Immunoglobulin gene segment usage, location and immunogenicity in mutated and unmutated chronic lymphocytic leukaemia

Negative feedback regulation of MAPK signaling is an important driver of chronic lymphocytic leukemia progression

Despite available targeted treatments for the disease, drug-resistant chronic lymphocytic leukemia (CLL) poses a clinical challenge. The objective of this study is to examine whether the dual-specific phosphatases DUSP1 and DUSP6 are required to negatively regulate mitogen-activated protein kinases (MAPKs) and thus counterbalance excessive MAPK activity. We show that high expression of DUSP6 in CLL correlates with poor clinical prognosis. Importantly, genetic deletion of the inhibitory phosphatase DUSP1 or DUSP6 and blocking DUSP1/6 function using a small-molecule inhibitor reduces CLL cell survival in vitro and in vivo. Using global phospho-proteome approaches, we observe acute activation of MAPK signaling by DUSP1/6 inhibition. This promotes accumulation of mitochondrial reactive oxygen species and, thereby, DNA damage and apoptotic cell death in CLL cells. Finally, we observe that DUSP1/6 inhibition is particularly effective against treatment-resistant CLL and therefore suggest transient DUSP1/6 inhibition as a promising treatment concept to eliminate drug-resistant CLL cells.

MYD88-Mutated Chronic Lymphocytic Leukaemia/Small Lymphocytic Lymphoma as a Distinctive Molecular Subgroup Is Associated with Atypical Immunophenotypes in Chinese Patients

Chronic lymphocytic leukaemia/small lymphocytic lymphoma (CLL/SLL) is a heterogeneous disease in Western and Chinese populations, and it is still not well characterized in Chinese patients. Based on a large cohort of newly diagnosed CLL/SLL patients from China, we investigated immunophenotypes, genetic abnormalities, and their correlations. Eighty-four percent of the CLL/SLL patients showed typical immunophenotypes with scores of 4 or 5 points in the Royal Marsden Hospital (RMH) scoring system (classic group), and the remaining 16% of patients were atypical with scores lower than 4 points (atypical group). Trisomy 12 and variants of TP53, NOTCH1, SF3B1, ATM, and MYD88 were the most recurrent genetic aberrations. Additionally, unsupervised genomic analysis based on molecular genetics revealed distinctive characteristics of MYD88 variants in CLL/SLL. By overlapping different correlation grouping analysis from genetics to immunophenotypes, the results showed MYD88 variants to be highly related to atypical CLL/SLL immunophenotypes. Furthermore, compared with mantle cell lymphoma (MCL), the genetic landscape showed potential value in clinical differential diagnosis of atypical CLL/SLL and MCL patients. These results reveal immunophenotypic and genetic features, and may provide insights into the tumorigenesis and clinical management of Chinese CLL/SLL patients.

The Hydropathy Index of the HCDR3 Region of the B-Cell Receptor Identifies Two Subgroups of IGHV-Mutated Chronic Lymphocytic Leukemia Patients With Distinct Outcome

The HCDR3 sequences of the B-cell receptor (BCR) undergo constraints in length, amino acid use, and charge during maturation of B-cell precursors and after antigen encounter, leading to BCR and antibodies with high affinity to specific antigens. Chronic lymphocytic leukemia consists of an expansion of B-cells with a mixed immature and "antigen-experienced" phenotype, with either a mutated (M-CLL) or unmutated (U-CLL) tumor BCR, associated with distinct patient outcomes. Here, we investigated the hydropathy index of the BCR of 138 CLL patients and its association with the IGHV mutational status and patient outcome. Overall, two clearly distinct subgroups of M-CLL patients emerged, based on a neutral (mean hydropathy index of -0.1) vs. negatively charged BCR (mean hydropathy index of -1.1) with molecular features closer to those of B-cell precursors and peripheral/mature B-cells, respectively. Despite that M-CLL with neutral HCDR3 did not show traits associated with a mature B-cell repertoire, important differences in IGHV gene usage of tumor cells and patient outcome were observed in this subgroup of patients once compared to both U-CLL and M-CLL with negatively charged HCDR3 sequences. Compared to M-CLL with negatively charged HCDR3 sequences, M-CLL with neutral HCDR3 sequences showed predominance of men, more advanced stages of the disease, and a greater frequency of genetic alterations-e.g., del(17p)-together with a higher rate of disease progression and shorter time to therapy (TTT), independently of other prognostic factors. Our data suggest that the hydropathy index of the HCDR3 sequences of CLL cells allows the identification of a subgroup of M-CLL with intermediate prognostic features between U-CLL and the more favorable subgroup of M-CLL with a negatively charged BCR.

The Traf2DNxBCL2-tg Mouse Model of Chronic Lymphocytic Leukemia/Small Lymphocytic Lymphoma Recapitulates the Biased IGHV Gene Usage, Stereotypy, and Antigen-Specific HCDR3 Selection of Its Human Counterpart

Chronic lymphocytic leukemia (CLL)/Small lymphocytic lymphoma (SLL) is a heterogeneous disease consisting of at least two separate subtypes, based on the mutation status of the immunoglobulin heavy chain variable gene (IGHV) sequence. Exposure to antigens seems to play a role in malignant transformation and in the selection and expansion of more aggressive CLL clones. Furthermore, a biased usage of particular IGHV gene subgroups and the existence of stereotyped B-cell receptors (BCRs) are distinctive characteristics of human CLL. We have previously described that Traf2DN/BCL2 double-transgenic (tg, ^+/+) mice develop CLL/SLL with high incidence with aging. In this model, TNF-Receptor Associated Factor (TRAF)-2 deficiency cooperates with B cell lymphoma (BCL)-2 in promoting CLL/SLL in mice by specifically enforcing marginal zone (MZ) B cell differentiation and rendering B cells independent of BAFF for survival. In this report, we have performed the sequencing of the IGHV-D-J rearrangements of B cell clones from the Traf2DN/BCL2-tg^+/+ mice with CLL/SLL. The results indicate that these mice develop oligoclonal and monoclonal B cell expansions. Allotransplantation of the oligoclonal populations into immunodeficient mice resulted in the preferential expansion of one of the parental clones. The analysis of the IGHV sequences indicated that 15% were mutated (M) and 85% unmutated (UM). Furthermore, while the Traf2DN/BCL2-tg^-/- (wild-type), ^-/+ (BCL2 single-tg) and ^+/- (Traf2DNDN single-tg) littermates showed the expression of various IGHV gene subgroups, the CLL/SLL expanded clones from the Traf2DN/BCL2-tg^+/+ (double-transgenic) mice showed a more restricted IGHV gene subgroup usage and an overrepresentation of particular IGHV genes. In addition, the HCDR3-encoded protein sequence indicates the existence of stereotyped immunoglobulin (Ig) in the BCRs and strong similarities with BCR recognizing autoantigens and pathogen-associated antigens. Altogether, these results highlight the remarkable similarities between the CLL/SLL developed by the Traf2DN/BCL2-tg^+/+ mice and its human counterpart.

Lack of specific T- and B-cell clonal expansions in multiple sclerosis patients with progressive multifocal leukoencephalopathy

Progressive multifocal leukoencephalopathy (PML) is a rare, potentially devastating myelin-degrading disease caused by the JC virus. PML occurs preferentially in patients with compromised immune system, but has been also observed in multiple sclerosis (MS) patients treated with disease-modifying drugs. We characterized T and B cells in 5 MS patients that developed PML, 4 during natalizumab therapy and one after alemtuzumab treatment, and in treated patients who did not develop the disease. Results revealed that: i) thymic and bone marrow output was impaired in 4 out 5 patients at the time of PML development; ii) T-cell repertoire was restricted; iii) clonally expanded T cells were present in all patients. However, common usage or pairings of T-cell receptor beta variable or joining genes, specific clonotypes or obvious “public” T-cell response were not detected at the moment of PML onset. Similarly, common restrictions were not found in the immunoglobulin heavy chain repertoire. The data indicate that no JCV-related specific T- and B-cell expansions were mounted at the time of PML. The current results enhance our understanding of JC virus infection and PML, and should be taken into account when choosing targeted therapies.

Autoantibodies against mono- and tri-methylated lysine display similar but also distinctive characteristics

Autoantibodies can be either harmful or beneficial to the body. The beneficial autoantibodies play important roles in immunosurveillance, clearance of body waste and maintenance of immune homeostasis. Despite their importance, however, people’s knowledge on the protective autoantibodies is still very limited. In the current study, we examined two autoantibodies that recognized epitopes with only one amino acid. One was against mono-methylated lysine (Kme) and the other was against tri-methylated lysine (Kme3). We found that the antibodies were highly specific and not polyreactive. They did not cross-react each other. Although anti-Kme antibodies were IgM only, a large proportion of the anti-Kme3 antibodies were switched to the IgG isotype. Mass spectrometric analysis showed that both of the antibodies were mainly derived from IGHV 3–7 and/or IGHV3-74 germ line genes with conserved CDR2. De novo sequencing showed that there was a mutation at either of the SS positions on the CDR1 region, which changed one of the serine residues to a basic amino acid, i.e., arginine or lysine. We also found that neither of the antibodies was expressed at birth, and their earliest appearance was approximately 5 months after birth. All healthy human beings expressed the antibodies when they reached age two and maintained the expression thereafter throughout their life. Patients with systemic lupus erythematosus had lower levels of the IgM isotype antibodies. Serum levels of the two IgM antibodies were closely correlated, implying that they were produced by cells from the same B cell subset. We also found that both anti-Kme and anti-Kme3 antibodies could bind and might take part in the clearance of neutrophil extracellular traps released from activated cells. In conclusion, although anti-Kme and anti-Kme3 antibodies share many similarities in their origins, they are different antibodies and have different characteristics.

t(14;18)(q32;q21) in chronic lymphocytic leukemia patients: Report of two cases and a literature review

The chromosomal abnormality t(14;18)(q32;q21) is most commonly associated with germinal center-derived B-cell lymphomas, particularly follicular lymphoma (FL). Generally, it is considered a hallmark of FL. The t(14;18)(q32;q21) translocation is rare in chronic lymphocytic leukemia (CLL) and its prognostic significance remains unclear. In the present study, two cases of CLL with t(14;18)(q32;q21) were diagnosed using conventional cytogenetic analysis and fluorescence in situ hybridization. Both patients presented with leukemia and the morphological features and immunophenotypes were typical of CLL. Case 2 underwent a further lymph node biopsy, which established a diagnosis of CD5^- CLL/small lymphocyte lymphoma. In addition to t(14;18)(q32;q21), trisomy 12 was identified in the same clone in Case 2. Both cases exhibited immunoglobulin heavy chain variable mutations, and heavy-chain variable region gene (VH) 4-39 and VH3-62 were used in Case 1 and Case 2, respectively. In addition, direct Sanger sequencing of exons 4-9 revealed that Case 2 harbored the tumor protein p53 mutation, c.829T>G. Both cases had indications for therapy. Case 1 responded well to chlorambucil treatment, and was still alive at the last follow-up. Conversely, Case 2 exhibited aggressive disease that appeared refractory to treatment, and eventually succumbed to the disease.

Cytogenetic prioritization with inclusion of molecular markers predicts outcome in previously untreated patients with chronic lymphocytic leukemia treated with fludarabine or fludarabine plus cyclophosphamide: a long-term follow-up study of the US intergroup phase III trial E2997

Fludarabine (F) and cyclophosphamide (C) remain backbones of up-front chemotherapy regimens for chronic lymphocytic leukemia (CLL). We report long-term follow-up of a randomized F vs. FC trial in untreated CLL (#) . With median follow-up of 88 months, estimated median progression-free survival (PFS) was 19.3 vs. 48.1 months for F (n = 109) and FC (n = 118), respectively (p < 0.0001), and median overall survival (OS) was 88.0 vs. 79.1 months (p = 0.96). In multivariable analyses, variables associated with inferior PFS and OS respectively were age (p = 0.002, p < 0.001), Rai stage (p = 0.006, p = 0.02) and sex (p = 0.03, PFS only). Del(17)(p13.1) predicted shorter PFS and OS (p < 0.0001 for each), as did del(11q)(22.3) (p < 0.0001, p = 0.005, respectively), trisomy 12 with mutated Notch1 (p = 0.003, p = 0.03, respectively) and unmutated IGHV (p = 0.009, p = 0.002, respectively), all relative to patients without these features. These data confirm results from shorter follow-up and further justify targeted therapies for CLL.

Targeting the B-cell receptor signaling pathway in B lymphoid malignancies

PURPOSE OF REVIEW

Normal B cells that have failed to productively rearrange immunoglobulin V region genes encoding a functional B-cell receptor (BCR) are destined to die. Likewise, the majority of B-cell malignancies remain dependent on functional BCR signaling, whereas in some subtypes BCR expression is missing and, apparently, counterselected. Here, we summarize the recent experimental evidence for the importance of BCR signaling and clinical concepts to target the BCR pathway in B-cell leukemia and lymphoma.

RECENT FINDINGS

Although the dependency on pre-BCR signaling in pre-B acute lymphoblastic leukemia (ALL) seems to be limited to few ALL subtypes (e.g. TCF3-PBX1), most mature B-cell lymphomas rely on BCR signaling provided by different stimuli, for example tonic B-cell signaling, chronic (auto)-antigen exposure, and self-binding properties of the BCR. The finding that in chronic lymphocytic leukemia, BCRs bind to an epitope on the BCR itself unravels a novel concept for chronic lymphocytic leukemia pathogenesis.

SUMMARY

Targeting of the B-cell receptor tyrosine kinases spleen tyrosine kinase, Bruton's tyrosine kinase, and phosphatidylinositol 3-kinase achieve promising clinical responses in various mature B-cell malignancies and might also be useful in defined subsets of ALL. However, further understanding of the BCR signal integration in the different disease groups is required to accurately predict which groups of patients will benefit from BCR pathway inhibition.

IGHV1-69-encoded antibodies expressed in chronic lymphocytic leukemia react with malondialdehyde-acetaldehyde adduct, an immunodominant oxidation-specific epitope

The immunoglobulins expressed by chronic lymphocytic leukemia (CLL) B cells are highly restricted, suggesting they are selected for binding either self or foreign antigen. Of the immunoglobulin heavy-chain variable (IGHV) genes expressed in CLL, IGHV1-69 is the most common, and often is expressed with little or no somatic mutation, and restricted IGHD and IGHJ gene usage. We found that antibodies encoded by one particular IGHV1-69 subset, designated CLL69C, with the HCDR3 encoded by the IGHD3-3 gene in reading frame 2 and IGHJ6, specifically bound to oxidation-specific epitopes (OSE), which are products of enhanced lipid peroxidation and a major target of innate natural antibodies. Specifically, CLL69C bound immunodominant OSE adducts termed MAA (malondialdehyde–acetaldehyde-adducts), which are found on apoptotic cells, inflammatory tissues, and atherosclerotic lesions. It also reacted specifically with MAA-specific peptide mimotopes. Light chain shuffling indicated that non-stochastically paired L chain of IGLV3-9 contributes to the antigen binding of CLL69C. A nearly identical CLL69C Ig heavy chain was identified from an MAA-enriched umbilical cord phage displayed Fab library, and a derived Fab with the same HCDR3 rearrangement displayed identical MAA-binding properties. These data support the concept that OSE (MAA-epitopes), which are ubiquitous products of inflammation, may play a role in clonal selection and expansion of CLL B cells.

Immunoglobulin gene rearrangements and mutational status in argentinian patients with chronic lymphocytic leukemia

BACKGROUND

Chronic lymphocytic leukemia (CLL) is a clinically heterogeneous disease. The mutational status of the immunoglobulin heavy chain variable (IGHV) region represents one of the best prognostic markers and defines 2 disease subgroups: mutated (M-CLL) and unmutated (UM-CLL), with different clinical course.

MATERIALS AND METHODS

IGHV-D-J gene rearrangements and mutational status were analyzed in 73 Argentinian patients with CLL, 22 previously treated, by reverse transcriptase-polymerase chain reaction and bidirectional sequencing. The results were compared with those reported in other geographic regions. Fluorescence in situ hybridization analysis was also performed.

RESULTS

A total of 43 (58.9%) cases were of patients with M-CLL, and 30 (41.1%) were patients with UM-CLL. Deletion of chromosome 13q14 as a single alteration was more frequently observed in the M-CLL group (48%) than in the UM-CLL group (24%). In the M-CLL group, the proportion of cases with deletion of chromosome 13q14 was significantly higher than those with +12 and those with deletions of chromosomes 17p and 11q (P = .003). The most frequently used IGHV families were IGHV3 > IGHV1 > IGHV4, which are different from those observed in Asian, Brazilian, and Uruguayan series. The IGHV3-23 gene (10.8%) was the most commonly used, followed by IGHV1-69 (9.5%), IGHV4-59 and IGHV2-5 (6.8% each), and IGHV3-21 and IGHV3-30 (5.4% each). IGHV4-34 showed the lowest frequency (2.7%) in our cohort compared with published data, whereas IGHV4-59, IGHV3-72, and IGHV2-5 were overexpressed in our series. Stereotyped HCDR3 (heavy chain complementary determining region 3) was found in 9.5% of patients.

CONCLUSIONS

Our results showed that Argentinian patients with CLL display an IGHV gene usage that resembles that observed in Western countries and exhibited interesting similarities and differences with respect to published series from other Latin American populations, which reflect variations in the genetic background.

Lipoprotein lipase: a new prognostic factor in chronic lymphocytic leukaemia

The clinical course of patients with chronic lymphocytic leukemia (CLL) is highly heterogeneous. Gene expression analyses have revealed that leukemic cells with unmutated immunoglobulin heavy chain genes (IgV H ) differ from CLL cells with mutated IgV H in the expression level of some genes, i.e. encoding kinase ZAP-70 and antigen CD38. Recently, additional markers in CLL, including the expression level of apoptosis-regulating genes/proteins (Bcl-2, Mcl-1) and microRNAs, have been suggested. In this review, we attempt to provide data concerning the properties of lipoprotein lipase (LPL), as well as to present its prognostic value in CLL. LPL mRNA expression level was able to predict mutational status in a high percentage of CLL cases and high LPL expression was associated with shorter treatment-free survival. Importantly, since LPL activity is low (or absent) in other blood cell types, its expression can be determined by PCR technique in peripheral blood mononuclear cells or in lysed blood samples.

Synthetic antibodies: concepts, potential and practical considerations

The last 100 years of enquiry into the fundamental basis of humoral immunity has resulted in the identification of antibodies as key molecular sentinels responsible for the in vivo surveillance, neutralization and clearance of foreign substances. Intense efforts aimed at understanding and exploiting their exquisite molecular specificity have positioned antibodies as a cornerstone supporting basic research, diagnostics and therapeutic applications [1]. More recently, efforts have aimed to circumvent the limitations of developing antibodies in animals by developing wholly in vitro techniques for designing antibodies of tailored specificity. This has been realized with the advent of synthetic antibody libraries that possess diversity outside the scope of natural immune repertoires and are thus capable of yielding specificities not otherwise attainable. This review examines the convergence of technologies that have contributed to the development of combinatorial phage-displayed antibody libraries. It further explores the practical concepts that underlie phage display, antibody diversity and the methods used in the generation of and selection from phage-displayed synthetic antibody libraries, highlighting specific applications in which design approaches gave rise to specificities that could not easily be obtained with libraries based upon natural immune repertories.

Mutational status and gene repertoire of IGHV-IGHD-IGHJ rearrangements in Serbian patients with chronic lymphocytic leukemia

The mutational status and configuration of immunoglobulin heavy variable (IGHV) gene rearrangements was analyzed in 85 Serbian patients with chronic lymphocytic leukemia (CLL). We found that 55.3% of cases belonged to mutated and 44.7% to unmutated CLL, progressive disease predominating in the unmutated subset. IGHV gene use resembled that obtained for Mediterranean countries, except for underrepresentation of the IGHV4 subgroup in our cohort.

BACKGROUND

Chronic lymphocytic leukemia (CLL) results from the clonal expansion of mature B lymphocytes and is characterized by extreme clinical heterogeneity. One of the most reliable prognostic markers in chronic lymphocytic leukemia (CLL) is the mutational status of immunoglobulin heavy variable (IGHV) genes, which defines 2 subsets, mutated CLL (M-CLL) and unmutated CLL (U-CLL), with different clinical courses. Biased IGHV gene use between M-CLL and U-CLL clones, as well as population differences in the IGHV gene repertoire have been reported.

PATIENTS AND METHODS

In this study, mutational status and configuration of IGHV-IGHD-IGHJ rearrangements in 85 Serbian patients were analyzed using reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing methodology.

RESULTS

We found that 55.3% of cases belonged to M-CLL and 44.7% belonged to U-CLL, with progressive disease predominating in the unmutated subset. Most frequently expressed was the IGHV3 subgroup (55.7%), followed by IGHV1 (27.3%), IGHV4 (12.5%), IGHV5 (2.3%), IGHV2 (1.1%), and IGHV6 (1.1%). The distribution of IGHD subgroups was as follows: IGHD3, 39.1%; IGHD2, 21.8%; IGHD6, 12.6%; IGHD1, 10.3%; IGHD4, 8%; IGHD5, 6.9%; and IGHD7, 1.1%. The most frequent IGHJ gene was IGHJ4 (48.9%), followed by IGHJ6 (28.4%), IGHJ3 (11.4%), and IGHJ5 (11.4%). In 15.3% of cases, heavy complementarity-determining region 3 (VH CDR3) amino acid sequences could be assigned to previously defined stereotyped clusters.

CONCLUSIONS

Our study showed a strong correlation between IGHV gene mutational status and clinical course of CLL. IGHV gene use was comparable to that obtained for Mediterranean countries, with the exception of the IGHV4 subgroup, which was underrepresented in our cohort.

Evidence of canonical somatic hypermutation in hairy cell leukemia

To compare hairy cell leukemia (HCL) with chronic lymphocytic leukemia (CLL) and normal B cells with respect to their B-cell receptors, somatic hypermutation (SHM) features in HCL were examined in a series of 130 immunoglobulin gene heavy chain rearrangements, including 102 from 100 classic (HCLc) and 28 from 26 variant (HCLv) patients. The frequency of unmutated rearrangements in HCLc was much lower than that in HCLv (17% vs 54%, P < .001) or historically in CLL (17% vs 46%, P < .001), but HCLv and CLL were similar (P = .45). As previously reported for CLL, evidence of canonical SHM was observed in HCLc rearrangements, including: (1) a higher ratio of replacement to silent mutations in the complementarity determining regions than in the framework regions (2.83 vs 1.41, P < .001), (2) higher transition to transversion ratio than would be expected if mutations were random (1.49 vs 0.5, P < .001), and (3) higher than expected concentration of mutations within RGYW hot spots (13.92% vs 3.33%, P < .001). HCLv met these 3 criteria of canonical SHM to a lesser extent. These data suggest that, whereas HCLc cells may recognize antigen-like CLL and normal B cells before malignant transformation, HCLv cells from some patients may originate differently, possibly without undergoing antigen recognition.

Update on therapy of chronic lymphocytic leukemia

There have been tremendous advances in the treatment of chronic lymphocytic leukemia (CLL) over the past decade, with the goal of therapy no longer being just to palliate symptoms but now to achieve complete remission, eradicate minimal residual disease, and improve survival. During this period, there have also been major advances in identification of molecular factors associated with increased risk of progression. The clinical utility of these factors is being explored to determine whether we can identify groups of patients who should be treated earlier in their disease course and whether we can tailor therapy for groups of patients with specific molecular markers of disease. First-line chemoimmunotherapy approaches now offer prolonged survival, and there is a need to identify patients who are suitable candidates for allogeneic stem-cell transplantation that uses reduced-intensity conditioning regimens. The vast majority of CLL patients are either too old or do not have sufficiently high-risk disease to warrant these approaches, and effective therapies that can be tolerated by the more frail elderly patients with this disease are urgently needed. Numerous novel agents are being developed, and their role in the first-line treatment of frail patients or those who relapse after previous treatment is being explored in clinical trials.

Immunoglobulin heavy chain V-D-J gene rearrangement and mutational status in Uruguayan patients with chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (CLL) is characterized by the accumulation of long-lived circulating clonal leukemic B-cells, although the etiopathogenesis remains unclear. The incidence of CLL is variable in different regions around the world. While it is the most frequent chronic leukemia in Western countries, it has a low incidence in Asia. In this work we have investigated the immunoglobulin heavy chain gene rearrangements and mutational status in 80 Uruguayan patients with CLL, and compared these results with those obtained in other geographic regions. Our results demonstrate that Uruguayan patients with CLL display an IGHV gene usage which resembles that observed in Mediterranean countries and exhibits certain differences compared with Brazilian and Asian series, as expected, considering the ethnic basis of the Uruguayan population. This suggests that genetic influences could be important in the development and etiopathogenesis of CLL, but larger studies are necessary to substantiate this possibility.

How I treat CLL up front

Although chronic lymphocytic leukemia (CLL) remains incurable, over the past decade there have been major advances in understanding the pathophysiology of CLL and in the treatment of this disease. This has led to greatly increased response rates and durations of response but not yet improved survival. Advances in the use of prognostic factors that identify patients at high risk for progression have led us to the question whether there is still a role for a "watch and wait" approach in asymptomatic high-risk patients or whether they should be treated earlier in their disease course. Questions remain, including, what is the optimal first-line treatment and its timing and is there any role of maintenance therapy or stem cell transplantation in this disease? CLL is a disease of the elderly and not all patients are eligible for aggressive up-front chemoimmunotherapy regimens, so what is the optimal treatment approach for more frail elderly patients? It is highly likely that our treatment approaches will continue to evolve as the results of ongoing clinical trials are released and that further improvements in the outcome of this disease will result from identification of therapies that target the underlying pathophysiology of CLL.

Identification of human idiotype-specific T cells in lymphoma and myeloma

Idiotype protein, among the first identified tumor-specific antigens, has been found to stimulate both humoral and cellular responses in lymphoma and myeloma patients. With the increasing use of B cell depletion treatments such as rituximab in clinic, the cellular response mediated by idiotype-specific T cells has become increasingly important as an adjunct therapy for lymphoma and myeloma. Here, we review the idiotype protein as a tumor antigen and the characteristics of the T cell response elicited idiotype vaccination. We also analyze the T cell epitopes that have been identified in idiotype protein and introduce our new findings of additional T cell epitopes derived from the Ig light chain. Finally, we propose new directions in the generation of idiotype-specific T cells for tumor therapy.

Immunoglobulin heavy chain variable region gene usage and mutational status of the leukemic B cells in Iranian patients with chronic lymphocytic leukemia

The mutational status of the immunoglobulin variable region heavy chain genes (IGHV) is an important prognostic marker in chronic lymphocytic leukemia (CLL). The data accumulated in the literature has largely been derived from studies conducted on Caucasian Western populations. Little is known about Asian CLL patients. In this study the IGHV genes usage and somatic hypermutation status have been investigated in 87 Iranian CLL patients. Based on a cut-off of 98% nucleotide sequence homology, 64.4% and 35.6% of the patients expressed mutated and unmutated IGHV genes, respectively, with most non-progressive patients being in the mutated group (35/44 vs 19/40; P = 0.009). Progression-free survival (PFS) and time to first treatment (TTFT) were significantly higher in our mutated and non-progressive patients compared to unmutated and progressive subtypes, respectively. The most frequently used IGHV gene was IGHV3-7 (12.6%) followed by IGHV3-30 (11.4%), IGHV3-48 (9.2%), IGHV4-39 (6.9%), and IGHV1-8 (6.9%) genes, which taken together comprised nearly half of the IGHV genes expressed in the Iranian CLL patients. Of the IGHV genes, IGHV3-7 was significantly over-represented in non-progressive compared to progressive CLL patients (P = 0.036), whereas IGHV1-69 and IGHV1-2 were expressed at a higher frequency in unmutated compared to mutated CLL patients (P < 0.03). Comparison of IGHV gene usage in our patients with that of Western CLL patients revealed significant differences in expression of IGHV1-69, IGHV3-7, IGHV3-21, and IGHV4-34 genes. Analysis of the IGHV third complementary determining region (HCDR3) sequences revealed a high frequency use of certain HCDR3 motifs, such as YYYGMDV, in our samples. These findings imply contribution of antigen selection and regional (ethnic/geographic) parameters in the leukomogenesis of CLL.

Analysis of the immunoglobulin heavy chain variable region gene expression in Iranian patients with chronic lymphocytic leukemia

B-cell chronic lymphocytic leukemia (B-CLL) results from clonal expansion of phenotypically mature but functionally immature B-lymphocytes. The incidence of this type of leukemia is low in Asian countries, whereas it is the most frequent type of leukemia in the West. Previous investigations mainly conducted in Western populations have demonstrated non-random rearrangement of certain immunoglobulin variable region heavy (VH) and/or light (VL) chain genes in different groups of B-CLL patients. Little is known about the profile of VH gene expression in Asian patients. In the present study, we determined the frequency of VH gene family usage in 59 Iranian patients with B-CLL. VH gene family of patients was determined by reverse transcriptase-polymerase chain reaction using VH1-VH7 family specific primers. The most frequently expressed VH gene family was found to be VH3 (45.8%) followed by VH4 (32.2%), VH1 (18.6%), VH5 (1.7%) and VH6 (1.7%), with no expression of VH2 and VH7 gene families. The results indicate a lower representation of the VH1 and VH2 gene families and a higher representation of the VH4 gene family in Iranian B-CLL patients compared to Western patients, suggesting involvement of ethnic and/or environmental factors in B-CLL disease initiation.

Spleen tyrosine kinase is overexpressed and represents a potential therapeutic target in chronic lymphocytic leukemia

B-cell receptor signaling contributes to apoptosis resistance in chronic lymphocytic leukemia (CLL), limiting the efficacy of current therapeutic approaches. In this study, we investigated the expression of spleen tyrosine kinase (SYK), a key component of the B-cell receptor signaling pathway, in CLL and its role in apoptosis. Gene expression profiling identified enhanced expression of SYK and downstream pathways in CLL compared with healthy B cells. Immunoblotting showed increased expression and phosphorylation of SYK, PLCgamma(2), signal transducers and activators of transcription 3, and extracellular signal regulated kinase 1/2 in CLL compared with healthy B cells, suggesting enhanced activation of these mediators in CLL. SYK inhibitors reduced phosphorylation of SYK downstream targets and induced apoptosis in primary CLL cells. With respect to prognostic factors, SYK inhibitors exerted stronger cytotoxic effects in unmutated and ZAP70(+) cases. Cytotoxic effects of SYK inhibitors also associated with SYK protein expression, potentially predicting response to therapy. Combination of fludarabine with SYK Inhibitor II or R406 increased cytotoxicity compared with fludarabine therapy alone. We observed no stroma-contact-mediated drug resistance for SYK inhibitors as described for fludarabine treatment. CD40 ligation further enhanced efficacy of SYK inhibition. Our data provide mechanistic insight into the recently observed therapeutic effects of the SYK inhibitor R406 in CLL. Combination of SYK inhibitors with fludarabine might be a novel treatment option particularly for CLL patients with poor prognosis and should be further evaluated in clinical trials.

Molecular and cellular mechanisms of CLL: novel therapeutic approaches

The mainstay of therapy of chronic lymphocytic leukemia (CLL) is cytotoxic chemotherapy; however, CLL is still an incurable disease with resistance to therapy developing in the majority of patients. In recent years, our understanding of the biological basis of CLL pathogenesis has substantially improved and novel treatment strategies are emerging. Tailoring and individualizing therapy according to the molecular and cellular biology of the disease is on the horizon, and advances with targeted agents such as monoclonal antibodies combined with traditional chemotherapy have lead to improved remission rates. The proposed key role of the B-cell receptor (BCR) in CLL pathogenesis has led to a number of possible opportunities for therapeutic exploitation. We are beginning to understand that the microenvironment is of utmost importance in CLL because certain T-cell subsets and stromal cells support the outgrowth and development of the malignant clone. Furthermore, an increase in our understanding of the deregulated cell-death machinery in CLL is a prerequisite to developing new targeted strategies that might be more effective in engaging with the cell-death machinery. This Review summarizes the progress made in understanding these features of CLL biology and describes novel treatment strategies that have also been exploited in current clinical trials.

Vaccine therapy and chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (CLL) should be an ideal target for immune-mediated responses. CLL arises from B cells that can act as antigen-presenting cells (APCs), expresses unique tumour antigens, and has been shown to be a target of the allogeneic T cells which mediate a graft-versus-leukaemia effect. Despite these potential benefits, immune responses against CLL cells have been difficult to elicit. CLL induces immune defects in the host, the tumour cells are inefficient APCs, and therapies given to patients with CLL are themselves immunosuppressive. Successful vaccination approaches in this disease will require steps to overcome these difficulties, including identification of the targets of immune responses in this disease to enable monitoring of the immune response after vaccination, improved presentation of antigens, and steps to improve the immune defects that accompany this disease.

Immunoglobulin diversity gene usage predicts unfavorable outcome in a subset of chronic lymphocytic leukemia patients

Survival of patients with B cell chronic lymphocytic leukemia (B-CLL) can be predicted by analysis of mutations in the immunoglobulin heavy chain variable gene (IGHV). Patients without mutations (unmutated [UM]) are at greater risk for disease progression and death than patients with mutations (M). Despite this broad prognostic difference, there remains wide intragroup variation in the clinical outcome of UM patients, especially those with low/intermediate Rai risk disease. We evaluated UM B-CLL patients with low/intermediate Rai risk to determine the relationship between IGHV, IGH diversity (IGHD), and IGH joining (IGHJ) gene usage and time to treatment (TTT). Irrespective of IGHV usage, UM patients whose B-CLL cells expressed the IGHD3-3 gene had a significantly shorter TTT than other UM B-CLL patients, and specifically, use of the IGHD3-3 gene in reading frame 2 (RF2) predicted shorter TTT. As expected, Rai risk was the best single prognostic factor for TTT; however, IGHD usage was also a significant variable for TTT. Therefore, both IGHD gene and IGHD RF usage have prognostic relevance in UM B-CLL patients with low/intermediate Rai risk disease. In addition, these data support the concept that antigen-driven selection of specific Ig receptors plays a role in the clinical course of B-CLL.

Distinctive IgVH gene segments usage and mutation status in Chinese patients with chronic lymphocytic leukemia

BACKGROUND AND OBJECTIVES

The incidence of chronic lymphocytic leukemia (CLL) in Asian countries is lower than that in the Western ones, where CLL is the most common leukemia. It is a clinically heterogeneous disease, with survival ranging from a few months to decades. The mutation status of the immunoglobulin variable heavy chain (IgVH) gene has significantly improved prediction of the risk for disease progression. We investigated the frequency and mutation status of IgVH gene expression in Chinese patients with CLL.

METHODS

IgVH gene segments usage and mutation status were investigated by multiplex RT-PCR, and the relationship between IgVH somatic mutation status and the expression of CD38 and ZAP-70 was analyzed in 65 CLL patients.

RESULTS

Forty-five (69.2%) patients had mutated IgVH, and 20 (30.8%) had unmutated IgVH. The most frequently expressed VH gene family was found to be VH3 (47.7%) followed by VH4 (40%), VH1 (6.2%), VH2 (4.6%) and VH7 (1.5%), with no expression of VH5 or VH6 gene families. VH1-69 and VH3-21 which commonly overused in Western CLL were very low in our cohort. IgVH gene mutation status was significantly associated with the expression of CD38.

CONCLUSIONS

The frequency of IgVH gene families indicates significant difference in Chinese CLL patients compared with Western patients, suggesting involvement of ethnic and/or environmental factors in CLL disease initiation. The expression of them may be simple and reliable surrogates for the identification of IgVH mutations.

Molecular Profiling in CLL

Chronic lymphocytic leukemia (CLL) has an extremely heterogeneous clinical course, with some patients requiring immediate therapy and others living without need for treatment for decades. There has been considerable interest in the underlying molecular mechanisms of this heterogeneity to understand not only the expected clinical course for individual patients but also the underlying pathogenesis of this disease. A number of clinical parameters have been identified that are predictive of the clinical course. More recently, a number of molecular biomarkers, most notably cytogenetics by fluorescent in situ hybridization (FISH), immunoglobulin heavy chain (IgVH) mutational status and expression of ZAP70, have been identified and verified as also providing prognostic information. The current challenge is to understand how we should use this new information in clinical practice and whether we should alter treatment based upon the detection of “high-risk” features. Over the past decade there has been considerable progress in development of more effective treatments for CLL, but current consensus is that treatment of CLL should be based upon the treatment of symptomatic disease. Specific treatment decisions based upon the detection of “high-risk” features remains a question for clinical trials, which will address the potential value of early treatment for specific groups of patients and whether all patients with CLL should receive a standard treatment or whether treatment should be modified in different risk groups.

[Chronic lymphocytic leukaemia: an autoimmune disorder? Prognostic factors and the current view of pathogenesis]

The heterogeneity of clinical course in chronic lymphocytic leukaemia has been known for a long time. The easily applicable staging systems described by Rai and Binet decades ago have represented one of the decisive obstacles against the proper development of clinical decision making as they correlated well with survival data in more advanced diseases, but could not differentiate progressive versus stable diseases of low stages. This might have been responsible for the development of the "watch and wait" clinical strategy potentially resulting in the lack of therapeutical intervention in early due time. Application of recent research data on gene expression, molecular biological, cytogenetic and phenotypic analysis of the malignancy can provide the opportunity of stratifying the disease - although with different predictive value - at the onset or early stages. All these represent a new challenge for the diagnostics and expose important aspects in the management of this work. The author reviews the theory and practice of these diagnostic approaches with special emphasis on the immunoglobulin heavy chain mutational status, expression of CD-38 and ZAP-70 markers as well as the significance of karyotyping and interphase cytogenetics. In the light of current data a putative pathogenetic scheme is outlined implying the fundamental recognition that all individual forms of this heterogeneous disease arise from similar and unique polyreactive - autoreactive B-cell clones which underlies the key role of autoimmunization in the pathogenesis of the disease.

Comprehensive assessment of genetic and molecular features predicting outcome in patients with chronic lymphocytic leukemia: results from the US Intergroup Phase III Trial E2997

PURPOSE

Genomic features including unmutated immunoglobulin variable region heavy chain (IgVH) genes, del(11q22.3), del(17p13.1), and p53 mutations have been reported to predict the clinical course and overall survival of patients with chronic lymphocytic leukemia (CLL). In addition, ZAP-70 and Bcl-2 family proteins have been explored as predictors of outcome.

PATIENTS AND METHODS

We prospectively evaluated the prognostic significance of a comprehensive panel of laboratory factors on both response and progression-free survival (PFS) using samples and data from 235 patients enrolled onto a therapeutic trial. Patients received either fludarabine (FL; n = 113) or fludarabine plus cyclophosphamide (FC; n = 122) as part of a US Intergroup randomized trial for previously untreated CLL patients.

RESULTS

Complete response (CR) rates were 24.6% for patients receiving FC and 5.3% for patients receiving FL (P = .00004). PFS was statistically significantly longer in patients receiving FC (median, 33.5 months for patients receiving FC and 19.9 months for patients receiving FL; P < .0001). The occurrence of del(17p13.1) (hazard ratio, 3.428; P = .0002) or del(11q22.3) (hazard ratio, 1.904; P = .006) was associated with reduced PFS. CR and overall response rates were not significantly different based on cytogenetics, IgVH mutational status, CD38 expression, or p53 mutational status. Expression of ZAP-70, Bcl-2, Bax, Mcl-1, XIAP, Caspase-3, and Traf-1 was not associated with either clinical response or PFS.

CONCLUSION

These results support the use of interphase cytogenetic analysis, but not IgVH, CD38 expression, or ZAP-70 status, to predict outcome of FL-based chemotherapy. Patients with high-risk cytogenetic features should be considered for alternative therapies.

Temporal genetic program following B-cell receptor cross-linking: altered balance between proliferation and death in healthy and malignant B cells

Gene expression in cells is a dynamic process but is usually examined at a single time point. We used gene expression profiling over time to build temporal models of gene transcription after B-cell receptor (BCR) signaling in healthy and malignant B cells and chose this as a model since BCR cross-linking induces both cell proliferation and apoptosis, with increased apoptosis in chronic lymphocytic leukemia (CLL) compared to healthy B cells. To determine the basis for this, we examined the global temporal gene expression profile for BCR stimulation and developed a linear combination method to summarize the effect of BCR simulation over all the time points for all patients. Functional learning identified common early events in healthy B cells and CLL cells. Although healthy and malignant B cells share a common genetic pattern early after BCR signaling, a specific genetic program is engaged by the malignant cells at later time points after BCR stimulation. These findings identify the molecular basis for the different functional consequences of BCR cross-linking in healthy and malignant B cells. Analysis of gene expression profiling over time may be used to identify genes that might be rational targets to perturb these pathways.

Update on risk-stratified management for chronic lymphocytic leukemia

Major recent advances in understanding the biology of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL) have improved clinical evaluation and influenced treatment decisions. CLL can be diagnosed early and accurately, and biological measurements can be used to predict a prognosis at diagnosis. Individual patient care can be risk stratified to optimize benefit and minimize complications of therapy. Purine analogs and monoclonal antibodies have markedly improved the efficacy of initial therapy but are not curative. The treatment of relapsed and refractory CLL is less successful. However, recent developments suggest that allogeneic stem cell transplant could have a larger role in a selected group of these patients. Potential new treatment modalities include targeted molecules that interrupt key components of CLL cell survival pathways, and active and passive immunotherapy. The management of CLL is in a dynamic phase of rapid evolution. Risk stratification using biological prognostic markers can improve current patient care and direct future clinical research.

Cytotoxic T cells generated against heteroclitic peptides kill primary tumor cells independent of the binding affinity of the native tumor antigen peptide

Heteroclitic peptide modifications increase immunogenicity, allowing generation of cytotoxic T lymphocytes (CTLs) against weakly immunogenic tumor-associated antigens (TAAs). A critical issue is whether T cells generated against heteroclitic peptides retain the ability to recognize and kill tumor cells expressing the original weak TAAs, and whether there is a lower threshold of binding affinity of the native peptides, below which such CTLs can still kill primary tumor cells. To examine this we used a model examining the ability of native and heteroclitic immunoglobulin (Ig)-derived peptides to generate CTLs that can kill chronic lymphocytic leukemia (CLL) cells. We demonstrate that CTLs generated against heteroclitic peptides have enhanced killing of CD40-activated B cells pulsed with either heteroclitic (P < .001) or native peptide (P = .04) and primary CLL cells (P = .01). The novel finding reported here is that the rate-limiting factor appears to be the ability to generate CTLs and that once generated, CTL lysis of primary tumor cells is independent of the binding affinity of the native peptide. These findings have implications for vaccination strategies in malignancies and are currently being further examined in vivo in murine models.