Expression levels of CD38 in T cells predict course of disease in male patients with B-chronic lymphocytic leukemia

CD4+CD38+ central memory T cells contribute to HIV persistence in HIV-infected individuals on long-term ART

Background

Despite the effective antiretroviral treatment (ART) of HIV-infected individuals, HIV persists in a small pool. Central memory CD4⁺ T cells (Tcm) make a major contribution to HIV persistence. We found that unlike HLA-DR, CD38 is highly expressed on the Tcm of HIV-infected subjects receiving ART for > 5 years. It has been reported that the half-life of total and episomal HIV DNA in the CD4⁺CD38⁺ T cell subset, exhibits lower decay rates at 12 weeks of ART. Whether CD38 contributes to HIV latency in HIV-infected individuals receiving long-term ART is yet to be addressed.

Methods

Peripheral blood mononuclear cells (PBMCs) were isolated from the whole blood of HIV-infected subjects receiving suppressive ART. The immunophenotyping, proliferation and apoptosis of CD4⁺ T cell subpopulations were detected by flow cytometry, and the level of CD38 mRNA and total HIV DNA were measured using real-time PCR and digital droplet PCR, respectively. A negative binomial regression model was used to determine the correlation between CD4⁺CD38⁺ Tcm and total HIV DNA in CD4⁺ T cells.

Results

CD38 was highly expressed on CD4⁺ Tcm cells from HIV infected individuals on long-term ART. Comparing with HLA-DR⁻Tcm and CD4⁺HLA-DR⁺ T cells, CD4⁺CD38⁺ Tcm cells displayed lower levels of activation (CD25 and CD69) and higher levels of CD127 expression. The proportion of CD38⁺ Tcm, but not CD38⁻ Tcm cells can predict the total HIV DNA in the CD4⁺ T cells and the CD38⁺ Tcm subset harbored higher total HIV DNA copy numbers than the CD38⁻ Tcm subset. After transfected with CD38 si-RNA in CD4⁺ T cells, the proliferation of CD4⁺ T cells was inhibited.

Conclusion

The current date indicates that CD4⁺CD38⁺ Tcm cells contribute to HIV persistence in HIV-infected individuals on long-term ART. Our study provides a potential target to resolve HIV persistence.

Investigating epigenetic effects of activation-induced deaminase in chronic lymphocytic leukemia

Activation induced deaminase (AID) has two distinct and well defined roles, both relying on its deoxycytidine (dC) deaminating function: one as a DNA mutator and another in DNA demethylation. In chronic lymphocytic leukemia (CLL), AID was previously shown to be an independent negative prognostic factor. While there is substantial impact on DNA mutations, effects of AID on gene expression by promoter demethylation of disease related target genes in leukemia has not been addressed. To shed light on this question, we aimed at determining genome wide methylation changes as well as gene expression changes in response to AID expression in CLL. Although we found minor differences in individual methylation variable positions following AID expression, we could not find recurrent methylation changes of specific target sites or changes in global methylation.

B-cell and T-cell activation in South African HIV-1-positive non-Hodgkin's lymphoma patients

Background

Altered immune mechanisms play a critical role in the pathogenesis of non-Hodgkin’s lymphoma (NHL). HIV-1 (HIV) infection is associated with a state of excessive T-cell activation, which can lead to increased T-cell turnover and lymph node fibrosis.

Objectives

This study aimed to determine the serum levels of circulating B-cell activation markers, and the expression of T-cell activation and regulatory markers in HIV-positive NHL patients.

Method

The serum levels of circulating soluble(s) sCD20, sCD23, sCD27, sCD30 and sCD44 molecules, all of which are biomarkers of B-cell activation, were determined by enzyme-linked immunosorbent assays (ELISA), while biomarkers of T-cell activation (CD8+CD38+) and regulation (FoxP3) were determined by flow cytometry in 141 subjects who were divided into five groups: Combination antiretroviral therapy (ART)-naïve HIV-positive patients; ART-treated HIV-positive patients; HIV-negative NHL patients; HIV-positive NHL patients on ART; and healthy controls.

Results

HIV-positive NHL patients had significantly higher serum levels of sCD20, sCD23, sCD30 and sCD44 than HIV-negative NHL patients, while all five biomarkers were significantly elevated in HIV-positive NHL patients when compared with ART-treated HIV-positive patients. HIV-positive NHL patients had higher CD8+CD38+ and lower FoxP3 expression than HIV-negative NHL and ART-treated HIV-positive patients.

Conclusion

B-cell activation is increased in HIV-positive NHL patients and is associated with reduced regulatory T-cell populations and increased CD8+ T-cell activation.

Fludarabine and rituximab with escalating doses of lenalidomide followed by lenalidomide/rituximab maintenance in previously untreated chronic lymphocytic leukaemia (CLL): the REVLIRIT CLL-5 AGMT phase I/II study

Despite recent advances, chemoimmunotherapy remains a standard for fit previously untreated chronic lymphocytic leukaemia patients. Lenalidomide had activity in early monotherapy trials, but tumour lysis and flare proved major obstacles in its development. We combined lenalidomide in increasing doses with six cycles of fludarabine and rituximab (FR), followed by lenalidomide/rituximab maintenance. In 45 chemo-naive patients, included in this trial, individual tolerability of the combination was highly divergent and no systematic toxicity determining a maximum tolerated dose was found. Grade 3/4 neutropenia (71%) was high, but only 7% experienced grade 3 infections. No tumour lysis or flare > grade 2 was observed, but skin toxicity proved dose-limiting in nine patients (20%). Overall and complete response rates after induction were 89 and 44% by intention-to-treat, respectively. At a median follow-up of 78.7 months, median progression-free survival (PFS) was 60.3 months. Minimal residual disease and immunoglobulin variable region heavy chain mutation state predicted PFS and TP53 mutation most strongly predicted OS. Baseline clinical factors did not predict tolerance to the immunomodulatory drug lenalidomide, but pretreatment immunophenotypes of T cells showed exhausted memory CD4 cells to predict early dose-limiting non-haematologic events. Overall, combining lenalidomide with FR was feasible and effective, but individual changes in the immune system seemed associated with limiting side effects. clinicaltrials.gov (NCT00738829) and EU Clinical Trials Register (www.clinicaltrialsregister.eu, 2008-001430-27)

CD1d expression on chronic lymphocytic leukemia B cells affects disease progression and induces T cell skewing in CD8 positive and CD4CD8 double negative T cells

Chronic lymphocytic leukemia develops within a complex network driven by genetic mutations and microenvironmental interactions. Among the latter a complex interplay with the immune system is established by the clone. Next to a proposed recruitment of support from T and myeloid cells, potential anti-CLL immune reactions need to be subverted. By using TCL1 mice as a CLL model, we show that TCR-Vβ7+ NK1.1+ T cells are overrepresented in this disease model and constitute a main subset of peripheral CD3+ cells with biased TCR usage, showing that these cells account for a major part for T cell skewing in TCL1 mice. Moreover, we show that overrepresentation is dependent on CD1d expression in TCL1 mice, implicating that these cells belong to a NKT-like cell fraction which are restricted to antigen presented by the MHC-like surface marker CD1d. Accordingly, we observed a high fraction of CD161+ cells within overrepresented T cells in CLL patients and we found downregulation of CD1d on the surface of CLL cells, both in TCL1 mice and patients. Finally, we show that in TCL1 mice, CD1d deficiency resulted in shortened overall survival. Our results point to an interaction between CLL and CD161+ T cells that may represent a novel therapeutic target for immune modulation.

Intracellular IL-4 and IFN-γ expression in iNKT cells from patients with chronic lymphocytic leukemia

Malignant B cells in chronic lymphocytic leukemia serve an essential role in the whole immune response, so their interactions with other immune cells are more complex than observed in solid tumors. The latest study results indicate that the immune dysregulation in chronic lymphocytic leukemia (CLL) also affects a small population of invariant natural killer T cells (iNKT). Using peripheral blood iNKT cells obtained from patients with CLL, the objective of the present study was to assess the intracellular expression of typical cytokines involved in the Th1 (IFN-γ) and Th2 (IL-4) response pathways following stimulation with the iNKT-specific ligand α-galactosylceramide. iNKT cells from patients with CLL exhibited upregulated IL-4 and IFN-γ expression in comparison to those from HVs. No significant association between the ability of iNKT cells to produce IL-4 or IFN-γ and the expression of CD1d on leukemic B lymphocytes or monocytes was identified. However, the function of iNKT cells was compromised in patients with CLL by a strong Th2 bias (high IL-4 and low IFN-γ expression). The ratio of iNKT+IFN-γ+:iNKT+IL-4+ was significantly decreased in the CLL group when compared with HVs, and this decreased further as the disease progressed. This change may result in the promotion of leukemic B lymphocyte survival. Therefore, in the pathogenesis of CLL, Th2 bias may delay the antitumor response that relies on stimulation of the Th1 immune response.

Imprecision and DNA Break Repair Biased towards Incompatible End Joining in Leukemia

Cancer is a genetic disease caused by mutations and chromosomal abnormalities that contribute to uncontrolled cell growth. In addition, cancer cells can rapidly respond to conventional and targeted therapies by accumulating novel and often specific genetic lesions leading to acquired drug resistance and relapsing disease. In chronic lymphocytic leukemia (CLL), however, diverse chromosomal aberrations often occur. In many cases, improper repair of DNA double-strand breaks (DSB) is a major source for genomic abnormalities. Therefore, this study examined the repair of DNA DSBs by nonhomologous end joining (NHEJ) in CLL by performing plasmid-based repair assays in primary CLL cells and normal B cells, isolated from patients, as well as TALEN/Cas9-induced chromosomal deletions in the CLL cell line Mec1. It is demonstrated that DNA repair is aberrant in CLL cells, featuring perturbed DNA break structure preference with efficient joining of noncohesive ends and more deletions at repair junctions. In addition, increased microhomology-mediated end joining (MMEJ) of DNA substrates was observed in CLL together with increased expression of MMEJ-specific repair factors. In summary, these data identify major differences in DNA repair efficiency between CLL cells and normal B cells isolated from patients.Implications: This study suggests inherently aberrant DNA DSB repair in the acquisition of subclonal genomic structural variations important for clonal evolution and treatment resistance in CLL. Mol Cancer Res; 16(3); 428-38. ©2017 AACR.

Th17/IL-17A might play a protective role in chronic lymphocytic leukemia immunity

Th17 cells, a recently discovered subset of T helper cells that secrete IL-17A, can affect the inflammation process autoimmune and cancer diseases development. The purpose of this study was to evaluate the role of Th17 cells and IL17A in biology of CLL. The study group included 294 untreated CLL patients in different clinical stages. Here, we show that higher Th17 and IL-17A values were associated with less advanced clinical stage of CLL. Th17 cells' percentages in PB were lower in patients who died due to CLL during follow-up due to CLL (as compared to surviving patients) and in patients responding to first-line therapy with fludarabine-based regimens (as compared to non-responders). IL-17A inversely correlated with the time from CLL diagnosis to the start of therapy and was lower in patients who required treatment during follow-up. Th-17 and IL-17A values were lower in patients with adverse prognostic factors (17p and 11q deletion, CD38 and ZAP-70 expression). CLL patients with detectable IL-17A mRNA in T cells were in Rai Stage 0 and negative for both ZAP-70 and CD38 expression. Th17 percentages positively correlated with iNKT and adversely with Treg cells. The results of this study suggest that Th17 may play a beneficial role in CLL immunity.

Surface profiles for subclassification of chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) has a variable clinical course. Some patients have stable disease while others progress and require treatment. Levels of several cluster of differentiation (CD) antigens are known to correlate with prognosis and may be used to stratify patients according to risk. In this review, we summarize current information on surface CD antigens found on CLL, their pathological significance and their detection using CD antibody microarrays. The use of extensive immunophenotypic patterns or surface profiles as disease signatures for CLL subclassification, prognosis and patient management is discussed with a focus on triaging patients with CLL with progressive disease.

Fludarabine modulates composition and function of the T cell pool in patients with chronic lymphocytic leukaemia

The combination of cytotoxic treatment with strategies for immune activation represents an attractive strategy for tumour therapy. Following reduction of high tumour burden by effective cytotoxic agents, two major immune-stimulating approaches are being pursued. First, innate immunity can be activated by monoclonal antibodies triggering antibody-dependent cellular cytotoxicity. Second, tumour-specific T cell responses can be generated by immunization of patients with peptides derived from tumour antigens and infused in soluble form or loaded onto dendritic cells. The choice of cytotoxic agents for such combinatory regimens is crucial since most substances such as fludarabine are considered immunosuppressive while others such as cyclophosphamide can have immunostimulatory activity. We tested in this study whether fludarabine and/or cyclophosphamide, which represent a very effective treatment regimen for chronic lymphocytic leukaemia, would interfere with a therapeutic strategy of T cell activation. Analysis of peripheral blood samples from patients prior and during fludarabine/cyclophosphamide therapy revealed rapid and sustained reduction of tumour cells but also of CD4(+) and CD8(+) T cells. This correlated with a significant cytotoxic activity of fludarabine/cyclophosphamide on T cells in vitro. Unexpectedly, T cells surviving fludarabine/cyclophosphamide treatment in vitro had a more mature phenotype, while fludarabine-treated T cells were significantly more responsive to mitogenic stimulation than their untreated counterparts and showed a shift towards T(H)1 cytokine secretion. In conclusion, fludarabine/cyclophosphamide therapy though inducing significant and relevant T cell depletion seems to generate a micromilieu suitable for subsequent T cell activation.

Regulatory T cells predict the time to initial treatment in early stage chronic lymphocytic leukemia

BACKGROUND

Early stage chronic lymphocytic leukemia is characterized by a highly variable course of disease. Because it is believed that regulatory T cells (T(regs) ) are potent suppressors of antitumor immunity, the authors hypothesized that increased T(regs) may favor disease progression.

METHODS

T(reg) levels (cluster of differentiation 3 [CD3]-positive, [CD4]-positive, CD25-positive, and CD127-negative) in peripheral blood from 102 patients were analyzed by flow cytometry. Statistical analysis was used to evaluate correlations with clinical data.

RESULTS

The relative T(reg) numbers in CD4-positive T cells were significantly greater in patients with chronic lymphocytic leukemia compared with the numbers in a control group of 170 healthy individuals (P = .001). Patients were divided into 2 groups using a median T(reg) value of 9.7% (the percentage of CD4-positive T cells). Patients with higher T(reg) levels had a significantly shorter time to initial treatment (median, 5.9 years) compared with patients who had lower T(reg) levels (median, 11.7 years; log-rank P = .019). Furthermore, T(reg) levels (the percentage of CD4-positive T cells) had significant prognostic power to predict the time to initial treatment in univariate analysis (P = .023) and in multivariate Cox regression analysis that included the variables Rai stage, immunoglobulin heavy-chain variable region gene mutational status, chromosomal aberrations, and CD38 expression (P = .028).

CONCLUSIONS

Higher T(reg) levels had significant and independent prognostic power for predicting the time to initial treatment in patients with low to intermediate stage chronic lymphocytic leukemia.

Prognostic impact of ZAP-70 expression in chronic lymphocytic leukemia: mean fluorescence intensity T/B ratio versus percentage of positive cells

BACKGROUND

ZAP-70 is an independent negative prognostic marker in chronic lymphocytic leukemia (CLL). Usually, its expression is investigated by flow cytometric protocols in which the percentage of ZAP-70 positive CLL cells is determined in respect to isotypic control (ISO-method) or residual ZAP-70 positive T cells (T-method). These methods, however, beside suffering of an inherent subjectivity in their application, may give discordant results in some cases. The aim of this study was to assess the prognostic significance of these methods in comparison with another in which ZAP-70 expression was evaluated as a Mean-Fluorescence-Intensity Ratio between gated T and CLL cells (T/B Ratio-method).

METHODS

Cytometric files relative to ZAP-70 determination according to the three readouts were retrospectively reviewed on a cohort of 173 patients (test set), all with complete clinical and biological prognostic assessment and time-to-treatment (TTT) available. Findings were then validated in an independent cohort of 341 cases from a different institution (validation set).

RESULTS

The optimal prognostic cut-offs for ZAP-70 expression were selected at 11% (ISO-method) or 20% of positive cells (T-method), as well as at 3.0 (T/B Ratio-method) in the test set; these cut-offs yielded 66, 60 and 73 ZAP-70+ cases, respectively. Univariate analyses resulted in a better separation of ZAP-70+ vs. ZAP-70- CLL patients utilizing the T/B Ratio, compared to T- or ISO-methods. In multivariate analyses which included the major clinical and biological prognostic markers for CLL, the prognostic impact of ZAP-70 appeared stronger when the T/B-Ratio method was applied. These findings were confirmed in the validation set, in which ZAP-70 expression, evaluated by the T- (cut-off = 20%) or T/B Ratio- (cut-off = 3.0) methods, yielded 180 or 127 ZAP-70+ cases, respectively. ZAP-70+ patients according to the T/B Ratio-method had shorter TTT, both if compared to ZAP-70- CLL, and to cases classified ZAP-70+ by the T-method only.

CONCLUSIONS

We suggest to evaluate ZAP-70 expression in routine settings using the T/B Ratio-method, given the operator and laboratory independent feature of this approach. We propose the 3.0 T/B Ratio value as optimal cut-off to discriminate ZAP-70+ (T/B Ratio less than 3.0) from ZAP-70- (T/B Ratio more/equal than 3.0) cases.

microRNA-34a expression correlates with MDM2 SNP309 polymorphism and treatment-free survival in chronic lymphocytic leukemia

In chronic lymphocytic leukemia (B-CLL), aberrations along the p53 axis lead to decreased overall survival and therapy resistance. Recent studies identified microRNA-34a (miR-34a) as a major downstream target of p53. We monitored the expression of miR-34a during disease development in a murine B-CLL model. miR-34a was up-regulated more than 20-fold during the leukemic but not during the preleukemic phase. In the human system, B-CLL cells also had 4.6-fold higher miR-34a expression compared with B cells of healthy controls. In B-CLL cells of patients with p53 aberrations, miR-34a expression was consistently low. The broad distribution of miR-34a levels in p53 wild-type patients prompted us to study the correlation between single nucleotide polymorphism 309 (SNP309) in the intronic promoter of MDM2 and miR-34a expression. B-CLL cells of patients with the SNP309 GG genotype had significantly lower miR-34a expression levels compared with patients with the TT genotype (P = .002). Low miR-34a levels were able to predict shorter time to treatment (P = .003) and were associated with an abbreviated lymphocyte doubling time. Further, overexpression of miR-34a in primary B-CLL cells induced apoptosis. These findings suggest miR-34a as a possible therapeutic avenue and a sensitive indicator of the activity of the p53 axis in B-CLL.

T-cell CD38 expression in B-chronic lymphocytic leukaemia

B-cell chronic lymphocytic leukaemia (B-CLL) is a heterogeneous disease with some patients having an indolent course never needs treatment, while others having rapidly progressive one requires intensive treatment. In recent decades, numerous prognostic markers, such as immunoglobulin variable region heavy-chain (IgVH) mutational status, ZAP-70 and the expression of CD38 on leukaemic cells were introduced to screen for patients likely to have progressive course of B-CLL bearing the potential to facilitate risk-adapted treatment strategies. In B-CLL, T cell function is shown to be dysregulated. CD38 has been demonstrated to be an important transmembrane signalling molecule of T cell with a direct effect on its function. The present study was conducted to analyse CD38 expression on T cells by flow cytometry to evaluate its impact on the clinical course of 88 unselected B-CLL patients and correlate it with other risk factors. CD38 expression level on T cells was shown to predict the clinical course of B-CLL in male patients but not in female patients. Male patients showed CD38 expression on T cells in a stage-dependent manner, in contrast to female patients who showed higher expression irrespective to clinical staging. CD38 expression on T cells negatively interacted with treatment-free survival in male patients. Multivariate analysis revealed that CD38 expression level on T cells is an independent prognostic factor in B-CLL male patients. Simultaneous evaluation of CD38 expression on both B-CLL cells and T cells allowed predicting male patient groups with the most favourable prognosis as well as those with the worst.

Difference in the relative distribution of CD4+ T-cell subsets in B-CLL with mutated and unmutated immunoglobulin (Ig) VH genes: implication for the course of disease

B-cell chronic lymphocytic leukemia (B-CLL) is a clinically heterogeneous disease in which the clinical course is influenced by the presence or absence of immunoglobulin (Ig) variable heavy chain (VH) gene mutations. The poor clinical outcome of the subgroup with unmutated Ig VH genes has been linked to the persistent ability of the B-cell receptor in tumor cells from these cases to respond to antigen. As B-cell receptor signaling generally relies on T-cell help, we hypothesized that the course of B-CLL might not only be influenced by the Ig VH mutational status but also by the activation/differentiation status of T cells. We assessed the relative distribution of naive and memory T-cell subsets in peripheral blood from patients with mutated (M-CLL, n=71) and unmutated Ig VH genes (UM-CLL, n=42) and correlated it with the course of disease. We also compared the prosurvival potential of naive and memory T cells cocultured with B-CLL cells in vitro. A significant increase in relative numbers of central and effector memory T cells was observed in the CD4 T-cell pool from UM-CLL as compared with M-CLL cases and was associated with high Rai stage, progressive disease and shorter treatment-free survival (TFS). In a multivariate analysis, the relative number of CD4 central and effector memory T cells remained a significant prognostic parameter for TFS after correction for CD38 expression, Ig VH status, genomic aberrations, and Rai stage. The inverse correlation of memory CD4 T cells with TFS might be explained by their potential to support survival of B-CLL cells.

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.

PKCβ is essential for the development of chronic lymphocytic leukemia in the TCL1 transgenic mouse model: validation of PKCβ as a therapeutic target in chronic lymphocytic leukemia

The development and the propagation of chronic lymphocytic leukemia (CLL) has been linked to signaling via the B-cell receptor (BCR). Protein kinase C β (PKCβ) is an essential signaling element of the BCR and was recently shown to be overexpressed in human CLL. We used the TCL1 transgenic mouse model to directly target PKCβ in the development of murine CLL. TCL1 overexpression did restore the CD5+ B-cell population that is absent in PKCβ-deficient mice. However, PKCβ-deleted TCL1 transgenic mice did not develop a CLL disease, suggesting a role of PKCβ in the establishment of the malignant clone. Moreover, targeting of PKCβ with the specific inhibitor enzastaurin led to killing of human CLL samples in vitro. We thus propose that PKCβ may be a relevant target for the treatment of CLL.

Expression levels of CD38 on leukemic B cells but not on non-leukemic T cells are comparably stable over time and predict the course of disease in patients with chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is characterized by a number of T-cell abnormalities, which may play a causative role in disease progression and immune dysfunction. Recently, expression levels of CD38 in T cells have been suggested as a novel adverse prognostic factor in male CLL patients. In the current study, CD38 expression on CLL T cells was examined by flow cytometry in 126 patients with B-CLL and correlated with clinical parameters and established molecular risk factors. In line with previous results we observed a positive correlation of CD38 expression on leukemic B and non-leukemic T cells with clinical stage. CD38 expression on B-CLL cells, cytogenetic aberrations and mutations of IgVH genes were found to significantly influence treatment-free survival. By contrast, CD38 expression on T cells was not significantly associated with an adverse clinical outcome.

Arsenic trioxide induces apoptosis preferentially in B-CLL cells of patients with unfavourable prognostic factors including del17p13

In the last decade, arsenic trioxide (As2O3) has been used very successfully to treat acute promyelocytic leukaemia (APL). Much less is known about the effectiveness of As2O3 in other neoplastic disorders. In this paper, we report that after 18 h in vitro treatment with 4 microM As2O3, 75+/-18% of B cell chronic lymphocytic leukaemia (B-CLL) cells (n=52) underwent apoptosis. It is important to note that B-CLL cells harboring a deletion of chromosome 17p13, which predisposes to fludarabine resistance and has been identified as an important negative predictor of clinical outcome, were more susceptible to As2O3 toxicity than cells lacking this aberration. Furthermore, unfavourable risk profiles such as unmutated IgVH status, high CD38 expression and prior treatment were associated with significantly higher sensitivity of B-CLL cells to As2O3. As2O3 also preferentially killed B-CLL cells compared to B cells from healthy age-matched controls. Molecular analysis revealed that basal superoxide dismutase activity was positively correlated with the pro-apoptotic activity of As2O3 pointing to a role of reactive oxygen species in cell death induction. The high activity of As2O3 in B-CLL cells from high-risk patients makes it a promising drug for high-risk and/or fludarabine-refractory B-CLL patients.

Lack of the leukocyte-associated Ig-like receptor-1 expression in high-risk chronic lymphocytic leukaemia results in the absence of a negative signal regulating kinase activation and cell division

In this study, we analysed 30 patients with B-cell chronic lymphocytic leukaemia (CLL), compared with 10 healthy donors, for the expression and function of the leukocyte-associated Ig-like receptor-1 (LAIR-1). LAIR-1 is an inhibitory receptor containing a cytoplasmic tyrosine-based inhibitory motif (ITIM) that binds to the SH2 domain of phosphatases, leading to dephosphorylation of different kinases. Constitutive activation of c-Jun aminoterminal kinase (JNK), p38 mitogen-activated protein kinase and extracellular signal-regulated kinase, has been reported in CLL. We show that LAIR-1 is absent in high-risk (HR) CLL and differently expressed on intermediate- and low-risk CLL and the intensity of expression, which is always significantly lower than in healthy donors, correlates with disease stage and progression. Interestingly, both constitutive and sIgM-induced phosphorylation of p38 and JNK is inhibited by LAIR-1 through an ITIM-dependent signal, as demonstrated by the use of specific ITIM-binding peptides; importantly, this inhibitory signal is missing when LAIR-1 is not expressed as occurs in HR CLL. Moreover, engagement of LAIR-1 blocks constitutive and sIgM-induced Akt phosphorylation, besides nuclear factor kappa-B nuclear translocation, and prevents CLL division. These results suggest that CLL lacking LAIR-1 may miss one of the molecular mechanisms controlling B-cell activation and proliferation.