Busulfan, fludarabine, and melphalan are effective conditioning for pediatric and young adult patients with myeloid malignancies underdoing matched sibling or alternative donor transplantation.

BACKGROUND: Allogeneic hematopoietic cell transplantation (allo-HCT) remains a curative option for patients with high-risk myeloid malignancies. PROCEDURE: We present our 10-year experience (October 2012 to October 2021) of consecutive allo-HCT in patients with myeloid malignancies treated on the pediatric HCT service and conditioned with myeloablative targeted dose-busulfan (BU), fludarabine (FLU), and melphalan (MEL). Twenty-three children, adolescents, and young adult patients (CAYA) (median age 15.4 years) with acute myeloid leukemia (AML, n = 17), myelodysplastic syndrome (MDS, n = 4), or chronic myeloid leukemia (CML, n = 2) underwent allo-HCT post-BU-FLU-MEL. Four patients had treatment-related AML/MDS. Donor/stem cell source was matched sibling donor (MSD) PBSC (n = 7), matched unrelated donor (MUD) PBSC (n = 2), umbilical cord blood (UCB) (n = 3), or haploidentical-BMT (n = 11). Risk stratification was low (n = 2), intermediate (n = 15), high (n = 3), and very high risk (n = 1). The two patients with CML had failed tyrosine kinase inhibitor therapies. RESULTS: With a median follow-up of 41.6 months, the relapse rate is only 4.5% with an overall survival (OS) 100%, progression-free survival (PFS) 95.5%, and graft-versus-host-free-relapse-free survival (GRFS) 67.8%. The donor source and the acute graft-versus-host disease (GvHD) prophylaxis regimen significantly impacted grade II-IV aGvHD 66.7% versus 19.2% (p = .039) and chronic graft-versus-host-disease (cGvHD) 66.7% versus 0% (p = .002) in the patients receiving MSD or MUD PBSC compared to haplo-BMT, respectively, resulting in improved GRFS in haplo-BMT, 83.3% compared to 40% matched donor peripheral blood stem cell transplant (PBSCT) (p = .025). CONCLUSIONS: Our results demonstrate that BU-FLU-MEL is efficacious conditioning for disease control in young patients with myeloid malignancies undergoing MSD or alternative donor allo-HCT, but in the setting of PBSC grafts with cyclosporine A-methotrexate (CSA-MTX) GvHD prophylaxis, it results in an unacceptably high incidence of GvHD.

Hematopoietic Cell Transplantation for Congenital Dyserythropoietic Anemia: A Report from the Pediatric Transplant and Cellular Therapy Consortium.

Hematopoietic cell transplantation (HCT) is the sole curative option for congenital dyserythropoietic anemia (CDA), a rare type of hemolytic anemia characterized by anemia, ineffective erythropoiesis, and secondary hemochromatosis. In this retrospective multicenter study, we report the outcomes of children with CDA who underwent HCT at participating Pediatric Transplantation and Cellular Therapy Consortium centers. Clinical information on HCT and associated outcomes was collected retrospectively using a common questionnaire. Data were analyzed using descriptive statistics and appropriate analysis. Eighteen patients with CDA who underwent allogeneic HCT between 2002 and 2020 were identified. The majority of patients (n = 13) had CDA type II, and the remainder had either CDA type I (n = 2) or CDA of unknown type (n = 3). Mutations were identified in 7 patients (39%), including SEC23B in 5, GATA1 in 1, and abnormality of chromosome 20 in 1. Thirteen patients had evidence of iron overload pre-HCT and received chelation therapy for a median duration of 10 months (range, 2 months to 17 years) pre-HCT. The median age at the time of HCT was 5.5 years (range, 0.7 to 26 years). Donors were HLA-matched (sibling, 4; unrelated, 10) and mismatched (haploidentical, 1; unrelated, 3). Graft sources were bone marrow in 15 patients, umbilical cord blood in 2 patients, or both in 1 patient. Conditioning included busulfan-based myeloablative (67%), fludarabine-based reduced-intensity (27%), or nonmyeloablative (6%) regimens. Five patients developed veno-occlusive disease, and 4 had viral reactivation. The cumulative incidence of acute graft-versus-host disease (GVHD) was 33%, and that of chronic GVHD was 22%. Four patients (22%) experienced graft failure; all engrafted following either a second HCT (n = 2) or third HCT (n = 2) but sustained considerable morbidities (3 GVHD, 1 death, 2 viral reactivation). With a median follow-up of 3.2 years (range, 0.6 to 14 years)), the 2-year overall survival, event-free survival (EFS), and GVHD-free EFS were 88% (95% confidence interval [CI], 73% to 100%), 65% (95% CI, 45% to 92%), and 60% (95% CI, 40% to 88%), respectively. Univariate analysis did not identify any patient- or transplantation-related variables impacting outcomes. Our study indicates that HCT can be curative for patients with CDA. Strategies such as aggressive chelation, use of preconditioning therapy, and early HCT in the presence of a suitable donor before comorbidities occur are needed to improve engraftment without increasing the risk for toxicity and mortality.

Vesiculated alpha-tocopheryl succinate enhances the anti-tumor effect of dendritic cell vaccines.

Alpha tocopheryl succinate (alpha-TOS) is a non-toxic vitamin E analog under study for its anti-cancer properties. In an earlier study, we showed that alpha-TOS, when used in combination with non-matured dendritic cells (nmDC) to treat pre-established tumors, acts as an effective adjuvant. In this study, we have used vesiculated alpha-TOS (Valpha-TOS), a more soluble form of alpha-TOS that is relevant for clinical use, in combination with dendritic cells to treat pre-established murine tumors. We demonstrate that Valpha-TOS kills tumor cells in vitro and inhibits the growth of pre-established murine lung carcinoma (3LLD122) as effectively as alpha-TOS. The combination of Valpha-TOS plus non-matured or TNF-alpha-matured DC is more effective at inhibiting the growth of established tumors than Valpha-TOS alone. We also observed that Valpha-TOS induces expression of heat shock proteins in tumor cells and that co-incubation of non-matured DC with lysate derived from Valpha-TOS-treated tumor cells leads to DC maturation evidenced by up-regulation of co-stimulatory molecules and secretion of IL-12p70. This study therefore demonstrates the immunomodulatory properties of Valpha-TOS that may account for its adjuvant effect when combined with DC vaccines to treat established tumors.

Exogenous stress proteins enhance the immunogenicity of apoptotic tumor cells and stimulate antitumor immunity.

We have previously reported that apoptotic tumor cells can be either immunogenic or nonimmunogenic in vivo, depending on whether or not these cells are heat stressed before induction of apoptosis. Stressed apoptotic cells express heat shock proteins on their plasma membranes and dendritic cells are capable of distinguishing them from nonstressed apoptotic cells. Here we provide evidence that when purified heat shock protein 70 or chaperone-rich cell lysate (CRCL) from syngeneic normal tissue is used as an adjuvant with nonimmunogenic apoptotic tumor cells in vaccination, potent antitumor immunity can be generated. This antitumor immunity is mediated by T cells because antitumor effects are not observed in either severe combined immunodeficiency or T cell-depleted mice. We further demonstrate that vaccination of mice with apoptotic tumor cells mixed with liver-derived CRCL as adjuvant were capable of enhancing the production of T(H)1 cytokines, inducing specific cytotoxic T lymphocytes and eliciting long-lasting antitumor immunity. Stress proteins from autologous normal tissue components therefore can serve as danger signals to enhance the immunogenicity of apoptotic tumor cells and stimulate tumor-specific immunity

Stressed apoptotic tumor cells stimulate dendritic cells and induce specific cytotoxic T cells.

We have previously reported that stressed apoptotic tumor cells are more immunogenic in vivo than nonstressed ones. Using confocal microscopy we have confirmed our previous observation that heat-stressed apoptotic 12B1-D1 leukemia cells (BCR-ABL(+)) express HSP60 and HSP72 on their surface. To explore how the immune system distinguishes stressed from nonstressed apoptotic tumor cells, we analyzed the responses of dendritic cells to these 2 types of apoptotic cells. We found that nonstressed and heat-stressed apoptotic 12B1-D1 cells were taken up by dendritic cells in a comparable fashion. However, when stressed apoptotic 12B1-D1 cells were coincubated with immature dendritic cells for 24 hours, this resulted in greater up-regulation of costimulatory molecules (CD40, CD80, and CD86) on the surface of dendritic cells. Moreover, stressed apoptotic 12B1-D1 cells were more effective in stimulating dendritic cells to secrete interleukin-12 (IL-12) and in enhancing their immunostimulatory functions in mixed leukocyte reactions. Furthermore, we demonstrated that immunization of mice with stressed apoptotic 12B1-D1 cells induced the secretion of T helper-1 (T(H)1) profile of cytokines by spleen cells. Splenocytes from mice immunized with stressed apoptotic cells, but not nonstressed ones, were capable of lysing 12B1-D1 and the parental 12B1 line, but not a B-cell leukemia line, A20. Our data indicate that stressed apoptotic tumor cells are capable of providing the necessary danger signals, likely through increased surface expression of heat shock proteins (HSPs), resulting in activation/maturation of dendritic cells and, ultimately, the generation of potent antitumor T-cell responses.