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Genomic Analysis of Relapsed Pediatric Acute Lymphoblastic Leukemia

ABSTRACT:

Although multi-agent combination chemotherapy is curative in a significant fraction of childhood acute lymphoblastic leukemia (ALL) patients, 20% of cases relapse and most die due to chemo-refractory disease. Here we used whole-exome and whole-genome sequencing to analyze the mutational landscape and pattern of clonal evolution at relapse in pediatric ALL cases. These analyses showed that ALL relapses originate from a common ancestral precursor clone of the diagnosis and relapsed populations and frequently harbor mutations implicated in chemotherapy resistance. RAS-MAPK pathway activating mutations in NRAS, KRAS and PTPN11 were present in 24/55 (44%) cases in our series. Notably, while some cases showed emergence of RAS mutant clones at relapse, in others, RAS mutant clones present at diagnosis were replaced by RAS wild type populations. Mechanistically, functional dissection of mouse and human wild type Kras and mutant Kras (Kras G12D) isogenic leukemia cells demonstrated induction of methotrexate resistance, but also improved response to vincristine, in mutant Kras- expressing lymphoblasts. These results identify chemotherapy driven selection as a central mechanism of leukemia clonal evolution and pave the road for the development of tailored personalized therapies for the treatment of relapsed ALL.

PROVIDER: phs001072 | dbGaP |

SECONDARY ACCESSION(S): PRJNA311979PRJNA311978

REPOSITORIES: dbGaP

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Project description:The frequent occurrence of persistent or relapsed disease following induction chemotherapy in AML necessitates a better understanding of the clonal relationship of AML in various disease phases. In this study, we employed 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 that achieved complete remission with chemotherapy and subsequently relapsed and 11 sample pairs from patients with persistent disease following induction chemotherapy. Through review of aCNA/cnLOH and gene mutation profiles in informative cases we demonstrate that relapsed AML invariably represents reemergence 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 two 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 This study is based on 39 patients with AML for which either paired enrollment or relapse samples or persistent disease samples were available. The patients were enrolled into this study at the University of Michigan Comprehensive Cancer Center. The study was approved by the University of Michigan Institutional Review Board (IRBMED #2004-1022) and written informed consent was obtained from all patients prior to enrollment. Genomic DNA was extracted from purified AML blasts and paired buccal cells. DNA thus obtained was hybridized to Affymetrix SNP 6.0 arrays. Note: There is no normal sample available for MIAML015.

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Genomic Analysis of Relapsed Pediatric Acute Lymphoblastic Leukemia

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