Abstract 736: Cell lineage-oriented clinical sequencing unveils distinct clonal ontogeny of acute myeloid leukemia with myelodysplasia-related changes
Authors: Yokoyama Kazuaki , Yusa Nozomi , Nakamura Sousuke , Ito Mika , Kobayashi Asako , Kobayashi Masayuki , Kasajima Rika , Yui Hiroaki , Shimizu Eigo , Niida Atushi , Yamaguti Rui , Ikenoue Tsuneo , Imoto Seiya , Frukawa Yoichi , Miyano Satoru , Tojo Arinobu 
Published: July 2017

Acute myeloid leukemia (AML) is characterized by unregulated clonal expansion and maturation arrest of myeloid committed progenitors (MP). AML generally represents de novo onset or evolves from preceding myelodysplastic syndrome (MDS), which is defined by refractory cytopenias, clonal hematopoiesis, and/or multi-lineage dysplasia. The WHO classification 2008 includes this entity as “AML with myelodysplasia-related changes (AML-MRC)”, and currently, diagnosis of AML-MRC is based on either previous history of MDS, multi-lineage dysplasia, or MDS-related cytogenetic abnormality. However, AML-MRC often represents de novo onset without these MDS-compatible clinical features. Considering that AML-MRC exhibits rather poor prognosis with refractoriness to conventional chemotherapy against AML, more accurate and objective diagnostic approach is requisite to unveil hidden “MDS signatures” in patients with apparently de novo AML. A certain set of gene mutations is specific and recurrent in MDS. Given the pre-existing “MDS signatures”, the founder gene mutations might be detected in not only blast cells but also neutrophils and/or T cells in AML-MRC. To test this hypothesis, we performed FACS sorting of neutrophils, T cells, and blasts fractions, respectively, followed by mutation screening using targeted deep sequencing, namely, cell lineage-oriented sequencing (CLS). Genomic DNA both from each cell fraction and buccal swab was subjected to screening mutations in 54 genes which are tightly involved in MDS and AML. Pair-end deep sequencing was performed on an Illumina MiSeq, using library prepared by TruSight Myeloid Panel (Illumina, San Diego, CA). Bioinformatic analysis was performed by in-house pipeline. We performed CLS of clinically diagnosed AML-MRC (n=7), suspected AML-MRC (n=2), de novo AML (AML with t(15;17) or AML with inv16, n=4), MDS (RAEB-1 and RAEB-II, n=3), and familial MDS (n=1). As expected, in a familial MDS case, overlapping germline RUNX1 driver mutation was demonstrated in granulocytes, blast cells and T cells, supporting that it would be originated from a hematopoietic stem cell. Notably, in MDS, AML-MRC, and suspected AML-MRC cases with no germ-line mutations, the founder mutations present in neutrophils were also retained in the AML blast cells, irrespective of a history of MDS, suggesting that these are derived from a myeloid progenitor cell. In marked contrast, there were no overlapping driver mutations between blast cell and neutrophil fractions in de novo AML characterized by recurrent chromosomal abnormalities. In summary, CLS revealed that founder mutations are shared by neutrophils and AML blast cells in AML-MRC, but not in de novo AML. Although our data should be validated in a larger cohort of AML cases, CLS is a promising approach to molecular diagnosis of latent AML-MRC which require distinct therapeutic options from de novo AML.

Citation Format: Kazuaki Yokoyama, Nozomi Yusa, Sousuke Nakamura, Mika Ito, Asako Kobayashi, Masayuki Kobayashi, Rika Kasajima, Hiroaki Yui, Eigo Shimizu, Atushi Niida, Rui Yamaguti, Tsuneo Ikenoue, Seiya Imoto, Yoichi Frukawa, Satoru Miyano, Arinobu Tojo. Cell lineage-oriented clinical sequencing unveils distinct clonal ontogeny of acute myeloid leukemia with myelodysplasia-related changes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 736. doi:10.1158/1538-7445.AM2017-736