Program DHC-Virtual
20 - 21 January 2021
Abstracts Myeloid session 4
Mutational consequences of hematopoietic stem cell transplantation in humans
21 January
10:24 10:36
F. Peci

Mutational consequences of hematopoietic stem cell transplantation in humans

Mirjam Belderbos Belderbos (1,2), Jurrian de Kanter (1,2), Flavia Peci (1,2), Eline Bertrums (1,2), Axel Rosendahl-Huber (1,2), Markus J. van Roosmalen (1,2), Mark Verheul (1,2), Rurika Oka (1,2), Arianne M. Brandsma (1,2), Marc Bierings (1), Ruben Van Boxtel (1,2)
(1) Princess Máxima Center for Pediatric Oncology, Medicine, Utrecht , (2) Oncode Institute, Utrecht
No potential conflicts of interest

Genetic instability can be a major drawback for successful application of stem cells in regenerative medicine. Hematopoietic stem cell transplantation (HSCT) is the first and most commonly applied type of stem cell therapy in humans, which is used in over 50,000 patients annually. Although mutations gradually accumulate in hematopoietic stem and progenitor cells (HSPCs) with age and can drive pathological clonal expansion, the consequences of transplantation on HSPC mutagenesis remain elusive. Here, we aimed to determine the mutational consequences of HSCT in human recipients and identify underlying mechanisms. 



To measure genome-wide mutations at single-cell resolution, we combined in vitro clonal expansion with whole genome sequencing (WGS). For this, we isolated CD34-positive hematopoietic stem and progenitor cells (HSPCs) from residual graft material and peripheral blood of pediatric HSCT recipients as well as their donors. We included six pediatric HSCT recipients, all transplanted for malignancy after chemotherapy-based myeloablative conditioning, with an umbilical cord blood (UCB, n=3) or matched sibling bone marrow donor (n=3). WGS data were filtered to correct for germline variants as well as in vitro acquired mutations, leaving only the somatic mutations that were present in the original HSPC. 


In the majority of subjects (26 clones of four recipients), we did not observe any mutational consequences of the HSCT procedure, and the mutation loads in the assessed HSPCs followed normal healthy aging. However, in five HSPCs of two UCB recipients, the somatic mutation load was increased at least 2-fold. This increase could be exclusively explained by a novel mutational process signature, which is characterized by C > A transversions at CpA dinucleotides. Using in-house and publicly available cancer sequencing databases, we detected the same mutational signature in a therapy-related AML that arose after HSCT as well as in two solid tumors of patients who underwent renal transplantation early in life. 


Our study provides evidence for transplantation-associated stem cell mutagenesis in humans as well as insight into the underlying processes and potential adverse health consequences.