Autocrine transforming growth factor-beta from chronic lymphocytic leukemia-B cells interferes with proliferative T cell signals

Modulation the expression of natural killer cell activating receptor (NKp44) in the peripheral blood of diffuse large B-cell lymphoma patients and the correlation with clinic pathological features

NK cell activation is one strategy to improve the immunotherapy of non-Hodgkin's lymphoma. So, we aimed to investigate expression of Natural killer cell activating receptor NKp44 in patients with diffuse large B-cell lymphoma (DLBCL) and its correlation with clinic pathological data. In this study, 30 new cases with DLBCL in addition to 20 healthy control were involved. All were submitted to full history, clinical examination, histopathology, Routine laboratory investigations including CBC, LDH, β2microgloubine and bone marrow examination. Cell culture of peripheral blood mononuclear cells and expression of CD56 and NKp44 by flowcytometry was done. We demonstrated increased NK cell populations (CD 56 +ve NKp44 -ve, CD 56 -veNKp44 +ve, total CD 56 +ve) and NKp44 MFI after in-vitro activation in both healthy control and DLBCL cases except for CD 56 +ve NKp44 +ve which significantly increased in patients not in healthy control (p=0.005, 0.601) respectively. No significant difference between the DLBCL and healthy control regarding all NK cell populations without PHA stimulation. However, the culture with PHA in DLBCL showed significant increase in NK cell populations than the healthy control (CD 56 +ve NKp44 +ve 12.37±7.52vs 6.80±4.07, p=0.008), (Total CD 56 +ve 18.80±8.74vs 12.66±5.17, p=0.017), (MFI of NKp44 10.95±6.18vs 5.58±1.70, p=0.001). Regarding the association with clinic pathologic features, increased expression of NKp44 was associated with lower values of LDH and earlier stages of DLBCL (p<0.05). So, activating receptor NKp44 can be modulated by in-vitro activation, hence improvement of its function as an approach of immunotherapy of DLBCL.

An update on current and prospective immunotherapies for chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) is the most common leukemia. Combined agent chemotherapy is the current standard front-line treatment for physically fit patients with CLL. Use of chemotherapy can be complicated by significant toxicity, especially in patients with advanced age or comorbid conditions. Moreover, patients may relapse and become refractory to further chemotherapy. Immunotherapy targets the aberrant immunological processes in CLL without the toxicity of chemotherapy. Immunotherapeutic strategies can also be combined with chemotherapy to improve response rates in this incurable disease. In this review, we evaluate current and future immune-based options in the treatment of CLL.

Immunomodulatory drugs and active immunotherapy for chronic lymphocytic leukemia

BACKGROUND

The last decade witnessed the emergence of several therapeutic options for patients with chronic lymphocytic leukemia (CLL) for first-line and relapsed settings. The vast majority of patients with relapsed or refractory CLL carry poor prognostic features, which are strong predictors of shorter overall survival and resistance to first-line treatment, particularly fludarabine-based regimens.

METHODS

This article highlights the current role of immunomodulatory drugs (IMiDs) and active immunotherapy as treatment options for this select group. The rationale of using IMiDs is discussed from the perspective of lenalidomide as a novel active agent. Relevant clinical trials using IMiDs alone or in combinations are discussed. New immunotherapeutic experimental approaches are also described.

RESULTS

As a single agent, lenalidomide offers an overall response rate of 32% to 47% in patients with relapsed/refractory disease. Recent studies have shown promising activity as a single agent in treatment-naive patients. The combination of lenalidomide with immunotherapy (rituximab and ofatumumab) has also shown clinical responses. Encouraging preclinical and early clinical data have been observed with different immunotherapeutic approaches.

CONCLUSIONS

The use of IMiDs alone or in combination with immunotherapy represents a treatment option for relapsed/refractory or treatment-naive patients. Mature data and further studies are needed to validate overall and progression-free survival. The toxicity profile of lenalidomide might limit its use and delay further studies. Immunotherapy offers another potential alternative, but further understanding of the immunogenicity of CLL cells and the mechanisms of tumor fl are reaction is needed to improve the outcomes in this field.

Expression of natural killer cell activating receptors in patients with chronic lymphocytic leukaemia

Recent advances in chronic lymphocytic leukaemia (CLL) treatment, more particularly through upfront use of anti-CD20 monoclonal antibodies, have prolonged patient progression-free survival. Nonetheless, apart from allogeneic stem cell transplantation, no curative treatment is available. One possible explanation for the lack of cure in CLL could be a defective immune anti-tumour response. As the result of abnormal HLA class I molecule expression, CLL cells escape from specific T-lymphocyte immunity but should be the target for the innate natural killer (NK) cell-mediated immune response. Defective NK cytotoxicity as the result of decreased expression of the natural cytotoxicity receptors (NCRs) NKp30/NCR3, NKp44/NCR2 and NKp46/NCR1 has been described in haematological malignancies such as acute myeloid leukaemia. This prompted us to focus our attention on NCR expression on NK cells from patients with CLL. Although we failed to detect any difference between CLL patients and healthy age-matched controls, a precise analysis of clinical data showed a correlation between decreased NCR expression and poor prognosis factors such as low haemoglobin level, high (>30×10(9) per litre) lymphocyte count or elevated C-reactive protein. Together, these observations support the rationale for restoration of normal NK cell functions in patients with CLL, putatively through the use of immune therapy protocols that already have demonstrated some benefit in acute myeloid leukaemia such as interleukin-2 plus histamine dihydrochloride.

Regulatory B cells and allergic diseases

B cells are generally considered to positively regulate immune responses by producing antigen-specific antibodies. B cells are classified into classical CD5^- conventional B cells and CD5⁺ B1 cells. The latter produce multi-specific autoantibodies and are thought to be involved in autoimmune diseases. However, evidence supporting a B cell negative regulatory function has accumulated over the past 30 years. Multiple reports have suggested that absence, or loss, of regulatory B cells exacerbates symptoms of both allergic (including contact hypersensitivity and anaphylaxis) and autoimmune (such as experimental autoimmune encephalomyelitis, chronic colitis, and collagen-induced arthritis) diseases, and in lupus-like models of autoimmunity. Regulatory B cells are characterized by production of the negative regulatory cytokines, IL-10 and TGF-β. IL-10-producing B cells were the first regulatory B cells to be recognized and were termed 'B10' cells. IL-10-producing regulatory B cells are of the CD19⁺CD5⁺IgM^hiIgD^loCD1d^hi type. Recently, a TGF-β-producing regulatory B cell subset, Br3, has been shown to be related to immune tolerance in food allergies. Moreover, forkhead box P3 (Foxp3)-expressing B cells have also been identified in humans and may act as regulatory B cells (Bregs). The functional image of regulatory B cells is similar to that of regulatory T cells. Because of the proliferative and apoptotic responses of Br1 and Br3 cells in immune tolerance in non-IgE-mediated food allergy, reciprocal roles and counter-regulatory mechanisms of Br1 and Br3 responses are also suspected. Additionally, different roles for regulatory B and T cells at different time points during initiation and progression of autoimmune disease are described.

Allergen-specific transforming growth factor-β-producing CD19+CD5+ regulatory B-cell (Br3) responses in human late eczematous allergic reactions to cow's milk

CD19(+)CD5(+) regulatory B cells produce transforming growth factor β (TGF-β) in both mouse and human B-cell leukemias. In this study, TGF-β was uniquely produced by normal human regulatory B cells. TGF-β-producing regulatory B-cell (Br3) responses were characterized through allergic responses to cow's milk. In total, 10 subjects allergic to milk and 13 milk-tolerant subjects were selected following double-blinded, placebo-controlled food challenges. Their peripheral blood mononuclear cells were stimulated in vitro with casein. Following allergen stimulation, the percentage of Br3s among CD5(+) B cells decreased from 11.5% ± 13.7% to 8.0% ± 9.6% (P = 0.042, n = 5) in the milk-allergy group and increased from 14.7% ± 15.6% to 18.9% ± 20.1% (P = 0.006, n = 7) in the milk-tolerant group. However, the numbers of Br3s increased only in the milk-tolerant group, from 1,954 ± 1,058 to 4,548 ± 1,846 per well (P = 0.026), whereas the numbers of Br3s in the milk-allergy group were unchanged [2,596 ± 823 to 2,777 ± 802 per well (P = 0.734)]. The numbers of apoptotic events were similar to the numbers of total Br3 responses. The percentage of non-TGF-β-producing CD5(+) B cells with apoptotic changes increased from 13.4% ± 17.1% to 16.4% ± 20.3% (P = 0.047, n = 5) in the milk-allergy group and remained unchanged [from 9.9% ± 11.9% to 9.3% ± 11.4% (P = 0.099, n = 7)] in the milk-tolerant group. Using carboxyfluorescein succinimidyl ester labeling, we observed that the percentage of proliferating Br3s among CD5(+) B cells was unchanged [from 6.1% ± 2.8% to 6.4% ± 2.9% (P = 0.145)] in the milk-allergy group and increased from 6.8% ± 3.9% to 10.2% ± 5.3% (P = 0.024) in the milk-tolerant group. In conclusion, Br3s proliferated in response to allergen stimulation in the milk-tolerant group and not in the milk-allergy group. TGF-β-producing regulatory B cells (Br3) may be involved in allergy tolerance by negatively regulating the immune system with TGF-β, and this negative regulation may be controlled by apoptosis.

Development of a dendritic cell-based vaccine for chronic lymphocytic leukemia

Evidence for the existence of CLL-specific antigens recognized by the immune system can be gathered from the observation that many patients display monoclonal or oligoclonal expansions and skewed repertoire of T cells. In vitro functional studies have shown that tumor-specific T-cells are able to lyse the leukemic cells. Antileukemic cellular immunity may be boosted in vivo using dendritic cell-based immunotherapy. Our preclinical studies provide evidence that DC that had endocytosed apoptotic CLL cells (Apo-DC) were superior to fusion hybrids, tumor lysate or RNA in eliciting antileukemic T-cell responses in vitro. We have validated a method for enriching the small number of monocyte precursors present in the peripheral blood of CLL patients and utilize them for generating individualized, Apo-DC cellular vaccines. In most cases, a minimum of 50 x 10(6) Apo-DC could be generated, beginning with immunomagnetically enriched monocytes from a single leukapheresis product containing at least 1% CD14+ cells. Cryopreservation and thawing did not affect the phenotype or the T cell stimulatory function of Apo-DC. A phase I/II, open label clinical trial examining the feasibility, safety and immunogenicity of Apo-DC vaccination has been initiated. CLL patients receive 10(7) Apo-DC for at least five immunizations and monitored clinically and immunologically for 52 weeks. Three cohorts are accrued stepwise. Cohort I receives Apo-DC alone; Cohort II: Apo-DC+ repeated doses of low-dose GM-CSF; Cohort III: low-dose cyclophosphamide followed by Apo-DC + GM-CSF.

Natural phosphorylation of CD5 in chronic lymphocytic leukemia B cells and analysis of CD5-regulated genes in a B cell line suggest a role for CD5 in malignant phenotype

Chronic lymphocytic leukemia (CLL) results in the accumulation of B cells, presumably reflecting the selection of malignant cell precursors with Ag combined with complex alterations in protein activity. Repeated BCR stimulation of normal B cells leads to anergy and CD5 expression, both of which are features of CLL. Because CD5 is phosphorylated on tyrosine following BCR engagement and negatively regulates BCR signaling in normal B cells, we investigated its phosphorylation status and found it to be naturally phosphorylated on tyrosine but not on serine residues in CLL samples. To analyze the role of CD5, we established a B cell line in which CD5 is phosphorylated. Gene profiling of vector vs CD5-transfected B cells pointed out gene groups whose expression was enhanced: Apoptosis inhibitors (BCL2), NF-kappaB (RELB, BCL3), Wnt, TGFbeta, VEGF, MAPKs, Stats, cytokines, chemokines (IL-10, IL-10R, IL-2R, CCL-3, CCL-4, and CCR7), TLR-9, and the surface Ags CD52, CD54, CD70, and CD72. Most of these gene groups are strongly expressed in CLL B cells as compared with normal B cells. Unexpectedly, metabolic pathways, namely cholesterol synthesis and adipogenesis, are also enhanced by CD5. Conversely, CD5 inhibited genes involved in RNA splicing and processing, ribosome biogenesis, proteasome, and CD80 and CD86 Ags, whose expression is low in CLL. Comparison of CD5- vs tailless CD5-transfected cells further demonstrated the role of CD5 phosphorylation in the regulation of selected genes. These results support a model where CLL cells are chronically stimulated, leading to CD5 activation and cell survival. In addition to CD5 itself, we point to several CD5-induced genes as potential therapeutic targets.

Fibromodulin, an extracellular matrix protein: characterization of its unique gene and protein expression in B-cell chronic lymphocytic leukemia and mantle cell lymphoma

Fibromodulin is an extracellular matrix protein normally produced by collagen-rich tissues; the fibromodulin gene has been found to be the most overexpressed gene in B-cell chronic lymphocytic leukemia. In this study, fibromodulin was expressed at the gene level (reverse transcription-polymerase chain reaction [RT-PCR]) in all patients with B-CLL (n = 75) and in most (5 of 7) patients with mantle cell lymphoma (MCL). No mutations in the fibromodulin gene were detected. Fibromodulin was also detected at the protein level in the cytoplasm of the B-CLL cells and in the supernatant after in vitro cultivation, but not at the cell surface. Fibromodulin was not found in patients with T-cell chronic lymphocytic leukemia (T-CLL), B-cell prolymphocytic leukemia (B-PLL), T-cell prolymphocytic leukemia (T-PLL), hairy cell leukemia, follicular lymphoma, lymphoplasmacytic lymphoma, multiple myeloma, acute lymphoblastic leukemia (ALL), acute myelogenous leukemia (AML), or chronic myelogenous leukemia (CML) or in 36 hematologic cell lines. Normal blood mononuclear cells (T and B lymphocytes, monocytes), tonsil B cells, and granulocytes did not express fibromodulin. Activation (phorbol 12-myristate 13-acetate [PMA]/ionomycin) of normal T and B lymphocytes induced weak fibromodulin gene expression, but not to the extent seen in freshly isolated B-CLL cells. The reason for the exclusive ectopic expression of fibromodulin in B-CLL and MCL is unknown. However, its unique protein expression makes it likely that fibromodulin is involved in the pathobiology of B-CLL and MCL. (Blood. 2005;105:4828-4835)

Circulating proangiogenic cytokines and angiogenesis inhibitor endostatin in untreated patients with chronic lymphocytic leukemia

The serum concentration of two pro-angiogenic cytokines: basic fibroblast growth factor (bFGF) and transforming growth factor beta1 (TGF-beta1), and anti-angiogenic factor endostatin in the serum of 80 never treated B-cell chronic lymphocytic leukemia (CLL) patients and 27 healthy volunteers was measured using an enzyme linked immunosorbent assay. The serum levels of both bFGF and TGF-beta1 were found to be significantly higher in the CLL group (median 40.5 pg/ml and 38.6 ng/ml respectively) when compared to the control group (median 9.4 pg/ml and 18.9 ng/ml, respectively) (p<0.001). The levels of endostatin were not significantly different in CLL and control groups (median 12.3 ng/ml and 8.4 ng/ml, respectively) (p=0.09). In the group of CLL patients the level of bFGF was significantly higher in patients with progressive disease as compared with patients with stable disease (median 90.5 pg/ml and 40.5 pg/ml respectively) (p<0.001). Patients in Rai stage III and IV also had significantly higher levels of bFGF than patients in Rai stage 0-II (median 100.1 pg/ml and 29.3 pg/ml respectively) (p<0.001). The levels of both TGF-beta1 and endostatin were lower in patients in Rai stage III and IV (median 28.9 ng/ml and 9.1 ng/ml respectively) than in patients in Rai stage 0-II (42.8 ng/ml and 13.1 ng/ml respectively) (p<0.001 and p=0.002 respectively). The level of endostatin was also lower in the group of CLL patients with progressive disease (median 10.0 ng/ml) as compared to patients with stable disease (median 20.5 ng/ml) (p=0.008). In conclusion, the disturbance in the balance between pro- and anti-angiogenic factors may have an important influence on the course of CLL.

B-CLL cells are capable of synthesis and secretion of both pro- and anti-angiogenic molecules

Initial work has shown that clonal B cells from B-chronic lymphocytic leukemia (B-CLL) are able to synthesize pro-angiogenic molecules. In this study, our goal was to study the spectrum of angiogenic factors and receptors expressed in the CLL B cell. We used ELISA assays to determine the levels of basic fibroblast growth factors (bFGF), vascular endothelial growth factor (VEGF), endostatin, interferon-alpha (IFN-alpha) and thrombospondin-1 (TSP-1) secreted into culture medium by purified CLL B cells. These data demonstrated that CLL B cells spontaneously secrete a variety of pro- and anti-angiogenic factors, including bFGF (23.9 pg/ml +/- 7.9; mean +/- s.e.m.), VEGF (12.5 pg/ml +/- 2.3) and TSP-1 (1.9 ng/ml +/- 0.3). Out of these three factors, CLL B cells consistently secreted bFGF and TSP-1, while VEGF was expressed in approximately two-thirds of CLL patients. Of interest, hypoxic conditions dramatically upregulated VEGF expression at both the mRNA and protein levels. We also employed ribonuclease protection assays to assay CLL B cell expression of a variety of other angiogenesis-related molecules. These analyses revealed that CLL B cells consistently express mRNA for VEGF receptor 1 (VEGFR1), thrombin receptor, endoglin, and angiopoietin. Further analysis of VEGFR expression by RT-PCR revealed that CLL B cells expressed both VEGFR1 mRNA and VEGFR2 mRNA. In summary, these data collectively indicate that CLL B cells express both pro- and anti-angiogenic molecules and several vascular factor receptors. Because of the co-expression of angiogenic molecules and receptors for some of these molecules, these data suggest that the biology of the leukemic cells may also be directly impacted by angiogenic factors as a result of autocrine pathways of stimulation.