Introduction: The 2022 European Leukemia Network (ELN) recommendations defined several efficacy endpoints for acute myeloid leukemia (AML) treatment, including complete remission (CR), CR with partial hematologic recovery (CRh), CR with incomplete hematologic recovery (CRi), and morphological leukemia-free state (MLFS). In pediatric AML, subsequent chemotherapy courses are often initiated before full hematologic recovery as part of treatment intensification. However, regulatory agencies frequently regard CRh, CRi, and MLFS as treatment failure due to survival differences observed in adult AML, which poses challenges for pediatric drug development. This study evaluated whether survival outcomes differ according to the degree of hematologic recovery in pediatric AML. Methods: We analyzed pediatric patients (< 18 years) with newly diagnosed AML who were enrolled in two nationwide multicenter clinical trials conducted in Japan: JPLSG AML-05 (UMIN000000511) and AML-12 (UMIN000013288/jRCTs041180128). Both trials employed two courses of induction therapy. The initial induction therapy was standard-dose cytarabine (ECM) in AML-05, and either ECM or high-dose cytarabine (HD-ECM) in AML-12 based on randomization. In both trials, these were followed by a second induction therapy (HCEI). In AML-12, flow cytometry-based measurable residual disease (MRD) was centrally monitored at the end of inductions 1 and 2, although MRD results did not guide subsequent therapies. MRD ≥ 0.1% was considered positive. Intensification therapies were initiated following hematologic recovery, defined as an absolute neutrophil count ≥ 0.5 × 109/L and a platelet count ≥ 75–80 × 109/L. A total of 757 patients (422 from AML-05 and 335 from AML-12) who underwent response assessment after induction 2 were included in this analysis. Treatment response after induction 2 was re-evaluated according to the ELN2022 criteria. Survival comparisons between response groups were performed using the log-rank test, Gray's test, and multivariable Cox regression analysis. Results: After induction 2, 313 patients achieved CR, 352 achieved CRh, 14 achieved CRi, 4 were in MLFS, and 74 did not achieve remission (NR). Compared with the 5-year event-free survival (EFS) probability from registration in patients with CR (63.4%; 95% confidence interval [CI], 57.4%–68.7%), the EFS in those with CRh (65.8%; 95% CI, 60.3%–70.7%; P = 0.434) and CRi (57.1%; 95% CI, 28.4%–78.0%; P = 0.484) did not differ significantly. In contrast, patients with MLFS (5 years not attained; P = 0.029) and NR (0.0%; P < 0.001) had significantly worse EFS. Similarly, the 5-year overall survival (OS) probability from registration in patients with CR was 79.1% (95% CI, 73.7–83.5%). There was no significant difference in OS for patients with CRh (79.7%; 95% CI, 74.4%–84.1%; P = 0.619) or CRi (67.7%; 95% CI, 34.4%–86.7%; P = 0.275), whereas OS was significantly lower in the MLFS group (0.0%; P = 0.002) and NR group (29.2%; 95% CI, 17.9%–41.5%; P < 0.001). The cumulative incidence of relapse (CIR) did not differ significantly between those with CR and CRh, CRi, or MLFS. The cumulative incidence of non-relapse mortality was also not significantly different between the CR group and the CRh or CRi groups, but was significantly higher in the MLFS group compared with the CR group (P < 0.001). In the AML-12 cohort, among both the CR and incomplete CR (CRh, CRi, and MLFS) groups, patients who were MRD-positive at the end of induction 2 had significantly inferior 5-year disease-free survival (DFS) and OS compared to MRD-negative patients (P < 0.001, multivariable Cox regression). Furthermore, among MRD-negative patients, no statistically significant differences were observed between the CR and incomplete CR groups in terms of 5-year DFS (65.6% vs. 76.9%, P = 0.080) or OS (84.2% vs. 85.7%, P = 0.778). Conclusions: In pediatric AML, EFS and OS in patients with CRh and CRi were comparable to those in CR, supporting the validity as effective treatment responses. In contrast, MLFS was associated with inferior EFS and OS, a comparable CIR, and a higher incidence of non-relapse mortality compared to CR. This suggests that inadequate hematologic recovery in MLFS may contribute to complications such as infections; however, caution is warranted due to the limited number of cases analyzed. Moreover, MRD should be further explored as a more precise surrogate endpoint for assessing treatment response in pediatric AML.

BACKGROUND:Dyskeratosis congenita (DKC) is a genetic disorder frequently complicated by bone marrow failure (BMF). Hematopoietic stem cell transplantation (HSCT) remains the only curative treatment option for BMF in DKC. However, late complications of DKC, especially pulmonary fibrosis (PF), pose significant challenges. PROCEDURES:This retrospective study analyzed the outcomes of seven patients with DKC who underwent HSCT at our institution from 1985 to 2020. RESULTS:Median age of these patients was 6 (range: 2-11) years. Conditioning regimens included cyclophosphamide, fludarabine, anti-thymocyte globulin, and 3-Gy thoracoabdominal irradiation with lung shielding. Stem cells were sourced from siblings (n = 3) and unrelated (n = 4) bone marrow. All patients achieved engraftment. Late complications, such as PF, pulmonary arteriovenous malformations, liver fibrosis (LF), and hepatopulmonary syndrome, were observed. Four patients (57%) died at a median age of 10 (range: 8.2-13.3) years post-HSCT from PF, LF, and intestinal bleeding. CONCLUSIONS:These findings emphasize the high risk of late mortality associated with pulmonary and hepatic complications post-HSCT in DKC. Further studies are warranted to elucidate the risk factors contributing to such late complications.

Juvenile myelomonocytic leukemia (JMML), which is classified as a myelodysplastic/myeloproliferative neoplasm, is a rare hematologic malignancy of childhood. Most patients with JMML require allogeneic hematopoietic cell transplantation (HCT) as a curative therapy. A Japanese retrospective analysis demonstrated favorable outcomes for a busulfan (BU) + fludarabine (FLU) + melphalan (MEL) regimen, with an overall survival (OS) of 72% and an event-free survival (EFS) of 53%. To further validate the efficacy and safety of this regimen, the Japan Pediatric Leukemia/Lymphoma Study Group (JPLSG) conducted a nationwide prospective study, JMML-11. Between July 2011 and June 2017, 28 patients with newly diagnosed JMML were enrolled in JMML11. Low-dose chemotherapy for tumor control before HCT was recommended, and patients treated with AML-type

Hematopoietic stem cell transplants for inherited metabolic disorders performed at Tokai University Hospital between June 5, 1986, and May 28, 2021, were analyzed and compared between the period before 2007 and the period from 2007 onward based on availability of medical resources. Transplants were performed for 38 patients with mucopolysaccharidosis, 33 with adrenoleukodystrophy, and 16 with another disorder. Before 2007, oral busulfan-based regimens were mainly used. From 2007 onward, intravenous busulfan-based regimens or 4 Gy of thoracoabdominal irradiation (TAI), fludarabine, and melphalan (Mel)/treosulfan were adopted. Between 2002 and 2010, adrenoleukodystrophy was treated with 12 Gy of TAI and Mel. HLA-identical sibling bone marrow was used in 43

Introduction Fanconi anemia (FA) is an inherited bone marrow failure syndrome characterized with chromosomal instability and a high propensity to myeloid malignancy. Although causative genes have been identified in most patients, the genetic background of the leukemic transformation in FA has not been fully understood. Methods We studied 2 acute myeloid leukemia (AML) and 7 myelodysplastic syndromes (MDS) developed in patients with FA using whole-genome sequencing and analyzed somatic mutations, structural variants and copy number alterations. Results The number of somatic mutations and copy number alterations (CNAs) in AML were 1,071 mutations and 4 CNAs per patient on average, which tended to be higher than those in MDS (265 mutations and 2.3 CNAs per patient). For mutational signatures, three known signatures were identified, which included SBS1 and SBS5 caused by endogenous mutational processes, and SBS3 related to defective homologous recombination. Mutations and structural variants affected known driver genes in myeloid malignancies, such as RUNX1 (n = 3), ASXL1 (n = 1), CBL (n = 1), NRAS (n = 1) and KDM6A (n = 1). Recurrent copy number alterations were more frequently detected, including +3q (n = 6), +1q (n = 4) and -7q (n = 2). The majority of these CNAs were clonal and all but one patient harbored either of +3q or +1q, indicating the early acquisition of copy number changes and their driver role in leukemic transformation. Conclusions Myeloid neoplasms related with FA were characterized by a unique pattern of CNAs and common driver mutations in myeloid malignancies.

Background Fanconi anemia (FA) is an inherited bone marrow failure syndrome which develops on the basis of defective cellular responses to DNA damage. Aldehyde degradation deficiency (ADD) syndrome has been recently found as a disease caused by the defect of degradation of endogenous formaldehyde, which shares similar clinical features with FA. Although genomic abnormalities in these diseases have been associated with the high propensity of myeloid malignancies such as myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), the mechanism of the early development of MDS/AML remains unclear. Therefore, in this study, we aimed to understand the mechanism of the development of hematological malignancies by analyzing the genomic abnormalities seen in these diseases. Method We performed whole-exome sequencing (WES) and whole-genome sequencing (WGS) for 2 AML and 6 MDS developed in Japanese patients with FA (n = 6) and ADD syndrome (n = 2). Skin or bone marrow fibroblasts derived from the same patients were also studied as germline controls. We investigated somatic mutations, structural variants (SVs), and copy number alterations (CNAs) by WES and WGS. Mutational signature was analyzed to understand the mutational processes in these diseases. Result The number of somatic mutations and CNAs in AML identified by WES were 24 and 5 per patient on average, respectively, which were higher than those in MDS (6.8 mutations and 1.8 CNAs per patient) (P=0.07 and 0.06, respectively). However, no significant difference was observed for the number of SVs identified by WGS between MDS (35 counts per patient) and AML (52 counts per patient). Somatic mutations affected known driver genes in myeloid malignancies, such as RUNX1 (n = 1), ASXL1 (n = 1), SRSF2 (n = 1) and NRAS (n = 1) (Figure1). SVs also involved known driver genes in myeloid malignancies, such as CBL (n = 1), KDM6A (n = 1), PHF6 (n = 1), and RUNX1 (n = 1). In total, RUNX1 was most frequently altered (2/6, 33%). CNAs were more frequently accumulated in recurrent regions, including +1q (n = 5), +3q (n = 4), and -7q (n = 2) (Figure1). As previously reported, MDM4 and EVI1 were contained in +1q and +3q, respectively. Higher cancer cell fraction implied that most of these copy number changes were clonal, which suggested the early acquisition of copy number changes and their driver role in leukemic transformation. For mutational signatures, three known signatures were identified, which included clock-like SBS1 and SBS5 caused by endogenous mutational processes, and SBS3 related to defective homologous recombination. In addition, a novel mutational signature (Sig-A) was also detected. SBS3 and Sig-A were mainly detected in patients with FA and ADD syndrome, respectively, indicating that the different mutational processes are operating in the two diseases. Conclusion WES and WGS revealed the genetic landscape of FA and ADD syndrome mutation accumulation. Myeloid neoplasms related with FA and ADD syndrome were characterized by a unique pattern of driver mutations and CNAs, such as RUNX1 mutations/SVs, +1q and +3q. Although the two diseases share some clinical features, our study has revealed the different mutational processes in these diseases. Further investigation is warranted to reveal the underling mechanisms of mutation accumulation and the role of driver mutations in these diseases.

Fanconi anemia (FA) is a disorder of genomic instability characterized by progressive bone marrow failure (BMF), developmental abnormalities, and an increased susceptibility to cancer. Although various consequences inhematopoietic stem/progenitor cells havebeenattributed to FA-BMF, thequest to identify the initial pathological event is still ongoing. To address this issue, we established induced pluripotent stem cells (iPSCs) from fibroblasts of six patients with FA and FANCAmutations. An improved reprogramming method yielded iPSC-like colonies from all patients, and iPSC clones were propagated from two patients. Quantitative evaluation of the differentiation ability demonstrated that the differentiation propensity toward the hematopoietic and endothelial lineages is already defective in early hemoangiogenic progenitors. The expression levels of critical transcription factors were significantly downregulated in these progenitors. These data indicate that the hematopoietic consequences in FA patients originate from the early hematopoietic stage and highlight the potential usefulness of iPSC technology for elucidating the pathogenesis of FA-BMF. STEM CELLS TRANSLATIONAL MEDICINE 2015;4:1–6

SLX4/FANCP is a key Fanconi anemia (FA) protein and a DNA repair scaffold for incision around a DNA interstrand crosslink (ICL) by its partner XPF nuclease. The tandem UBZ4 ubiquitin-binding domains of SLX4 are critical for the recruitment of SLX4 to damage sites, likely by binding to K63-linked polyubiquitin chains. However, the identity of the ubiquitin E3 ligase that mediates SLX4 recruitment remains unknown. Using small interfering RNA (siRNA) screening with a GFP-tagged N-terminal half of SLX4 (termed SLX4-N), we identify the RNF168 E3 ligase as a critical factor for mitomycin C (MMC)-induced SLX4 foci formation. RNF168 and GFP-SLX4-N colocalize in MMC-induced ubiquitin foci. Accumulation of SLX4-N at psoralen-laser ICL tracks or of endogenous SLX4 at Digoxigenin-psoralen/UVA ICL is dependent on RNF168. Finally, we find that RNF168 is epistatic with SLX4 in promoting MMC tolerance. We conclude that RNF168 is a critical component of the signal transduction that recruits SLX4 to ICL damage.

The risk of carcinogenesis increases after 20 years old in patients with Fanconi anemia (FA). We herein report three rare cases of FA combined with esophageal cancer in women; all patients were diagnosed with FA in early childhood. Patients 1 and 2 were diagnosed with advanced and superficial esophageal cancer, respectively, at 21 and 30 years old, respectively. Patient 3 was diagnosed with superficial esophageal cancer, underwent curative surgery at 26 years old, and survived for over 5 years without recurrence. Therefore, establishing a protocol for the early detection of esophageal cancer in FA patients over 20 years old is important.

Fanconi anemia is a rare recessive disease characterized by multiple congenital abnormalities, progressive bone marrow failure, and a predisposition to malignancies. It results from mutations in one of the 22 known FANC genes. The number of Japanese Fanconi anemia patients with a defined genetic diagnosis was relatively limited. In this study, we reveal the genetic subtyping and the characteristics of mutated FANC genes in Japan and clarify the genotype-phenotype correlations. We studied 117 Japanese patients and successfully subtyped 97% of the cases. FANCA and FANCG pathogenic variants accounted for the disease in 58% and 25% of Fanconi anemia patients, respectively. We identified one FANCA and two FANCG hot spot mutations, which are found at low percentages (0.04-0.1%) in the whole-genome reference panel of 3,554 Japanese individuals (Tohoku Medical Megabank). FANCB was the third most common complementation group and only one FANCC case was identified in our series. Based on the data from the Tohoku Medical Megabank, we estimate that approximately 2.6% of Japanese are carriers of disease-causing FANC gene variants, excluding missense mutations. This is the largest series of subtyped Japanese Fanconi anemia patients to date and the results will be useful for future clinical management.

Reactive aldehydes arise as by-products of metabolism and are normally cleared by multiple families of enzymes. We find that mice lacking two aldehyde detoxifying enzymes, mitochondrial ALDH2 and cytoplasmic ADH5, have greatly shortened lifespans and develop leukemia. Hematopoiesis is disrupted profoundly, with a reduction of hematopoietic stem cells and common lymphoid progenitors causing a severely depleted acquired immune system. We show that formaldehyde is a common substrate of ALDH2 and ADH5 and establish methods to quantify elevated blood formaldehyde and formaldehyde-DNA adducts in tissues. Bone-marrow-derived progenitors actively engage DNA repair but also imprint a formaldehyde-driven mutation signature similar to aging-associated human cancer mutation signatures. Furthermore, we identify analogous genetic defects in children causing a previously uncharacterized inherited bone marrow failure and pre-leukemic syndrome. Endogenous formaldehyde clearance alone is therefore critical for hematopoiesis and in limiting mutagenesis in somatic tissues.

Hematopoietic stem cell transplantation (HSCT) is the only curative treatment for juvenile myelomonocytic leukemia (JMML), but few large studies of HSCT for JMML exist. Using data from the Japan Society for Hematopoietic Cell Transplantation registry, we analyzed the outcomes of 129 children with JMML who underwent HSCT between 2000 and 2011. The 5-year overall survival (OS) rate and cumulative incidence of relapse were 64% and 34%, respectively. A regimen of busulfan/fludarabine/melphalan was the most commonly used (59 patients) and provided the best outcomes; the 5-year OS rate reached 73%, and the cumulative incidences of relapse and transplantation-related mortality were 26% and 9%, respectively. In contrast, the use of the irradiation-based myeloablative regimen was the most significant risk factor for OS (hazard ratio [HR], 2.92; P = .004) in the multivariate model. In addition, chronic graft-versus-host disease (GVHD) was strongly associated with lower relapse (HR, 0.37; P = .029) and favorable survival (HR, 0.22; P = .006). The current study has shown that a significant proportion of children with JMML can be cured with HSCT, especially those receiving the busulfan/fludarabine/melphalan regimen. Based on the lower relapse and better survival observed in patients with chronic GVHD, additional treatment strategies that focus on enhancing graft-versus-leukemia effects may further improve survival. (C) 2019 American Society for Transplantation and Cellular Therapy. Published by Elsevier Inc.

We retrospectively analyzed nationwide records of 163 Fanconi anemia (FA) patients [aplastic anemia (AA), n = 118; myelodysplastic syndrome (MDS), n = 30; acute leukemia, n = 15] who underwent first allogeneic hematopoietic stem cell transplantation (HSCT) between 1987 and 2015 in Japan. An alternative donor was used in 119 (73%) patients, and 160 (98%) patients received a non-T-cell-depleted graft. With an 8.7-year median follow-up, 5-year overall survival (OS) was 81%. The 5-year OS was significantly higher in AA patients than in MDS and acute leukemia patients (89%, 71%, and 44%, respectively). In the MDS/leukemia group, factors associated with poor outcome in univariate analysis were older age at HSCT (≥ 18 years), conditioning regimen without anti-thymocyte or lymphocyte globulin, and grade II–IV acute graft-versus-host disease. After 1 year, of 137 survivors, 15 developed subsequent malignancies, of whom 12 were diagnosed with head and neck (HN)/esophageal cancer. An irradiation regimen and older age were associated with the risk of HN/esophageal cancer. Five of seven deaths were attributed to subsequent malignancies more than 5 years after HSCT. On the basis of the risk factors for HSCT in MDS/leukemia patients and subsequent malignancies, a more effective HSCT approach is required.

Fludarabine/cyclophosphamide-based conditioning regimens are standard in bone marrow transplantation (BMT) for acquired bone marrow failure in children, however, graft failure may occur. Using the data from a nationwide transplantation registry, we compared the outcomes of children aged <16 years with acquired aplastic anemia and refractory cytopenia of childhood who underwent allogeneic BMT with either fludarabine/melphalan (n = 71) or fludarabine/cyclophosphamide (n = 296) between 2000 and 2016. The fludarabine/melphalan regimen provided excellent outcomes, with 3-year overall survival and failure-free survival rates of 98% and 97%, respectively. The 83% 3-year failure-free survival in the fludarabine/cyclophosphamide group was significantly inferior (P = 0.002), whereas the overall survival did not differ between the two groups. Late graft failure was the most common cause of treatment failure in the fludarabine/cyclophosphamide group, which experienced a significantly higher incidence of late graft failure than the fludarabine/melphalan group (11% vs. 3%; P = 0.035). Multivariate analyses showed that the fludarabine/melphalan regimen was associated with a better failure-free survival (hazard ratio [HR] 0.12; P = 0.005) and lower risk of late graft failure (HR 0.16; P = 0.037). Fludarabine/melphalan-based conditioning regimen can be a promising option for children with acquired bone marrow failure receiving BMT.