A. John Barrett

Antithymocyte globulin for patients with myelodysplastic syndrome

Twenty‐five transfusion‐dependent myelodysplastic syndrome (MDS) patients (with < 20% blasts) were treated in a phase II study with antithymocyte globulin (ATG) at 40 mg/kg/d for four doses and then followed with blood counts every 2 weeks and clinic visits every 3 months, for a median of 14 months (range 1–38 months). 11 (44%) patients responded and became transfusion‐independent after ATG, including three complete responses, six partial responses, and two minimal responses. Responses were observed in 9/14 patients (64%) with refractory anaemia (RA) and 2/6 patients (33%) with refractory anaemia with excess blasts (RAEB). Median response duration was 10 months (range 3–38 months). The Kaplan‐Meier estimate of overall survival was 84% at 38 months, with one early death due to pneumonia and two deaths from disease progression to leukaemia. Side‐effects consisted mainly of mild serum sickness in all patients. A single course of ATG restored haemopoiesis in some patients with MDS and was well tolerated.

Infusion of donor-derived CD19-redirected virus-specific T cells for B-cell malignancies relapsed after allogeneic stem cell transplant: a phase 1 study

Autologous T cells expressing a CD19-specific chimeric antigen receptor (CD19.CAR) are active against B-cell malignancies, but it is unknown whether allogeneic CD19.CAR T cells are safe or effective. After allogeneic hematopoietic stem cell transplantation (HSCT), infused donor-derived virus-specific T cells (VSTs) expand in vivo, persist long term, and display antiviral activity without inducing graft-vs-host disease; therefore, we determined whether donor VSTs, engineered to express CD19.CAR, retained the characteristics of nonmanipulated allogeneic VSTs while gaining antitumor activity. We treated 8 patients with allogeneic (donor-derived) CD19.CAR-VSTs 3 months to 13 years after HSCT. There were no infusion-related toxicities. VSTs persisted for a median of 8 weeks in blood and up to 9 weeks at disease sites. Objective antitumor activity was evident in 2 of 6 patients with relapsed disease during the period of CD19.CAR-VST persistence, whereas 2 patients who received cells while in remission remain disease free. In 2 of 3 patients with viral reactivation, donor CD19.CAR-VSTs expanded concomitantly with VSTs. Hence CD19.CAR-VSTs display antitumor activity and, because their number may be increased in the presence of viral stimuli, earlier treatment post-HSCT (when lymphodepletion is greater and the incidence of viral infection is higher) or planned vaccination with viral antigens may enhance disease control.

Prospective trial of chemotherapy and donor leukocyte infusions for relapse of advanced myeloid malignancies after allogeneic stem-cell transplantation

PURPOSE Patients with advanced myeloid malignancies who experience relapse after allogeneic bone marrow transplantation (BMT) have a poor prognosis. Long-term survival after chemotherapy alone, second myeloablative transplant, or donor leukocyte infusions (DLIs) alone is unusual. DLIs may have minimal effectiveness in advanced disease because adequate cellular responses are not able to develop in the presence of bulky, fast-growing disease. A chemotherapy strategy was used to debulk disease before administration of granulocyte colony-stimulating factor (G-CSF)-primed DLIs. PATIENTS AND METHODS Sixty-five patients experiencing hematologic relapse of myeloid malignancy after HLA-matched sibling BMT were prospectively treated with cytarabine-based chemotherapy, then G-CSF-primed DLIs. No prophylactic immunosuppression was provided. RESULTS Twenty-seven of 57 assessable patients experienced a complete response. Graft-versus-host disease (GVHD) was observed in 56% of the patients. Treatment-related mortality was 23%. Overall survival at 2 years for the entire cohort was 19%. Patients with a complete response were more likely to survive, with 1- and 2-year survival rates of 51% and 41%, respectively, with a median follow-up of more than 2 years. The 1-year survival for nonresponders was 5%. A posttransplant remission lasting more than 6 months before relapse was associated with a higher likelihood of response. GVHD was not required for durable remission. CONCLUSION Salvage treatment with chemotherapy before DLI can help some patients with advanced myeloid relapse and is not dependent on GVHD. Patients with short remissions after BMT are unlikely to benefit from this approach, and the approach is associated with significant treatment-related mortality. Modifications of this approach or entirely different approaches will be required for most patients with this difficult clinical problem.

Bone marrow transplants from HLA-identical siblings as compared with chemotherapy for children with acute lymphoblastic leukemia in a second remission

BACKGROUND It is unclear how best to treat children with acute lymphoblastic leukemia who are in a second remission after a bone marrow relapse. For those with HLA-identical siblings, the question of whether to perform a bone marrow transplantation or to continue chemotherapy has not been answered. METHODS We compared the results of treatment with marrow transplants from HLA-identical siblings in 376 children, as reported to the International Bone Marrow Transplant Registry, with the results of chemotherapy in 540 children treated by the Pediatric Oncology Group. A preliminary analysis identified variables associated with treatment failure in both groups. We selected cohorts by matching these variables. A possible bias associated with differences in the interval between remission and treatment was controlled for by choosing matched pairs in which the duration of the second remission in the chemotherapy recipient was at least as long as the time between the second remission and transplantation in the transplant recipient. A total of 255 matched pairs were studied. RESULTS The mean (+/- SE) probability of a relapse at five years was significantly lower among the transplant recipients than among the chemotherapy recipients (45 +/- 4 percent vs. 80 +/- 3 percent, P < 0.001). At five years the probability of leukemia-free survival was higher after transplantation than after chemotherapy (40 +/- 3 percent vs. 17 +/- 3 percent, P < 0.001). The relative benefit of transplantation as compared with chemotherapy was similar in children with prognostic factors indicating a high or low risk of relapse (the duration of the first remission, age, leukocyte count at the time of the diagnosis, and phenotype of the leukemic cells). CONCLUSIONS For children with acute lymphoblastic leukemia in a second remission, bone marrow transplants from HLA-identical siblings result in fewer relapses and longer leukemia-free survival than does chemotherapy.

Differentiation of human bone marrow-derived cells into buccal epithelial cells in vivo: a molecular analytical study

BACKGROUND Adult bone marrow-derived (BMD) cells could be used to repair damaged organs and tissues, but the intrinsic plasticity of these cells has been questioned by results of in-vitro studies suggesting that such cells might fuse with other cells giving the appearance of differentiation. We aimed to determine whether fusion events are important in vivo. METHODS To test whether BMD cells can colonise an epithelial tissue and differentiate there without fusion, we did in-situ hybridisation with Y and X chromosome probes labelled with 35-sulphur or digoxigenin, or labelled fluorescently. We did immunohistochemistry with anticytokeratin 13 along with fluorescence in-situ hybridisation to identify Y-chromosome positive buccal epithelial cells in cheek scrapings obtained from five females who had received either a bone-marrow transplant or an allogeneic mobilised peripheral-blood progenitor-cell transplant (enriched in CD34+ cells) from male donors. FINDINGS When examined 4-6 years after male-to-female marrow-cell transplantation, all female recipients had Y-chromosome-positive buccal cells (0.8-12.7%). In more than 9700 cells studied, we detected only one XXXY-positive cell (0.01%) and one XXY cell (0.01%), both of which could have arisen when an XY cell fused with an XX cell. INTERPRETATION Male BMD cells migrate into the cheek and differentiate into epithelial cells, an occurrence that does not depend on fusion of BMD cells to recipient cells. This finding might be an example of transdifferentiation of haemopoietic or stromal progenitor cells. Plasticity of BMD cells could be useful in regenerative medicine.

Haematological response of patients with myelodysplastic syndrome to antithymocyte globulin is associated with a loss of lymphocyte‐mediated inhibition of CFU‐GM and alterations in T‐cell receptor Vβ profiles

We have demonstrated that 44% of myelodysplastic syndrome (MDS) patients with cytopenia have a haematological response to antithymocyte globulin (ATG). Three ATG responders and two non‐responders with refractory anaemia were further studied for lymphocyte‐mediated inhibition of bone marrow using a standard CFU‐GM assay. In responders, peripheral blood lymphocytes (PBL) added at a 5:1 ratio suppressed CFU‐GM by 54 ± 9% (P = 0.04) and was reversed by ATG treatment. Pre‐treatment marrow depleted of CD3 lymphocytes, increased CFU‐GM by 32% (P = 0.02) in an ATG responder, but not in a non‐responder. CD3 lymphocytes from 6‐month post‐treatment marrow did not inhibit pre‐treatment CFU‐GM, indicating ATG had affected the T cells. Pre‐treatment marrow depleted of CD8 lymphocytes, increased CFU‐GM by 60% (P = 0.01) and 49% (P = 0.03) in two ATG responders, but not in a non‐responder. Inhibition required cell–cell interaction through MHC I. TCR Vβ families, analysed by SSCP, changed from clonal to polyclonal in one ATG responder after 6 months, but clones persisted in a non‐responder. These results indicate patients with refractory anaemia who respond to ATG have CD8 T‐cell clones that mediate MHC‐I‐restricted suppression of CFU‐GM which are replaced by polyclonal T cells that do not suppress CFU‐GM after ATG treatment.

Chemotherapy compared with bone marrow transplantation for adults with acute lymphoblastic leukemia in first remission.

OBJECTIVE To compare efficacy of intensive postremission chemotherapy with allogeneic bone marrow transplantation in adults with acute lymphoblastic leukemia (ALL) in first remission. DESIGN Retrospective comparison of two cohorts of patients. SETTING Chemotherapy recipients were treated in 44 hospitals in West Germany in two cooperative group trials; transplants were done in 98 hospitals worldwide. PATIENTS Patients (484) receiving intensive postremission chemotherapy and 251 recipients of HLA-identical sibling bone marrow transplants for ALL in first remission. Patients ranged from 15 to 45 years of age and were treated between 1980 and 1987. MAIN RESULTS Similar prognostic factors predicted treatment failure (non-T-cell phenotype, high leukocyte count at diagnosis, and 8 or more weeks to achieve first remission) of both therapies. After statistical adjustments were made for differences in disease characteristics and time-to-treatment, survival was similar in the chemotherapy and transplant cohorts: Five-year leukemia-free survival probability was 38% (95% CI, 33% to 43%) with chemotherapy and 44% (CI, 37% to 52%) with transplant. No specific prognostic group had a significantly better outcome with one treatment compared with the other (6% for the difference; CI, -3% to 15%). Causes of treatment failure differed: With chemotherapy, 268 (96%) failures were from relapse and 11 (4%) were treatment-related; with transplants, 43 (32%) failures were from relapse and 92 (68%) were treatment-related. CONCLUSIONS These results suggest that bone marrow transplants currently offer no special advantage over chemotherapy for adults with acute lymphoblastic leukemia in first remission.

The graft-versus-leukemia effect using matched unrelated donors is not superior to HLA-identical siblings for hematopoietic stem cell transplantation.

Do some patients benefit from an unrelated donor (URD) transplant because of a stronger graft-versus-leukemia (GVL) effect? We analyzed 4099 patients with acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML) undergoing a myeloablative allogeneic hematopoietic cell transplantation (HCT) from an URD (8/8 human leukocyte antigen [HLA]-matched, n=941) or HLA-identical sibling donor (n=3158) between 1995 and 2004 reported to the CIBMTR. In the Cox regression model, acute and chronic GVHD were added as time-dependent variables. In multivariate analysis, URD transplant recipients had a higher risk for transplantation-related mortality (TRM; relative risk [RR], 2.76; P< .001) and relapse (RR, 1.50; P< .002) in patients with AML, but not ALL or CML. Chronic GVHD was associated with a lower relapse risk in all diagnoses. Leukemia-free survival (LFS) was decreased in patients with AML without acute GVHD receiving a URD transplant (RR, 2.02; P< .001) but was comparable to those receiving HLA-identical sibling transplants in patients with ALL and CML. In patients without GVHD, multivariate analysis showed similar risk of relapse but decreased LFS for URD transplants for all 3 diagnoses. In conclusion, risk of relapse was the same (ALL, CML) or worse (AML) in URD transplant recipients compared with HLA-identical sibling transplant recipients, suggesting a similar GVL effect.

Mitochondrial Metabolism Modulates Differentiation and Teratoma Formation Capacity in Mouse Embryonic Stem Cells

Relatively little is known regarding the role of mitochondrial metabolism in stem cell biology. Here we demonstrate that mouse embryonic stem cells sorted for low and high resting mitochondrial membrane potential (ΔΨmL and ΔΨmH) are indistinguishable morphologically and by the expression of pluripotency markers, whereas markedly differing in metabolic rates. Interestingly, ΔΨmL cells are highly efficient at in vitro mesodermal differentiation yet fail to efficiently form teratomas in vivo, whereas ΔΨmH cells behave in the opposite fashion. We further demonstrate that ΔΨm reflects the degree of overall mammalian target of rapamycin (mTOR) activation and that the mTOR inhibitor rapamycin reduces metabolic rate, augments differentiation, and inhibits tumor formation of the mouse embryonic stem cells with a high metabolic rate. Taken together, our results suggest a coupling between intrinsic metabolic parameters and stem cell fate that might form a basis for novel enrichment strategies and therapeutic options.

Allogeneic virus-specific T cells with HLA alloreactivity do not produce GVHD in human subjects

Adoptive transfer of viral antigen-specific memory T cells can reconstitute antiviral immunity, but in a recent report a majority of virus-specific cytotoxic T-lymphocyte (CTL) lines showed in vitro cross-reactivity against allo-human leukocyte antigen (HLA) molecules as measured by interferon-γ secretion. We therefore reviewed our clinical experience with adoptive transfer of allogeneic hematopoietic stem cell transplantation donor-derived virus-specific CTLs in 153 recipients, including 73 instances where there was an HLA mismatch. There was no de novo acute graft-versus-host disease after infusion, and incidence of graft-versus-host disease reactivation was low and not significantly different in recipients of matched or mismatched CTL. However, we found that virus-specific T cell lines recognized up to 10% of a panel of 44 HLA disparate targets, indicating that virus-specific T cells can have cross-reactivity with HLA-mismatched targets in vitro. These data indicate that the adoptive transfer of partially HLA-mismatched virus-specific CTL is safe despite in vitro recognition of recipient HLA molecules.