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Biomedical subjects

T de Witte

Publications and source records attributed to T de Witte.

At least 37 records · Page 2Linked to original sources
PubMed2002

Acquired skewing of Lyonization remains stable for a prolonged period in healthy blood donors.

The pattern of X-chromosome inactivation (XCIP), or Lyonization, can be used to distinguish monoclonal from polyclonal cell populations in females. However, a skewed XCIP exists in hematopoietic cells in approximately 40% of healthy elderly females, interfering with interpretation of clonality assays. In hematopoiesis, an active stem cell pool is assumed to be present within a larger population of inactive stem cells, with a continuous exchange of cells between the two compartments. The assumption that the active stem cell pool size decreases with age may explain the phenomenon of acquired skewing occurring by chance and predicts the XCIP of this population to fluctuate. This fluctuation should be reflected in the XCIP of peripheral granulocytes. We examined the XCIP for fluctuations in time in peripheral granulocytes, monocytes and T cells of young, middle-aged and elderly healthy females. We used an optimized HUMARA PCR assay that eliminates unbalanced DNA amplification. We found no fluctuations in XCIP in any age group in up to 18 months follow-up. We conclude that acquired skewing arises gradually in life without fluctuations in XCIP and that analysis at multiple time points cannot distinguish monoclonal hematopoiesis from normal, skewed hematopoiesis.

Adult↗
PubMed2002

Chemotherapy only compared to chemotherapy followed by transplantation in high risk myelodysplastic syndrome and secondary acute myeloid leukemia; two parallel studies adjusted for various prognostic factors.

Comparisons of the effectiveness of chemotherapy and transplantation in AML in first complete remission (CR) have focused almost exclusively on patients with de novo disease. Here we used Cox modelling to compare these strategies in patients with MDS and s-AML treated by the Leukemia Group of the EORTC or at the MD Anderson Cancer Center. All patients were aged 15-60. The 184 EORTC patients received conventional dose ara-C + idarubicin + etoposide for remission induction, and after one consolidation course, were scheduled to receive an allograft, or an autograft if a sibling donor was unavailable. The 215 MDA patients received various high-dose ara-C containing induction regimens, and in CR, continued to receive these regimens at reduced dose for 6-12 months. CR rates were 54% EORTC and 63% MDA (P = 0.09). Sixty-five of the 100 EORTC patients who entered CR received a transplant in first CR. Disease-free survival in patients achieving CR was superior in the EORTC cohort, the 4-years DFS rates were 28.9% (s.e. = 4.8%) EORTC vs 17.3% (s.e. = 3.7%) MDA (P = 0.017). Survival from CR was not significantly different in the EORTC and MDA groups, as was survival from start of treatment. After accounting for prognostic factors the conclusions were unchanged. Despite various problems with the analysis discussed below, the data suggest that neither transplantation nor chemotherapy, as currently practised, can be unequivocally recommended for these patients in first CR and that questions as to the superior modality may be less important than the need to improve results with both.

Acute Disease↗
PubMed2001

Intensive chemotherapy followed by allogeneic or autologous stem cell transplantation for patients with myelodysplastic syndromes (MDSs) and acute myeloid leukemia following MDS.

This study investigated the feasibility of allogeneic (alloSCT) and autologous stem cell transplantation (ASCT) as postconsolidation therapy for patients with myelodysplastic syndromes (MDSs) or acute myeloid leukemia after MDS. Patients with a histocompatible sibling were candidates for alloSCT and the remaining patients for ASCT. Remission-induction therapy consisted of 1 or 2 courses with idarubicin, cytarabine, and etoposide, followed by one intensive consolidation course with cytarabine and mitoxantrone. Initially, bone marrow cells were used for ASCT. Subsequently, mobilized blood stem cells were used in an attempt to shorten posttransplantation hypoplasia. With a median follow-up of 3.6 years the 184 evaluable patients showed a 4-year survival rate of 26% and a median survival of 13 months. The remission-induction chemotherapy induced complete remission (CR) in 100 patients (54%). The 4-year disease-free survival (DFS) rate was 29% and the median DFS was 12 months. Twenty-eight of 39 patients (72%) with a donor were allografted in CR-1, including 2 patients who underwent transplantation in CR-1 without a consolidation course. Thirty-six of 59 patients (61%) without a donor received ASCT in CR-1. The 4-year DFS rates in the group of patients with or without a donor were 31% and 27%, respectively. The 4-year survival rates from CR were 36% and 33%, respectively. This large prospective study shows the feasibility of both alloSCT and ASCT. This treatment approach leads to a relatively high remission rate, and the majority of patients in remission received the SCT in CR-1. The ongoing study investigates whether this approach is better than treatment with chemotherapy only.

Adult↗
PubMed2001

Heme is a potent inducer of inflammation in mice and is counteracted by heme oxygenase.

Various pathologic conditions, such as hemorrhage, hemolysis and cell injury, are characterized by the release of large amounts of heme. Recently, it was demonstrated that heme oxygenase (HO), the heme-degrading enzyme, and heme are able to modulate adhesion molecule expression in vitro. In the present study, the effects of heme and HO on inflammation in mice were analyzed by monitoring the biodistribution of radiolabeled liposomes and leukocytes in conjunction with immunohistochemistry. Small liposomes accumulate in inflamed tissues by diffusion because of locally enhanced vascular permeability, whereas leukocytes actively migrate into inflammatory areas through specific adhesive interactions with the endothelium and chemotaxis. Exposure to heme resulted in a dramatic increase in liposome accumulation in the pancreas, but also intestines, liver, and spleen exhibited significantly increased vascular permeability. Similarly, intravenously administered heme caused an enhanced influx of radiolabeled leukocytes into these organs. Immunohistochemical analysis showed differential up-regulation of the adhesion molecules ICAM-1, P-selectin, and fibronectin in liver and pancreas in heme-treated animals. Heme-induced adhesive properties were accompanied by a massive influx of granulocytes into these inflamed tissues, suggesting an important contribution to the pathogenesis of inflammatory processes. Moreover, inhibition of HO activity exacerbated heme-induced granulocyte infiltration. Here it is demonstrated for the first time that heme induces increased vascular permeability, adhesion molecule expression, and leukocyte recruitment in vivo, whereas HO antagonizes heme-induced inflammation possibly through the down-modulation of adhesion molecules.

Animals↗
PubMed2001

Production of anti-CD3 and anti-CD7 ricin A-immunotoxins for a clinical pilot study.

This report describes the preparation of an immunotoxin-combination, consisting of an anti-CD3 and anti-CD7 monoclonal antibody (MoAb) both conjugated to the A-chain of plant toxin ricin, for the experimental treatment of graft-versus-host disease. MoAbs and toxin were conjugated by conventional biochemical and chromatographic techniques. Raw materials, intermediate and final products were evaluated in accordance with the relevant 'points to consider' of the FDA. Yields, purity and sterility of the two final products were all satisfactory. Preservation of MoAb-affinity and toxin-activity were confirmed in biological assays. The LD50, 25-45 mg immunotoxin-combination/kg mouse, equalled that of similar immunotoxins already in clinical use. Because in vitro cross-reactivity screening revealed an unexpected binding of the CD3-MoAb to the esophagus epithelium, human doses of immunotoxin-combination were administered to two cynomolgus monkeys. Clinically relevant serum concentrations were obtained without irreversible toxicities occurring. The T(1/2) varied between approximately 6 and 9 h and the C(max) ranged from 1.8 to 3.9 microg/ml. The main side effect was a transient rise of serum creatine kinase. Importantly, neither damage nor binding of the CD3-immunotoxin to the monkey esophagus epithelium could be demonstrated. It was concluded that sufficient material of proper quality and with an acceptable toxicity profile was produced, warranting the evaluation in a clinical pilot-study.

Animals↗
PubMed2001

TCR gamma delta cytotoxic T lymphocytes expressing the killer cell-inhibitory receptor p58.2 (CD158b) selectively lyse acute myeloid leukemia cells.

Cytotoxic T lymphocytes (CTL) are thought to play an important role in the graft-versus-leukemia (GVL) response. Unfortunately, GVL reactivity is often associated with life-threatening graft-versus-host disease (GVHD). Characterization of CTL that selectively attack leukemic cells but not normal cells may lead to the development of adjuvant immunotherapy that separates GVL from GVHD. Here, we describe TCR gamma delta (V gamma 9/V delta 1) CTL, isolated from the peripheral blood of an AML patient after stem cell transplantation (SCT), that very efficiently lysed freshly isolated acute myeloid leukemia (AML) cells and AML cell lines. Interestingly, HLA-matched non-malignant hematopoietic cells were not killed. We revealed that the killer cell-inhibitory receptor (KIR) p58.2 (CD158b) specific for group 2 HLA-C molecules negatively regulates the cytotoxic effector function displayed by these TCR gamma delta CTL. First, an antibody against HLA-C enhances lysis of non-malignant cells. Secondly, stable transfection of HLA-Cw*0304 into the class I-negative cell line 721.221 inhibited lysis. Finally, engagement of p58.2 by antibodies immobilized on Fc gamma R-expressing murine P815 cells inhibits CD3- and TCR gamma delta-directed lysis. Compared to non-malignant hematopoietic cells, AML cells express much lower levels of MHC class I molecules making them susceptible to lysis by p58.2(+) TCR gamma delta CTL. Such KIR-regulated CTL reactivity may have a role in the GVL response without affecting normal tissues of the host and leading to GVHD.

Acute Disease↗
PubMed2001

Cyclosporin increases cellular idarubicin and idarubicinol concentrations in relapsed or refractory AML mainly due to reduced systemic clearance.

The feasibility of adding both the multidrug resistance modulator cyclosporin (CsA) and granulocyte colony-stimulating factor (G-CSF) to a standard salvage regimen of idarubicin (IDA) and cytarabine was evaluated in patients with resistant or relapsed acute myeloid leukemia and myelodysplastic syndrome. Three patients received IDA 12 mg/m2/day, the next four patients 9 mg/m2/day. The dose of CsA was 16 mg/kg/day. Six patients showed Pgp expression and none MRP1 expression. Grade III or IV toxicity (CTC-NCIC criteria) was registered in six patients for gastrointestinal, two patients for cardiovascular and one patient for neurological complications. Three patients died in hypoplasia and three patients showed leukemic regrowth. Three control patients were treated with IDA 12 mg/m2/day and cytarabine, but no CsA and G-CSF. The plasma IDA and idarubicinol (ida-ol) area under the curve's of patients treated with IDA 12 mg/m2 plus CsA were higher (P< 0.05) than in controls. Cellular IDA concentrations were almost similar, but cellular ida-ol concentrations were significantly higher (P < 0.05) in the presence of CsA than in controls. We conclude that the toxicity either with IDA 12 or 9 mg/m2/day was too high. The modulating effect of CsA was mainly based on changes in plasma kinetics of IDA and ida-ol, although ida-ol cellular clearance was delayed in the presence of CsA.

Acute Disease↗
PubMed2001

Induction of graft-versus-leukemia to prevent relapse after partially lymphocyte-depleted allogeneic bone marrow transplantation by pre-emptive donor leukocyte infusions.

In this prospective study we analyzed pre-emptive donor leukocyte infusions (DLI) in 82 consecutive patients transplanted with partially T cell-depleted grafts for acute myeloid leukemia, acute lymphoid leukemia, chronic myeloid leukemia, refractory anemia with excess of blasts, refractory anemia with excess of blasts in transformation and multiple myeloma. Donors were HLA-identical siblings. Patients without significant acute (>grade 1) and/or chronic GVHD were scheduled to be treated with DLI (35 patients) and 31 actually received DLI. Patients who developed acute GVHD >grade 1 and/or chronic GVHD were not scheduled to receive DLI and served as a comparison group (47 patients). The median interval between BMT and DLI was 22 weeks. The first six patients received 0.7 x 10(8) CD3+ cells/kg body weight (b.w.). Five out of these six patients developed acute GVHD (grade 1: n = 2, grade 3: n = 2 and grade 4: n= 1) which was more frequent and more severe than we had anticipated. In the next 25 patients the number of T lymphocytes was diminished to 0.1 x 10(8) CD3+ cells/kg b.w. which resulted in less frequent and less severe GVHD. Eight patients in this group developed acute GVHD (grade 1: n = 4, grade 2: n = 4) and three patients had limited chronic GVHD. Patients in the DLI group needed more time to establish complete donor chimerism confirmed by a higher number of mixed chimeras at 6 months after BMT. The projected 3-year probability of disease-free survival was 77% for the 35 patients intended to treat with DLI and 45% for the patients of the comparison group (P = 0.024). Relapse rate at 36 months after transplantation was 18% in the patients who were intended to treat with DLI and 44% in the comparison group (P = 0.026). We conclude that pre-emptive DLI is feasible and generates favorable relapse rates in patients who are at high risk for relapse. Furthermore, the incidence and severity of GVHD disease after DLI is dependent on the number of CD3+ cells infused.

Adolescent↗
PubMed2001

Genotypically nonidentical related donors for transplantation of patients with myelodysplastic syndromes: comparison with unrelated donor transplantation and autologous stem cell transplantation.

Transplantation with histocompatible identical siblings is a curative treatment for patients with myelodysplastic syndromes (MDS). Alternative treatments, such as transplantation with other family donors, are an option for patients without HLA-identical siblings. This study evaluated transplantation with genotypically nonidentical family donors and compared the results to those obtained with unrelated donors and autologous stem cell transplantation. Overall 3-year survival was 35% for the 79 patients transplanted using genotypically nonidentical donors, DFS was 31%, relapse risk 16%, and the treatment-related mortality (TRM) 62%. Patients transplanted using phenotypically identical family donors had a significantly superior survival and a lower TRM than patients transplanted with mismatched family donors. Age had no influence on the outcome of transplantation. The DFS of patients transplanted in early stage of the disease was 42% compared to 28% in patients transplanted with more advanced disease (P = 0.03). The results of transplantation with mismatched family donors were comparable to those obtained with unrelated donor transplantation. This suggests that nonidentical family donors may be considered if a fully matched unrelated donor is not available. The TRM of patients transplanted with nonidentical family donors is significantly higher than the TRM of patients transplanted with autologous stem cells. The disease-free survival of ASCT is not inferior to allogeneic transplantation using nonidentical family donors, and the intensity of the treatment is much lower. The choice of ASCT or alternative donor transplantation must be influenced by the age of the patient and the risk of relapse. For patients under the age of 20 years the treatment of choice may indeed be an alternative donor transplantation.

Adolescent↗
PubMed2000

A combination of anti-CD3 and anti-CD7 ricin A-immunotoxins for the in vivo treatment of acute graft versus host disease.

This study evaluated the anti-graft versus host disease (GVHD) potential of a combination of immunotoxins (IT), consisting of a murine CD3 (SPV-T3a) and CD7 (WT1) monoclonal antibody both conjugated to deglycosylated ricin A. In vitro efficacy data demonstrated that these IT act synergistically, resulting in an approximately 99% elimination of activated T cells at 10(-8 )mol/L (about 1.8 microg/mL). Because most natural killer (NK) cells are CD7(+), NK activity was inhibited as well. Apart from the killing mediated by ricin A, binding of SPV-T3a by itself impaired in vitro cytotoxic T-cell cytotoxicity. Flow cytometric analysis revealed that this was due to both modulation of the CD3/T-cell receptor complex and activation-induced cell death. These results warranted evaluation of the IT combination in patients with refractory acute GVHD in an ongoing pilot study. So far, 4 patients have been treated with 3 to 4 infusions of 2 or 4 mg/m(2) IT combination, administered intravenously at 48-hour intervals. The T(1/2) was 6.7 hours, and peak serum levels ranged from 258 to 3210 ng/mL. Drug-associated side effects were restricted to limited edema, fever, and a modest rise of creatine kinase levels. One patient developed low-titer antibodies against ricin A. Infusions were associated with an immediate drop of circulating T cells, followed by a more gradual but continuing elimination of T/NK cells. One patient mounted an extensive CD8 T-cell response directly after treatment, not accompanied with aggravating GVHD. Two patients showed nearly complete remission of GVHD, despite unresponsiveness to the extensive pretreatment. These findings justify further investigation of the IT combination for treatment of diseases mediated by T cells. (Blood. 2000;95:3693-3701)

Acute Disease↗
PubMed2000

Risk assessment in patients with Ph+ chronic myelogenous leukemia at first relapse after allogeneic stem cell transplant: an EBMT retrospective analysis. The Chronic Leukemia Working Party of the European Group for Blood and Marrow Transplantation.

Patients with Ph+ chronic myelogenous leukemia who relapse after a first allogeneic stem cell transplant still have a possibility of long-term survival. To assess the value of the individual therapeutic options, the factors predicting outcome should be identified. We investigated data from 500 patients who relapsed before July 1996; follow-up was updated during 1998. The actuarial survival from relapse was 34.2% (95% confidence interval [CI]: 29. 9%-38.5%) at 5 years and 23.4% (95% CI: 18.9%-27.9%) at 10 years. Survival after relapse was significantly related to 5 factors: time from diagnosis to transplant (< 2 years vs >/= 2 years), disease phase at transplant (first chronic phase vs other), disease stage at relapse (cytogenetic or chronic phase vs advanced phase), time from transplant to relapse (< 1 year vs >/= 1 year), and donor type (HLA-identical sibling vs volunteer unrelated donor). The effects of individual adverse risk factors were cumulative: The probability of survival at 10 years decreased stepwise from 42% (0 factors), 32% (1 factor), 14% (2 factors), 3% (3 factors), to 0% (4 or 5 factors). Novel strategies for high-risk patients are warranted. We conclude that these 5 factors should be taken into account when comparing results of salvage therapies in patients with Ph+ chronic myeloid leukemia relapsing after allogeneic stem cell transplant.

Actuarial Analysis↗
PubMed2000

Effect of centre on outcome of bone-marrow transplantation for acute myeloid leukaemia. Acute Leukaemia Working Party of the European Group for Blood and Marrow Transplantation.

BACKGROUND: There is increasing pressure for the recognition and replication of good clinical practice. We undertook a study to assess the variability in outcome of allogeneic bone-marrow transplantation among major European centres. METHODS: We studied 13 centres, including 522 patients (aged 16-55 years), which had undertaken more than 30 bone-marrow transplantations between Jan 1, 1987, and Dec 31, 1995, for acute myeloid leukaemia in first complete remission. We undertook a (global) multivariate analysis of all factors known previously to influence outcome and a stratified analysis that initially defined, by multivariate analysis, significant variables in this study and then used a proportional-hazard model including centres. FINDINGS: The overall results at 3 years were 57% (95% CI 53-61) for leukaemia-free survival (LFS), 23% (19-27) for relapse incidence (RI), and 26% (22-30) for treatment-related mortality (TRM) with a range for centres of 36-75%, 10-37%, and 8-54%, respectively. Both methods of analysis showed the centre effect to be highly significant for LFS and TRM, but not for RI. Variables associated with a significantly poor outcome were age over 43 years (p=0.01), time from diagnosis to first complete remission longer than 65 days (p=0.02), and centre (p=0.013) for LFS, and age over 43 years (p=0.023), time from first complete remission to transplantation of longer than 93 days (p=0.03), and centre (p=0.001) for TRM. Moreover, different centres had different prognostic criteria for good-risk or bad-risk patients indicating that risk factors do not have the same impact in each individual centre. INTERPRETATION: The outcome of bone-marrow transplantation for acute myeloid leukaemia in first complete remission is influenced by the centre in which the procedure is done, even with adjustment for known prognostic risk factors. Significant prognostic factors vary among centres, which means that the relative risk is not the same in each individual centre. However, centres may treat populations with different risks of as yet unidentified prognostic factors. Experience may partly account for the difference in outcome among centres.

Adolescent↗
PubMed2000

Roquinimex (Linomide) vs placebo in AML after autologous bone marrow transplantation.

Roquinimex, Linomide, a quinoline derivative with pleiotropic immunomodulatory activity, has previously been shown to enhance natural killer (NK) cell number and activity after ABMT in patients with AML. In this study 278 AML patients in remission were randomized to receive Roquinimex 0.2 mg/kg body weight or placebo twice weekly for 2 years following ABMT. Out of 139 patients in each group, 109 Roquinimex patients and 108 placebo patients were in their first CR. Median age at inclusion was 41 years for Roquinimex patients and 39 years for placebo patients. Twelve patients in each group had their marrow purged prior to reinfusion. Relapse and death were study endpoints. Surviving patients were followed for 2.6 to 6. 9 years. The total number of relapses was 60 in the Roquinimex group and 63 in the placebo group (not significant). Leukemia-free and overall survivals were similar in the two groups. Recovery of platelet counts was significantly delayed in the Roquinimex group as compared to placebo. No other significant differences regarding toxicity parameters were recorded. In conclusion, previous findings on NK cells could not be confirmed and the study showed no benefit for Roquinimex over placebo regarding relapse or survival following ABMT for AML in remission.

Adolescent↗
PubMed2000

Outcome of T cell-depleted transplantation after conditioning with an intensified regimen in patients aged 50 years or more is comparable with that in younger patients.

One hundred and thirty-one patients were transplanted for AML-CR1, ALL-CR1 or CML-CP1 after conditioning with 120 mg/kg body weight cyclophosphamide and 2 x 4.5 Gy TBI. Conditioning was intensified with the addition of 42 mg/m2 idarubicin. Grafts were T cell-depleted using counterflow centrifugation. Donors were HLA-identical siblings. We compared outcome of BMT in 109 patients aged less than 50 (median, 35) years with that of 22 patients with an age of 50 years or more (median, 53 years). For the patients aged <50 years, 2-year probabilities of treatment-related mortality, relapse, survival and leukemia-free survival were 26% (95% CI, 17% to 35%), 26% (95% CI, 17% to 35%), 64% (95% CI, 55% to 73%), and 56% (95% CI, 47% to 65%). For the patients aged > or =50 years, these figures were 13% (95% CI, 0% to 30%), 24% (95% CI, 6% to 42%), 66% (95% CI, 46% to 86%), and 67% (95% CI, 47% to 87%), respectively. Outcome did not differ significantly between the two age groups. TRM was within the range of that reported in the literature for recipients of T cell-depleted grafts. We conclude that T cell-depleted transplantation after a conditioning regimen that was intensified with the addition of idarubicin is feasible in patients aged > or =50 years. For this age group of patients, results of nonmyeloablative regimens should be compared with that obtained with T cell-depleted grafts.

Adolescent↗
PubMed2000

Red blood cell phenotyping is a sensitive technique for monitoring chronic myeloid leukaemia patients after T-cell-depleted bone marrow transplantation and after donor leucocyte infusion.

Fifteen consecutive patients with Philadelphia chromosome (Ph)-positive chronic myeloid leukaemia (CML) who relapsed from T-cell-depleted bone marrow transplantation (BMT) were successfully treated with donor leucocyte infusions (DLIs). Chimaerism was analysed using red blood cell phenotyping (RCP), and the results were compared with cytogenetic analysis and outcome of qualitative and quantitative polymerase chain reaction (PCR) for breakpoint molecules. In all patients, an increase in autologous erythrocytes and/or a decrease in donor red cells indicated relapse. Donor erythrocytes started to increase from 4 to 20 (median 12) weeks after DLI. At 6 and 12 months after DLI, complete donor chimaerism was found in 11 and 15 patients, respectively, and all patients were in cytogenic remission. A high percentage of autologous red cells at the time of DLI predicted pancytopenia. During relapse and after DLI, the percentage of autologous red cells was strongly correlated with the reappearance and disappearance of Ph-positive metaphases (r = 0.90; P < 0.001 and r = 0.96; P < 0.001 respectively). The same was true for the correlation between the percentage of autologous red cells and positivity/negativity in PCR for Bcr-Abl breakpoint molecules (r = 0.94; P < 0.001). A normalized Bcr-Abl dose of greater than 10-3 in real-time quantitative PCR correlated well with relapse and the presence of autologous red blood cells (r = 0.77; P < 0.001). We conclude that RCP is a sensitive, easy to perform and fast technique for the prediction of pending relapse after BMT for CML. RCP also predicts the response to DLI and the occurrence of bone marrow aplasia after DLI.

Adult↗