Do B-cell chronic lymphocytic leukemia patients with Ig VH3-21 genes constitute a new subset of chronic lymphocytic leukemia?

Comprehensive characterization of immunoglobulin gene rearrangements in patients with chronic lymphocytic leukaemia

Previous studies have suggested a geographical pattern of immunoglobulin rearrangement in chronic lymphocytic leukaemia (CLL), which could be as a result of a genetic background or an environmental antigen. However, the characteristics of Ig rearrangements in the population from the South of France have not yet been established. Here, we studied CLL B-cell repertoire and mutational pattern in a Southern French cohort of patients using an in-house protocol for whole sequencing of the rearranged immunoglobulin heavy-chain genes. Described biased usage of variable, diversity and joining genes between the mutated and unmutated groups was found in our population. However, variable gene frequencies are more in accordance with those observed in the Mediterranean patients. We found that the third complementary-determining region (CDR) length was higher in unmutated sequences, because of bias in the diversity and joining genes usage and not due to the N diversity. Mutations found in CLL followed the features of canonical somatic hypermutation mechanism: preference of targeting for activation-induced cytidine deaminase and polymerase motifs, base change bias for transitions and more replacement mutations occurring in CDRs than in framework regions. Surprisingly, localization of activation-induced cytidine deaminase motifs onto the variable gene showed a preference for framework regions. The study of the characteristics at the age of diagnosis showed no difference in clinical outcome, but suggested a tendency of increased replacement and transition-over-transversion mutations and a longer third CDR length in older patients.

The clinical and biological features of a series of immunophenotypic variant of B-CLL

OBJECTIVES

To describe the clinical and biological features of a series of immunophenotypic variant of B-CLL (v-CLL) characterised by intermediate RMH score, in the absence of t(11;14)(q13;q32) in FISH analysis in comparison with a series of typical CLL.

METHODS

We studied the clinical and biological features of 63 cases of v-CLL and 130 cases of CLL.

RESULTS

We observed significant differences in terms of age <70 yr (P < 0.001), lymphocytosis <20 x 10(9)/L (P < 0.001), lymphocyte doubling time <or=12 months (P = 0.02), high serum beta2-microglobulin levels (P < 0.001) and splenomegaly (P = 0.002); CD38, CD49d, CD1c were more expressed in v-CLL, CD43 in CLL (P < 0.001). IgV(H) mutation and trisomy 12 were more frequent in v-CLL group (P = 0.001; P < 0.001); del13q14 in CLL (P = 0.008). Gene expression profiling of nine v-CLL and 60 CLL indicated that the atypical group presented a specific molecular pattern. After a median follow-up of respectively, 55 (4-196) and 60 months (6-180), 25/42 patients with v-CLL (48%) and 55/93 patients with CLL (59%) were treated. Time to treatment was significantly shorter in IgV(H)-mutated v-CLL vs. mutated CLL (P = 0.006). The median overall survival was worse in v-CLL-mutated cases (P = 0.062).

CONCLUSION

v-CLL should be identified and dealt with separately from classic CLL. In particular, the prognostic markers that are routinely used to characterise classical B-CLL should not be interpreted as having the same meaning.

Use of IGHV3-21 in chronic lymphocytic leukemia is associated with high-risk disease and reflects antigen-driven, post-germinal center leukemogenic selection

We examined the chronic lymphocytic leukemia (CLL) cells of 2457 patients evaluated by the CLL Research Consortium (CRC) and found that 63 (2.6%) expressed immunoglobulin (Ig) encoded by the Ig heavy-chain-variable-region gene (IGHV), IGHV3-21. We identified the amino acid sequence DANGMDV (motif-1) or DPSFYSSSWTLFDY (motif-2) in the Ig heavy-chain (IgH) third complementarity-determining region (HCDR3) of IgH, respectively, used by 25 or 3 cases. The IgH with HCDR3 motif-1 or motif-2, respectively, was paired with Ig light chains (IgL) encoded by IGLV3-21 or IGKV3-20, suggesting that these Ig had been selected for binding to conventional antigen(s). Cases that had HCDR3 motif-1 had a median time from diagnosis to initial therapy comparable with that of cases without a defined HCDR3 motif, as did cases that used mutated IGHV3-21 (n = 27) versus unmutated IGHV3-21 (n = 30). Of 7 examined cases that used Ig encoded by IGHV3-21/IGLV3-21, we found that 5 had a functionally rearranged IGKV allele that apparently had incurred antigendriven somatic mutations and subsequent rearrangement with KDE. This study reveals that CLL cells expressing IGHV3-21/IGLV3-21 most likely were derived from B cells that had experienced somatic mutation and germinal-center maturation in an apparent antigen-driven immune response before undergoing Ig-receptor editing and after germinal-center leukemogenic selection.

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.

CD5 + Diffuse Large B-Cell Lymphoma Consists of Germline Cases and Hypermutated Cases in the Immunoglobulin Heavy Chain Gene Variable Region

CD5+ diffuse large B-cell lymphoma (DLBCL) has recently been identified as a subgroup with different clinical characteristics from CD5- DLBCL and as having a poorer outcome than CD5- DLBCL. Data regarding differences in gene alteration between CD5+ and CD5- DLBCL have accumulated. In this article, we report an analysis of the immunoglobulin heavy-chain gene variable region (VH) gene in 35 cases of CD5+ DLBCL and compare these cases with those with the germline of the VH gene (GL-VH) and those with a somatically hypermutated VH gene (HM-VH). When the CD5+ DLBCL cases were subdivided with a cutoff value of 98% homology in the VH gene, there were 7 cases (20%) of GL-VH and 28 cases (80%) of HM-VH. The proportion of GL-VH cases in CD5+ DLBCL was more than that in CD5 DLBCL. Although we found no significant difference in pretreatment clinical parameters between the GL-VH and HM-VH subgroups, there was a tendency for the GL-VH subgroup to show lower incidences of elevation of lactate dehydrogenase and >1 site of extranodal involvement compared to the HM-VH subgroup. The overall survival curve of the HM-VH subgroup showed a rapid decline followed by a plateau, whereas that of the GL-VH subgroup declined constantly after 5 years, suggesting that GL-VH disease may not be curable by standard therapies. These findings suggest that CD5+ DLBCL with GL-VH shares clinical features with mantle cell lymphoma, the cellular origin of which has been considered to be pre-germinal center B-cells. We therefore propose that analysis of the VH gene is important for predicting the clinical course of CD5+ DLBCL.

Immunoglobulin heavy chain genes somatic hypermutations and chromosome 11q22-23 deletion in classic mantle cell lymphoma: a study of the Swiss Group for Clinical Cancer Research

Mantle cell lymphoma (MCL) shares immunophenotypic and karyotypic features with chronic lymphocytic leukaemia. The latter comprises two distinct entities with prognosis dependent upon immunoglobulin heavy chain (IgH) gene mutational status and the presence of 11q deletion. We evaluated the relevance of IgH gene mutational status, IgV gene family usage and presence of 11q deletion in a series of 42 histologically reviewed classical MCL cases to determine the prognostic impact. VH3 was the most common VH family, with VH3-21 being the most frequent individual VH gene. Approximately 30% of the cases had a IgH somatic mutation rate higher than 2%, but was only higher than 4% in <10% of cases. Half of the cases had deletion of chromosome 11q21-telomere (11q21->ter), with two minimal deleted regions, at 11q22.2 and 11q23.2. There was no association between 11q loss and IgH gene somatic mutation rate; the use of VH3-21 gene could be associated with a better prognosis.

Chronic lymphocytic leukemias utilizing the VH3-21 gene display highly restricted Vlambda2-14 gene use and homologous CDR3s: implicating recognition of a common antigen epitope

The immunoglobulin variable heavy chain (IgVH) gene mutation status is an important prognostic factor in chronic lymphocytic leukemia (CLL), since cases with mutated VH genes show significantly longer survival than unmutated cases. Recently, we reported a preferential use of the VH3-21 gene in mutated CLL and showed that mutated VH3-21 cases had an inferior overall survival compared with other mutated CLL. In order to further characterize this subset, we performed VH gene analysis in 265 CLL cases and identified 31 VH3-21 cases (11.7%); 21 cases had mutated and 10 cases unmutated VH genes. Regardless of VH gene mutation status, a poor overall survival was found in the VH3-21 cases with a median survival of 83 months. These survival data confirm that VH3-21 cases do not fit into the general prognostic grouping of mutated and unmutated CLL. A large fraction of VH3-21 cases also demonstrated unique features with shorter lengths of the third complementarity determining region (CDR3) and CDR3s with highly homologous amino acid sequences. Furthermore, the VH3-21 cases showed a striking dominance of lambda light chain expression, and analysis of the Iglambda gene rearrangements revealed highly restricted use of the Vlambda2-14/Jlambda3 genes in the majority of cases. Taken together, our new findings strengthen the suggestion that VH3-21-using cases comprise a new CLL entity, irrespective of VH gene mutation status, and implicate that a common antigen epitope, perhaps of pathogenic significance, is recognized by the highly homologous VH3-21/Vlambda2-14 Ig molecules expressed in individual tumors.

High expression of activation-induced cytidine deaminase (AID) and splice variants is a distinctive feature of poor-prognosis chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), analysis of immunoglobulin heavy chain variable regions for somatic hypermutation identifies 2 prognostic subsets, mutated and unmutated. Investigators have postulated that unmutated and mutated CLL arises from malignant transformation of pre- and post-germinal center (GC) B cells, respectively. Alternatively, unmutated cases may arise from B cells stimulated by T-cell-independent antigens or from GC B cells with inactive somatic hypermutation. Activation-induced cytidine deaminase (AID), a protein essential for somatic hypermutation, is expressed by GC B cells in which this process occurs. We investigated AID mRNA expression in 20 CLL cases. In 8 cases we detected high expression of wild-type AID mRNA and 2 splice variants; in 12 cases and 5 normal peripheral blood B-cell samples we detected no expression using standard conditions. Of 8 CLL cases that highly expressed AID, 7 were unmutated, suggesting that this subset may arise from GC-experienced B cells with inactive somatic hypermutation, and may predict prognosis.