PF542 MITOCHONDRIAL GENOMIC ANALYSIS IN PATIENTS WITH MYELOID MALIGNANCIES

Abstract

Background: Mitochondrial DNA (mtDNA) somatic mutation frequently occur in neoplasms. Because of heteroplasmy of mDNA, it is difficult to determine whether genetic variations in mtDNA occur as germline variants or truly somatic variant. Genetic abnormalities in nuclear DNA in myelodysplastic syndrome (MDS) and other myeloid malignancies are massively investigated. However, the molecular abnormalities in mtDNA in MDS and other myeloid malignancies have not been poorly revealed. In this study, we analyzed full sequence of mtDNA using next generation sequencing (NGS) technique in patients with MDS or other myeloid malignancies to investigate possible variants in mtDNA in these patients. Aims: The aim of this study is to find mtDNA variants and to select possible somatic mtDNA variants and investigate possible association with disease characteristics. Methods: We collected total DNA from bone marrow or peripheral blood samples with malignant cells in 35 patients with various myeloid malignancies [15 MDS, 7 acute myeloid leukemia (AML) without recurrent genetic abnormalities, 6 primrary myelofibrosis (PMF), 4 myelomomocytic leukemia (CMML), and 2 atypical chronic myeloid leukemia (aCML)]. In addition, 49 patients with non-hematologic diseases are included as controls. Whole mitochondrial genomic sequencing was amplified, and NGS was performed by HiSeq 2000 (illumine). In addition, targeted sequencing using genomic DNA for 138 genes including well-known genes in MDS was also performed. Results: We selected candidate mtDNA single nucleotide variants (mt-SNVs) according to the heteroplasmy levels of variants and filtering from reference database and control patients’ results. We discarded small insertion or deletions from our analysis. When same selection criteria were applied in control samples, no candidate mt-SNVs were found except 1 known mutation in MELAS patients. We finally selected 53 candidate mt-SNVs in 26 patients (74.3%). The 40/53 (75.5%) of mt-SNVs were found in protein coding genes, 10/53 (18.9%) were found in rRNA genes, and 3/53 (5.7%) were found in tRNA genes. The mt-SNVs were most frequently found in CYTB and CO3, and ND3, ND4, ND4, RNR1, and RNR2 in descending order. mt-SNVs in CO3 were most frequently found in MPN patients, and variants in ND3 and ND4 were most frequently found in AML patients. Most of patients with ND3 variants had ASXL1 mutations. Summary/Conclusion: Our results suggested that somatic mtDNA may present different distributions among disease subtypes of myeloid malignancies, which may give new insight on the pathogenesis of myeloid malignancies.