Deficient production of tumor necrosis factor by peripheral-blood monocytes in chronic lymphocytic leukemia

The role of chemotherapy in managing chronic lymphocytic leukemia: optimizing combinations with targeted therapy

For many years, alkylating agents were the standard treatment for chronic lymphocytic leukemia (CLL). The advent of purine analogs improved response rates, but not overall survival, and although the monoclonal antibody rituximab is generally active against B-cell malignancies, it has demonstrated limited benefits as monotherapy for the treatment of CLL. However, specific combinations of chemotherapy, antibodies and targeted therapies have demonstrated additive or synergistic activity in CLL cells and deliver substantial clinical benefits. A greater understanding of the actions of chemotherapies and targeted agents on cellular pathways will advance the development of rationally designed combinations corresponding to individual patients' disease profiles.

The clinical application of monoclonal antibodies in chronic lymphocytic leukemia

Chronic lymphocytic leukemia (CLL) represents the most prevalent adult leukemia. Treatment with chemotherapy over the past 3 decades has been palliative. The introduction of therapeutic antibodies has increased the number of treatment options for this disease. Despite this increase, our true understanding of the mechanism of action of antibody therapy in CLL remains limited. Rituximab, a CD20 antibody, is currently widely used in combination-based strategies for both previously untreated symptomatic CLL and as salvage therapy. Recent data suggest that the addition of rituximab to fludarabine with or without cyclophosphamide prolongs survival in younger patients with CLL. Other improved CD20 antibodies with promising clinical activity, including ofatumumab and GA-101, are coming forward. Alemtuzumab, a CD52 antibody, likewise has demonstrated benefit in both symptomatic, previously untreated CLL and in patients with relapsed disease but has less selectivity. Development of other therapeutic antibodies targeting alternative B-cell-specific antigens in CLL has been less successful, although many promising candidate antibodies and/or small modular immune pharmaceuticals (SMIPs) are coming forward. In addition, recent efforts to combine currently applied therapeutic antibodies with other biologic and targeted therapies with efficacy in CLL offers the potential to move toward alternative non-chemotherapy-based treatment approaches.

Rituximab in chronic lymphocytic leukemia

Rituximab is a class I chimeric anti-CD20 antibody that has shown efficacy in chronic lymphocytic leukemia (CLL), both as a single agent and in combination with traditional chemotherapies. The modest activity demonstrated in early studies evaluating rituximab in relapsed CLL was improved with higher doses or more dose-intensive regimens that overcame the unfavorable pharmacokinetic features commonly found in CLL. These studies led to a variety of combination trials of rituximab with chemotherapy, where both phase II and later phase III studies have shown great promise for the advancement of CLL therapy. Despite the therapeutic success of rituximab in CLL, studies demonstrating the definitive relative mechanism of tumor clearance are still lacking and this requires further investigation. In addition to being used as a therapy for CLL, rituximab is an effective treatment for autoimmune CLL complications such as hemolytic anemia and immune thrombocytopenia (ITP). Patients with CLL may experience early infusion-related side effects that can be diminished with corticosteroid pretreatment and stepped-up dosing. Risk factors for infusion-related toxicity may relate to atypical CLL expressing bright CD20 antigen expression, although several different studies have not clearly implicated elevated white blood cell count as a risk factor. Other adverse events, including delayed cytopenias, reactivation of hepatitis B, and development of progressive multifocal leukoencephalopathy, are rare. Future efforts focusing on novel combination-based strategies will be required to fully appreciate the benefit of this therapy in CLL.

Targets and strategies for T-cell based vaccines in patients with B-cell chronic lymphocytic leukemia

T-cell based immunotherapies might be a novel option for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), a disease characterized by a prolonged natural course. Different strategies of active immunotherapy have been tested in vitro to enhance a specific T-cell response against tumor cells and an anti-leukemic effect has been observed in B-CLL patients after allogenic stem cell transplantation. Several antigens have been characterized as tumor/leukemia associated antigens (T/LAAs) in B-CLL with the potential to elicit specific anti-tumor response encompassing idiotype immunoglobulin, oncofetal antigen-immature laminin receptor protein (OFAiLRP), survivin, as well as fibromodulin, the receptor for hyaluronic acid mediated motility (RHAMM/CD168) and the murine double-minute 2 oncoprotein (MDM2). This study presents an overview of possible targets and genetherapeutical maneuvers for future immunotherapies of B-CLL patients and summarizes recent clinical vaccination trials with dendritic cells (DCs) for B-CLL.

Phenotypic and functional characterization of monocyte-derived dendritic cells in chronic lymphocytic leukaemia patients: influence of neoplastic CD19+ cells in vivo and in vitro

Dendritic cells (DCs) are the most potent antigen-presenting cells and are therefore an attractive option as antigen carriers in vaccination protocols. Chronic lymphocytic leukaemia (CLL) represents a potential good target for these approaches. The present study was designed to investigate the feasibility of generating in vitro fully functional DCs from peripheral blood (PB) monocytes of CLL patients at different phases of the disease. Although functional DCs could be obtained from CLL samples, in patients with active disease the expression of some co-stimulatory molecules appeared to be reduced. In contrast, DCs from CLL patients in remission showed no difference from those of normal controls. Moreover, patients with active disease produced DCs with reduced allostimulatory ability when compared with normal ones, whereas the functional capacities appeared to be restored in CLL DCs from remission patients. To more precisely assess the possible inhibitory effect of CLL cells on DC development, the influence of autologous leukaemic CD19(+) cells on the generation of monocyte-derived CLL DCs in vitro was investigated. The addition of CLL neoplastic cells markedly affected monocyte-derived DC maturation. In conclusion, monocytes from CLL patients with active disease give rise to DCs, which show phenotypic and functional defects that are not observed in remission CLL patients. These results need to be taken into account in the design of DC-based immunotherapeutic approaches in CLL.

Factor(s) released from irradiated B-CLL cells induce apoptosis in leukemic lymphocytes

Photon irradiation of peripheral blood lymphocytes from 25 patients with untreated B-chronic lymphocytic leukemia (B-CLL) induced an increase in apoptotic response by 270%. No significant increase in apoptosis was observed after irradiation of peripheral blood mononuclear cells from 15 healthy volunteers. Supernatants (sups) derived from irradiated leukemic cells incubated with non-irradiated autologous cells induced a 75% enhancement in number of apoptotic cells, as compared with sups from non-irradiated CLL cells. The level of tumor necrosis factor alpha, a cytokine known to prevent apoptosis, was reduced in the sups of irradiated CLL cells in comparison to that of non-irradiated lymphocytes. The interleukin (IL)-10 level, an IL reported to induce apoptosis, was similar in the sups of irradiated and non-irradiated lymphocytes from B-CLL patients. No change in IL-2 levels was observed. The significance of these findings and the role of factor(s) in the sups of irradiated leukemic lymphocytes as inducers of apoptosis are discussed.

Value of the determination of TNF-alpha in the plasma of patients with non-Hodgkins lymphoma

The present report describes the value of the plasma determination of TNF-alpha, at diagnosis, in 43 patients with non-Hodgkin's lymphoma (NHL), related to their clinical presentation and the new International Prognosis Index (IPI). We also compare the levels of TNF-alpha with those of LDH, beta-2-microglobulin (beta-2-m), and ferritin. At diagnosis, the mean values of the quotients between the marker values and the maximum value of normal (ratio:r-) are placed 7 times higher than normal for r-TNF-alpha, whereas those of r-beta-2-m and r-LDH are 2,4 and 1,4 times more respectively. We found a relationship between the value of r-TNF-alpha and the ECOG, Ann Arbor stage, the number of affected extranodal sites, and between the values of r-beta-2-m with r-LDH. The best correlation was obtained between the values of r-TNF-alpha and r-beta-2-m and IPI, however r-TNF-alpha best stratify the four risk groups in this prognosis index.

Tumor necrosis factor as marker for monocyte function in chronic myeloid leukemia

The intactness of monocyte function in chronic myeloid leukemia (CML) patients as assessed by their ability to secret tumor necrosis factor was evaluated. Monocytes from CML patients continued to respond to lipopolysaccharide (LPS) stimulation even during the refractory period, suggesting different pathways for stimulation by LPS and malignant processes.

Decreased production of TNF and IL-6 in whole blood of CLL patients

Monocyte derived cytokines, tumor necrosis factor (TNF) and interleukin-6 (IL-6), were determined in cell free plasma after stimulation of heparinized whole blood from chronic lymphocytic leukemia (CLL) patients with lipopolysaccharide (LPS) at 1 microgram/ml for 6 hr. Compared to control donors (390 U/ml), CLL patients in average had eight-fold lower levels of TNF bioactivity (50 U/ml). The depressed levels were observed over a wide range of LPS concentrations (0.01 to 10 micrograms/ml). Furthermore, after stimulation with S. aureus bacteria, CLL samples gave three-fold lower levels, as well. TNF levels were not decreased because of defective bioactivity of TNF, since strongly reduced levels of TNF protein were also detected in an immunoassay. Finally, interleukin-6 levels after LPS stimulation were decreased threefold. Flow cytometry analysis with CD14 antibodies demonstrated comparable numbers of monocytes for control donors and CLL patients (698 +/- 802 and 427 +/- 267, respectively). This suggests that deficient cytokine production was not due to a reduction in monocyte number, but rather to a functional impairment. The deficiency in cytokine production observed after ex vivo stimulation of whole blood from CLL patients suggests that in vivo during bacterial infection, CLL patients will exhibit an inappropriate response as well.

A novel non-radioactive cellular cytotoxicity test based on the differential assessment of living and killed target and effector cells

Monocyte/macrophage-mediated cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) are slow processes, requiring cocultivation of effector and target cells for up to several days. Because of the high spontaneous release and possible reutilization of isotopic labels, the conventional radioactive release assays are unsuited for measuring long term cytotoxicity. We developed a non-radioactive flow cytometric assay for the quantitative analysis of cell-mediated cytotoxicity. Because dead cells can dissolve and disappear during the incubation period (lysis, phagocytosis), we determined the absolute numbers of living cells in the well. Prior to incubation the effector cells are stained with the red lipophilic fluorescent dye PKH26 and the target cells with the green fluorescent dye PKH2. At the end of the incubation (1-6 days) a defined number of bright fluorescent cell standards and propidium iodide for staining of dead cells was added to each well. Using flow cytometric analysis, we determined the ratio of targets to standards and calculated the absolute target cell number by multiplication with the known number of standards added. The main advantages of the assay are the possibility of extended incubation periods, the avoidance of radioactivity and its potential applicability to autologous culture systems, where effector and tumor cells are derived from the same patient. The assay opens new avenues for preclinical testing of tumor therapeutics such as monoclonal antibodies and/or cytokines.

Treatment of hypogammaglobulinaemia in chronic lymphocytic leukaemia by low-dose intravenous gammaglobulin

Intravenous immunoglobulin replacement therapy reduces the number of bacterial infections in B-cell chronic lymphocytic leukaemia (B-CLL) patients. However, due to the complexity of immunodeficiency in B-CLL and the cost-effectiveness of replacement therapy, it is important to identify patients who are likely to benefit from the treatment and to investigate which dose should be used. 15 patients with hypogammaglobulinaemia and a history of recurrent infections received a fixed dose of 10 grams of gammaglobulin intravenously every 3 weeks. Serum IgG levels were significantly higher after three doses (p = 0.0002), and stabilized just above lower reference value after 11 doses. The total number of infection-related events during 168 months before therapy was compared to the total number of infection-related events in 169 months during therapy. The number of antibiotic prescriptions was reduced from 78 to 54 (N.S.), the number of admissions to hospital due to infections was reduced from 16 to 5 (p = 0.047) and the number of febrile episodes was reduced from 63 to 31 (p = 0.004). We conclude that a fixed low dose of gammaglobulin intravenously can restore normal serum IgG levels in hypogammaglobulinaemic B-CLL patients, and leads to a decreased number of febrile episodes and admissions to hospital due infections.

Serum levels of tumour necrosis factor-alpha in patients with B-cell chronic lymphocytic leukaemia

Serum levels of tumour necrosis factor-alpha (TNF-alpha) have been evaluated in the peripheral blood of 91 patients with B-cell chronic lymphocytic leukaemia (B-CLL), and have been correlated with the clinical stage (according to Rai's staging system) and relevant haematological and immunological data. Increased values were detected, compared to 36 normal age-matched controls (36 pg/ml +/- 5 versus 0.11 pg/ml +/- 0.08; P < 0.05). An increase of TNF-alpha serum levels was observed in all stages including stage 0, with a progressive increase in relation to the stage of the disease. A significant relationship between serum TNF-alpha levels and the number of circulating monocytes (P < 0.002) and an inverse correlation with the level of the haemoglobin (P < 0.001) was established, as defined by the Pearson's correlation test. In contrast, no correlation was observed between TNF-alpha serum levels and the other parameters taken into account, including the white blood cell and platelet counts, the absolute number of peripheral blood (PB) lymphocytes, CD5+ B lymphocytes, CD57+ lymphocytes, serum levels of lactic dehydrogenase, total serum immunoglobulins and the serum levels of IgG, IgA and IgM. These data suggest that, in addition to the B-CLL neoplastic cells, the PB monocytes may be involved in the release of TNF-alpha.