Martin Körbling

The immune-mediated graft-versus-leukemia effect is important to prevent relapse after allogeneic progenitor cell transplantation. This process requires engraftment of donor immuno-competent cells. The objective of this study was to assess the feasibility of achieving engraftment of allogeneic peripheral blood or bone marrow progenitor cell after purine analog containing nonmyeloablative chemotherapy. Patients with advanced leukemia or myelodysplastic syndromes (MDS) who were not candidates for a conventional myeloablative therapy because of older age or organ dysfunction were eligible. All patients had an HLA-identical or one-antigen-mismatched related donor. Fifteen patients were treated (13 with acute myeloid leukemia and 2 with MDS). The median age was 59 years (range, 27 to 71 years). Twelve patients were either refractory to therapy or beyond first relapse. Eight patients received fludarabine at 30 mg/m2/d for 4 days with idarubicin at 12 mg/m2/d for 3 days and ara-c at 2 g/m2/d for 4 days (n = 7) or melphalan at 140 mg/m2/d (n = 1). Seven patients received 2-chloro-deoxyadenosine at 12 mg/m2/d for 5 days and ara-C 1 at g/m2/d for 5 days. Thirteen patients received allogeneic peripheral blood stem cells and 1 received bone marrow after chemotherapy. Graft-versus-host disease (GVHD) prophylaxis consisted of cyclosporine and methyl-prednisolone. Treatment was generally well tolerated, with only 1 death from multiorgan failure before receiving stem cells. Thirteen patients achieved a neutrophil count of greater than 0.5 x 10(9)/L a median of 10 days postinfusion (range, 8 to 17 days). Ten patients achieved platelet counts of 20 x 10(9)/L a median of 13 days after progenitor cell infusion (range, 7 to 78 days). Eight patients achieved complete remissions (bone marrow blasts were < 5% with neutrophil recovery and platelet transfusion independence) that lasted a median of 60 days posttransplantation (range, 34 to 170+ days). Acute GVHD grade > or = 2 occurred in 3 patients. Chimerism analysis of bone marrow cells in 6 of 8 patients achieving remission showed > or = 90% donor cells between 14 and 30 days postinfusion, and 3 of 4 patients remaining in remission between 60 and 90 days continued to have > or = 80% donor cells. We conclude that purine analog-containing nonmyeloablative regimens allow engraftment of HLA-compatible hematopoietic progenitor cells. This approach permits us to explore the graft-versus-leukemia effect without the toxicity of myeloablative therapy and warrants further study in patients with leukemia who are ineligible for conventional transplantation with myeloablative regimens either because of age or concurrent medical conditions.

Adult human stem cells that are intrinsic to various tissues have been described and characterized, some only recently. Analysis of recent data suggests that adult stem cells can generate differentiated cells beyond their own tissue boundaries, a process termed “developmental stem-cell plasticity.” This review focuses on in vivo models of adult stem cells derived from bone marrow and peripheral blood and their potentially novel therapeutic applications.

BACKGROUND: Bone marrow contains stem cells with the potential to differentiate into mature cells of various organs. We determined whether circulating stem cells have a similar potential. METHODS: Biopsy specimens from the liver, gastrointestinal tract, and skin were obtained from 12 patients who had undergone transplantation of hematopoietic stem cells from peripheral blood (11 patients) or bone marrow (1 patient). Six female patients had received transplants from a male donor. Five had received a sex-matched transplant, and one had received an autologous transplant. Hematopoietic stem-cell engraftment was verified by cytogenetic analysis or restriction-fragment--length polymorphism analysis. The biopsies were studied for the presence of donor-derived epithelial cells or hepatocytes with the use of fluorescence in situ hybridization of interphase nuclei and immunohistochemical staining for cytokeratin, CD45 (leukocyte common antigen), and a hepatocyte-specific antigen. RESULTS: All six recipients of sex-mismatched transplants showed evidence of complete hematopoietic donor chimerism. XY-positive epithelial cells or hepatocytes accounted for 0 to 7 percent of the cells in histologic sections of the biopsy specimens. These cells were detected in liver tissue as early as day 13 and in skin tissue as late as day 354 after the transplantation of peripheral-blood stem cells. The presence of donor cells in the biopsy specimens did not seem to depend on the intensity of tissue damage induced by graft-versus-host disease. CONCLUSIONS: Circulating stem cells can differentiate into mature hepatocytes and epithelial cells of the skin and gastrointestinal tract.

Poor engraftment due to low cell doses restricts the usefulness of umbilical-cord-blood transplantation. We hypothesized that engraftment would be improved by transplanting cord blood that was expanded ex vivo with mesenchymal stromal cells.

Postulating favorable antileukemic effect with improved safety, we used intravenous busulfan and fludarabine as conditioning therapy for allogeneic hematopoietic stem cell transplantation (HSCT) for acute myelogenous leukemia (AML) and myelodysplastic syndrome (MDS). Fludarabine 40 mg/m2 and intravenous busulfan 130 mg/m2 were given once daily for 4 days, with tacrolimus-methotrexate as graft-versus-host disease (GVHD) prophylaxis. We treated 74 patients with AML and 22 patients with MDS; patients had a median age of 45 years (range, 19-66 years). Only 20% of the patients were in first complete remission (CR) at transplantation. Donors were HLA-compatible related (n = 60) or matched unrelated (n = 36). The CR rate for 54 patients with active disease was 85%. At a median follow-up of 12 months, 1-year regimen-related and treatment-related mortalities were 1% and 3%, respectively. Two patients had reversible hepatic veno-occlusive disease. Actuarial 1-year overall survival (OS) and event-free survival (EFS) were 65% and 52% for all patients, and 81% and 75% for patients receiving transplants in CR. Recipient age and donor type did not influence OS or EFS. Median busulfan clearance was 109 mL/min/m2 and median daily area-under-the-plasma-concentration-versus-time-curve was 4871 micromol-min, with negligible interdose variability in pharmacokinetic parameters. The results suggest that intravenous busulfan-fludarabine is an efficacious, reduced-toxicity, myeloablative-conditioning regimen for patients with AML or MDS undergoing HSCT.