Whole-exome sequencing reveals acquisition of mutations leading to the onset of donor cell leukemia after hematopoietic transplantation: a model of leukemogenesis

Germline assessment for alloHSCT candidates over 50 years: A 'Fast-Track' screening in myeloid neoplasms

Patients aged 50 or above diagnosed with myeloid neoplasms (MNs) are typically not candidates for germline testing. However, approximately 8% carry pathogenic germline variants. Allogeneic haematopoietic stem cell transplantation (alloHSCT) remains an option for those aged over 50; neglecting germline testing could mask the risk for relative donor cell-derived MN. We propose a germline-augmented somatic panel (GASP), combining MN predisposition genes with a myeloid somatic panel for timely germline variant identification when initial testing is not indicated. Out of our 133 whole-exome-sequenced MN cases aged over 50 years, 9% had pathogenic/likely variants. GASP detected 92%, compared to 50% with somatic-only panel. Our study highlights the relevance of germline screening in MN, particularly for alloHSCT candidates without established germline-testing recommendations.

Lessons Learned from Donor Cell-Derived Myeloid Neoplasms: Report of Three Cases and Review of the Literature

Donor-cell derived myeloid neoplasm (DDMN), a rare complication after allogeneic hematopoietic cell transplantation (HCT), is of interest for its potential to reveal donor-derived and host-derived factors that contribute to the pathogenesis of leukemia. The accurate diagnosis of donor-derived leukemias has been facilitated by the more frequent use of molecular techniques. In this study, we describe three additional cases of DDMN; the first reported case of donor-derived chronic myelomonocytic leukemia (CMML), one acute myeloid leukemia (AML) with t(8;21)(q22;22); RUNX1-RUNX1T1 and one donor-derived MDS with deletion 5q. A review of the cytogenetic profiles of previously reported DDMN indicates a significant contribution of therapy-related myeloid neoplasms. Cases with direct evidence of donor- or recipient-dependent factors are rare; a role of direct transfer of leukemic cells, genomic instability of the donor, abnormal gene methylation in donor cells, proleukemic potential of abnormal stromal niche, and the role of immunological surveillance after transplantation has been observed. The role of additional potential pathogenetic factors that are without clinically observed evidence are also reviewed.

Donor cell leukemia/myelodysplastic syndrome after allogeneic stem cell transplantation: a rare phenomenon with more challenges for hematologists

Donor cell leukemia (DCL) or Donor cell myelodysplastic syndrome (DC-MDS) is a rare type of leukemia or MDS and originates from the donor cells. It has very low frequency, but it seems to be steadily increasing as the physiopathology and mechanisms remain largely unknown. Here we report one case of acute lymphocytic leukemia (ALL) and one case of MDS of donor origin after allogeneic hematopoietic stem cell transplantation (HSCT). We also collated and reviewed literatures regarding DCL, and discuss the morbidity of DCL, the methods used to confirm donor origin and the etiology and pathogenesis of DCL. A new proposed theory will help us to better understand the mechanism for the oncogenesis of DCL.

Clonal Hematopoiesis of Indeterminate Potential as a Novel Risk Factor for Donor-Derived Leukemia

Hematopoietic stem cell transplantation (HSCT) is a critical treatment modality for many hematological and non-hematological diseases that is being extended to treat older individuals. However, recent studies show that clonal hematopoiesis of indeterminate potential (CHIP), a common, asymptomatic condition characterized by the expansion of age-acquired somatic mutations in blood cell lineages, may be a risk factor for the development of donor-derived leukemia (DDL), unexplained cytopenias, and chronic graft-versus-host disease. CHIP may contribute to the pathogenesis of these significant transplant complications via various cell-autonomous and non-cell-autonomous mechanisms, and the clinical presentation of DDL may be broader than anticipated. A more comprehensive understanding of the contributions of CHIP to DDL may have important implications for the screening of donors and will improve the safety of HSCT. The objective of this review is to discuss studies linking DDL and CHIP and to explore potential mechanisms by which CHIP may contribute to DDL.

Stem cell donors should be screened for CHIP

This article has a companion Counterpoint by Gibson and Lindsley.

Establishment and characterization of HXWMF-1: the first mouse fibroblastic tumor cell line derived from leukemia-associated fibroblasts

Background

Chemo-resistance is still a major obstacle in leukemia treatment. Accumulating evidence indicates that cancer-associated fibroblasts (CAFs), the most abundant stromal cells in tumor microenvironment (TME), play a crucial role in cancer progression and response to chemotherapy. To Figure out the role of leukemia-associated fibroblasts (LAFs) in relapsed/refractory leukemia, we constructed the first leukemia-associated fibroblastic tumor cell line, HXWMF-1.

Methods

A cell culture technique was used to establish the leukemia-associated fibroblastic tumor cell line. Molecular and cellular biological techniques including flow cytometry, MTT assay, western blotting, and short tandem repeat (STR) analysis were used to characterize the cell line. Nude mice were used for xenograft studies.

Results

We established a LAFs derived tumor cell line HXWMF-1, originated from the subcutaneous xenografts of HXEX-ALL1, a cell line originated from a patient with acute lymphoblastic leukemia (ALL) at the second relapse. The HXWMF-1 cell line was authenticated as a tumor cell line and being derived from CAFs based on morphologic, immunophenotypic, cytogenetic and STR analyses and tumorigenicity test in nude mice. To clarify the reliability of the method, we got the LAFs derived tumor cells from three different tumor mass of HXEX-ALL1 xenografts.

Conclusions

To our knowledge, HXWMF-1 is the first fibroblastic tumor cell line derived from LAFs or CAFs. In addition, the cell line provided firm evidence for that leukemia cells may induce LAFs/CAFs malignant transformation, which may help to develop brand new theory and therapeutic strategies for patients with relapsed /refractory ALL.

Short Tandem Repeats (STRs) as Biomarkers for the Quantitative Follow-Up of Chimerism after Stem Cell Transplantation: Methodological Considerations and Clinical Application

Chimerism refers to the relative proportion of donor and recipient DNA after hematopoietic stem cell transplantation (HSCT) and its quantitative follow-up is of great clinical utility in this setting. PCR of short tandem repeats (STR-PCR) constitutes the gold standard method for chimerism quantification, although more sensitive PCR techniques (such as qPCR) have recently arisen. We compared the sensitivity and the quantification capacity of both techniques in patient samples and artificial mixtures and demonstrated adequate performance of both methods, with higher sensitivity of qPCR and better quantification skills of STR-PCR. By qPCR, we then prospectively followed up 57 patients that were in complete chimerism (CC) by STR-PCR. Twenty-seven patients (59%) showed 0.1–1% recipient DNA in the bone marrow. Only 4 patients presented 0.1–1% recipient DNA in peripheral blood (PB), and one of them relapsed. Finally, by qPCR, we retrospectively studied the last sample that showed CC by STR-PCR prior to relapse in 8 relapsed patients. At a median of 59 days prior to relapse, six patients presented mixed chimerism by qPCR in PB. Since both approaches have complementary characteristics, we conclude that different techniques should be applied in different clinical settings and therefore propose a methodological algorithm for chimerism follow-up after HSCT.

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.