The effect of graft purging with 4-hydroperoxycyclophosphamide in autologous bone marrow transplantation for acute myelogenous leukemia

Secure transplantation by tissue purging using photodynamic therapy to eradicate malignant cells

The field of photodynamic therapy (PDT) for treating various malignant neoplasms has been given researchers' attention due to its ability to be a selective and minimally invasive cancer therapy strategy. The possibility of tumor cell infection and hence high recurrence rates in cancer patients tends to restrict autologous transplantation. So, the photodynamic tissue purging process, which consists of selective photoinactivation of the malignant cells in the graft, is defined as a compromising strategy to purify contaminated tissues before transplantation. In this strategy, the direct malignant cells' death results from the reactive oxygen species (ROS) generation through the activation of a photosensitizer (PS) by light exposure in the presence of oxygen. Since new PS generations can effectively penetrate the tissue, PDT could be an ideal ex vivo tissue purging protocol that eradicates cancer cells derived from various malignancies. The challenge is that the applied pharmacologic ex vivo tissue purging should efficiently induce tumor cells with minor influence on normal tissue cells. This review aims to provide an overview of the current status of the most effective PDT strategies and PS development concerning their potential application in ex vivo purging before hematopoietic stem cell or ovarian tissue transplantation.

History and Development of Autologous Stem Cell Transplantation for Acute Myeloid Leukemia

This review describes the development of cryopreservation, the birth of autologous stem cell transplantation (ASCT) and its past and present use to consolidate adult patients with acute myelogenous leukemia (AML). It summarizes the first autografts in patients in relapse, the experience of autografting in complete remission (CR), using bone marrow unpurged or purged in vitro with cyclophosphamide-derivatives, and the important shift to peripheral blood stem cells. The review also discusses the results of recent studies in favor of the use of ASCT to consolidate good- and intermediate-risk patients who reach CR with no detectable minimal residual disease, and those which support the inclusion of maintenance therapy post autograft with hypomethylating agents, anti-BCL-2, and, possibly, in the future, anti AML chimeric antigen receptor-T cells. Carefully applied to well-selected patients, ASCT may regain interest, because of its simplicity, its reduced toxicity, lower non-relapse mortality and better quality of life.

Somatostatin receptor mediated targeting of acute myeloid leukemia by photodynamic metal complexes for light induced apoptosis

Acute myeloid leukemia (AML) is characterized by relapse and treatment resistance in a major fraction of patients, underlining the need of innovative AML targeting therapies. Here we analysed the therapeutic potential of an innovative biohybrid consisting of the tumor-associated peptide somatostatin and the photosensitizer ruthenium in AML cell lines and primary AML patient samples. Selective toxicity was analyzed by using CD34 enriched cord blood cells as control. Treatment of OCI AML3, HL60 and THP1 resulted in a 92, and 99 and 97% decrease in clonogenic growth compared to the controls. Primary AML cells demonstrated a major response with a 74 to 99% reduction in clonogenicity in 5 of 6 patient samples. In contrast, treatment of CD34⁺ CB cells resulted in substantially less reduction in colony numbers. Subcellular localization assays of RU-SST in OCI-AML3 cells confirmed strong co-localization of RU-SST in the lysosomes compared to the other cellular organelles. Our data demonstrate that conjugation of a Ruthenium complex with somatostatin is efficiently eradicating LSC candidates of patients with AML. This indicates that receptor mediated lysosomal accumulation of photodynamic metal complexes is a highly attractive approach for targeting AML cells.

Autologous stem cell transplantation for adult acute leukemia in 2015: time to rethink? Present status and future prospects

The use of autologous stem cell transplantation (ASCT) as consolidation therapy for adult patients with acute leukemia has declined over time. However, multiple randomized studies in the past have reported lower relapse rates after autologous transplantation compared with chemotherapy and lower non-relapse mortality rates compared with allogeneic transplantation. In addition, quality of life of long-term survivors is better after autologous transplantation than after allogeneic transplantation. Further, recent developments may improve outcomes of autograft recipients. These include the use of IV busulfan and the busulfan+melphalan combination, better detection of minimal residual disease (MRD) with molecular biology techniques, the introduction of targeted therapies and post-transplant maintenance therapy. Therefore, ASCT may nowadays be reconsidered for consolidation in the following patients if and when they reach a MRD-negative status: good- and at least intermediate-1 risk acute myelocytic leukemia in first CR, acute promyelocytic leukemia in second CR, Ph-positive acute lymphocytic leukemia. Conversely, patients with MRD-positive status or high-risk leukemia should not be considered for consolidation with ASCT.

T-cell-replete haploidentical transplantation versus autologous stem cell transplantation in adult acute leukemia: a matched pair analysis

Adult patients with acute leukemia in need of a transplant but without a genoidentical donor are usually considered upfront for transplantation with stem cells from any other allogeneic source, rather than autologous stem cell transplantation. We used data from the European Society for Blood and Marrow Transplantation and performed a matched pair analysis on 188 T-cell-replete haploidentical and 356 autologous transplants done from January 2007 to December 2012, using age, diagnosis, disease status, cytogenetics, and interval from diagnosis to transplant as matching factors. "Haploidentical expert" centers were defined as having reported more than five haploidentical transplants for acute leukemia (median value for the study period). The median follow-up was 28 months. Multivariate analyses, including type of transplant categorized into three classes ("haploidentical regular", "haploidentical expert" and autologous), conditioning intensity (reduced intensity versus myeloablative conditioning) and the random effect taking into account associations related to matching, showed that non-relapse mortality was higher following haploidentical transplants in expert (HR: 4.7; P=0.00004) and regular (HR: 8.98; P<10(-5)) centers. Relapse incidence for haploidentical transplants was lower in expert centers (HR:0.39; P=0.0003) but in regular centers was similar to that for autologous transplants. Leukemia-free survival and overall survival rates were higher following autologous transplantation than haploidentical transplants in regular centers (HR: 1.63; P=0.008 and HR: 2.31; P=0.0002 respectively) but similar to those following haploidentical transplants in expert centers. We conclude that autologous stem cell transplantation should presently be considered as a possible alternative to haploidentical transplantation in regular centers that have not developed a specific expert program.

The ex vivo purge of cancer cells using oncolytic viruses: recent advances and clinical implications

Hematological malignancies are treated with intensive high-dose chemotherapy, with or without radiation. This is followed by hematopoietic stem cell (HSC) transplantation (HSCT) to rescue or reconstitute hematopoiesis damaged by the anticancer therapy. Autologous HSC grafts may contain cancer cells and purging could further improve treatment outcomes. Similarly, allogeneic HSCT may be improved by selectively purging alloreactive effector cells from the graft rather than wholesale immune cell depletion. Viral agents that selectively replicate in specific cell populations are being studied in experimental models of cancer and immunological diseases and have potential applications in the context of HSC graft engineering. This review describes preclinical studies involving oncolytic virus strains of adenovirus, herpes simplex virus type 1, myxoma virus, and reovirus as ex vivo purging agents for HSC grafts, as well as in vitro and in vivo experimental studies using oncolytic coxsackievirus, measles virus, parvovirus, vaccinia virus, and vesicular stomatitis virus to eradicate hematopoietic malignancies. Alternative ex vivo oncolytic virus strategies are also outlined that aim to reduce the risk of relapse following autologous HSCT and mitigate morbidity and mortality due to graft-versus-host disease in allogeneic HSCT.

Wilms' tumor gene 1 transcript levels in leukapheresis of peripheral blood hematopoietic cells predict relapse risk in patients autografted for acute myeloid leukemia

Autologous hematopoietic stem cell transplantation (ASCT) is a curative option alternative to allogeneic transplantation for patients with acute myeloid leukemia (AML). Relapse after ASCT can be due to contamination with leukemic blasts of autologous peripheral blood stem cells (PBSCs) collected by leukapheresis (LK). Identification and quantification of a minimal residual disease (MRD) marker in PBSCs could be relevant in determining the relapse risk after ASCT. High levels of the WT1 gene transcript in bone marrow of AML patients after treatment completion predict disease relapse. We evaluated WT1 transcript levels in autologous PBSC from LK used for ASCT in 30 consecutive AML patients in complete remission (CR) and established a correlation with clinical outcome. At diagnosis, all patients had WT1 overexpression. All patients were in morphological and genetic CR at the time of PBSC collection and before ASCT. Real-time quantitative PCR of WT1 was performed in samples of each LK, using TaqMan technology on RNA from mononucleated cells. The median WT1 transcript level in the PBSC graft (WT1-LK) of patients who relapsed was significantly higher than of those who did not relapse after transplantation (P <.0001). We defined a cut-off level of 80 WT1-LK copies/ABL 10e4 copies to discriminate between positive and negative PBSC grafts. The cut-off level was strongly associated with disease recurrence, DFS and OS. Our study represents the largest series of patients evaluating WT1 as a marker of MRD in PBSC LK products using a completely standardized real-time WT1-reverse transcriptase-PCR based assay. These data, if confirmed by prospective study, will help to determine an individual patient's adapted postremission allocation strategy.

Aldehyde dehydrogenases in acute myeloid leukemia

Acute myeloid leukemia (AML) affects approximately 15,000 persons per year in the United States and is the sixth leading cause of cancer-related deaths. The treatment of AML has advanced little in the past thirty years, in part because of the biologic heterogeneity of the disease and the difficulty in targeting AML cells while sparing normal hematopoietic cells. Advances in preventing and treating AML are likely to occur once the cellular and molecular differences between leukemia and normal hematopoietic cells are better understood. Aldehyde dehydrogenase (ALDH) activity is highly expressed in hematopoietic stem cells (HSCs), while, in contrast, a subset of AMLs are lacking this activity. This difference may be relevant to the development of AML and may also provide a better avenue for treating this disease. In this review, we summarize what is known about the ALDHs in normal HSCs and AML and propose strategies for capitalizing on these differences in the treatment of acute leukemia, and possibly other cancers as well.

Autologous Stem Cell Transplantation in elderly Acute Myeloid Leukemia

Treatment outcome in elderly Acute Myeloid Leukemia (AML) is still very disappointing. Although complete remission rate is around 50–60% the 2 years survival is only in the magnitude of 10–20%. This is mainly due to an overrepresentation of adverse prognostic factors present in elderly AML. As relapses emerge from residual disease present after chemotherapy, intensification of treatment could emerge as a rational strategy. Intensification of chemotherapy by increasing the dose of anthracyclines or addition of gemtuzumab ozogamycin (Mylotarg) to standard chemotherapy indeed has proved to be of advantage in elderly AML. In younger AML autologous peripheral blood stem cell transplantation (AuPBSCT) as post remission treatment in comparison to intensive consolidation chemotherapy has been investigated in a few randomized studies. AuPBSCT showed reduced relapse rates with low non-relapse mortality rates. In elderly AML intensification by AuPBSCT also have been performed although randomized studies are lacking. Nevertheless, in the previous years various reports have suggested the potential utility of AuHSCT in AML of the elderly with encouraging results, albeit mostly in highly selected patients. Acceptable toxicity and a relatively low rate of transplant-related mortality has been notified. However relapses occurred which, irrespective of age, still remains the major cause of treatment failure of AuHSCT in AML. In this review we summarize the experience of AuPBSCT in elderly AML.

Prospects and challenges of induced pluripotent stem cells as a source of hematopoietic stem cells

Many life-threatening hematological diseases are now treated by bone marrow transplantations, i.e., infusion of hematopoietic stem cells (HSCs). HSC transplantations are a valid option for the treatment of a variety of metabolic disorders, and even for solid tumors and some refractory severe autoimmune diseases. Unfortunately, the frequency and outcome of HSC transplantations are limited by a shortage of suitable donors. Induced pluripotent stem cells (iPSCs)--somatic cells that have acquired pluripotent stem cell characteristics by the ectopic expression of pluripotency-inducing factors--have been proposed as an alternative source of HSCs. Possible applications include cells of autologous, of autologous and genetically modified, or of allogeneic origin. Here, we provide a perspective on the distinct opportunities of iPSCs and discuss the challenges that lie ahead.

Higher incidence of relapse in patients with acute myelocytic leukemia infused with higher doses of CD34+ cells from leukapheresis products autografted during the first remission

The stem cell source for autologous transplantation has shifted from bone marrow to peripheral blood (PB). We previously showed that relapse incidence in patients with acute myelocytic leukemia autografted in first remission (CR1) was greater with PB than bone marrow, and a poorer outcome was associated with a shorter CR1 to PB transplantation interval (≤ 80 days). Leukemic and normal progenitors are CD34(+) and can be concomitantly mobilized; we assessed whether an association exists between the infused CD34(+) cell dose and outcome. The infused CD34(+) cell doses were available for 772 patients autografted more than 80 days after CR1 and were categorized by percentiles. We selected the highest quintile (> 7.16 × 10(6)/kg) as the cutoff point. By multivariate analysis, relapse was more probable in patients who received the highest dose (hazard ratio = 1.48; 95% confidence interval, 1.12-1.95; P = .005), and leukemia-free survival was worse (hazard ratio = 0.72; 95% confidence interval, 0.55-0.93; P = .01). In conclusion, in patients autografted in first remission, relapse was higher and leukemia-free survival lower for those who received the highest CD34(+) PB doses.

Higher incidence of relapse with peripheral blood rather than marrow as a source of stem cells in adults with acute myelocytic leukemia autografted during the first remission

PURPOSE

The cell source for autologous stem cell transplantation has shifted from bone marrow (BM) to peripheral blood (PB). In acute myelocytic leukemia (AML), for patients who receive transplants during first complete remission (CR1), no prospective randomized study has compared relapse incidence (RI) to cell source.

PATIENTS AND METHODS

We analyzed 2,165 patients who received autografts (1,607 PB and 558 BM) from 1994 to 2006 and were reported to the European Cooperative Group for Blood and Marrow Transplantation with complete research data. Relative to the time of CR1, PB transplants were performed earlier than BM transplants. Because a poorer outcome was associated with a shorter interval from CR1 to transplantation, patients were divided into three groups: BM, early PB (< or = 80 days after CR1), and late PB (> 80 days after CR1) transplantation.

RESULTS

In a multivariate analysis adjusted for differences between groups and center, RI was higher with both early PB (56% +/- 3%; hazard ratio [HR], 1.45; 95% CI, 1.11 to 1.9; P = .006) and late PB transplantation (46% +/- 2%; HR, 1.3; 95% CI, 1.06 to 1.59; P = .01) as compared with BM transplantation (39% +/- 2%). This translated into a significantly worse leukemia-free survival (LFS) for early PB transplantation (36% +/- 3%; HR, 0.75; 95% CI, 0.58 to 0.96; P = .02) and a trend for a poorer LFS for late PB (46% +/- 2%; HR, 0.84; 95% CI, 0.7 to 1.01; P = .06) as compared with BM (52% +/- 2%).

CONCLUSION

For patients with AML in CR1, risk of relapse is greater with PB transplantation rather than BM, independent of the interval from CR1 to transplantation.

Clinical management of primary non-acute promyelocytic leukemia acute myeloid leukemia: Practice Guidelines by the Italian Society of Hematology, the Italian Society of Experimental Hematology, and the Italian Group for Bone Marrow Transplantation

As many options are now available to treat patients with de novo acute myeloid leukemia, the Italian Society of Hematology and two affiliated societies (SIES and GITMO) commissioned project to an Expert Panel aimed at developing clinical practice guidelines for acute myeloid leukemia treatment. After systematic comprehensive literature review, the Expert Panel formulated recommendations for the management of primary acute myeloid leukemia (with the exception of acute promyelocytic leukemia) and graded them according to the supporting evidence. When evidence was lacking, consensus-based statements have been added. First-line therapy for all newly diagnosed patients eligible for intensive treatment should include one cycle of induction with standard dose cytarabine and an anthracycline. After achieving complete remission, patients aged less than 60 years should receive consolidation therapy including high-dose cytarabine. Myeloablative allogeneic stem cell transplantation from an HLA-compatible sibling should be performed in first complete remission: 1) in children with intermediate-high risk cytogenetics or who achieved first complete remission after the second course of therapy; 2) in adults less than 40 years with an intermediate-risk; in those aged less than 55 years with either high-risk cytogenetics or who achieved first complete remission after the second course of therapy. Stem cell transplantation from an unrelated donor is recommended to be performed in first complete remission in adults 30 years old or younger, and in children with very high-risk disease lacking a sibling donor. Alternative donor stem cell transplantation is an option in high-risk patients without a matched donor who urgently need transplantation. Patients aged less than 60 years, who either are not candidate for allogeneic stem cell transplantation or lack a donor, are candidates for autologous stem cell transplantation. We describe the results of a systematic literature review and an explicit approach to consensus techniques, which resulted in recommendations for the management of primary non-APL acute myeloid leukemia.

The role of cytotoxic therapy with hematopoietic stem cell transplantation in the therapy of acute myelogenous leukemia in adults: an evidence-based review

Clinical research examining the role of hematopoietic stem cell transplantation (HSCT) in the therapy of acute myelogenous leukemia (AML) in adults is presented and critically evaluated in this systematic evidence-based review. Specific criteria were used for searching the published literature and for grading the quality and strength of the evidence and the strength of the treatment recommendations. Treatment recommendations based on the evidence are presented in Table 3, entitled Summary of Treatment Recommendations Made by the Expert Panel for Adult Acute Myelogenous Leukemia, and were reached unanimously by a panel of AML experts. The identified priority areas of needed future research in adult AML include: (1) What is the role of HSCT in treating patients with specific molecular markers (eg, FLT3, NPM1, CEBPA, BAALC, MLL, NRAS, etc.) especially in patients with normal cytogenetics? (2) What is the benefit of using HSCT to treat different cytogenetic subgroups? (3) What is the impact on survival outcomes of reduced intensity or nonmyeloablative versus conventional conditioning in older (>60 years) and intermediate (40-60 years) aged adults? (4) What is the impact on survival outcomes of unrelated donor HSCT vesus chemotherapy in younger (<40 years) adults with high risk disease?

Positive selection for CD90 as a purging option in acute myeloid leukemia stem cell transplants

BACKGROUND

Several studies showed the benefit of purging of acute myeloid leukemia (AML) stem cell transplants. We reported previously that purging by positive selection of CD34+ and CD133+ cells resulted in a 3-4 log tumor cell reduction (TCR) in CD34- and/or CD133- AML, but has been shown to be potentially applicable in only about 50% of cases. Similar to CD34 and CD133, CD90 marks the hematopoietic CD34 positive stem cells capable of full hematopoietic recovery after myeloablative chemotherapy, and therefore, in the present study, we explored whether a similar purging approach is possible using CD90.

METHODS

CD90 expression was established by flowcytometry in diagnosis AML on the clonogenic AML CD34+ blast population by flow cytometry. Positivity was defined as >3% CD90 (CD34+) expression on blasts. For the calculation of the efficacy of TCR by positive selection, AML blasts were recognized by either prelabeling diagnosis blasts with CD45-FITC in spiking model experiments or using expression of leukemia associated marker combinations both in spiking experiments and in real transplants.

RESULTS

In 119 patients with AML and myelodysplastic syndrome, we found coexpression of CD34 and CD90 (>3%) in 42 cases (35%). In AML patients 60 years or younger, representing the patients who are eligible for transplantation, only 23% (16/69) of the patients showed CD90 expression. Positive selection for CD90 in transplants containing CD90 negative AML resulted in a 2.8-4 log TCR in the models used.

CONCLUSIONS

Purging by positive selection using CD90 can potentially be applied effectively in the majority of AML patients 60 years or younger.

Delivering cellular therapies: lessons learned from ex vivo culture and clinical applications of hematopoietic cells

Advances in stem cell biology and cellular therapy have led to promising treatments in a range of incurable diseases. However, it is unclear whether primitive stem cells can be delivered to damage tissue for regeneration of functional mature cells or stem cells must be stimulated to differentiate into mature cells in vitro and these cells delivered to patients. A range of other questions remains to be determined including how to formulate cellular products for in vivo delivery and how to undertake pharmacological testing of cellular products. Insights into these questions can be obtained from hematopoietic stem cells (HSC) which have been used for the past 50 years in bone marrow transplantation for regeneration of blood cells in patients undergoing high dose chemotherapy to treat cancer. The differentiation of HSC into mature blood cells is controlled by proteins called hematopoietic growth factors and these factors have been used to generate cellular products in vitro for clinical applications. This chapter will review some of the results of cellular therapies performed with HSC and the lessons that can be learned from these studies.

Ex vivo expansion of mafosfamide-purged PBPC products

BACKGROUND

Multiple studies have demonstrated that 'purging' of autografts with 4-hydroperoxycyclophosphamide (4HC) or the related compound mafosfamide (Mf), to eradicate residual leukemia, produces the best results associated with autologous blood and marrow transplantation for AML. However, 4HC purging results in prolonged aplasia. Therefore, we evaluated the potential of ex vivo expansion of Mf-treated CD34+ cells from mobilized PBPC.

METHODS

CD34+ cells were isolated from PBPC products and treated with 30 microg/mL Mf. The Mf-treated CD34+ cells were washed and cultured for 14 days in StemLine II-defined media containing recombinant human (rh) SCF, G-CSF and thrombopoietin (Tpo).

RESULTS

Treatment with Mf resulted in 90% killing of progenitor cells (GM-CFC) but maintenance of SCID-repopulating cells (SRC). Ex vivo culture of the Mf-treated CD34+ cells resulted in decreased cell numbers (10-20% of the starting cell dose) during the first week. Nevertheless, in the second week of culture the total cell numbers expanded to approximately 20-fold above starting cell numbers and progenitor cells returned to approximately pre-treatment levels.

DISCUSSION

These studies demonstrate the potential of ex vivo culture to expand both total cell numbers and progenitor cells following treatment of PBPC CD34+ cells with Mf. Clinical studies are currently being initiated to evaluate the engraftment potential of these purged and expanded products.

Treatment and long-term results in children with acute myeloid leukaemia treated according to the AIEOP AML protocols

Since 1982, four consecutive studies on childhood acute myeloid leukaemia (AML) (namely LAM-82, -87, -87M and -92) have been conducted in Italy by the Associazione Italiana di Ematologia e Oncologia Pediatrica (AIEOP) group. The induction therapy of the first three studies consisted of daunorubicin and cytarabine structured in a 3+7 backbone. In the most recent protocol (LAM92), patients received two induction courses including idarubicin, cytarabine and etoposide. Patients with acute promyelocytic leukaemia (20% of diagnoses) were included in LAM-87 and 87M studies. Postremissional therapy significantly changed over time, with an ever-increasing role given to stem cell transplantation (SCT). The long-term outcome of patients enrolled in the LAM-82, 87 and 87M studies was comparable, whereas that of children treated according to LAM-92 study was significantly better (P<0.005). Either allogeneic or autologous SCT was employed as consolidation therapy in more than 75% of cases enrolled in this latter study. Patients enrolled in the LAM-92 study were stratified in standard and high-risk groups with different outcome (67 vs 47%, respectively, P=0.04). Altogether, the results obtained in these four studies have permitted a progressive refinement of treatment, contributing to the structure of the ongoing LAM-2002 protocol that stratifies patients according to the presence of definite genetic anomalies and response to induction therapy.

Immunologic purging of autologous peripheral blood stem cell products based on CD34 and CD133 expression can be effectively and safely applied in half of the acute myeloid leukemia patients

PURPOSE

Several studies have shown survival benefit by autologous stem cell transplantation in acute myeloid leukemia (AML) after purging of grafts. This has, however, not been confirmed in randomized studies due to high toxicity of purging modalities for normal progenitor/stem cells. In this study, we investigated whether positive selection for CD34+ and/or CD133+ cells, which results in high recovery of normal progenitor/stem cells, is applicable for purging AML grafts.

EXPERIMENTAL DESIGN

Positive selections of normal stem cells using CD34 and/or CD133 can be done if one or both markers are absent or have dim expression and remain so during the course of the disease. Marker expressions in newly diagnosed AML were measured with flow cytometry using a cutoff value for positivity of 1%. Stability of marker expression was studied by pairwise comparison of material at diagnosis and relapse. Leukemia associated phenotype expression was used to measure the efficacy of tumor cell reduction.

RESULTS

In newly diagnosed AML (n = 165), we found no CD34 and/or CD133 expression in 32% of the cases and dim expression in 20% of the cases. No increase in the percentage of CD34+ cells (n = 44) and CD133+ cells (n = 29) was found in corresponding relapses. Positive selection using grafts contaminated with AML blasts, showing either no or dim expression of CD34 or CD133, resulted in a 3 to 4 log tumor cell reduction (n = 11) with median 50% recovery of normal stem cells.

CONCLUSIONS

Purging by positive selection of CD34+ and/or CD133+ cells can safely, effectively, and reproducibly be applied in about 50% of AML cases.

The significance of minimal residual disease in stem cell grafts and the role of purging: is it better to purge in vivo or in vitro?

Contamination of autologous graft by tumor, in addition to incomplete tumor eradication, can partly explain why relapse remains the commonest cause of treatment failure after autologous stem cell transplantation (ASCT) in patients with malignant hematologic disorders. Monitoring of minimal residual disease (MRD) is now recognized as an important diagnostic tool for assessment either of the response to treatments aimed at maximal cytoreduction and the individual risk of relapse. In order to improve cure rates, many strategies to achieve in vivo or in vitro reduction, if not eradication, of residual disease have been proposed. We discuss the significance of MRD and the role of purging in the ASCT setting, focusing on acute myeloid leukemia, chronic myeloid leukemia, multiple myeloma and follicular lymphoma.

Development of a gene therapy based bone marrow purging system for leukemias

Although viable gene therapy based methods have been reported for the selective removal or purging of contaminating epithelial derived cancer cells from stem cell grafts, similar strategies for the purging of leukemia cells have been significantly less efficient. Hematopoietic cells are difficult targets for transduction with currently available vectors. Polylysine based molecular conjugate vectors (MCV) were previously found to effectively transduce both normal and malignant hematopoietic cells. A panel of human leukemia cell lines as well as CD34+ selected primary human hematopoietic progenitor cells (HPC) were tested for differential gene expression utilizing different promoters. Reporter gene expression under the control of RSV and SV40 promoters showed a 6-log fold increase in leukemia cells when compared to primary HPC. Using a polylysine based recombinant molecular conglomerate vector (recMCV) encoding the HSV-tk suicide gene under control of RSV, we demonstrated effective and specific cell killing in all leukemia cell lines as well as in primary human leukemia cells derived from chemotherapy refractory patients, while HPC survived under the same conditions at approximately 20% viability. These proof of principle experiments demonstrate that gene therapy technology could be utilized to successfully purge leukemia cells from HPC.

Purging of peripheral blood stem cell transplants in AML: a predictive model based on minimal residual disease burden

OBJECTIVE

Minimal residual disease (MRD) present in peripheral blood stem cell (PBSC) products of AML patients may contribute to relapse. Our goal was to 1) predict leukemia recurrence based on the frequency of MRD present in PBSC products, 2) establish the efficacy of different purging procedures, and 3) integrate this into a model that enables to predict whether or not to purge.

METHODS

Minimal residual disease was measured with flow cytometry using leukemia-associated phenotypes as established at diagnosis. Toxicity of purging procedures was established using clonogenic assays. Purging procedures used were cryopreservation, hyperthermia, ether lipid ET-18-OCH3, and combinations.

RESULTS

Minimal residual disease in PBSC products correlated significantly with relapse-free survival (n=24, p=0.003). At a cut-off value of 0.05% MRD the relative risk of relapse was 4.6 times lower in the group with less than 0.05% MRD. As measured in 54 PBSC products, the MRD level was less than 0.05% in 17 of 54 cases, between 0.05% and 0.5% in 19 of 54 cases, and higher than 0.5% in 18 of 54 cases. Based on the MRD cut-off of 0.05%, the log tumor reduction needed to achieve this threshold is zero for the 17 of 54 cases in which MRD was below 0.05%, less than or equal to 1 log in 19 of 54 cases, and greater than 1-2 log in 18 of 54 cases. When applying purging with 25 mug/mL ET-18-OCH3 combined with cryopreservation at 10% DMSO and hyperthermia at 42 degrees C combined with cryopreservation at 10% or 4% DMSO, there was greater than or equal to 1 log depletion of AML blasts.

CONCLUSION

This study establishes (1) a threshold level for MRD above which prognosis is worse, (2) that stem cell products from 69% of patients have higher than this "safe" MRD level, and (3) that ET-18-OCH3 and hyperthermia may be used to purge products in part of these patients.

The therapy of relapsed acute leukaemia in adults

Although the cure of acute leukaemia has improved significantly, many patients will still relapse and die. The unraveling of the molecular pathogenesis of acute leukaemia has lead to the identification of new prognostic factors and improved the detection of minimal residual disease. The treatment of relapsed acute leukaemia with chemotherapy remains unsatisfactory. Allogeneic or autologous blood and marrow transplant (BMT) can cure a subset of patients with relapsed acute leukaemia. The identification of the graft-vs-leukaemia (GVL) effect has lead to the development of donor lymphocyte infusions to re-induce remission in patients with relapsed leukaemia after allogeneic BMT and also stimulated the development of the less toxic nonmyeloablative allogeneic transplant approach. The identification of molecular targets of therapy and the development of monoclonal antibody-directed therapy has generated optimism. It is possible that combinations of chemotherapy, molecularly directed therapy, and immunotherapy may be combined to cure an increasing proportion of patients with acute leukaemia.

Meta-analysis of autologous bone marrow transplantation versus chemotherapy in adult patients with acute myeloid leukemia in first remission

In the present study, we have conducted a meta-analysis comparing autologous bone marrow transplantation (ABMT) and intensive chemotherapy in adult acute myeloid leukemia (AML) patients in first remission. Combined results of the six appropriate randomised controlled studies indicate that ABMT had no advantage over chemotherapy or no further treatment concerning death rate (overall rate ratio (RR)-0.95, 95% CI, 0.81-1.11), while was superior to chemotherapy concerning event rate (overall RR--0.82, 95% CI, 0.71-0.94). In conclusion, ABMT did not improve survival but it improved event-free survival (EFS) when compared with chemotherapy or no further treatment in patients with AML in first complete remission.

Outcome in children with relapsed acute myeloid leukemia after initial treatment with the French Leucemie Aique Myeloide Enfant (LAME) 89/91 protocol of the French Society of Pediatric Hematology and Immunology

PURPOSE

After present first-line therapies for childhood acute myeloid leukemia (AML), nearly 40% of patients still relapse. The goals of this retrospective study were to determine whether these children could be treated successfully with a salvage regimen and to establish the optimal therapeutic strategy.

PATIENTS AND METHODS

In the multicentric, prospective, Leucémie Aiquë Myéloïde Enfant 89/91 protocol, 106 of the 308 children enrolled between 1988 and 1998 relapsed. Initial treatment after the first complete remission (CR1) had been allogenic HLA-identical bone marrow transplantation (BMT; n = 21) or chemotherapy (n = 85). Treatment procedures were scheduled according to the choice of each participating institution.

RESULTS

When reinduction therapy was attempted, second complete remission (CR2) was obtained in 71% of patients (68 of 96 patients). BMT was performed in 53 (78%) of these 68 patients (autograft, mainly harvested in CR1, n = 25; matched sibling-donor BMT, n = 12; or alternative-donor BMT, n = 16). The 5-year overall survival (OS) rate for all 106 patients was 33%, and the disease-free survival (DFS) rate for children in CR2 was 45%. Multivariate analysis of re-treated children showed that the 5-year OS was higher if the CR1 had been longer than 12 months compared with less than 12 months (54% v 24%, respectively; P =.001) and lower if maintenance therapy had been given after CR1 compared with chemotherapy without maintenance therapy or HLA-identical BMT (12% v 40% v 52%, respectively; P =.002). For patients attaining CR2, the 5-year DFS rate was not significantly different for matched sibling-donor BMT (60%), autograft (47%), or alternative-donor BMT (44%).

CONCLUSION

After aggressive first-line therapy, one third of unselected, relapsing AML children could be cured. Further prospective trials are warranted to define the optimal reinduction regimen and megadose chemotherapy and to evaluate the late effects of these therapies.

Autologous stem cell transplantation for acute myeloid leukemia

Autologous bone marrow transplant (ABMT) and stem cell transplantation (ASCT) are important treatment modalities for acute myeloid leukemia (AML). The role of ASCT in first remission patients remains controversial. Phase II and phase III studies demonstrate that patients with favorable-risk cytogenetics benefit from ASCT, with reduction in relapse and improvement in leukemia-free survival (LFS). Patients with poor-risk cytogenetics do not appear to benefit significantly from ASCT and should preferentially be treated with allogeneic transplant. The role of ASCT for patients with intermediate risk disease is uncertain. It appears that ASCT in first remission will improve disease-free survival compared to standard chemotherapy. Sufficient patients who relapse after chemotherapy treatment can be salvaged with ASCT in second remission such that the beneficial effect on overall survival is blunted. ASCT produces equivalent results to ABMT but with reduced morbidity. The collection of stem cells during recovery from intensive dose consolidation therapy appears to be an attractive strategy that can increase the percentage of patients who are able to receive their intended transplant. Consolidation therapy prior to stem cell collection and transplant has been shown to decrease the relapse rate and improve outcomes, but the optimal nature of this consolidation therapy is unknown. For patients with AML in second remission, ABMT/ASCT offers a substantial salvage rate, and is particularly effective for patients with acute promyelocytic leukemia.

Hematopoietic cell transplantation in the treatment of leukemia

OBJECTIVES

To review the current evidence regarding the role and benefits of hematopoietic cell transplantation (HCT) in leukemia.

DATA SOURCES

Review articles, original articles, internet web sites, and books.

CONCLUSION

HCT is a potentially curative treatment modality for patients with hematologic malignancies such as leukemia.

IMPLICATIONS FOR NURSING PRACTICE

Nurses working with patients undergoing HCT need awareness of the type of leukemia, source of the hematopoietic cell product, type of preparative regimen used, and the complications of the procedure will enable nurses to educate and intervene with patients and their family members throughout the transplant trajectory.

Preferential inactivation of paediatric solid tumour cells by sequential exposure to Merocyanine 540-mediated photodynamic therapy and Edelfosine: implications for the ex vivo purging of autologous haematopoietic stem cell grafts

Paediatric solid tumours exhibit steep dose-response curves to alkylating agents and are therefore considered candidates for high-dose chemotherapy and autologous stem cell support. There is growing evidence that autologous stem cell grafts from patients with solid tumours are frequently contaminated with live tumour cells. The objective of this study was to perform, in a preclinical purging model, an initial assessment of the safety and efficacy of a two-step purging procedure that combined Merocyanine 540-mediated photodynamic therapy (MC540-PDT) with a brief exposure to the alkyl-lysophospholipid, Edelfosine. Human and murine bone marrow cells and Neuro-2a murine neuroblastoma, SK-N-SH human neuroblastoma, SK-ES-1 and U-2 OS human osteosarcoma, G-401 and SK-NEP-1 human Wilms' tumour, and A-204 human rhabdomyosarcoma cells were exposed to a fixed dose of MC540-PDT followed by a brief incubation with graded concentrations of Edelfosine. Survival was subsequently assessed by in vitro clonal assay or, in the case of CD34-positive haematopoietic stem cells, by an immunohistochemical method. Combination purging with MC540-PDT and Edelfosine depleted all tumour cells by >4 log while preserving at least 15% of murine granulocyte/macrophage progenitors (CFU-GM), 34% of human CFU-GM, and 31% of human CD34-positive cells. The data suggest that combination purging with MC540-PDT and Edelfosine may be useful for the ex vivo purging of autologous stem cell grafts from patients with paediatric solid tumours.

New approaches to hematopoietic cell transplantation in oncology

The use of high-dose chemotherapy followed by autologous HCT and the use of allogeneic HCT in children and adolescents with high-risk ALL, AML, and NBL has successfully improved outcomes. For other diseases, however, the role of HCT in treatment remains a subject of further research. The availability of HCT was significantly expanded by developing alternative graft sources that currently include BM, peripheral blood, and UCB from autologous and allogeneic related or unrelated donors. Progress in autologous HCT has been achieved by the identification of more effective and less toxic preparative regimens and by ex vivo purging of stem cell products. In allogeneic HCT, graft-versus-leukemia or graft-versus-tumor effects are being exploited increasingly to lower relapse rates. In addition, immunomodulation to promote tolerance, as well as allogeneic antitumor reactions have been achieved by antibody therapy, cytokine therapy, or cell-based immunotherapy. Future improvements are likely, as evidenced by promising preliminary results in the development of stem cell collection techniques, in vitro stem cell expansion, and purging techniques of stem cell grafts. The development of less intensive or nonmyeloablative preparative regimens may further reduce regimen-related morbidity and mortality Specific immunotherapy may facilitate tolerance induction in mismatched allogeneic HCT and support allogeneic HCT in the setting of donor-host HLA disparity. Ultimately, advances in cytokine therapy, tumor-specific vaccines, and gene therapy may decrease or even eradicate recurrence of the malignant disease after HCT.

Anti-tumor effect of Merocyanine 540-mediated photochemotherapy combined with Edelfosine: potential implications for the ex vivo purging of hematopoietic stem cell grafts from breast cancer patients

High-dose chemotherapy combined with autologous stem cell support has improved response rates in high-risk and metastatic breast cancer, but has failed to improve long-term survival. Breast cancer has a tendency to metastasize to the bone marrow, and live tumor cells are known to circulate in the peripheral blood of breast cancer patients. Sensitive immunohistochemical, culture-based, and reverse transcriptase polymerase chain reaction (RT-PCR)-based methods have shown that about 50% of histologically normal stem cell grafts from breast cancer patients are contaminated with occult tumor cells, which may cause or contribute to tumor recurrences. Merocyanine 540 (MC540)-mediated photodynamic therapy (PDT) inactivates a wide range of leukemia and lymphoma cells and is well tolerated by normal hematopoietic stem and progenitor cells. Unfortunately, most solid tumor cells (including breast cancer cells) are only moderately sensitive or refractory to MC540-PDT. We report here that if MC540-PDT is followed by a 1-h incubation with the alkyl-lysophospholipid, Edelfosine (ET-18-OCH(3)), the depletion of murine and human breast cancer cells is greatly enhanced whereas the recovery of normal hematopoietic stem and progenitor cells is only minimally degraded. When used under conditions that reduce CD34-positive human bone marrow cells only 5.1-fold, and murine and human granulocyte/macrophage progenitors 6.8- and 3-fold, respectively, combination purging with MC540-PDT and Edelfosine depletes murine (Mm5MT) and human (MDA-MB-435S) breast cancer cells >17,000- and >125,000-fold, respectively. These data suggest that combination purging with MC540-PDT and Edelfosine may offer a simple, safe and effective method for the ex vivo purging of autologous stem cell grafts from breast cancer patients.

Sensitivity of myeloid leukemia cells to calcium influx blockade: application to bone marrow purging

OBJECTIVE

The aim of this study was to assess the potential of store-operated Ca(2+) channel (SOC) antagonists as purging agents for leukemia cells.

MATERIALS AND METHODS

Clonogenic, limiting dilution, and nuclear condensation assays were used to evaluate SOC antagonist efficacy. SOC activity and endoplasmic reticulum Ca(2+) content were measured by flow cytometry. Murine bone marrow transplantation was used to determine purging efficacy and effects on hemopoietic reconstitution.

RESULTS

Econazole (Ec) and ketotifen (Ke) were variably effective against human and murine leukemia cell lines after 24 hours of incubation. However, a 2-hour serum and bovine serum albumin-free treatment protocol with Ec was found to maximize differential sensitivity between leukemic cells and normal hemopoietic progenitors. Primary acute myelogenous leukemia blast cell viability was reduced 4.2 to 5.1 logs by 2-hour Ec treatment as measured by limiting dilution. An inverse relationship between endoplasmic reticulum Ca(2+) content and Ke sensitivity in leukemia and untransformed cells was observed. Nuclear condensation, an index of apoptosis, which occurred after 24-hour treatments with either Ec or Ke, was not observed after 2-hour serum- and bovine serum albumin-free Ec exposures; however, condensed nuclei were observed after an additional 10-hour incubation in growth medium without drug. Using bone marrow deliberately contaminated with 1% P815 cells, we showed that highly effective in vitro purging can be accomplished using Ec with no adverse effects on bone marrow reconstitution in mice.

CONCLUSIONS

These studies suggest that SOC antagonists have potential as purging agents for residual leukemia cells present in bone marrow in the context of high-dose chemotherapy and autologous transplantation for leukemia.