at diagnosis demonstrated a strong prognostic significance of CLLU1 expression in patients younger than 70 years (P < .001), but not in patients aged 70 or older (P = .61). The prognostic significance of IgVH mutational status and ZAP-70 expression had a similar age-dependent variation. Multivariate analysis in the younger age group showed that CLLU1 expression analysis added further prognostic information within all prognostic subgroups, with the exception of patients with unmutated IgVH CLL. Only CLLU1 expression and IgVH mutational status had independent predictive power. Thus, analysis of CLLU1 expression is highly applicable in risk prediction in CLL for patients of an age eligible for risk stratification.