HSCT for Fanconi anemia in children: factors that influence early and late results

Bone marrow transplant using fludarabine-based reduced intensity conditioning regimen with in vivo T cell depletion in patients with Fanconi anemia

FA is the most common cause of inherited BMF syndromes. The only cure for BMF in FA remains HSCT. Due to DNA instability in FA, RIC has been used to decrease immediate and late complications of HSCT. Most FA conditioning regimens in mismatched and unrelated donor transplants rely on TBI, which increases the risk of secondary malignancies. Most of the non-TBI conditioning regimens use an ex vivo T-cell depletion approach, but this is not feasible at all pediatric stem cell transplant programs. To evaluate the success of HSCT in patients with FA using non-TBI conditioning regimens with in vivo T-cell depletion approach. HSCT using non-TBI based conditioning was performed on two siblings with FA. The first sibling underwent matched unrelated donor transplant with a BM graft using fludarabine, alemtuzumab, busulfan, and cyclophosphamide conditioning and cyclosporine and mycophenolate as GVHD prophylaxis. The second sibling underwent MSD transplant with UCB and BM grafts using similar approach, but without busulfan and mycophenolate. Both siblings had engraftment without signs of acute or chronic GVHD. Acute post-transplant complications included brief viral reactivations. At last follow-up, both siblings continued to have full immune reconstitution with stable chimerism. Conditioning regimens without radiation and inclusion of alemtuzumab can lead to successful engraftment without development of GVHD and reduce risk of developing secondary neoplasms, even with unrelated donor transplants.

Haploidentical Stem Cell Transplantation with Post-Transplant Cyclophosphamide in Fanconi Anemia: Improving Outcomes with Improved Supportive Care in India

Fanconi anemia is the most common inherited bone marrow failure syndrome, and hematopoietic stem cell transplantation (HSCT) is the only curative option. Post-transplant cyclophosphamide (PTCy) is challenging in this group of children, given their increased sensitivity to chemotherapy. We performed a retrospective analysis of the data on children diagnosed with Fanconi anemia who underwent a haploidentical HSCT with PTCy from January 2014 to December 2019. Nineteen children (male/female, 0.75:1) underwent 21 haplo-HSCTs with PTCy. Fludarabine, low-dose cyclophosphamide, and 200 centi-gray total body irradiation were included in the conditioning regimen with 25 mg/kg PTCy on days +3 and +4. Haplo-graft was from a sibling in 38% and father in 57% of transplants. The source of stem cells was peripheral blood stem cells in 81% and bone marrow in 19% of transplants, with a median CD34 dose of 5.0 × 10⁶/kg. We documented engraftment in 84% and primary graft failure in 10% of transplants. N-acetylcysteine (NAC) was infused concomitantly during cyclophosphamide in 13 children. Grade 2 and 3 mucositis was lower among those who received NAC as compared to those who did not (30% and 15% versus 33% and 50%), while transaminitis was higher among those who did not receive the infusion. The incidence of acute graft-versus-host disease (GVHD) was 68%, and 81% of these were steroid responsive (grade I/II). We documented chronic GVHD in 25% children, predominantly involving the skin and mouth, which responded to low-dose steroids and ruxolitinib. Serum ferritin was monitored twice weekly as a surrogate marker for cytokine release syndrome due to nonavailability of IL-6 levels. A 1- or 2-log increase in the titers of ferritin associated with clinical features guided the early addition of steroids in the periengraftment period. The mean survival was found to be less among those with high serum ferritin (>10,000 ng/dL) in the periengraftment period as compared to those with ferritin <10,000 ng/dL (mean survival of 25 ± 10 months versus 50 ± 6 months, respectively). The overall survival in our cohort was 68.4%, with a mean survival time of 41.5 months (95% confidence interval, 29.3 to 53.8 months), with a statistically significant correlation between inferior outcome and having received over 15 transfusions before HSCT (P = .01). PTCy can be considered a viable option in children with Fanconi anemia, particularly in resource-limited settings given the high costs of HSCTs. Focused interventions in this subset of children help improve survival outcomes. Early identification of cytokine release syndrome and risk-adapted steroid therapy during engraftment helps prevent mortality. The concomitant use of NAC during cyclophosphamide infusion helps reduce oxygen free radical related tissue damage and regimen-related toxicity.

Mesenchymal COX2-PG secretome engages NR4A-WNT signalling axis in haematopoietic progenitors to suppress anti-leukaemia immunity

The bone marrow (BM) microenvironment (niche) plays important roles in supporting normal/abnormal haematopoiesis. We investigated the interaction between leukaemic mesenchymal niche and haematopoietic stem and progenitor cells (HSPCs) using the model of Fanconi anaemia (FA), a genetic disorder characterized by BM failure and leukaemia. Healthy donor HSPCs co-cultured on mesenchymal stromal cells (MSCs) derived from FA patients with acute myeloid leukaemia (AML) exhibited higher human engraftment and myeloid expansion in Non-obese diabetic severe combined immunodeficiency IL-2γ^-/- /SGM3 recipients. Untargeted metabolomics analysis revealed the progressively elevated prostaglandins (PGs) in the MSCs of FA patients with myelodysplastic syndromes (MDS) and AML. Reduced secretion of PGs subsequent to inflammatory cyclooxygenase 2 (COX2) inhibition ameliorated HSPC/myeloid expansion. Transcriptome analysis demonstrated dysregulation of genes involved in the NR4A family of transcription factors (TFs) and WNT/β-catenin signalling pathway in FA-AML-MSC-co-cultured-CD34⁺ cells. COX2 inhibition led to significantly decreased NR4A TFs and WNT signalling genes expression. Mechanistically, NR4A1 and NR4A2 synergistically activate the CTNNB1 gene promoter . Knocking down CTNNB1 or NR4A1 in AML-MSC-co-cultured-CD34⁺ cells increased leukaemia-reactive T-effector cells production and rescued anti-leukaemia immunity. Together, these findings suggest that specific interactions between leukaemic mesenchymal niche and HSPCs orchestrate a novel COX2/PG-NR4A/WNT signalling axis, connecting inflammation, cellular metabolism and cancer immunity.

Non-genotoxic conditioning for hematopoietic stem cell transplantation using a hematopoietic-cell-specific internalizing immunotoxin

Hematopoietic stem cell transplantation (HSCT) offers curative therapy for patients with hemoglobinopathies, congenital immunodeficiencies, and other conditions, possibly including AIDS. Autologous HSCT using genetically corrected cells would avoid the risk of graft-versus-host disease (GVHD), but the genotoxicity of conditioning remains a substantial barrier to the development of this approach. Here we report an internalizing immunotoxin targeting the hematopoietic-cell-restricted CD45 receptor that effectively conditions immunocompetent mice. A single dose of the immunotoxin, CD45-saporin (SAP), enabled efficient (>90%) engraftment of donor cells and full correction of a sickle-cell anemia model. In contrast to irradiation, CD45-SAP completely avoided neutropenia and anemia, spared bone marrow and thymic niches, enabling rapid recovery of T and B cells, preserved anti-fungal immunity, and had minimal overall toxicity. This non-genotoxic conditioning method may provide an attractive alternative to current conditioning regimens for HSCT in the treatment of non-malignant blood diseases.

Successful Outcome With Fludarabine-Based Conditioning Regimen for Hematopoietic Stem Cell Transplantation From Related Donor in Fanconi Anemia: A Single Center Experience From Turkey

BACKGROUND

Fanconi anemia (FA) is a heterogeneous autosomal recessive (and rarely X linked) disorder, which is characterized by congenital malformations, progressive bone marrow failure, and predisposition to malignancies. Hematopoietic stem cell transplantation (HSCT) is the only definitive treatment for the hematological manifestations in FA.

PROCEDURE

Twenty-seven patients with FA underwent HSCT using fludarabine (Flu) based regimen at our center between April 2004 and May 2014. One patient who developed acute leukemia before HSCT was excluded from the study. The remaining 26 patients were included. The median age of the patients at the time of transplantation was 9.6 years (range 5.6-17.0 years) and male/female ratio was 19/7. Donors were Human leukocyte antigen (HLA)-identical sibling in 18 patients, HLA-identical other relatives in six patients, and HLA 1-antigen mismatched sibling in two patients. Conditioning regimen consisted of Flu, cyclophosphamide, and antithymocyte globulin.

RESULTS

All patients engrafted but one developed poor graft function and underwent second HSCT. Acute graft versus host disease (GVHD) (≥grade 2) occurred in two patients (7.6%) and chronic GVHD in one patient (3.9%). Three patients developed venoocclusive disease (11.5%). Survival rate was 96.2% (25/26) at a median follow-up of 54 months (10-131 months) and all patients who survived were in good clinical condition. None of the patients developed secondary malignancy during the follow-up period.

CONCLUSIONS

The present study from Turkey, a middle-income country, shows successful transplant outcome with low toxicity using Flu-based conditioning in patients with FA who underwent HSCT from HLA-related donors.

Immune reconstitution in patients with Fanconi anemia after allogeneic bone marrow transplantation

BACKGROUND AIMS

Fanconi anemia is an autosomal recessive or X-linked genetic disorder characterized by bone marrow (BM) failure/aplasia. Failure of hematopoiesis results in depletion of the BM stem cell reservoir, which leads to severe anemia, neutropenia and thrombocytopenia, frequently requiring therapeutic interventions, including hematopoietic stem cell transplantation (HSCT). Successful BM transplantation (BMT) requires reconstitution of normal immunity.

METHODS

In the present study, we performed a detailed analysis of the distribution of peripheral blood subsets of T, B and natural killer (NK) lymphocytes in 23 patients with Fanconi anemia before and after BMT on days +30, +60, +100, +180, +270 and +360. In parallel, we evaluated the effect of related versus unrelated donor marrow as well as the presence of graft-versus-host disease (GVHD).

RESULTS

After transplantation, we found different kinetics of recovery for the distinct major subsets of lymphocytes. NK cells were the first to recover, followed by cytotoxic CD8(+) T cells and B cells, and finally CD4(+) helper T cells. Early lymphocyte recovery was at the expense of memory cells, potentially derived from the graft, whereas recent thymic emigrant (CD31(+) CD45RA(+)) and naive CD4(+) or CD8(+) T cells rose only at 6 months after HSCT, in the presence of immunosuppressive GVHD prophylactic agents. Only slight differences were observed in the early recovery of cytotoxic CD8(+) T cells among those cases receiving a graft from a related donor versus an unrelated donor. Patients with GVHD displayed a markedly delayed recovery of NK cells and B cells as well as of regulatory T cells and both early thymic emigrant and total CD4(+) T cells.

CONCLUSIONS

Our results support the utility of post-transplant monitoring of a peripheral blood lymphocyte subset for improved follow-up of patients with Fanconi anemia undergoing BMT.

Interleukin-22 protects intestinal stem cells from immune-mediated tissue damage and regulates sensitivity to graft versus host disease

Little is known about the maintenance of intestinal stem cells (ISCs) and progenitors during immune-mediated tissue damage or about the susceptibility of transplant recipients to tissue damage mediated by the donor immune system during graft versus host disease (GVHD). We demonstrate here that deficiency of recipient-derived IL-22 increased acute GVHD tissue damage and mortality, that ISCs were eliminated during GVHD, and that ISCs as well as their downstream progenitors expressed the IL-22 receptor. Intestinal IL-22 was produced after bone marrow transplant by IL-23-responsive innate lymphoid cells (ILCs) from the transplant recipients, and intestinal IL-22 increased in response to pretransplant conditioning. However, ILC frequency and IL-22 amounts were decreased by GVHD. Recipient IL-22 deficiency led to increased crypt apoptosis, depletion of ISCs, and loss of epithelial integrity. Our findings reveal IL-22 as a critical regulator of tissue sensitivity to GVHD and a protective factor for ISCs during inflammatory intestinal damage.

Formation of cyclophosphamide specific DNA adducts in hematological diseases

BACKGROUND

Fanconi anemia (FA) patients are hypersensitive to DNA alkylating agents and require lower doses than non-FA patients to minimize serious toxicity. The mechanism by which hypersensitivity occurs is thought to be due to the inability of these individuals to effectively repair drug-induced interstrand DNA-DNA crosslinks. We recently developed a highly sensitive assay for cyclophosphamide specific interstrand DNA-DNA crosslinks (G-NOR-G) and are able to quantify and compare formation of these adducts in the blood of patients. Therefore we sought to determine whether FA patients have higher in vivo exposure to the cyclophosphamide specific interstrand DNA crosslink, G-NOR-G, relative to patients without FA.

PROCEDURE

Cyclophosphamide interstrand DNA crosslinks were measured with the first dose of cyclophosphamide in FA and non-FA patients receiving a cyclophosphamide based preparative regimen prior to hematopoietic cell transplantation (HCT). FA patients received a lower cyclophosphamide dose than the non-FA patients (5-10 mg/kg/day vs. 50-60 mg/kg/day).

RESULTS

Despite the lower cyclophosphamide dose and lower plasma concentrations in FA patients, they had G-NOR-G amounts similar to the non-FA patients (area under the curve (AUC)(0-∞) , 99.8 vs. 144.9 G-NOR-G adducts/10(6) nucleotides hour, respectively, P = 0.47). When G-NOR-G AUC was normalized for cyclophosphamide plasma concentrations, FA study subjects produced 15-fold higher adducts than non-FA patients (P = 0.05).

CONCLUSIONS

FA patients are hypersensitive to DNA alkylating agents possibly as a result of greater formation of cyclophosphamide specific interstrand DNA crosslinks and/or diminished capacity for DNA repair. Identification and quantification of these adducts may be important determinant of cyclophosphamide related toxicity.

Excellent outcome of allogeneic bone marrow transplantation for Fanconi anemia using fludarabine-based reduced-intensity conditioning regimen

Fanconi anemia (FA) is a disorder characterized by developmental anomalies, bone marrow failure and a predisposition to malignancy. It has recently been shown that hematopoietic stem cell transplantation using fludarabine (FLU)-based reduced-intensity conditioning is an efficient and quite safe therapeutic modality. We retrospectively analyzed the outcome of bone marrow transplantation (BMT) in eight patients with FA performed in two institutes between 2001 and 2011. There were seven females and one male with a median age at diagnosis = 4.5 years (range 2-12 years). The constitutional characteristics associated with FA, such as developmental anomalies, short stature and skin pigmentation, were absent in three of the patients. One patient showed myelodysplastic features at the time of BMT. All patients received BMT using FLU, cyclophosphamide (CY) and rabbit anti-thymocyte globulin (ATG) either from a related donor (n = 4) or an unrelated donor (n = 4). Acute graft-versus-host disease (GVHD) of grade I developed in one patient, while chronic GVHD was not observed in any patient. All patients are alive and achieved hematopoietic recovery at a median follow-up of 72 months (range 4-117 months). BMT using FLU/low-dose CY/ATG -based regimens regardless to the donor is a beneficial therapeutic approach for FA patients.

How the fanconi anemia pathway guards the genome

Fanconi Anemia (FA) is an inherited genomic instability disorder, caused by mutations in genes regulating replication-dependent removal of interstrand DNA crosslinks. The Fanconi Anemia pathway is thought to coordinate a complex mechanism that enlists elements of three classic DNA repair pathways, namely homologous recombination, nucleotide excision repair, and mutagenic translesion synthesis, in response to genotoxic insults. To this end, the Fanconi Anemia pathway employs a unique nuclear protein complex that ubiquitinates FANCD2 and FANCI, leading to formation of DNA repair structures. Lack of obvious enzymatic activities among most FA members has made it challenging to unravel its precise modus operandi. Here we review the current understanding of how the Fanconi Anemia pathway components participate in DNA repair and discuss the mechanisms that regulate this pathway to ensure timely, efficient, and correct restoration of chromosomal integrity.