Accessory cells, cytokine loops and cell-to-cell interactions in chronic lymphocytic leukemia

Role of decreased production of interleukin-10 and interferon-gamma in spontaneous apoptosis of B-chronic lymphocytic leukemia lymphocytes in vitro

BACKGROUND AND AIMS

B-chronic lymphocytic leukemia (B-CLL) is characterized by the progressive accumulation of small B lymphocytes that do not undergo apoptosis due to an underlying defect. One potential mechanism of defective apoptosis may be irregular cytokine production. The goal of our investigation was to determine in vitro production of relevant cytokines by lymphocytes of B-CLL patients.

METHODS

Thirty untreated (stage A) B-CLL patients, as well as 20 stage B and C patients and 30 healthy volunteers as a control group were examined. Interleukin-4 (IL-4), interferon-gamma (IFN-gamma), interleukin-10 (IL-10) and tumor necrosis factor-alpha (TNF-alpha) were measured by enzyme-linked immunosorbent assay (ELISA) in supernatants of lymphocyte cultures of all three investigated groups. The method applied for detecting apoptosis was fluorescence microscopic analysis using acridine orange/ethidium bromide (AO/EB) double staining.

RESULTS

Investigation showed that in vitro lymphocyte production of IL-10 and IFN-gamma were significantly decreased in B-CLL patients, whereas there were no statistically significantly differences of IL-4 and TNF-alpha production among the tested groups. Compared with the spontaneous apoptosis observed in control subjects' lymphocytes, B-CLL lymphocytes showed increased percentages of apoptotic cells after incubation for 24h. Interestingly, increased spontaneous apoptosis of B-CLL lymphocytes was followed by decreased IL-10 and IFN-gamma production. Stage of disease did not influence B-CLL lymphocyte spontaneous apoptosis in vitro.

CONCLUSIONS

These changes in cytokine production in cultures of B-CLL lymphocytes may be one of the potential mechanisms in the pathogenesis of abnormal apoptosis.

Down-regulation of CXCR4 and CD62L in chronic lymphocytic leukemia cells is triggered by B-cell receptor ligation and associated with progressive disease

Progressive cases of B-cell chronic lymphocytic leukemia (CLL) are frequently associated with lymphadenopathy, highlighting a critical role for signals emanating from the tumor environment in the accumulation of malignant B cells. We investigated on CLL cells from 30 untreated patients the consequence of B-cell receptor (BCR) triggering on the membrane expression of CXCR4 and CD62L, two surface molecules involved in trafficking and exit of B-lymphocytes from lymph nodes. BCR stimulation promoted a strictly simultaneous down-regulation of CXCR4 and CD62L membrane expression to a variable extent. The variable BCR-dependent decrease of the two proteins was strikingly representative of the heterogeneous capacity of the CLL cells to respond to BCR engagement in a given patient. Functionally, cells down-regulating CXCR4 and CD62L in response to BCR engagement displayed a reduction in both migration toward CXCL12 and adhesion to lymphatic endothelial cells. Remarkably, the ability of CLL cells to respond to BCR ligation was correlated with unfavorable prognostic markers and short progression-free survival. In conclusion, BCR signaling promotes decrease of CXCR4 and CD62L membrane expression in progressive cases only. These results are consistent with the hypothesis that BCR-mediated signaling pathways favor accumulation of a proliferative pool within the lymph nodes of progressive CLL cases.

Peripheral blood and bone marrow TNF and TNF receptors in early and advanced stages of B-CLL in correlation with ZAP-70 protein and CD38 antigen

The aim of the study was to evaluate TNF and TNF receptor levels in peripheral blood (PB) and bone marrow (BM) in correlation with clinical and laboratory parameters of B-CLL patients. TNF concentration was significantly higher in BM than in PB. In B-CLL patients elevated TNF and sTNF-RII plasma levels had a high correlation with adverse prognostic factors such as ZAP-70 and CD38. Moreover, the percentage of TNF-producing T cells was significantly higher in ZAP-70-positive comparing to ZAP-70-negative patients. TNF and sTNF-RII plasma levels were higher in the group of patients requiring treatment comparing to the patients who did not.

Responses to human CD40 ligand/human interleukin-2 autologous cell vaccine in patients with B-cell chronic lymphocytic leukemia

PURPOSE

Human CD40 ligand activates the malignant B-cell chronic lymphocytic leukemia cells and enhances their capacity to present tumor antigens. Human interleukin-2 further potentiates the immunogenicity of human CD40 ligand in preclinical murine models.

EXPERIMENTAL DESIGN

We prepared autologous B-cell chronic lymphocytic leukemia cells that expressed both human CD40 ligand (>90% positive) and human interleukin-2 (median secretion, 1,822 pg/mL/10(6) cells; range, 174-3,604 pg). Nine patients were enrolled in a phase I trial, receiving three to eight s.c. vaccinations.

RESULTS

Vaccinations were administered without evidence of significant local or systemic toxicity. A B-cell chronic lymphocytic leukemia-specific T-cell response was detected in seven patients. The mean frequencies of IFN-gamma, granzyme-B, and IL-5 spot-forming cells were 1/1,230, 1/1,450, and 1/4,500, respectively, representing a 43- to 164-fold increase over the frequency before vaccine administration. Three patients produced leukemia-specific immunoglobulins. Three patients had >50% reduction in the size of affected lymph nodes. Nonetheless, the antitumor immune responses were observed only transiently once immunization ceased. High levels of circulating CD4+/CD25+/LAG-3+/FoxP-3+ immunoregulatory T cells were present before, during and after treatment and in vitro removal of these cells increased the antileukemic T-cell reactivity.

CONCLUSIONS

These results suggest that immune responses to B-cell chronic lymphocytic leukemia can be obtained with human CD40 ligand/human interleukin-2-expressing s.c. vaccines but that these responses are transient. High levels of circulating regulatory T cells are present, and it will be of interest to see if their removal in vivo augments and prolongs the antitumor immune response.

Loss of PKR activity in chronic lymphocytic leukemia

There are a number of observations that suggest the dsRNA-activated protein kinase, PKR, may play an active role in formation and maintenance of leukemia, including nonrandom chromosomal deletions in acute leukemia as well as truncations and deletions of the PKR gene in some leukemia cell lines. However, there is little direct evidence from patient material that this is so. Here we show that full-length PKR is present but not active in 21 of 28 patient samples from B-cell chronic lymphocytic leukemia (B-CLL). PKR from these patients was unable to auto-activate or phosphorylate substrates but was able to bind dsRNA. Furthermore, the lack of PKR activation was not due to differing levels of the PKR activator, PACT nor of the PKR inhibitor, p58(IPK). We compared PKR status with clinical parameters and disease staging. No differences were found between the 2 groups in terms of staging (modified Rai or Binet), age, CD38 status, p53 status, 11q23 deletion status or CEP12 deletion status. However, there was a significant correlation between deletion in 13q14.3 and lack of PKR activity. We show that B-CLL cells appear to contain a soluble inhibitor of PKR, as lysates from cells lacking PKR activity were able to inhibit exogenous PKR in mixing experiments. Finally, we show suppression of PKR activity was still present following ultrafilitration through a 10,000 Da cutoff filter but was lost upon extraction with phenol/chloroform or by high salt washing. This data suggests loss of PKR activity may contribute to the formation and/or maintenance of CLL.

Chronic lymphocytic leukaemia--the haematologic basis for diagnosis and treatment

Clinically diagnosis may be incidental when absolute lymphocytosis is uncovered at routine medical examination. More usually there is a recurrent sinopulmonary infection reflecting a varying degree of humoral and cellular immune deficiency. Autoimmune phenomena may result in haemolytic anaemia or thrombocytopenia. Expanding tumour bulk underlies the lymphadenopathy which may be prominent. Diagnosis is confirmed on morphology of the smear where atypical variants need to be distinguished from other indolent lymphoproliferative disorders. Immunophenotyping is indispensable in classification. Prognosis is predicated by cytogenetics and markers of tumour biology that include beta-2 microglobulin and peripheral blood lymphocyte doubling time. Management is dictated by symptoms and signs of progression superimposed upon performance status that includes age. Disease that is asymptomatic and truly indolent, particularly in the elderly, qualifies for a careful watch-and-wait policy. In other circumstances stratification to therapy requires entry into peer-reviewed protocols if optimal outcome is to be achieved. Established regimens, of demonstrably equal efficacy, are pulsed single-agents exemplified by chlorambucil or combinations of cyclophosphamide with vincristine and prednisone. The purine analogues, particularly when administered with an alkylating agent and mitoxantrone, are emerging as superior options. In selected patients any properly accredited program will make provision for escalation in chemotherapy requiring haematopoietic stem cell transplantation on the one hand or use of serotherapy with CD52 antibodies on the other. Less commonly, but in a defined subgroup, immunoglobulins directed against membrane CD20 may be effective. Perspective for the generalist is anchored in recognising that the previous cavalier approach to drug medication, with or without radiotherapy, is unwise whereas integrated management is now the international standard of practice. The previous anachronism of dabbling by occasional therapists is to be deprecated since this will generally deny patients access to proper diagnosis and risk-adjusted multi-disciplinary treatment.

Reduced susceptibility to apoptosis correlates with kinetic quiescence in disease progression of chronic lymphocytic leukaemia

The role of apoptosis and cell kinetics in the mechanisms of disease progression of chronic lymphocytic leukaemia (CLL) is still unclear. In the present study, we investigated the susceptibility of leukaemic cells taken from 75 CLL patients with either stable (STD) or progressive disease (PRD) to enter apoptosis. Particular attention was paid to the relationship between cell cycle status and autologous serum (AS). The susceptibility to enter apoptosis was significantly greater in STD than in PRD, both in standard medium (mean = 23.62% +/- 14.7 versus 14.23% +/- 7.2; P = 0.02) and in the presence of AS (mean = 23.03% +/- 17.9 versus 11.27% +/- 7.6; P = 0.01). Furthermore, cell kinetics studies revealed a higher quiescence in PRD than in STD cases, both in terms of a lower RNA content (P = 0.04) and of higher expression of the negative cell cycle regulator p27kip1 (P = 0.03). These kinetic differences were confirmed by short-term in vitro culture both in fetal calf serum and in AS. The results of this study indicate that CLL cells from PRD cases are characterized by a higher degree quiescence and much lower susceptibility to apoptosis when compared with STD ones. In this context, AS does not appear to play a specific role. The association between these kinetic characteristics and disease progression in CLL prompts further studies to establish whether higher quiescence may be responsible for the decreased susceptibility of PRD cells to enter apoptosis.