The rate of spontaneous mutations in human myeloid cells

Abstract

The mutation rate (μ) is likely to be a key parameter in leukemogenesis, but historically, it has been difficult to measure in humans. The PIG-A gene has some advantages for the detection of spontaneous mutations because it is X-linked, and therefore only one mutation is required to disrupt its function. Furthermore, the PIG-A-null phenotype is readily detected by flow cytometry. Using PIG-A, we have now provided the first in vitro measurement of μ in myeloid cells, using cultures of CD34+ cells that are transduced with either the AML-ETO or the MLL-AF9 fusion genes and expanded with cytokines. For the AML-ETO cultures, the median μ value was ∼ 9.4 × 10-7 (range ∼ 3.6 to 23 × 10-7) per cell division. In contrast, few spontaneous mutations were observed in the MLL-AF9 cultures. Knockdown of p53 or introduction of mutant NRAS or FLT3 alleles did not have much of an effect on μ. Based on these data, we provide a model to predict whether hypermutability must occur in the process of leukemogenesis.

MSH6 haploinsufficiency at relapse contributes to the development of thiopurine resistance in pediatric B-lymphoblastic leukemia

“… 34 To investigate the effect of MSH6 disruption on the rate of spontaneous mutations in PIG-A , which is required for expression of GPI, we used a flow cytometry-based assay that measures surface expression of several GPI-dependent markers (CD48, CD52, and CD59). 22 , 35 Although there was a trend to suggest that 697 MSH6 shRNA1 cells had a slightly higher mutation rate, statistical significance was not achieved ( Figure 5B ). Furthermore, treatment of the clones from each cell line with 6-TG did not lead to an increased mutation rate ( Figure 5B ).…”

The leukemia-associated RUNX1/ETO oncoprotein confers a mutator phenotype

“… 8 The mechanisms driving the acquisition of co-operating mutations remain unclear, although there is evidence that initiating lesions such as RUNX1/ETO may promote mutagenesis. 9 , 10 For example, ectopic expression of RUNX1/ETO downregulates several DNA-repair proteins (BRCA2, OGG1 and ATM) and increases the level of phosphorylated TP53 and γH2AX, indicating elevated DNA damage and a possible pro-mutagenic phenotype. 10 , 11 …”

Towards Quantitative Systems Pharmacology Models of Chemotherapy‐Induced Neutropenia

“…Most authors who have studied hematopoietic models with random dynamics have done so with the focus being the development of cancers (with detailed review in Ref. ).…”