Emergence of an unrelated highly aberrant clone in an AML patient at relapse four months after peripheral blood stem cell transplantation

Mutation position within evolutionary subclonal architecture in AML

Cytogenetic data suggest that acute myeloid leukemia (AML) develops through a process of branching evolution, especially during relapse and progression. Recent genomic data from AML cases using digital sequencing, temporal comparisons, xenograft cloning, and single-cell analysis indicate that most, if not all, AML cases emerge through branching evolution. According to a review of the current literature, the balanced translocations (t[15;17], t[8;21], and inv[16]) and nucleotide variants in DNMT3A and TET2 most commonly occur in the founding clone at diagnosis. These mutations are rarely gained or lost at relapse, and the latter 2 mutations are observed in elderly subjects with mosaic hematopoiesis antedating overt leukemia. In contrast, +8, +13, +22, -X, -Y, and nucleotide variants in FLT3, NRAS/KRAS, WT1, and KIT frequently occur in subclones and are observed either to emerge or to be lost at relapse. Because drugs that target mutations within a subclone are unlikely to eliminate all leukemic cells, it will be essential to understand not only which mutations a patient has but also how they organize within the leukemic subclonal architecture.