Dnmt3a-null hematopoietic stem and progenitor cells expand after busulfan treatment

• Published in: Experimental hematology 2020-11, Vol.91, p.39-45.e2
• Main Authors: Chen, Jichun, Matatall, Katie A., Feng, Xingmin, Hormaechea-Agulla, Daniel, Maharjan, Mukesh, Young, Neal, King, Katherine Y.
• Format: Article
• Language: English
• Subjects: Animals; Bone Marrow - pathology; Busulfan - pharmacology; Cell Division - drug effects; Cell Lineage; Clone Cells; DNA (Cytosine-5-)-Methyltransferases - deficiency; Fluorouracil - pharmacology; Hematopoiesis - genetics; Hematopoietic Cell Growth Factors - pharmacology; Hematopoietic Stem Cell Mobilization; Hematopoietic Stem Cell Transplantation; Hematopoietic Stem Cells - cytology; Hematopoietic Stem Cells - drug effects; Mice; Radiation Chimera
• ISSN: 0301-472X; 1873-2399
• DOI: 10.1016/j.exphem.2020.09.192

•Busulfan and a variety of chemotherapy agents such as 5-fluorouracil are commonly used as preconditioning agents before hematopoietic stem cell transplant.•Busulfan treatment, but not 5-fluorouracil, leads to a relative expansion of Dnmt3a-null HSCs compared with WT HSCs in the bone marrow of mice with mixed bone marrow.•The mutational profile of HSCT recipients and donors, especially older individuals with a high likelihood of clonal hematopoiesis, should be taken into consideration when choosing a preconditioning agent. Mutations in the gene encoding DNA methyltransferase 3A (DNMT3A) comprise the majority of mutations found in clonal hematopoiesis (CH), an age-related condition that was recently found to affect outcomes in patients undergoing hematopoietic stem cell transplant (HSCT). Recent studies have indicated that patients with CH have worse prognoses after HSCT, suggesting stress imposed by HSCT preconditioning agents may impact hematopoietic stem cell (HSC) dynamics in transplant recipients. In this study, we used a competitive transplantation mouse model to investigate how treatment with the common preconditioning agents 5-fluorouracil (5-FU) and busulfan (BU) affect the prevalence of Dnmt3a–/– HSCs and progenitor cells in competition with wild-type cells. We found that, though sufficient to deplete peripheral blood counts, 5-FU preconditioning did not significantly alter the frequency of Dnmt3a-null hematopoietic stem and progenitor cells (HSPCs) in mosaic mice. In contrast, mice treated with BU had a sevenfold decline in total bone marrow cells and an increase in Dnmt3a-null HSPCs that was detectable in peripheral blood. Indeed, even though all mosaic mice had a starting engraftment of ∼10%–40%, 85%–100% of HSPCs were Dnmt3a-null in four of seven mice after BU treatment, indicating these cells expand dramatically during recovery. Overall, these results suggest that individual preconditioning regimens have different effects on the expansion of Dnmt3a-mutant cells in patients with pre-existing CH. Thus, the presence of CH-associated mutants should be evaluated prior to selecting preconditioning regimens for HSCT. [Display omitted]