Oligodeoxynucleotide-mediated inhibition of c-myb gene expression in autografted bone marrow: a pilot study.
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Antisense oligodeoxynucleotide (ODN) drugs might be more effective if their delivery was optimized and they were targeted to short-lived proteins encoded by messenger RNA (mRNA) species with equally short half-lives. To test this hypothesis, an ODN targeted to the c-myb proto-oncogene was developed and used to purge marrow autografts administered to allograft-ineligible chronic myelogenous leukemia patients. CD34(+) marrow cells were purged with ODN for either 24 (n = 19) or 72 (n = 5) hours. After purging, Myb mRNA levels declined substantially in approximately 50% of patients. Analysis of bcr/abl expression in long-term culture-initiating cells suggested that purging had been accomplished at a primitive cell level in more than 50% of patients and was ODN dependent. Day-100 cytogenetics were evaluated in surviving patients who engrafted without infusion of unmanipulated "backup" marrow (n = 14). Whereas all patients were approximately 100% Philadelphia chromosome-positive (Ph(+)) before transplantation, 2 patients had complete cytogenetic remissions; 3 patients had fewer than 33% Ph(+) metaphases; and 8 remained 100% Ph(+). One patient's marrow yielded no metaphases, but fluorescent in situ hybridization evaluation approximately 18 months after transplantation revealed approximately 45% bcr/abl(+) cells, suggesting that 6 of 14 patients had originally obtained a major cytogenetic response. Conclusions regarding clinical efficacy of ODN marrow purging cannot be drawn from this small pilot study. Nevertheless, these results lead to the speculation that enhanced delivery of ODN, targeted to critical proteins of short half-life, might lead to the development of more effective nucleic acid drugs and the enhanced clinical utility of these compounds in the future. (+info)
Autologous stem cell transplantation in follicular non-Hodgkin's lymphoma.
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The failure of conventional chemotherapy to improve overall survival rates in follicular non-Hodgkin's lymphoma (NHL) has led to the development of alternative treatment regimens. One such regimen is high-dose chemotherapy (HDT) with autologous stem cell transplantation (ASCT). In ASCT stem cells, harvested predominantly from peripheral blood, are used to repopulate the haemopoietic system after high-dose chemotherapy. Comparison of failure-free survival rates following ASCT, with those previously obtained with conventional chemotherapy, suggests a benefit for ASCT in patients who have previously responded to chemotherapy. Other factors that adversely influence the outcome of ASCT include large tumour burden and bcl-2 overexpression. Although ASCT in follicular NHL can prolong the period of remission, relapse is still common and can be caused either by contamination of the stem cell harvest with tumour cells, or regrowth of residual malignant cells not eradicated by the high-dose chemotherapy. Several strategies have been developed to reduce the rate of relapse, including in vitro purging of the stem cell product to remove tumour cells and using allogenic stem cells from HLA-matched donors with no history of malignant disease. While both these methods may have some benefit, they also have limitations. In vitro purging is labour intensive, costly and, as yet, the effect on relapse is unclear. Allogenic stem cell transplants have been associated with a reduced risk of relapse, but this is offset by increased transplant-related mortality. The most promising strategy to reduce the rate of relapse following ASCT is in vivo purging using rituximab, a monoclonal antibody to CD20. Rituximab mobilises mechanisms to kill lymphoma cells, and causes a rapid depletion of B cells from peripheral blood. Rituximab has demonstrated good efficacy as monotherapy in patients with both aggressive and indolent lymphoma and has shown very high response rates (>95%) when used in combination with HDT. (+info)
In vivo purging and relapse prevention following ASCT.
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The combination of high-dose chemotherapy and autologous stem cell transplantation (ASCT) is a potentially curative therapy for patients with relapsed chemosensitive non-Hodgkin's lymphoma (NHL) and is increasingly being considered as a first-line treatment for NHL patients with poor prognosis or poor outcomes from chemotherapy. However, there is a degree of relapse following the latter which is associated with high levels of tumour cell contamination of the stem cells and/or the presence of residual malignant cells in the host following chemotherapy. Reducing the rate of relapse can be achieved by pre-transplant purging of the stem cell graft followed by post-transplant maintenance to minimise residual disease. Various methods of in vitro purging have been shown to reduce, but not eliminate, the level of stem cell contamination and invariably result in a reduced harvest. To date, this has been reflected in disappointing outcomes for the patient. In contrast, in vivo purging with rituximab during the process of stem cell mobilisation and collection does not adversely affect the yield or function of stem cells and shows a significant improvement in the level of tumour cell contamination as measured by bcl-2 clearance. The relapse potential from residual malignant cells in the host can be addressed by a programme of post-transplant rituximab maintenance therapy. In one study 17 patients with follicular lymphoma who underwent ASCT with in vivo rituximab-purged stem cells, followed by rituximab maintenance, have all remained in complete response at a median follow-up of 12.4 months. The optimum in vivo rituximab purging protocol and the precise effect in terms of overall and disease-free survival are currently being evaluated but appear to present an attractive first-line alternative for NHL patients with poor prognosis or poor outcomes following chemotherapy. (+info)
Rituximab: enhancing stem cell transplantation in mantle cell lymphoma.
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Mantle cell lymphoma (MCL) responds poorly to standard chemotherapy regimens used in non-Hodgkin's lymphoma. As a result, a combination of high-dose chemotherapy (HDT) with autologous stem cell transplantation (ASCT) is being investigated in patients with MCL. So far, however, there is no evidence for long-term remission -- believed, in part, to be due to contamination of the transfusion product with residual cancer cells. Many ex-vivo purging methods have been developed to remove tumour cells, but these are complicated, time-consuming and expensive. This study describes an in vivo purging method using rituximab to produce a tumour-free stem cell product for re-infusion following HDT. The regimen is split into a purging phase and a myeloablative phase, which together consist of four-step high-dose sequential chemotherapy (sHDT) and six infusions of rituximab immunotherapy. The sHDT comprises cyclophosphamide, cytosine arabinoside, melphalan and mitoxantrone plus melphalan. There are two separate stem cell harvests and three reinfusions. In a pilot study 28 patients with untreated MCL received standard chemotherapy followed by sHDT with rituximab in vivo purging. Preliminary results indicate that in PCR analyses of leukaphereses from 20 assessable patients, 100% lymphoma-negative harvests were achieved following in vivo purging. PCR analyses of the bone marrow following the four-step high-dose regimen with purging and transplantation showed that all patients achieved molecular remission. After a median follow-up of 22 months (range 10-42 months), two patients had died while 26 were alive and disease free. This method allows efficient in vivo purging in the context of an effective chemotherapy regimen and may have a role as first-line therapy in MCL patients who respond poorly to standard treatment. (+info)
Bcl-2 clearance: optimising outcomes in follicular non-Hodgkin's lymphoma.
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The long median survival time of patients with follicular non-Hodgkin's lymphoma (NHL), means that the efficacy of new treatments are difficult to assess in the short term. Bcl-2 is an inhibitor of apoptosis and overexpression of the bcl-2 gene in the blood or bone marrow is a feature in up to 85% of patients with follicular NHL. Levels of bcl-2(+) cells in the peripheral blood or bone marrow therefore are a useful measure of disease status in such patients and can be detected by polymerase chain reaction (PCR). Complete bcl-2 clearance from the bone marrow (molecular remission) following autologous stem cell transplant (ASCT) for follicular NHL is considered to be an important prognostic factor for disease-free survival. Tumour cell contamination of the stem cell grafts used in ASCT is commonly associated with relapse. This can be addressed by purging the stem cell harvest prior to transplantation. Various methods of in vitro purging after stem cell collection have been shown to reduce the level of contamination but yield is invariably reduced and grafts remain bcl-2 positive. However, in vivo purging with rituximab during the process of collection has been used to obtain bcl-2-negative stem cell harvests without compromising the yield. Rituximab is a monoclonal antibody licensed for treatment of relapsed and refractory low-grade or follicular NHL. Rituximab targets the CD20 antigen, which is found on cells of the B cell lineage. When used for in vivo purging it depletes the peripheral blood of CD20-positive cells and prevents contamination by lymphoma cells. Molecular remission, as measured by bone-marrow bcl-2 clearance, has been achieved in 7/7 patients with follicular NHL at 1 year after treatment with ASCT using rituximab as an 'in vivopurse', followed by rituximab maintenance. Early clinical outcomes are also encouraging. (+info)
Taurolidine: preclinical evaluation of a novel, highly selective, agent for bone marrow purging.
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Taurolidine has been shown to have remarkable cytotoxic activity against selected human tumor cells at concentrations that spare normal cells. In this study we have extended this observation and assessed the ability of Taurolidine to purge tumor cells from chimeric mixtures of bone marrow (BM) and neoplastic cells. Normal murine BM and human leukemic (HL-60) or ovarian (PA-1) tumor cell lines were used as models. Exposure of tumor cells to 2.5 mM Taurolidine for 1 h resulted in the complete elimination of viable cells. In contrast, exposure of BM to 5 mMTaurolidine for 1 h reduced CFU-GM, BFU-E and CFU-GEEM colony formation by only 23.0%, 19.6% and 25.2%, respectively. Inhibition of long-term BM culture (LTBMC) growth following a 1 h exposure to 5 mM Taurolidine also was approximately 20% compared to untreated LTBMC. Finally, chimeric cultures were generated from BM and HL-60GR or PA-1GR cells (tumor cells transfected with the geneticin resistance gene). Exposure of these chimeric cultures to 5 mM Taurolidine for 1 h totally eliminated viable cancer cells while minimally reducing viable BM cells. This finding was confirmed by subsequent positive selection for surviving tumor cells with geneticin. These findings reveal that Taurolidine holds promise for use in BM purging. (+info)
The role of molecular monitoring in autotransplantation for non-Hodgkin's lymphoma.
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Seventy-two patients with non-Hodgkin's lymphoma were evaluated for the presence of molecular markers (IgH, bcl-1, bcl-2 rearrangement) on bone marrow, at diagnosis and after PBSCT, and on harvests in order to find a possible predictive role of minimal residual disease on treatment outcome. At diagnosis, 41 (59%) out of 69 available bone marrows showed molecular involvement. Fifty-six percent of leukaphereses were involved, mainly indolent lymphoma (P = 0.001) or advanced disease (P = 0.01). Ex vivo purging cleared only one stem collection out of 31 PCR-positive leukaphereses. Aggressive lymphomas showed both a longer overall survival (OS) (P = 0.03) and relapse-free survival RFS (P = 0.02) when transplanted with unpurged stem cells, whereas indolent NHL survival was not influenced by ex vivo purging. Twenty out of 26 samples taken during follow-up had bone marrow involvement at diagnosis. Of these, 15 cleared their bone marrow; both OS and RFS were significantly longer in the PCR-negative cases (P = 0.05 and P = 0.005). At 1 year after PBSCT, 75% of patients were PCR negative, with 50% molecular remissions; the relapse rate was 55% for patients still PCR positive vs 29% for those who were PCR negative. Thus, after high-dose chemotherapy, close molecular monitoring of MRD using qualitative PCR techniques seems to represent a reliable prognostic indicator. (+info)
Autologous and allogeneic stem cell transplantation for chronic lymphocytic leukemia.
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Allogeneic and autologous stem cell transplantation (SCT) are increasingly considered for treatment of patients with chronic lymphocytic leukemia (CLL). In order to assess the potential therapeutic value of SCT for CLL, the present article aims at answering the following crucial questions: (1) Is SCT a curative treatment? (2) Does SCT improve the prognosis of poor-risk CLL? (3) Do risk factors exist which are useful for defining prognostic groups in terms of feasibility and post-transplant outcome? The efficacy of auto-SCT relies exclusively on the cytotoxic therapy administered. To date, there is only limited hope that autotransplantation can cure the disease. Nevertheless, the results of the published series suggest that auto-SCT is capable of improving the prognosis of CLL with poor-risk features. Well defined favorable conditions for successful autografting are the status of the disease (CR or VGPR) and the number of lines of therapy (<2) before transplantation. The crucial anti-leukemic principle of allo-SCT consists in the immune-mediated GVL effects conferred with the graft. The GVL activity explains that allografting seems to be curative for at least a subset of patients. However, as long as allo-SCT in CLL is still associated with an excessively high treatment-related mortality, only selected patients with advanced poor-risk disease should be considered for allografting. The development of conditioning regimens with reduced intensity may allow extending the indications of allogeneic SCT for CLL in the near future. (+info)