Donor cell leukemia after umbilical cord blood transplantation: recurrent or de novo? The importance of diagnosis for therapeutic decision making

Hypothesis: can transfer of primary neoplasm-derived extracellular vesicles and mitochondria contribute to the development of donor cell-derived hematologic neoplasms after allogeneic hematopoietic cell transplantation?

Allogeneic hematopoietic cell transplantation (allo-HCT) is an essential treatment option for various neoplastic and non-neoplastic hematologic diseases. Although its efficacy is modest, a significant proportion of patients experience relapse, graft-versus-host disease, infection or impaired hematopoiesis. Among these, the most frequent cause of post-transplant mortality is relapse, whereas the development of de novo hematologic neoplasms from donor cells after allo-HCT occurs on some occasion as a rare complication. The mechanisms involved in the pathogenesis of the de novo hematologic neoplasms from donor cells are complex, and a multifactorial process contributes to the development of this complication. Recently, extracellular vesicles, particularly exosomes, and mitochondria have been shown to play crucial roles in intercellular communication through the transfer of specific constituents, such as deoxyribonucleic acids, ribonucleic acids, lipids, metabolites and cytosolic and cell-surface proteins. Here, I discuss the potential causative roles of these subcellular components in the development of de novo hematologic neoplasms from donor cells after allo-HCT, in addition to other etiologies.

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.