Hematopoietic cell transplantation in older patients with hematologic malignancies: replacing high-dose cytotoxic therapy with graft-versus-tumor effects

Unrelated donor transplantation after reduced intensity conditioning as an approach for patients lacking related donors for allogeneic stem cell transplantation

Allogeneic stem cell transplantation (SCT) after reduced intensity conditioning (RIC) provides a new curative treatment option for patients usually not eligible for allogeneic SCT. Because the majority of patients lack HLA-identical sibling donors (SD), unrelated donor (UD) transplantation is performed increasingly. In this retrospective analysis, we have reviewed our experience with reduced-intensity conditioning regimens, comparing related and unrelated donors. From November, 1997, to February, 2002, 51 patients with hematological malignancies received allogeneic SCT after various RIC regimens. A total of 31 had a related donor, and the remaining 20 had an unrelated donor (UD). Both groups were comparable with respect to age and gender. We observed a trend toward higher rate of graft failure in the unrelated donor group with 11% compared to 3% in the related donor group (p = 0.55). The rate of acute graft-versus-host disease (GVHD) II-IV was 36% in the RD group versus 44% for the UD group; severe GVHD III-IV occurred in 26% and 22%, respectively. There were more serious infections in the unrelated donor group with 25% compared to 16%. Transplant-related mortality was 13% (RD group) versus 30% (UD group). At 21 months, progression-free survival was 30% in both groups. The Kaplan Meier estimate of overall survival was 40% (RD) and 30% (UD group). In summary, we found no statistically significant difference regarding progression free and overall survival, despite a trend for more graft failure and increased transplant-related complications associated with the use of stem cells from unrelated donors.

Reduced-intensity allogeneic hematopoietic cell transplantation: Graft versus tumor effects with decreased toxicity

The potentially curative role of allogeneic hematopoietic cell transplantation (HCT) in neoplastic and non-neoplastic diseases is offset by the substantial risks of morbidity and mortality from complications of the intensive myeloablative and immunosuppressive preparative regimen. These regimen-related toxicities have restricted allogeneic HCT to young, otherwise healthy individuals without comorbid diseases. Pediatric patients undergoing conventional allogeneic HCT have lower procedure-related mortality but are at risk for non-fatal late effects of the high-dose pretransplant chemoradiotherapy, such as growth retardation, sterility and other endocrine dysfunction. Evaluation of reduced-intensity preparative regimens is the major focus of current clinical research in allogeneic HCT. Reduced-intensity HCT (RI-HCT) relies on the use of immunosuppressive but non-myeloablative agents that allow engraftment of donor cells, which provide adoptive allogeneic cellular immunotherapy and graft versus tumor (GVT) effects, with decreased regimen-related toxicities. Although the experience with RI-HCT in pediatric patients is very limited at this time, results in adults indicate that attenuated-dose preparative regimens allow older patients and those with organ dysfunction to undergo successful allogeneic HCT with acceptable morbidity and mortality. In adults, the potency of the allogeneic GVT effect varies among neoplastic diseases, with better results observed in patients with indolent hematological malignancies or renal cell carcinoma. The effectiveness of RI-HCT as treatment for children with hemoglobinopathies, chronic granulomatous disease and cellular immunodeficiencies is encouraging, and the role of reduced-intensity preparative regimens for allogeneic HCT in pediatric malignancies is under investigation.

Administration of donor apoptotic cells: an alternative cell-based therapy to induce tolerance?

Apoptotic cells are endowed with immunomodulatory properties. The authors propose infusing apoptotic cells as a cell-based therapy product to facilitate allogeneic hematopoietic engraftment after a nonmyeloablative conditioning regimen. Such an approach may be used to obtain macrochimerism in combined hematopoietic cells and solid organ transplantation. In this article, the authors describe the mechanisms of combined hematopoietic and organ allograft transplantation and the potential difficulties. The authors discuss how intravenous apoptotic cell infusion may influence the outcome of combined transplantation. This may prove to be an interesting approach for future development in cell therapy.

Development and application of quantitative real time PCR and RT-PCR assays that discriminate between the full-length and truncated herpes simplex virus thymidine kinase gene

Allogeneic donor T lymphocytes manipulated genetically to express the herpes simplex virus thymidine kinase (HSV-TK) gene have emerged as promising tools to alter the balance between graft versus host disease and graft versus leukemia after allogeneic stem cell transplantation, since they can be eliminated selectively in vivo with ganciclovir. Recently, it was reported that in SFCMM-3, an HSV-TK-encoding retroviral vector, two cryptic splice sites in the HSV-TK sequence led to the generation of an HSV-TK splice variant (deltaHSV-TK) that encodes a ganciclovir-resistant gene product. In order to quantify wtHSV-TK and deltaHSV-TK RNA levels we have developed two real time Taqman PCR assays. We demonstrate that the sensitivity of both PCR assays is 10(-4). It was found that the splice variant is generated in the packaging cell line and results in approximately 4.8+/-1.9% of virions that contain deltaHSV-TK RNA. After transduction of human T cells no significant increase in deltaHSV-TK RNA could be detected. Thus, at maximum 4.2+/-1.2% of T cells transduced with SFCMM-3 will be resistant to ganciclovir due to this mechanism only. Together, these assays provide a powerful method to monitor patients in future clinical trials.

Follow-up of patients with progressive multiple myeloma undergoing allografts after reduced-intensity conditioning

Allogeneic stem cell transplantation (allo-SCT) after reduced-intensity conditioning was evaluated in 22 patients (median age 53, range 36-66 years) with multiple myeloma with progression after an autologous SCT. Seven patients received a transplant from a human leucocyte antigen (HLA)-identical sibling and 15 patients (68%) from an unrelated donor [including 3/22 (14%) from a HLA-mismatched unrelated donor]. Graft-versus-host disease (GVHD) prophylaxis consisted of serotherapy with antithymocyte globulin (ATG) and cyclosporine (CSA) (n = 12) or CSA plus mycophenolate mofetil (n = 10). Despite of heavy pretreatment, the transplant-related mortality (TRM) for all grafted patients was acceptable at 5/22 patients (23%). Seven of 21 patients (33%) that were evaluated developed grade II GVHD and one (5%) patient developed grade III/IV acute GVHD. Seven patients developed chronic GVHD (cGVHD), but only one was extensive. Eleven patients died of progressive disease within a median of 7 months (2-19 months) post transplant. Thirteen of all 22 patients (59%) achieved a partial or complete remission with six of these 13 patients (46%) remaining event free at a median of 24 months (range 8-36 months) post allografting. Estimated 2 year overall and event-free survival was, respectively, 25.5% and 22.0% for the whole patient group, and 62.5% and 57.1% for patients with chemosensitive disease. Chemorefractory disease prior to allogeneic stem cell transplantation (P = 0.0182) and absence of cGVHD (P = 0.069) were associated with shorter event-free survival. Thus long-term disease control can be achieved, but is restricted to patients responding to prior salvage chemotherapy.

Impact of prophylactic donor leukocyte infusions on mixed chimerism, graft-versus-host disease, and antitumor response in patients with advanced hematologic malignancies treated with nonmyeloablative conditioning and allogeneic bone marrow transplantation

In an attempt to capture graft-versus-tumor effects without graft-versus-host disease (GVHD), the authors initiated a trial of nonmyeloablative allogeneic bone marrow transplantation (BMT) in patients with advanced hematologic malignancies, with the majority of patients having chemotherapy-refractory disease. Forty-two patients received an HLA-matched related donor BMT after a cyclophosphamide and antithymocyte globulin-based conditioning that also included thymic irradiation for patients who had not received prior mediastinal radiotherapy. Prophylactic donor leukocyte infusion (pDLI) at a dose of 1 x 10(7) CD3(+) cells per kilogram were given beginning 5 weeks post-BMT to 16 patients with mixed chimerism (MC) but without GVHD, whereas 26 patients did not receive pDLI, either because of GVHD or early relapse. Twelve of 16 patients (75%) receiving pDLI had T cell chimerism at the time of pDLI >/=40%. These patients, by day 100 post-BMT, either converted to full donor chimerism (FDC) (n = 10) or had an increase in or stable donor chimerism (n = 2) after pDLI. Four of 4 patients whose T cell chimerism was </=20% at the time of pDLI, lost the graft. In contrast, only 5 of 18 evaluable patients (28%) not receiving a pDLI converted to FDC by day 100 post-BMT, 7 maintained MC, and 10 of an evaluable 22 lost the graft. Patients who had undergone a previous autologous stem cell transplant had a higher rate of conversion to FDC (69% v 31%) and higher incidence of GVHD (69% v 34%) compared with those who did not have a previous autologous SCT. Eleven of 16 patients (69%) who received a pDLI achieved a remission with 50% 1-year progression-free survival rate and 44% 3-year overall survival rate. Nineteen of 42 patients (45%) had >/=grade II acute GVHD, including 12 after BMT and 7 after pDLI. Approximately one third of patients, after having initial MC, eventually lost their donor graft. The authors conclude that (1) pDLI has the potential to convert MC to FDC; (2) sustained remissions can be achieved in patients with chemorefractory hematologic malignancies who receive a pDLI, albeit with a significant risk of acute GVHD; and (3) the degree of donor T cell chimerism at the time of pDLI is predictive of the fate of MC, ie, donor T cell chimerism >/=40% or </=20% at the time of pDLI correlates with conversion of MC or loss of the graft, respectively.

Hematopoietic stem cell transplantation for hematological malignancies in Europe

Hematopoietic stem cell transplants (HSCTs) are considered the best treatment option for many hematological malignancies, and transplant numbers have increased five-fold during the last decade. Only a few controlled prospective studies are available, and different opinions prevail. Data from 118 167 HSCT (36% allogeneic, 64% autologous) collected within the EBMT activity survey from 1990 to 2001 were used to assess trends over time, transplant rates and coefficient of variation (CV) of transplant rates among European countries for acute myeloid leukemia (AML; 18.5%), acute lymphocytic leukemia (ALL; 12%), chronic myeloid leukemia (CML; 11.5%), myelodysplastic syndromes (MDS; 3%), lymphoproliferative disorders (LPS; 36.3%) and multiple myeloma (MM; 18.7%). Transplant rates increased in all countries and for all indications from 1990 to 2001 from 1.7-fold (CML) to 24.8-fold (MM). Transplant rates have declined for CML since 1999. Autologous HSCT are the preferred choice for LPS and MM, allogeneic HSCT for ALL and myeloid malignancies. CVs of less than 50% suggest consensus for allogeneic HSCT in AML, ALL, CML, MDS and NHL, for autologous HSCT in LPS and MM. These data give an overview of the current status of HSCT for hematological malignancies in Europe and provide objective information for health-care providers and patient counselling.

Successful immunotherapy in early relapse of acute myeloid leukemia after nonmyeloablative allogeneic stem cell transplantation

We report on a 35-year-old woman who underwent allogeneic stem cell transplantation (SCT) in second complete remission (CR) of acute myeloid leukemia (AML) after reduced-intensity conditioning with fludarabine and 2 Gy of total body irradiation. For graft-versus-host disease (GVHD) prophylaxis, cyclosporin A (CsA) and mycophenolate mofetil (MMF) were given. On day 27 after SCT complete hematological remission and donor chimerism was documented. However, in CD34(+) bone marrow cells 28% of recipient hematopoiesis persisted. On day +59 leukemic relapse occurred. After discontinuation of CsA and onset of GVHD, complete donor chimerism and hematological CR were achieved which has been maintained for 14 months.

Peracute onset of severe tumor lysis syndrome immediately after 4 Gy fractionated TBI as part of reduced intensity preparative regimen in a patient with T-ALL with high tumor burden

We report a 30-year-old patient with therapy-refractory T-ALL undergoing unrelated allogeneic PBSCT. He developed severe tumor lysis syndrome (TLS) with extreme biochemical changes, cardiac and neurological symptoms and dialysis-dependent acute renal failure after TBI (4 Gy) on the first day of reduced intensity conditioning (RIC) for unrelated allogeneic PBSCT. The patient's clinical condition was stabilized after beginning daily hemodialysis and treatment for disturbed electrolytes, metabolic acidosis and plasma coagulation, as well as reduction of uric acid by rasburicase. The conditioning therapy and the allogenic PBSCT were scheduled according to the preparative regimen. According to our knowledge, severe TLS induced by 4 Gy TBI has not been reported so far. Regimen-related toxicity using RIC regimen was mild, allowing 30-50% of the patients to have an entirely outpatient transplantation. However, we would like to point out that severe TLS could also complicate PBSCT using RIC regimens in patients with relatively radiation-sensitive malignancies and high tumor burden.

Treatment-related mortality and graft-versus-leukemia activity after allogeneic stem cell transplantation for chronic lymphocytic leukemia using intensity-reduced conditioning

Allogeneic stem cell transplantation (SCT) using reduced-intensity conditioning (RIC) has potential to be a promising treatment of aggressive chronic lymphocytic leukemia (CLL). Since available clinical data obtained with this novel approach are very limited, we have performed a survey on this issue. Data of 77 patients were collected from 29 European Group for Blood and Marrow Transplantation centers. Median age was 54 (30-66) years, and the median number of previous chemotherapy regimens was 3 (0-8). HLA-identical sibling donors were used in 81% of the cases. Moderate conditioning regimens (mainly low-dose total body irradiation (TBI) or fludarabine-cyclophosphamide combinations) were administered to 56% of the patients, whereas the remainder received more intense conditioning consisting of fludarabine-busulfan or high-dose melphalan combinations. In 40% of the patients, in vivo T-cell depletion (TCD) with anti-thymocyte globulin or CAMPATH-1H was part of the conditioning regimen. Cumulative treatment-related mortality (TRM) was 18% (95% CI 9; 27) after 12 months. Complete chimerism as well as best response was not achieved immediately post-transplant but took a median of 3 months to develop. The 2-year probability of relapse was 31% (95% CI 18; 44), with no event occurring later than 12 months post transplant in the absence of TCD. With one exception, relapses were not observed after onset of chronic graft-versus-host disease. Event-free and overall survival at 24 months were 56% (95% CI 43; 69) and 72% (95% CI 61; 83), respectively. The median follow-up was 18 (1-44) months. Donor lymphocyte infusions or secondary transplants were performed in 19 patients with insufficient disease control and/or incomplete donor chimerism post-transplant, leading to a response in seven patients (37%). Preliminary multivariate analysis identified less than PR at transplant (hazard ratio (HR) 3.5; P&<0.01) and alternative donor (HR 3.1; P=0.02) as significant risk factors for relapse, whereas number of previous regimens >2 (HR 5.4; P=0.03), TBI (HR 2.5; P=0.05), and alternative donor (HR 2.3; P=0.08) were risk factors for survival. We conclude that RIC might favorably influence the outcome after allogeneic SCT for CLL by reducing TRM while preserving graft-versus leukemia activity.

'GVHD': graft-versus-host disease or graft-versus-Hodgkin's disease? An old acronym with new meaning

The majority of patients with relapsed or refractory Hodgkin's lymphoma (HL) will not be cured with standard therapy. Relapse rates remain high even after autologous stem cell transplantation (SCT), particularly for patients with high-risk disease. Allogeneic SCT offers several potential advantages for patients with HL. It is feasible when autologous stem cells are not available and stem cell grafts will be tumor free. Perhaps a more important advantage is the potential to generate a graft-versus-Hodgkin's lymphoma (GVHL) effect. Unfortunately, although allogeneic SCT may cure some HL patients, treatment-related mortality has been unusually high, and superior survival, when compared to autologous SCT, has not been demonstrated. Nonmyeloablative conditioning and allogeneic SCT may induce a direct GVHL reaction with less conditioning regimen-related toxicity and ultimately may have the potential to improve cure rates and survival for advanced HL patients.

FLT3 ligand promotes engraftment of allogeneic hematopoietic stem cells without significant graft-versus-host disease

BACKGROUND

Graft-versus-host (GVH) reactions contribute to stable engraftment of allogeneic hematopoietic stem cell transplants. It was hypothesized that the in vivo expansion of recipient dendritic cells (DC) with the administration of ligand for Flt3 (FL) could promote allogeneic engraftment after reduced-intensity conditioning by enhancing the GVH effect.

METHODS

FL was first administered to three nonirradiated healthy dogs for 13 days at a dosage of 100 microg/kg/day. Next, nine dogs received 4.5 Gy total-body irradiation (TBI) and unmodified marrow grafts from dog leukocyte antigen (DLA)-identical littermates without posttransplant immunosuppression. FL was administered to the recipients at a dosage of 100 microg/kg/day from day -7 until day +5.

RESULTS

In normal dogs, FL produced significant increases in monocytes (CD14+) and neutrophils in the peripheral blood, a marked increase in CD1c+ cells with DC-type morphology in lymph nodes, and increased alloreactivity of third-party responders to peripheral blood mononuclear cells in mixed lymphocyte reactions (P<0.001). Sustained engraftment was observed in eight of nine (89%) FL-treated dogs compared with 14 of 37 (38%) controls (P=0.02, logistic regression). All engrafted FL-treated dogs became stable complete (n=2) or mixed (n=6) hematopoietic chimeras without significant graft-versus-host disease (GVHD). Recipient chimeric dogs (n=4) were tolerant to skin transplants from their marrow donors but rejected skin grafts from unrelated dogs within 7 to 9 days (median, 8 days).

CONCLUSIONS

In this study, the authors showed that FL administered to recipients promotes stable engraftment of allogeneic marrow from DLA-identical littermates after 4.5 Gy TBI without significant GVHD.

Allogeneic stem-cell transplantation from related and unrelated donors in older patients with myeloid leukemia

PURPOSE

To improve outcome for older patients with poor-prognosis myeloid malignancies by using allogeneic hematopoietic stem-cell transplantation (alloHSCT) from unrelated and sibling donors after reduced-intensity conditioning (RIC).

PATIENTS AND METHODS

Nineteen older patients (median age, 64 years; range, 60 to 70 years) with active myeloid malignancies were treated with an RIC regimen that was based on fludarabine, melphalan, and carmustine followed by alloHSCT from matched unrelated (n = 12) or sibling donors (n = 7). Before transplantation, patients had a median of 50% bone marrow blasts (range, 0% to 70%). Graft-versus-host-disease (GvHD) prophylaxis consisted of cyclosporine and mycophenolate mofetil or methotrexate. Eleven of 12 patients with an unrelated donor also received anti-T-lymphocyte globulin (ATG).

RESULTS

Engraftment was successful for all 19 patients. Seventeen assessable patients achieved complete response (CR). Four patients experienced relapse; three achieved CR again after donor lymphocyte infusion (n = 1) or a second alloHSCT (n = 2). Six patients died as a result of relapse (n = 2), GvHD-associated complications (n = 2), or fungal infections (n = 2), resulting in a 1-year nonrelapse mortality rate of 22%. With a median follow-up of 825 days (range, 595 to 1,028 days), 13 of 19 patients are alive, resulting in a 1-year survival rate of 68% (95% confidence interval, 48% to 89%).

CONCLUSION

In older patients with untreated poor-prognosis leukemia, this RIC regimen combined with alloHSCT sufficiently reduces the leukemic burden, resulting in a high CR rate. When ATG is added, matched unrelated donor transplantation can be performed safely in older patients. For these patients, early transplantation after diagnosis offers a fair chance of cure.

Non-myeloablative hematopoietic stem cell transplantation for the treatment of adult T-cell lymphoma in a patient with advanced hepatic impairment

A 59-year-old man with liver cirrhosis due to hepatitis B virus infection received non-myeloablative stem-cell transplantation (NST) for the treatment of adult T-cell lymphoma. The preparative regimen consisted of cyclophosphamide and fludarabine. While the pharmacokinetics of these drugs was altered in this patient, his clinical course was uneventful without the development of severe hepatic damage. Complete remission was achieved on day 56. Although he finally died of hemorrhage from esophageal varices on day 68, this case suggests that ATL may be a good candidate for allogeneic HSCT, and that NST may be feasible for patients with hepatic impairment.

Reduced-intensity rituximab-BEAM-CAMPATH allogeneic haematopoietic stem cell transplantation for follicular lymphoma is feasible and induces durable molecular remissions

The indolent non-Hodgkin's lymphomas are theoretically curable through allogeneic haematopoietic stem cell transplantation (allo-HSCT). The applicability of standard conditioning allo-HSCT is, however, restricted by its toxicity. Recently, reduced-intensity conditioning regimens have demonstrated efficacy with significantly reduced early morbidity and mortality. We examined the safety and efficacy of rituximab-BEAM-CAMPATH as reduced-intensity conditioning for allo-HSCT in follicular lymphomas. Minimal residual disease was assessed by polymerase chain reaction (PCR) for bcl-2/IgH translocations, and chimerism by X,Y-FISH or PCR amplification of short tandem repeat sequences. At a median follow-up of 521 days (371-719), four of five patients were alive and three were in complete molecular remission. Three patients required pre-emptive treatment for CMV reactivation. One succumbed to a perforated viscus and one had slowly progressive disease. A graft-versus-lymphoma effect was demonstrable and quantitative PCR for bcl-2/IgH may allow better accuracy in scheduling post-allograft rituximab and/or donor lymphocyte infusions. Although follow-up is short, reduced-intensity allo-HSCT with BEAM-CAMPATH conditioning appears to be safe, effective in inducing a molecular remission and is potentially curative. Further recruitment and much longer follow-up will be necessary to determine if this impacts favourably upon disease-free and overall survival.

Impact of graft-versus-host disease in reduced-intensity stem cell transplantation (RIST) for patients with haematological malignancies

To clarify the impact of graft-versus-host disease (GVHD) on the outcome of reduced-intensity stem cell transplantation (RIST), 40 patients who received RIST were compared with those who received conventional stem cell transplantation (CST). RIST regimens consisted of either cladribine (0.11 mg/kg/d x 6, n = 13) or fludarabine (30 mg/m(2)/d x 6, n = 27) with busulphan (BU, 4 mg/kg/d orally x 2), with or without antithymocyte globulin (ATG). CST regimens were either cyclophosphamide/total body irradiation (CY/TBI, n = 23), BU/CY (n = 19) or others (n = 6). The RIST group contained more patients who were at high risk of transplant-related mortality, including older patients, while the two groups contained the same percentages of patients at high risk of relapse. There were no differences between these groups in the incidences of acute (grade II-IV, 31.6% RIST vs 33.3% CST, P = 0.6742) and chronic GVHD (56.2%vs 64.1%, P = 0.8512), relapse rate (15.0%vs 18.8%, P = 0.6642), or overall (69.3%vs 65.6%, P = 0.4817) and progression-free survival (64.7%vs 63.8%, P = 0.6920) at d 500. Multivariate analysis of progression-free survival identified only grade III-IV acute GVHD and relapse risk dose as adverse risk factors. Although GVHD is a major threat in RIST, appropriate induction of GVHD may be associated with anti-tumour activity in RIST comparable to that of CST.

Transplantation in Waldenstrom's macroglobulinemia--the French experience

Published data on transplantation in Waldenstrom's macroglobulinemia (WM) are still limited. We present a retrospective multicentric study of 27 WM patients who underwent 19 autologous (median age, 54 years) and 10 allogeneic (median age, 46 years) transplantations. Median time between diagnosis and transplantation was 36 months; 66% of patients had received three or more treatment lines and 72 % had chemosensitive disease. High-dose therapy (HDT) and autologous transplantation induced a 95% response rate (RR), including 10 major responses. With a median follow-up of 18 months, 12 patients are alive at 10 to 81 months and eight are free of disease progression at 10 to 34 months. The toxic mortality rate (TRM) was 6%. Allogeneic transplantation was preceded by HDT in nine patients and by a nonmyeloablative regimen in one patient. The RR was 80%, including seven major responses. With a median follow-up of 20.5 months, six patients are alive and free of progression at 3 to 76 months. Four patients died, all from toxicity, resulting in a TRM of 40%. HDT followed by autologous transplantation is feasible in WM, even in heavily pretreated patients, with some prolonged responses but a high relapse rate. Conversely, allogeneic transplantation is more toxic, but likely induces a graft-versus-WM effect and may, for some patients, result in long-term disease control.

Minor histocompatibility antigen-specific cytotoxic T lymphocytes generated with dendritic cells from DLA-identical littermates

Donor cytotoxic T lymphocytes (CTL) specific for minor histocompatibility antigens (mHA) mediate the graft-versus-host effect whereas host mHA-specific CTL mediate graft rejection in the setting of major histocompatibility complex identical allogeneic hematopoietic stem cell transplantation. Development of a large animal model from which mHA-specific CTL can be isolated would accelerate translation in clinical studies to improve control of the graft-versus-host effect as well as prevention of graft rejection in sensitized hosts. The aims of the current study were to isolate mHA-specific CTL from dog leukocyte antigen-identical littermate nonsensitized recipients before transplantation, from stable mixed hematopoietic chimeras, and from dogs sensitized to mHA after graft rejection. Donor dendritic cells (DCs) were cultured from bone marrow-derived CD34(+) cells and were used to stimulate recipient T lymphocytes on days 1, 10, and 20 of CTL culture. We reliably generated and expanded mHA-specific CTL ex vivo from sensitized dogs that were given a donor-specific blood transfusion to boost immune recall after graft rejection after a nonmyeloablative transplantation. The mHA-specific cytotoxicity measured by (51)Cr release assay was enriched from less than 5% in the starting population of sensitized peripheral blood mononuclear cells to a median of 63% after 4 weeks in CTL culture. The expanded mHA-specific CTLs were not tissue-specific: hematopoietic cells, fibroblast, and stromal cell lines were lysed in an mHA-specific manner. Allogeneic DCs, but not peripheral blood mononuclear cells, were necessary for stimulating ex vivo expansion of mHA-specific CTL. We were unable to generate mHA-specific CTL from nonsensitized dogs before transplantation, from previously sensitized dogs but without recent recall immunization, or from stable mixed hematopoietic chimeras. We conclude that after recent in vivo sensitization, large-scale ex vivo expansion of mHA-specific CTL was feasible using allogeneic DCs.

Allografting after nonmyeloablative conditioning as a treatment after a failed conventional hematopoietic cell transplant

Outcomes with conventional allogeneic hematopoietic cell transplantation (HCT) after failed HCT are typically poor. To reduce transplantation-related mortality (TRM), 55 patients (median age, 43 years; range, 18-69 years) who had failed conventional autologous (n = 49), allogeneic (n = 4), or syngeneic (n = 2) HCT received human leukocyte antigen-matched related (n = 31) or unrelated (n = 24) donor allografts after nonmyeloablative conditioning with 2 Gy of total body irradiation or 2 Gy of total body irradiation and 90 mg/m(2) of fludarabine. Postgrafting immunosuppression consisted of cyclosporine and mycophenolate mofetil. One rejection occurred. Thirty-three patients died a median of 127 days (range, 7-834 days) after HCT: 21 of relapse, 11 of TRM, and 1 of suicide. The TRM rate on day 100 was 11% with an estimated 1-year TRM rate of 20% (95% confidence interval [CI], 9% to 31%). The median follow-up among the 22 survivors is 368 days (range, 173-796 days). Seventeen of 22 survivors are progression-free. One-year estimates of overall and progression-free survival rates are 49% (95% CI, 35% to 62%) and 28% (95% CI, 16% to 41%), respectively. Untreated disease at the time of allografting after nonmyeloablative conditioning increased the risk of death (hazard ratio = 2.4; P =.04). Although the length of follow-up is still short, it appears that encouraging outcomes can be achieved with nonmyeloablative conditioning in patients expected to have poor outcomes with conventional allografting.

Nonmyeloablative allogeneic hematopoietic stem cell transplantation for metastatic breast cancer

Previously, there was very little interest in investigating allogeneic hematopoietic stem cell transplantation (alloHSCT) in breast cancer because of the significant morbidity and mortality associated with this procedure, as well as the disappointing results observed in clinical trials with high-dose chemotherapy and autologous hematopoietic stem cell transplantation in advanced breast cancer. However, the development of nonmyeloablative (reduced-intensity) conditioning regimens, which have less treatment-related mortality but preserve the T cell-mediated graft-versus-tumor (GVT) effect, has led to the investigation of nonmyeloablative alloHSCT in diseases that had not previously been considered for conventional alloHSCT, including metastatic breast cancer. Laboratory data demonstrate that T cell-mediated responses to breast cancer that inhibit tumor growth are possible and provide the rationale to pursue allogeneic adoptive cellular therapy as a strategy to eliminate breast cancer. Early reports of nonmyeloablative alloHSCT indicate that a clinical GVT effect against breast cancer does exist. The responses appear to be dependent on the development of complete donor lymphoid chimerism, and responses may be delayed. The results from these initial trials must be interpreted cautiously. It is unlikely that nonmyeloablative alloHSCT by itself will result in complete eradication of metastatic breast cancer; however, it may serve as a therapeutic platform to enhance the effects of currently available immunotherapies (eg, trastuzumab administration) and complement existing cytotoxic therapies. Well-designed studies will be necessary to determine the clinical efficacy of nonmyeloablative alloHSCT as adoptive cellular therapy in metastatic breast cancer.

Adjusted conditioning for allogeneic transplantation in a single center setting: mixed chimerism heralds relapse

The role of mixed chimerism on subsequent relapse was prospectively evaluated in an allotransplant program. Sixty-six patients with median age of 54 and mainly high-risk hematologic disease and/or solid tumors had individually adjusted non-myeloablative conditioning. Thirty-nine donors were siblings and 27 unrelated. Frequent chimerism analyses supported immune manipulation including donor lymphocyte infusions. The need for transfusions, i.v. fluids, and antibiotics, and weight loss was less than in a control cohort. Most patients had immediate full and consistent donor chimerism; one-third required immune manipulation. Eight of ten evaluable CML patients were BCR/ABL-negative at days 14-58 post-transplant. Mixed chimerism frequently preceded relapse, and the relapse rate was 38% in 26 patients with mixed chimerism vs. 11% among 35 with consistent full donor chimerism (p = 0.015). The current transplant- and disease-related mortality were 11 and 9%, respectively, among 35 non-high-risk patients, and 35 and 10% for 29 high-risk patients with hematologic malignancy. With a median follow-up of 15 months the 2-year overall survival is 73% for non-high-risk, and 46% for high-risk patients. Adjusted conditioning reduces early toxicity and resource requirements without impairing tumor control, probably due to a rapid establishment of the graft-versus-cancer effect. Mixed chimerism heralded relapse, and tumor-related mortality is not greater with adjusted than with conventional conditioning.

Recent developments in hematopoietic stem cell transplantation for multiple myeloma

Multiple myeloma (MM) is often successfully controlled with conventional chemotherapy; however, complete remissions are uncommon, and cure is rare. High-dose therapy followed by administration of autologous or allogeneic stem cells, used for the treatment of MM in the past 15 years, is promising as a means of increasing remission rates and improving survival. Autologous transplantation has not always demonstrated survival benefits in randomized studies because most of the patients receiving transplants have relapses, whereas patients given conventional therapy can receive salvage transplants when relapse occurs. Efforts to improve the results of autologous transplantation include targeted radiation, tandem transplantation, and posttransplantation immunotherapy. Only allogeneic hematopoietic stem cell transplantation is potentially curative, owing to a graft-versus-myeloma effect. Although patients who receive either allogeneic or autologous stem cell transplants for MM have similar 3- to 5-year survival rates, only allograft recipients appear to enjoy long-term disease-free survival. High transplantation-related mortality associated with allogeneic stem cell transplantation is currently the major limitation to wider use of this potentially curative modality. Strategies designed to improve the therapeutic index of allografts include the use of nonablative conditioning regimens, peripheral blood cells rather than bone marrow, graft engineering, and targeted conditioning therapies, such as bone-seeking radioisotopes.

Reduced intensity conditioning and prophylactic DLI can cure patients with high-risk acute leukaemias if complete donor chimerism can be achieved

23 patients with ALL (n=9) and AML (n=14) underwent nonmyeloablative stem cell transplantation (NST) from an HLA-identical donor after conditioning with fludarabine (180 mg/m(2)), busulfan (8 mg/kg) and anti-T-lymphocyte globulin (40 mg/kg). After NST, 20/23 patients engrafted. Ten out of 14 patients with uncontrolled disease reached complete remission. A multiplex-PCR using short tandem repeats was used for chimerism analysis and detected mixed chimerism (MC) in 14/22 evaluable patients (64%) after NST. Prophylactic donor lymphocyte infusions (DLI) were given to 11/14 patients with MC; MC converted to complete donor chimerism (CC) in 6/11 patients within 2-6 weeks. All patients with persistent MC with or without DLI relapsed during further follow-up. MC predicted impending relapse 4-52 weeks before clinical diagnosis. Ten of 23 patients (43%) are alive 2-34 months after stem cell transplantation. 12 of 23 patients (52%), have died from leukaemia after NST. One out of 23 patients has died from severe sepsis. In conclusion, NST leads to stable engraftment and complete remission in patients with advanced acute leukaemias. NST can cure a substantial proportion of these patients, but the relapse rate is still high. Repeated chimerism analysis is a useful tool to detect recipient cells, especially in patients without molecular markers of disease and can be used to monitor immunomodulatory therapies. MC is unstable in these patients and predicts impending relapse. Prophylactic DLI can convert MC to CC, which seemed to lower relapse risk.

Nonmyeloablative alternative donor transplants

The advent of nonmyeloablative preparative regimens and the expected lower regimen-related toxicities associated with them hold significant promise for extension of the use of allogeneic hematopoietic stem cell transplantation. Nonmyeloablative hematopoietic stem cell transplantation using human leukocyte antigen matched sibling donor, which carries a relatively low risk of transplant-related complications and can result in impressive antitumor responses, may benefit older patients and patients with preexisting organ impairment. However, more than 65% of patients in need of this procedure lack a human leukocyte antigen matched sibling donor. Therefore, attention has focused on alternative donors such as genotypically matched unrelated donors and partially mismatched related donors. Early clinical results suggest that the use of alternative donors is feasible, therefore potentially allowing full extension of the benefits of allografting to the group of patients in highest need.

Chimerism analysis following allogeneic peripheral blood stem cell transplantation with reduced-intensity conditioning

We have performed a prospective study to evaluate early chimerism and its kinetics after allogeneic peripheral blood stem cell transplantation among 68 patients who received a reduced-intensity conditioning (RIC) regimen with fludarabine plus melphalan (n=40) or busulphan (n=28). Chimerism was analyzed by polymerase chain reaction amplification of short tandem repeats in unfractionated (UF) and/or fractionated nucleated cells from bone marrow and peripheral blood (PB). All of the patients showed initial donor engraftment and no patient presented primary or secondary graft failure. In UF samples, the probability of achieving stable complete donor chimerism (CDC) in PB within the first 6 months was 70% on day +30, 85% on day +100 and 95% on day +180. CDC in granulocytes was observed in nearly all cases from day +30 onwards. CDC in T cells, however, differed among melphalan and busulphan recipients during the first 3 months (100 vs 0% on day +30 and 93 vs 20% on day +90, respectively). In multivariate analysis, the only significant variable associated with the achievement of early CDC was having received more than two lines of chemotherapy pretransplant (P<0.02). No correlation was found between the rate of achieving early CDC and the occurrence of acute graft-versus-host disease (GVHD) or disease progression post-transplant. In multivariate analysis, the only variable that influenced the incidence of disease progression post-transplant was the development of chronic extensive GVHD (P<0.05). In conclusion, a state of CDC is readily obtained within the first 6 months after our RIC protocols. Donor myeloid engraftment occurs rapidly in all cases, while early T-cell CDC is more common in more immunosuppressed hosts and, perhaps, in melphalan recipients.

Nonmyeloablative allogeneic hematopoietic stem cell transplantation for treatment of Dyskeratosis congenita

We describe the treatment of a 10-year-old girl with autosomal recessive Dyskeratosis congenita (DC), neutropenia, thrombocytopenia and combined immunodeficiency by nonmyeloablative hematopoietic stem cell transplantation. The conditioning regimen consisted of fludarabine 30 mg/m(2)/day (days -5, -4, -3) and 2 Gy TBI (0.07 Gy/min; day 0). For graft-versus-host disease (GVHD) prophylaxis a course of intravenous MMF and CSA was administered. At 2 years after transplantation of granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood stem cells from a healthy 11-year-old HLA-identical brother, peripheral blood counts and T- and B-cell functions have completely normalized and donor chimerism was 100% in all cell lineages. No GVHD occurred. Neurological examination and lung function remained normal. The current transplantation regimen appears suitable, safe and efficacious in patients with DC.

Successful therapy of metastatic cancer using tumor vaccines in mixed allogeneic bone marrow chimeras

A frequent outcome of allogeneic stem cell transplantation (alloSCT) in the treatment of leukemia is the destruction of the host hematolymphoid compartment and, thus, the malignancy, through the combined action of high-dose chemoradiotherapy and a T-cell-mediated graft-versus-host effect. Unfortunately, alloSCT is frequently limited by toxicity, including graft-versus-host disease (GVHD), and has not been successful in the treatment of tumors derived from solid organs. Here we report a novel cooperation between host and donor T cells in the response to a tumor cell vaccine given after a nonmyeloablative allogeneic stem cell transplantation (NST) protocol that achieves stable mixed bone marrow chimerism. Treatment of animals with NST, posttransplantation donor lymphocyte infusions (DLIs), and a vaccine, comprising irradiated autologous tumor cells mixed with a granulocyte-macrophage colony-stimulating factor (GM-CSF)-producing bystander line, results in potent and specific antitumor immunity. This combined modality immunotherapy, administered after surgical removal of the primary tumor, cured metastatic mammary cancer in most animals without inducing GVHD. Cured animals contained tumor-specific T cells of both host and donor origin, but immunodeficient hosts could not be cured by NST, DLI, and vaccine administration. Thus, transfer of allogeneic donor T cells may help break functional tolerance of a host immune system to a solid tumor, thereby providing a rationale for the generation of mixed hematopoietic chimerism by NST prior to tumor cell vaccination.

Adoptive immunotherapy against kidney targets in dog-leukocyte antigen-identical mixed hematopoietic canine chimeras

BACKGROUND

Stable mixed-donor-host-hematopoietic chimerism can serve as a platform for adoptive immunotherapy. Infusions of donor lymphocytes (DLI) sensitized against hematopoietic cells converted mixed hematopoietic into full-donor chimerism in dog-leukocyte antigen (DLA)-identical littermates. Whether sensitization against tissue of solid organs leads to organ-specific immunity that can be transferred by DLI was unknown and was investigated in these experiments using the kidney as target.

METHODS

DLA-identical recipients with established stable mixed-donor-host-hematopoietic chimerism were used. In five pairs, hematopoietic stem-cell transplant (HSCT) donors were sensitized by kidney transplantation from the respective chimeras. In a second group, five HSCT donors received vaccinations that were generated from kidney cells of the respective mixed chimeras. Twenty-eight days after sensitization, DLI were administered to the mixed-hematopoietic chimeras.

RESULTS

All HSCT donors rejected their kidney grafts from their mixed-chimeric recipients within 22 to 45 days. DLI caused no sustained graft-versus-kidney effects in the mixed-chimeric recipients. However, DLI donors sensitized by kidney transplantation converted 4 of 5 mixed chimeras into virtually complete (>95%) donor-type chimeras, compared with 1 of 5 mixed chimeras given DLI by vaccination from sensitized donors.

CONCLUSION

Although DLA-identical kidney grafts from mixed-hematopoietic chimeras were readily rejected by their HSCT donors, subsequent transfusions of sensitized-donor lymphocytes into mixed chimeras converted mixed to all-donor chimerism but failed to induce graft-versus-kidney effects. Vaccination strategies in lieu of kidney grafts failed to convert mixed chimerism.

Low-dose total body irradiation (TBI) and fludarabine followed by hematopoietic cell transplantation (HCT) from HLA-matched or mismatched unrelated donors and postgrafting immunosuppression with cyclosporine and mycophenolate mofetil (MMF) can induce durable complete chimerism and sustained remissions in patients with hematological diseases

Toxicities of high-dose conditioning regimens have limited the use of conventional unrelated donor hematopoietic cell transplantation (HCT) to younger, medically fit patients. Based on preclinical studies, an HCT approach has been developed for elderly or medically infirm patients with HLA-matched or mismatched unrelated donors. In this study, 52 patients with hematological diseases were included. Most (88%) had preceding unsuccessful conventional HCT or refractory/advanced disease. Patients were treated with fludarabine 30 mg/m(2)/d from days -4 to -2, 2 Gy total body irradiation on day 0, cyclosporine at 6.25 mg/kg twice daily from day -3, and mycophenolate mofetil at 15 mg/kg twice daily from day 0. Durable donor chimerism was attained in 88% of the patients. By day 28, a median of 100% of CD56(+) cells were of donor origin. Granulocyte and T-cell donor chimerism increased to medians of 100% on day 56 and day 180 (range, 55%-100%), respectively. Acute GVHD, grade II, was seen in 42% (CI, 29%-56%); grade III in 8% (CI, 0%-15%); and grade IV in 13% (CI, 4%-23%) of patients; it was fatal in 9%. The 100-day transplantation-related mortality was 11%. Complete remissions, including molecular remissions, were seen in 45% of patients with measurable disease before transplantation. Mortality from disease progression was 27% at one year. With a median follow-up of 19 months, 18 of the 52 patients (35%) were alive and 25% were in remission. HCT from HLA-matched or mismatched unrelated donors can be performed with a reduced intensity conditioning regimen in patients ineligible for conventional HCT.

Embryonic stem cells and potency to induce transplantation tolerance

In the past 40 years, many protocols have been extensively studied for the induction of sustainable transplantation tolerance which might lead to protection of allografts from immunological injury in the clinical setting. Despite the enormous success in rodents, there is still no established protocol available yet for widespread clinical trials. Whilst clonal deletion, clonal anergy and suppression, now coined regulation, have been elucidated as the key immunological elements of tolerance, a better understanding of these mechanisms has so far done little to improve on the survival of organ transplants in humans. Haematopoietic chimaerism, as previously described by Medawar and colleagues [1], remains the most robust tool for tolerance induction. Unfortunately, bone marrow or haematopoietic stem cell transplantation for patients awaiting solid organ transplantation remains a high risk therapy, due to the dangers of graft-versus-host disease. Most recent data, however, indicate the potential of embryonic stem cells (ESC) to offer a possible solution for low risk induction of multilineage mixed chimaerism and tolerance not involving any immunosuppression, due to their unique property of low immunogenicity and high plasticity. Here, what we know about ESC in various species, and the potency and drawbacks of ESC for widespread clinical use, will be discussed.

Therapeutic vaccination with tumor cells that engage CD137

Therapeutic cancer vaccination is based on the finding that tumors in both humans and experimental animals, such as mice, express potential immunological targets, some of which have high selectivity for cancer cells. In contrast to the successful vaccination against some infectious diseases, where most vaccines induce neutralizing antibodies that act prophylactically, the aim of therapeutic cancer vaccines is to treat established tumors (primarily micrometastases). Since most tumor-destructive immune responses are cell-mediated, therapeutic cancer vaccination needs to induce and expand such responses and also to overcome "escape" mechanisms that allow tumors to evade immunological destruction. Tumor antigens (as with other antigens) are presented by "professional" antigen-presenting cells, most notably dendritic cells (DC). Therefore DC that have been transfected or "pulsed" to present antigen provide a logical source of tumor vaccines, and some encouraging results have been obtained clinically as well as in preclinical models. An alternative and more physiological approach is to develop vaccines that deliver tumor antigen for in vivo uptake and presentation by the DC. Vaccines of the latter type include tumor cells that have been modified to produce certain lymphokines or express costimulatory molecules, as well as cDNAs, recombinant viruses, proteins, peptides and glycolipids which are often given together with an adjuvant. Several studies over the past 5 years have demonstrated dramatic therapeutic responses against established mouse tumors as a result of repeated injections of agonistic monoclonal antibodies (MAbs) to the costimulatory molecule CD137 (4-1BB). However, the clinical use of such MAbs may be problematic since they depress antibody formation, for example, to infectious agents. The alternative approach to transfect tumor cells to express the CD137 ligand (CD137L) increases their immunogenicity, but vaccination with tumor cells expressing CD137L is ineffective in several systems where injection of anti-CD137 MAb produces tumor regression. Recent findings indicate that a more effective way to engage CD137 towards tumor destruction is to transfect tumor cells to express a cell-bound form of anti-CD137 single-chain Fv fragments (scFv). Notably, tumors from melanoma K1735, growing either subcutaneously or in the lung, could be eradicated following vaccination with K1735 cells that expressed anti-CD137 scFv. This was in spite of the fact that K1735, as with many human neoplasms, expresses very low levels of MHC class I and has low immunogenicity. Similar results were subsequently obtained with other tumors of low immunogenicity, including sarcoma Ag104. We hypothesize that the concomitant expression of tumor antigen and anti-CD137 scFv effectively engages NK cells, monocytes and dendritic cells, as well as activated CD4(+) and CD8(+) T cells (all of which express CD137) so as to induce and expand a tumor-destructive Th1 response. While vaccines in the form of transfected tumor cells can be effective, at least in mouse models, the logical next step is to construct vaccines that combine genes that encode molecularly defined tumor antigens with a gene that encodes anti-CD137 scFv. Before planning any clinical trials, vaccines that engage CD137 via scFv need to be compared in demanding mouse models for efficacy and side effects with vaccines that are already being tested clinically, including transfected DC and tumor cells producing granulocyte-macrophage colony-stimulating factor.

Low-intensity conditioning and hematopoietic stem cell transplantation in patients with renal and colon carcinoma

We have evaluated whether allogeneic hematopoietic stem cell transplantation (HSCT) could induce an antitumor effect in patients with metastatic solid tumors. A total of 12 HLA-identical siblings and 6 HLA-A-, -B- and -DR beta 1-compatible unrelated grafts were used. Diagnoses were adenocarcinoma of kidney (n=10), colon (n=6), breast (n=1) and cholangiocarcinoma (n=1). Conditioning was fludarabine 30 mg/m(2)/day for 3 days and 2 Gy of total body irradiation. Recipients of unrelated HSCT were also given thymoglobuline and two additional days of fludarabine. The median CD34+ cell dose was 7.5 x 10(6)/kg. Immunosuppression was mycophenolate mofetil and cyclosporin. Among all, 12 patients became complete donor chimeras within a median of 28, 29 and 65 days for B, myeloid and T cells, respectively. Two patients rejected the grafts, one developed marrow aplasia and three were mixed chimeras. The probability of grades II-IV acute graft-versus-host-disease (GVHD) was 57%. Regression of all tumor metastases was seen in one patient with colon carcinoma. Another patient with colon and two with renal carcinoma had regression of lung metastases, but progression of metastases in the liver and/or bone. Necrosis of lung metastasis was found in one further patient with renal carcinoma who died of graft-versus-host-disease (GVHD). In all, 10 patients died; four of transplant-related complications, one of trauma and five of progressive disease. Thus, progression was common after allogeneic HSCT in unselected patients with advanced solid tumors. However, the regression of some metastases associated with GVHD provides suggestive evidence that the GVHD effect may occur in renal and colon adenocarcinoma using reduced intensity conditioning.

Clinical application of hematopoietic progenitor cell expansion: current status and future prospects

In the past decade, we have witnessed significant advances in ex vivo hematopoietic stem cell culture expansion, progressing to the point where clinical trials are being designed and conducted. Preclinical milestone investigations provided data to enable expansion of portions of hematopoietic grafts in a clinical setting, indicating safety and feasibility of this approach. Data derived from current clinical trials indicate successful reconstitution of hematopoiesis after myeloablative chemoradiotherapy using infusion of ex vivo-expanded perfusion cultures. Future avenues of exploration will focus upon refining preclinical and clinical studies in which cocktails of available cytokines, novel molecules and sophisticated expansion systems will explore expansion of blood, marrow and umbilical cord blood cells.

Dog leukocyte antigen-haploidentical stem cell allografts after anti-CD44 therapy and reduced-intensity conditioning in a preclinical canine model

OBJECTIVE

We previously described a nonmyeloablative hematopoietic stem cell transplantation regimen in dog leukocyte antigen (DLA)-identical littermate recipients consisting of low-dose total body irradiation (TBI) before and mycophenolate mofetil (MMF)/cyclosporine (CSP) given after transplant to control both graft-vs-host and residual host-vs-graft reactions. In this study, we sought to develop a reduced-intensity regimen to achieve engraftment across major histocompatibility complex barriers in DLA-haploidentical littermate recipients.

MATERIALS AND METHODS

We tested a regimen of 450-cGy TBI with or without postgrafting MMF/CSP for 28 and 35 days, respectively, and with the administration of monoclonal antibody (mAb) S5 (anti-CD44), at a dose of 0.2 mg/kg/day from days -7 through -2, prior to receiving TBI.

RESULTS

One of six dogs conditioned with 450-cGy TBI alone achieved engraftment of granulocyte colony-stimulating factor-mobilized peripheral blood stem cells. Three of six dogs achieved sustained donor cell engraftment using 450-cGy TBI and posttransplantation MMF/CSP. None of three dogs given mAb S5 followed by 450-cGy TBI showed signs of donor cell engraftment. However, when S5 mAb pretreatment was added to 450-cGy TBI and postgrafting MMF/CSP, 10 of 12 dogs achieved sustained engraftment (p = 0.008 or 0.007 vs 450-cGy alone or to S5 + 450-cGy TBI without MMF/CSP, respectively), with only three dogs developing severe graft-vs-host disease on this short regimen of immunosuppression.

CONCLUSION

These results show that engraftment across a DLA haplotype-mismatched barrier can be achieved after reduced-intensity conditioning when mAb S5 directed at CD44 is added to this regimen.

Kinetics of minimal residual disease and chimerism in patients with chronic myeloid leukemia after nonmyeloablative conditioning and allogeneic stem cell transplantation

The kinetics of minimal residual disease (MRD) and chimerism were studied in 15 patients with chronic myeloid leukemia (CML) receiving nonmyeloablative stem cell transplantation (NST) and in 10 patients receiving conventional stem cell transplantation (CST). All NST patients showed T-cell mixed chimerism (MC) while granulocyte and B-cell MC occurred in 80% and 60% of the NST patients, respectively. In CST patients, T-cell MC was detected in 5 patients, of whom 3 were mixed only during the first month. MRD was detected in all NST patients. During the first 3 months the median BCR-ABL/ABL ratio was 0.2% in NST patients compared with 0.01% in CST patients (P <.01). However, 12 months after transplantation, the percentage of reverse transcriptase-polymerase chain reaction (RT-PCR)-positive patients was 20% in NST patients and 50% in CST patients. In conclusion, molecular remission can be induced in most patients after NST, albeit with different kinetics from CST.

Nonmyeloablative allogeneic stem cell transplantation for the treatment of chronic myeloid leukemia in first chronic phase

Reduced-intensity or nonmyeloablative stem cell transplantation (NST) is designed to induce host-versus-graft tolerance by engraftment of donor stem cells. The rationale behind NST is to induce optimal graft-versus-leukemia (GVL) effects for elimination of all malignant cells by donor alloreactive immunocompetent cells as an alternative to standard high-dose myeloablative chemoradiotherapy. NST based on the use of fludarabine, low-dose busulfan, and anti-T-lymphocyte globulin (ATG) was employed in 24 patients aged 3 to 63 years with chronic myeloid leukemia (CML) in first chronic phase (CP). Graft-versus-host disease (GVHD) prophylaxis consisted of low-dose cyclosporine (CSP), in some cases with low-dose methotrexate. Early discontinuation of CSP was attempted in cases of mixed chimerism in an attempt to amplify GVL effects. All 24 patients showed rapid 3-lineage engraftment, mostly without complete aplasia; 6 patients did not require transfusion of any blood products. NST was associated with minimal procedure-related toxicity. The incidence of acute GVHD (grade I or higher) was 54%; however, this incidence increased following CSP withdrawal. After a follow-up of up to 70 months (median, 42 months), 21 of 24 patients remained alive and disease free. The GVL effects induced by donor immunocompetent lymphocytes eradicated all host hematopoietic cells, as evidenced by molecular testing. The Kaplan-Meier probability of survival and disease-free survival at 5 years is 85% +/- 8% (95% confidence interval, 70%-100%). NST may successfully replace myeloablative stem cell transplantation, providing a safer, well-tolerated therapeutic option for all patients with CML in first CP with a matched donor. However, this conclusion must be tested in a prospective randomized clinical trial.

A novel rapid single nucleotide polymorphism (SNP)-based method for assessment of hematopoietic chimerism after allogeneic stem cell transplantation

A major end point of nonmyeloablative hematopoietic stem cell transplantation is the attainment of either mixed chimerism or full donor hematopoiesis. Because the majority of human genetic disparity is generated by single nucleotide polymorphisms (SNPs), direct measurement of SNPs should provide a robust tool for the detection and quantitation of chimerism. Using pyrosequencing, a rapid quantitative sequencing technology, we developed a SNP-based assay for hematopoietic chimerism. Based on 14 SNPs with high allele frequencies, we were able to identify at least 1 informative SNP locus in 55 patients with HLA-identical donors. The median number of informative SNPs in related pairs was 5 and in unrelated pairs was 8 (P <.0001). Assessment of hematopoietic chimerism in posttransplantation DNA was shown to be quantitative, accurate, and highly reproducible. The presence of 5% donor cells was reliably detected in replicate assays. Compared with current measures of engraftment based on identification of short tandem repeats (STRs), variable number of tandem repeats (VNTRs), or microsatellite polymorphisms, this SNP-based method provides a more rapid and quantitative assessment of chimerism. A large panel of SNPs enhances the ability to identify an informative marker in almost all patient/donor pairs and also facilitates the simultaneous use of multiple markers to improve the statistical validity of chimerism measurements. The inclusion of SNPs that encode minor histocompatibility antigens or other genetic polymorphisms that may influence graft-versus-host disease or other transplantation outcomes can provide additional clinically relevant data. SNP-based assessment of chimerism is a promising technique that will assist in the analysis of outcomes following transplantation.

Myelodysplastic syndrome

The last decade has witnessed a multistep evolution in the understanding of the natural history, clinical manifestations, and some of the molecular mechanisms that underlie the ineffective hematopoiesis and leukemic transformation in the myelodysplastic syndrome (MDS). The international prognostic scoring system, FAB, and WHO classifications have helped define specific subgroups with their characteristic cytogenetic, molecular and immunological abnormalities. Until recently the mainstay of the treatment has been entirely supportive with blood and platelet transfusions. What is increasingly manifest now is the considerable excitement generated by the emergence of novel therapeutic strategies based on painstaking research findings from the laboratories. In Section I, Dr. Alan List reviews the therapeutic strategies with the specific emphasis on the relevance of molecular mechanism of apoptosis and targeted therapies using small molecules. Of particular interest is the excitement surrounding the clinical benefit obtained from potent immunomodulatory derivative (IMiD) of thalidomide CC5013. The review provides an update of the role of small molecule inhibitors of VEGF receptor tyrosine kinase, arsenic trioxide, oral matrix metalloprotease inhibitors, farnesyl transferase inhibitors, and imatinib mesylate in the treatment of MDS subgroups. In Section II, Dr. Steven Gore describes the results of clinical trials of inhibitors of DNA methylation such as 5 azacytidine (5 AC) and 5-aza 2-deoxycytidine (Decitabine). The review also provides an update on the rationale and results obtained from the combination therapy using histone deacetylases (HDAC) and DNA methyltransferase inhibitors in the treatment of MDS. In Section III, Professor Ghulam Mufti and Dr. Aloysius Ho describe the role of bone marrow transplantation with particular emphasis on recent results from reduced-intensity conditioned transplants, exploiting the graft versus leukemia effect without significant early treatment-related mortality. The section provides an update on the results obtained from the manipulation of the host's immune system with immunosuppressive agents such as ALG and/or cyclosporine A.

Hematopoietic Cell Transplantation for Benign Hematological Disorders and Solid Tumors

Allogeneic hematopoietic cell transplantation (HCT) has been successfully used as replacement therapy for patients with aplastic anemia and hemoglobinopathies. Both autologous and allogeneic HCT following high-dose chemotherapy can correct manifestations of autoimmune diseases. The impressive allogeneic graft-versus-tumor effects seen in patients given HCT for hematological malignancies have stimulated trials of allogeneic immunotherapy in patients with otherwise refractory metastatic solid tumors. This session will update the status of HCT in the treatment of benign hematological diseases and solid tumors.

In Section I, Dr. Rainer Storb reviews the development of nonmyeloablative conditioning for patients with severe aplastic anemia who have HLA-matched family members. He also describes the results in patients with aplastic anemia given HCT from unrelated donors after failure of responding to immunosuppressive therapy. The importance of leuko-poor and in vitro irradiated blood product transfusions for avoiding graft rejection will be discussed.

In Section II, Dr. Guido Lucarelli reviews the status of marrow transplantation for thalassemia major and updates results obtained in children with class I and class II severity of thalassemia. He also describes results of new protocols for class III patients and efforts to extend HCT to thalassemic patients without HLA-matched family members.

In Section III, Dr. Peter McSweeney reviews the current status of HCT for severe autoimmune diseases. He summarizes the results of autologous HCT for systemic sclerosis, multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus, and reviews the status of planned Phase III studies for autologous HCT for these diseases in North America and Europe. He also discusses a possible role of allogeneic HCT in the treatment of these diseases.

In Section IV, Dr. Richard Childs discusses the development and application of nonmyeloablative HCT as allogeneic immunotherapy for treatment-refractory solid tumors. He reviews the results of pilot clinical trials demonstrating graft-versus-solid tumor effects in a variety of metastatic cancers and describes efforts to characterize the immune cell populations mediating these effects, as well as newer methods to target the donor immune system to the tumor.

Allogeneic hematopoietic stem cell transplantation--yesterday, today, and tomorrow

During the past 50 years, intensive studies into the use of hematopoietic stem cell transplantation (HSCT) for therapy of cancer and nonmalignant hematologic diseases have changed this treatment modality from one that was thought to be plagued by insurmountable complications to one that is now standard therapy for some diseases. More-recent research has opened up the way to include elderly patients with a wide variety of hematologic malignant diseases. Continued research by transplant teams worldwide is likely to allow continued progress toward developing novel and improved treatment modalities and even wider application of the use of pluripotent hematopoietic stem cells in the treatment of human diseases.