Genomic Analysis of Cellular Hierarchy in Acute Myeloid Leukemia Using Ultrasensitive LC-FACS-Seq

Normal hematopoiesis is organized in a hierarchical manner and it has been hypothesized that acute myeloid leukemia (AML) is organized in a similar way with leukemia-initiating cells (LIC) at the top of the hierarchy, giving rise to more differentiated blasts to sustain AML. Therefore, elimination of LIC population is critical for cure. This may be accomplished via novel molecular targeted therapies. The mutational composition of LIC and non-LIC compartments in AML has not been fully elucidated and could provide new insights into biology and treatment. We investigated the distribution and variant allelic frequencies (VAFs) of recurrent gene mutations within these compartments in newly diagnosed CD34+ AML patients (pts). We studied a total of 88 pts. CD34- AML cases, defined as Clinical characteristics are summarized in Table 1. The median frequency of the LIC population was 0.5% (range, 0.01% - 69%). The prevalence of high LIC frequency (≥0.5%) was significantly higher in pts with adverse risk (AR) AML, as compared to intermediate (IR) and favorable risk groups (94% vs 34% vs 16%, respectively, p We re-validated the commonly used LIC markers with ELDA of primary AML cells. In one IR sample, stem cell frequencies in sorted CD34+CD38-, CD34+CD38+ and CD34- compartments were 1:3, 1:15 and 1:16, respectively (p Relapse samples obtained from 6 pts were analyzed and compared with diagnosis. In all cases, we could identify LIC clones that persisted after chemotherapy and led to relapse (see example in Figure). Similarly, 3 pts who were primary refractory showed persistence of LIC clones that were resistant to treatment. On the contrary, 6 pts in whom LIC clones could be eradicated with treatment did not experience disease recurrence. LICs exist at a very low frequency in pre-treatment AML samples. The mutational composition of LIC-enriched compartment shows differences from blasts constituting the bulk of leukemia, which is consistent with the sequence of mutations observed during the evolution of AML. LC-FACS-seq is an ultrasensitive method to detect mutations in a tiny population of residual LICs in pts at remission. Therapies targeting mutations that are concentrated in LICs may re-shape the clonal hierarchy and impact on disease course. Download : Download high-res image (325KB) Download : Download full-size image Disclosures Behbehani: Fluidigm corporation: Other: Travel funding. Byrd: Ohio State University: Patents & Royalties: OSU-2S; Genentech: Research Funding; Genentech: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; BeiGene: Research Funding; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; BeiGene: Research Funding; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Gilead: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Novartis: Other: Travel Expenses, Speakers Bureau; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Genentech: Research Funding; Pharmacyclics LLC, an AbbVie Company: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau; Acerta: Research Funding; Janssen: Consultancy, Other: Travel Expenses, Research Funding, Speakers Bureau; Ohio State University: Patents & Royalties: OSU-2S; Ohio State University: Patents & Royalties: OSU-2S; Acerta: Research Funding; TG Therapeutics: Other: Travel Expenses, Research Funding, Speakers Bureau. Lozanski: Boehringer Ingelheim: Research Funding; Beckman Coulter: Research Funding; Stemline Therapeutics Inc.: Research Funding; Genentec: Research Funding.