Integrated genetic and epigenetic analysis revealed heterogeneity of acute lymphoblastic leukemia in Down syndrome.

Children with Down syndrome (DS) are at a 20-fold increased risk for acute lymphoblastic leukemia (ALL). Compared to children with ALL and no DS (non-DS-ALL), those with DS and ALL (DS-ALL) harbor uncommon genetic alterations, suggesting DS-ALL could have distinct biological features. Recent studies have implicated several genes on chromosome 21 in DS-ALL, but the precise mechanisms predisposing children with DS to ALL remain unknown. Our integrated genetic/epigenetic analysis revealed that DS-ALL was highly heterogeneous with many subtypes. Although each subtype had genetic/epigenetic profiles similar to those found in non-DS-ALL, the subtype distribution differed significantly between groups. The Philadelphia chromosome-like subtype, a high-risk B-cell lineage variant relatively rare among the entire pediatric ALL population, was the most common form in DS-ALL. Hypermethylation of RUNX1 on chromosome 21 was also found in DS-ALL, but not non-DS-ALL. RUNX1 is essential for differentiation of blood cells, especially B cells; thus, hypermethylation of the RUNX1 promoter in B-cell precursors might be associated with increased incidence of B-cell precursor ALL in DS patients.

[Relapsed acute myeloid leukemia with Down syndrome showing long disease-free survival after bone marrow transplantation].

We report a sixteen-year-old boy with Down syndrome and relapse of AML (M7), who has been in complete remission (CR) more than 12 months after bone marrow transplantation (BMT) from an HLA-matched sibling donor. Because monosomy 7 was detected at onset of AML and he experienced relapse after the treatment of AML 99 Down protocol, his prognosis was considered very poor. However, he achieved CR following chemotherapy that included high-dose AraC and BMT from an HLA-matched sibling donor without severe complication. He has remained in CR for more than 12 months after BMT. In this case, GATA1 mutation was not detected at either onset or relapse of AML and it is suggested that this case is in a different risk group than the usual Down syndrome patient with AML showing GATA1 mutation.

Acute renal failure after high-dose methotrexate therapy in a patient with ileostomy.

High-dose methotrexate (HD-MTX) is an important treatment for Burkitt lymphoma, but can cause hepatic and renal toxicity when its clearance is delayed. We report a case of acute renal failure after HD-MTX therapy in a patient with ileostomy, The patient was a 3-year-old boy who had received a living-related liver transplantation for congenital biliary atresia. At day 833 after the transplantation, he was diagnosed with PTLD (post-transplantation lymphoproliferative disorder, Burkitt-type malignant lymphoma). During induction therapy, he suffered ileal perforation and ileostomy was performed. Subsequent HD-MTX therapy caused acute renal failure that required continuous hemodialysis. We supposed that intravascular hypovolemia due to substantial drainage from the ileostoma caused acute prerenal failure. After recovery of his renal function, we could safely treat the patient with HD-MTX therapy by controlling drainage from ileostoma with total parenteral nutrition.

Loss of DNA Damage Response in Neuroblastoma and Utility of a PARP Inhibitor.

Background: Neuroblastoma (NB) is the most common solid tumor found in children, and deletions within the 11q region are observed in 11% to 48% of these tumors. Notably, such tumors are associated with poor prognosis; however, little is known regarding the molecular targets located in 11q. Methods: Genomic alterations of ATM , DNA damage response (DDR)-associated genes located in 11q ( MRE11A, H2AFX , and CHEK1 ), and BRCA1, BARD1, CHEK2, MDM2 , and TP53 were investigated in 45 NB-derived cell lines and 237 fresh tumor samples. PARP (poly [ADP-ribose] polymerase) inhibitor sensitivity of NB was investigated in in vitro and invivo xenograft models. All statistical tests were two-sided. Results: Among 237 fresh tumor samples, ATM, MRE11A, H2AFX , and/or CHEK1 loss or imbalance in 11q was detected in 20.7% of NBs, 89.8% of which were stage III or IV. An additional 7.2% contained ATM rare single nucleotide variants (SNVs). Rare SNVs in DDR-associated genes other than ATM were detected in 26.4% and were mutually exclusive. Overall, samples with SNVs and/or copy number alterations in these genes accounted for 48.4%. ATM-defective cells are known to exhibit dysfunctions in homologous recombination repair, suggesting a potential for synthetic lethality by PARP inhibition. Indeed, 83.3% NB-derived cell lines exhibited sensitivity to PARP inhibition. In addition, NB growth was markedly attenuated in the xenograft group receiving PARP inhibitors (sham-treated vs olaprib-treated group; mean [SD] tumor volume of sham-treated vs olaprib-treated groups = 7377 [1451] m 3 vs 298 [312] m 3 , P = .001, n = 4). Conclusions: Genomic alterations of DDR-associated genes including ATM, which regulates homologous recombination repair, were observed in almost half of NBs, suggesting that synthetic lethality could be induced by treatment with a PARP inhibitor. Indeed, DDR-defective NB cell lines were sensitive to PARP inhibitors. Thus, PARP inhibitors represent candidate NB therapeutics.

Identification of the genetic and clinical characteristics of neuroblastomas using genome-wide analysis.

To provide better insight into the genetic signatures of neuroblastomas, we analyzed 500 neuroblastomas (included specimens from JNBSG) using targeted-deep sequencing for 10 neuroblastoma-related genes and SNP arrays analysis. ALK expression was evaluated using immunohistochemical analysis in 259 samples. Based on genetic alterations, the following 6 subgroups were identified: groups A (ALK abnormalities), B (other gene mutations), C (MYCN amplification), D (11q loss of heterozygosity [LOH]), E (at least 1 copy number variants), and F (no genetic changes). Groups A to D showed advanced disease and poor prognosis, whereas groups E and F showed excellent prognosis. Intriguingly, in group A, MYCN amplification was not a significant prognostic marker, while high ALK expression was a relevant indicator for prognosis (P = 0.033). Notably, the co-existence of MYCN amplification and 1p LOH, and the co-deletion of 3p and 11q were significant predictors of relapse (P = 0.043 and P = 0.040). Additionally, 6q/8p LOH and 17q gain were promising indicators of survival in patients older than 5 years, and 1p, 4p, and 11q LOH potentially contributed to outcome prediction in the intermediate-risk group. Our genetic overview clarifies the clinical impact of genetic signatures and aids in the better understanding of genetic basis of neuroblastoma.