Genome gains at chromosome 21q21/22 segment leads to co-amplification of Down Syndrome Critical Regions and known oncogenes in a case of donor cell-derived acute myeloid leukaemia following allogeneic sex mismatched umbilical cord blood transplantation for chronic myeloid leukaemia

Genetics of donor cell leukemia in acute myelogenous leukemia and myelodysplastic syndrome

Allogeneic hematopoietic stem cell transplantation (HSCT) is an important therapeutic modality for patients with acute myelogenous leukemia (AML) with poor risk features. Nonetheless, roughly 30% of such patients have leukemia recurrence and up to 2% of these are donor-derived leukemias, in which malignancy develops in the donor's transplanted cells, despite extremely low rates of leukemia in the donors themselves. Notably, over 20% of these malignancies carry chromosome 7 abnormalities nearly all of which are monosomies. Recent advances in whole exome and genome sequencing have allowed for detection of candidate genes that likely contribute to the development of AML in donor cells (donor leukemia, DCL). These genes include CEBPA, GATA2, JAK2, RUNX1, DDX41, EZH2, IDH1/2, DNMT3A, ASXL1, XPD, XRCC3, and CHEK1. The potential roles of variants in these genes are evaluated based on familial clustering of MDS/AML and corresponding animal studies demonstrating their leukemogenic nature. This review describes the spectrum of genetic aberrations detected in DCL cases in the literature with regard to the character of the individual cases, existing family cohorts that carry individual genes, and functional studies that support etiologic roles in AML development. DCL presents a unique opportunity to examine genetic variants in the donors and recipients with regards to progression to malignancy.

Jumping translocations of 1q in donor cell-derived myelodysplastic syndrome after cord blood transplantation: Case report and review of the literature

Donor cell-derived leukemia and myelodysplastic syndrome (DCL) is a rare complication in patients after allogenic stem cell transplantation (SCT). Since 1971, numerous cases of DCL have been reported, but the detailed mechanisms of DCL are still unclear. A patient with jumping translocations (JTs) of 1q in umbilical cord blood donor cell-derived myelodysplastic syndrome (MDS), which likely occurred due to genetic alterations of TET2 and ASXL1 after cord blood transplantation (CBT), was examined in this study. Previously reported DCL cases after CBT that focused on the cytogenetic and molecular characteristics of these patients and patient outcome were reviewed. A total of 30 cases of DCL after CBT were identified between 2005 and 2018. The median time from CBT to the development of DCL was 16 months. The number of patients with DCL who were diagnosed with acute myeloid leukemia (AML) and MDS was 19 and 8, respectively. JTs were frequently observed in 5 of 27 DCL patients who had cytogenetic abnormalities, including our patient. Molecular abnormalities were described in 7 of the cases, and the most frequent abnormality was an NPM1 mutation. Other gene mutations that were usually found in de novo MDS or AML were observed in JT-DCL after CBT. From these results, chromosomal abnormalities such as JTs that occur subsequent to genetic alterations were seemed an important mechanisms underlying DCL onset in patients after CBT. Further molecular analyses regarding the genetic alterations of JTs are required to understand the pathogenesis of umbilical cord blood-derived JT-DCL.

Donor cell-derived leukemia after cord blood transplantation and a review of the literature: differences between cord blood and BM as the transplant source

Donor cell-derived leukemia (DCL) is a rare complication of SCT. Here, we present a case of DCL following cord blood transplantation (CBT) and review the clinical features of previously reported DCL. To our knowledge, this is the first report comparing clinical characteristics of DCL from the standpoint of the transplant source, with umbilical cord blood and BM. AML and myelodysplastic syndrome (MDS) were recognized more frequently in DCL after CBT, whereas the incidence of AML and ALL was similar after BMT. The median duration between the occurrence of DCL following CBT and BMT was 14.5 and 36 months, respectively. DCL occurred in a significantly shorter period after CBT than after BMT. Abnormal karyotypes involving chromosome 7 were observed in 52.4% of CBT recipients and 17.3% of BMT recipients; this was a statistically significant difference. Particularly, the frequency of monosomy 7 was significantly higher in DCL after CBT than after BMT. The types of abnormal karyotypes in DCL following BMT were similar to those characteristically observed in adult de novo AML and MDS. DCL patients generally have a poor prognosis in both groups. SCT is the best treatment for curing DCL. DCL appears to have different clinical features according to the transplant source.

Amplified segment in the 'Down syndrome critical region' on HSA21 shared between Down syndrome and euploid AML-M0 excludes RUNX1, ERG and ETS2

Children with Down syndrome have a 20- to 50-fold increased risk of acute lymphocytic or myeloid leukaemia. Whole or partial gains of chromosome 21 have been described in multiple childhood leukaemias, and have recently been reported as a likely primary event in B-precursor-acute lymphoblastic leukaemia. It is unclear which amplified gene(s) on chromosome 21 play a key role in leukaemia progression. We describe a minimal amplified segment within the so-called 'Down syndrome critical region' shared between two cases of AML-M0; a Down syndrome, and a constitutionally normal individual. Interestingly, the amplified region does not include the oncogenes RUNX1, ETS2 and ERG.