ALBERT

Description: One of the best predictors of poor outcome in CLL is the absence of somatic hypermutations in the Ig-genes of the leukemic cells. This prognostic dichotomy, between cases of mutated and unmutated CLL, enabled us to screen for a gene associated with poor outcome CLL using differential display RT-PCR. We identified a novel transcript from chromosome 12q22, which by RT-PCR and Northern blotting seemed to be selectively over-expressed in CLL patients with poor prognosis. No matching genes or ESTs were annotated in the region, but screening of a cDNA library from unmutated CLL patients resulted in cloning of 7 cDNAs, which probably derived from alternative splicing of a common transcript. The majority of the transcripts had no significant reading frames, but one splice variant may encode a protein of 121 amino acids. Despite very low primary sequence similarity, structure modelling revealed that the peptide potentially can fold into a structure remarkably similar to human IL-4. By RT-PCR the various transcripts were undetectable in a panel of normal tissues and cell lines. Using quantitative RT-PCR (QRT-PCR), we could however detect minute amounts of the mRNAs in normal B-cells; the level was similar or slightly higher in good prognosis patients and much higher in poor prognosis patients. The expression level of the two major mRNAs was 24–50 fold higher in patients with unmutated Ig-genes compared to patients with somatic hypermutation (p

Description: Antibodies against CD20 can activate complement and induce antibody-dependent cellular cytotoxicity (ADCC) in B lymphocytes. In B-cell lines, such antibodies also induce apoptosis. In this study, the expression and function of CD20 on B-cell chronic lymphocytic leukemia (B-CLL) cells were analyzed. Flow cytometric analysis demonstrated that B-CLL cells express CD20 with a fluorescence intensity that is significantly weaker than that of normal CD5+ and CD5− B cells and that of malignant CD5− low-grade non-Hodgkin lymphoma cells. A small population of cells from healthy donors that have an expression pattern of CD5 and CD20 identical to that of B-CLL cells were identified, and this population was confirmed to be of T lineage, not B lineage. Culture of freshly isolated B-CLL cells in the presence of the chimeric anti-CD20 antibody rituximab and a cross-linking F(ab)2 fragment, resulted in dose- and time-dependent induction of apoptosis. The induction of apoptosis occurred under conditions in which the influence of complement activation and ADCC was negligible. Cross-linking of rituximab induced strong and sustained phosphorylation of the 3 mitogen activated protein (MAP) kinases c-Jun NH2-terminal protein kinase, extracellular signal–regulated kinase, and p38. Introduction of the p38 inhibitor SB203580 into the system completely blocked signaling downstream of p38, as evidenced by the absence of MAPKAP K2 activity, and significantly reduced the degree of anti-CD20–induced apoptosis. These results demonstrate that cross-linking of rituximab bound to CD20 on freshly isolated B-CLL cells induces apoptosis through a signaling pathway that is dependent on p38 MAP-kinase activation.

Description: Abstract 1254 Poster Board I-276 Introduction Chronic lymphocytic leukemia (CLL) is a heterogeneous disease with varying clinical outcome, where many patients have an indolent course for many years, whereas others show a more aggressive disease despite treatment. This has prompted the search for biomarkers that can predict outcome in this disease. Recent studies have proposed the RNA expression levels of certain genes, i.e. LPL, CLLU1, TCL1, MCL1 and ZAP70 to be novel predictors of clinical outcome in CLL. However, a comprehensive assessment of these RNA-based markers is still lacking. The current study aimed to investigate the potential of these markers in CLL prognostication, either as single markers or in combination with established markers. Patients and Methods By applying real-time quantitative PCR, we measured the RNA expression levels of LPL, CLLU1, TCL1, MCL1 and ZAP70 in 256 newly diagnosed CLL samples from a Scandinavian population-based cohort collected from 1999 to 2002 (median follow-up, 89 months) and correlated with clinical outcome. The expression cut-offs for each RNA marker was determined by constructing ROC curves. Additionally, Binet stage, IGHV mutation status, CD38 expression (cut-off 7%) and the presence of recurrent genomic aberrations (i.e. 11q-, 17p-, 13q- and +12) were evaluated for all cases. Results High expression of all RNA-based markers except MCL1 predicted significantly shorter overall survival (OS) and time to treatment (TTT), with LPL being the most significant prognostic marker in both log-rank (Table 1) and Cox univariate regression analyses. In multivariate analysis including the RNA markers, LPL expression was the only independent prognostic factor for OS, whereas both LPL and CLLU1 could predict TTT. When including all established markers, LPL lost its significance in the model, due to its close association to the IGHV mutation status. Once the mutation status was excluded from the analysis, LPL regained its prognostic power in addition to genomic aberrations and CD38. Interestingly, all of the RNA-based markers added further prognostic information to established markers in subgroups of patients, with LPL expression status giving the most significant results. Notably, high LPL expression predicted a worse outcome in favorable prognostic subgroups such as patients with Binet stage A, CD38 negativity or favorable genomic aberrations (Table 2). Conclusions Altogether, we conclude that LPL expression appear to be the strongest among the RNA-based markers for prediction of clinical outcome in CLL and thus could potentially be applied in the clinical laboratory to predict outcome, particularly in combination with established markers. Disclosures No relevant conflicts of interest to declare.

Description: 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.

Description: The eradication of minimal residual disease (MRD) in chronic lymphocytic leukemia (CLL) patients is associated with improved progression free and overall survival, when compared to patients with detectable disease following therapy. Unfortunately, the assays that allow for MRD detection, such as PCR analysis of patients specific immunoglobulin heavy chain rearrangements, or multiparametric multi-color flow cytometry are expensive, cumbersome, and require a high level of technical expertise. As such, MRD assessment in CLL is not routinely employed outside of specialized centers or clinical studies. Therefore, the development of new assays that can be employed uniformly for all CLL patients and easily implemented in general clinical practice would be of great benefit to the CLL community. The expression pattern of the CLLU1 gene (CLL Upregulated gene 1) is extremely restricted: elevated levels of CLLU1 expression has only been detected in CLL patient samples, not in any other tissue or cell line. In the majority of untreated CLL patients followed in longitudinal analysis the CLLU1 expression levels were stable over time. Furthermore, in CLL patient samples analyzed for CLLU1 expression before treatment and after treatment response followed by relapse, the CLLU expression levels were similar. Hence, the CLLU1 status appears to be an intrinsic, constant parameter for the CLL clone. We therefore hypothesized that CLLU1 expression levels will be very low or not detectable in patients who have experienced complete leukemia eradication, and likewise the persistence of elevated CLLU1 levels, should indicate persistent residual disease or relapsed leukemia. We performed a retrospective analysis on cryopreserved specimens from patients who were in clinical remissions that underwent marrow biopsies for MRD evaluation by 4-color flow. RNA from peripheral blood mononuclear cell samples collected at the time of the marrow biopsy was extracted and analyzed by realtime RT-PCR using the comparative Ct method of relative quantification with b2-microglobulin as endogenous control and a pool of purified normal B-lymphocytes as calibrator. Seventeen patients underwent a total of 26 response evaluations with MRD assessed by 4 color flow in the marrow. MRD negativity by 4-color flow was based on a threshold of detection of 0.1% leukocytes expressing CD5, CD19, CD20, and CD79b. For patients found to have MRD in the marrow, the mean CLLU1 level was 34.7 (95% CI 5.03–64.38). For patients with undetectable disease in the marrow by 4-color flow, the mean CLLU1 level was 0.07 (95% CI 0.02–0.14). In 3 cases, all of which demonstrated

Description: The pathogenesis of chronic lymphocytic leukemia (CLL) is unknown but may involve aberrant activation of signaling pathways. Somatic hypermutations in rearranged immunoglobulin heavy-chain (IgVH) genes allow a division of CLL patients into 2 categories: mutated IgVH genes are associated with an indolent disease, whereas unmutated IgVH genes define an aggressive form. Using differential display to compare gene expression in CLL cells with and without IgVH hypermutations, we identified a novel gene, CLL up-regulated gene 1 (CLLU1), that was highly up-regulated in CLL cells without IgVH hypermutations. CLLU1 mapped to chromosome 12q22, within a cluster of genes that are active in germinal center B cells. However, appreciable levels of CLLU1 were detectable only in CLL cells and not in a panel of normal tissue extracts or in any other tested hematologic malignancy. High expression of CLLU1 in CLL samples occurred irrespective of trisomy 12 or large chromosomal rearrangements. CLLU1 encodes 6 mRNAs with no sequence homology to any known gene, and most transcripts appear to be noncoding. Two transcripts, however, potentially encode a peptide with remarkable structural similarity to human interleukin 4. These data, in particular the unique and restricted expression pattern, suggest that CLLU1 is the first disease-specific gene identified in CLL.

Description: We have recently identified and cloned a novel disease specific gene CLLU1, with a strong prognostic significance in a small test cohort of CLL patients (ASH 2004, #770). To validate this finding in a larger series, 176 newly diagnosed, previously untreated CLL patients referred to Rigshospitalet, Copenhagen in 1991–1999, were investigated. Clinical characteristics of the population were: 116 stage A patients (66 %), median age 69.9 years, 98 males (56%), median follow up 59 months. The end points for the statistical analysis were overall survival and time to initiation of treatment. At time of analysis 91 (52%) patients had died and 104 (59%) had commenced treatment. Frozen patient samples, taken at time of diagnosis, were investigated for CLLU1 expression, as well as for mutational status, CD38 expression, ZAP-70 expression and cytogenetic aberrations. CLLU1 expression was assayed by QRT-PCR using the cDNA1 splice variant, and expressed as fold upregulation above the CLLU1 level in normal B-cells. CD38 and ZAP-70 analysis was performed by flow cytometry, using a 20 % cut-off level. Cytogenetic analysis was performed by FISH. The previously reported (ASH 2004, #770) median upregulation of CLLU1 in CLL cells was accurately reproduced and confirmed (25.5-fold (N = 176) vs. 27.7-fold (N = 59) in test population). Also in accordance with the pilot study, segregation of the patients based on the median CLLU1 expression level divided the population in two groups with significantly different times to initiation of treatment and borderline significant difference in overall survival. However, further analysis found an optimal cut-off level at 40-fold upregulation of CLLU1 expression; use of this cut-off demonstrated a highly significant difference in overall survival for patients with upregulated expression of CLLU1 (p = 0.0023). The median overall survival was 60.2 months for patients with CLLU1 expression above 40-fold compared to 100.8 months for the group with lower expression level. Likewise the time to initiation of first treatment was significantly shorter in the high-level expression group (p = 0.0018, median time to first treatment 9.3 months vs. 54.9 months). Furthermore, CLLU1 expression was upregulated in all poor prognostic subgroups investigated: Binet stage B or C, IgVH unmutated, unfavorable cytogenetics, high CD38 expression and high ZAP-70 expression. Our new study confirms that CLLU1 is a strong prognostic factor in CLL, comparable to other established prognostic markers. The exclusive upregulation of CLLU1 expression in CLL suggests a putative role for CLLU1 in the pathogenesis of CLL, and makes this gene a strong candidate for future gene-targeted treatment strategies. Figure Figure