Clonal evolution and devolution after chemotherapy in adult acute myelogenous leukemia

The frequent occurrence of persistent or relapsed disease after induction chemotherapy in AML necessitates a better understanding of the clonal relationship of AML in various disease phases. In this study, we used SNP 6.0 array-based genomic profiling of acquired copy number aberrations (aCNA) and copy neutral LOH (cnLOH) together with sequence analysis of recurrently mutated genes to characterize paired AML genomes. We analyzed 28 AML sample pairs from patients who achieved complete remission with chemotherapy and subsequently relapsed and 11 sample pairs from patients with persistent disease after induction chemotherapy. Through review of aCNA/cnLOH and gene mutation profiles in informative cases, we demonstrate that relapsed AML invariably represents re-emergence or evolution of a founder clone. Furthermore, all individual aCNA or cnLOH detected at presentation persisted at relapse indicating that this lesion type is proximally involved in AML evolution. Analysis of informative paired persistent AML disease samples uncovered cases with 2 coexisting dominant clones of which at least one was chemotherapy sensitive and one resistant, respectively. These data support the conclusion that incomplete eradication of AML founder clones rather than stochastic emergence of fully unrelated novel clones underlies AML relapse and persistence with direct implications for clinical AML research.