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3115 Clonal Architecture Analysis of TET2 Identified Distinct Origins in Myelodysplastic Syndromes

Program: Oral and Poster Abstracts
Session: 637. Myelodysplastic Syndromes—Clinical Studies: Poster III
Hematology Disease Topics & Pathways:
Clinically relevant
Monday, December 7, 2020, 7:00 AM-3:30 PM

Zhongxun Shi, MD1*, Bing Li, MD1*, Tiejun Qin, MD1*, Zefeng Xu, MD1*, Lijuan Pan, MD1*, Shiqiang Qu, MD1*, Gang Huang, PhD2 and Zhijian Xiao, MD3*

1Institute of Hematology and Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China
2Division of Experimental Hematology and Cancer Biology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
3State Key Laboratory of Experimental Hematology, National Clinical Research Center for Blood Diseases, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Tianjin, China

Next-generation sequencing (NGS) has deepened our understanding of myelodysplastic syndromes (MDS). Genetic mutations of TET2 were common in MDS and were also detected in asymptomatic elder persons, which were defined as aged related clonal haematopoiesis (ARCH) and considered as a myelodysplastic syndrome precursor state. In this study, we analyzed the mutation profiles of TET2 in 770 newly-diagnosed MDS subjects. 73 mutations were found in 67 of 770(8.7%) subjects. 14.9% were frame shifts, 29.9% were nonsense, 44.8% were missense and 10.7% harbored 2 TET2 mutations. TET2MT subjects were older than TET2WT subjects (P=0.024) and the variant allele frequency (VAF) of TET2 was positively correlated with age (r=0.318, P=0.009). Clonal architecture was determined using a copy number-adjusted VAF difference between 2 mutation events in 49 TET2MT subjects with 2 or more mutations. 19 (38.3%) were TET2ancestral and 30(61.2%) were TET2subclonal. TET2ancestral subjects were significantly older than TET2WT subjects (P=0.013) while no difference was found between TET2subclonal subjects and TET2WT subjects (P=0.509). The frequency of cytosine-to-thymine (C→T) transition was significantly higher in TET2ancestral subjects compared with TET2subclonal subjects (P=0.029), which was considered to be a somatic mutational signature of aging, indicating that MDS driven by TET2ancestral was likely derived from TET2MT ARCH. The most common upstream mutations in TET2subclonal subjects were U2AF1 (16.7%) and ASXL1 (13.3%), and the most common downstream mutations in TET2ancestral subjects were ASXL1 (21.1%) and RUNX1 (15.8%). TET2 mutations rarely existed alone in TET2ancestral subjects (14.3%) and were always accompanied by another mutations like U2AF1, SF3B1 and ASXL1, suggesting that the acquisition of another mutation led to the progress of ARCH to MDS in TET2ancestral subjects. TET2MT had no impact on survivals in overall cohort (P=0.218) while predicted poorer survivals in IPSS-R lower risk group (P=0.004). Additional ASXL1, U2AF1 and RUNX1 mutations in TET2MT subjects indicated poorer prognosis compared with TET2WT subjects (P=0.005; P=0.04; P<0.001) .There was no significant difference in OS of TET2MT subjects with different clonal architecture (P=0.76). Subjects with TET2 VAF≥30% had poorer survivals compared with TET2WT subjects (P=0.057). In conclusion, TET2MT MDS subjects with different clonal architectures may have different origins. TET2ancestral subjects may be derived from ARCH and progressed to MDS after secondary hits. The effects of TET2 mutation on the prognosis depended on the accompanying mutations and clonal burdens.

Disclosures: No relevant conflicts of interest to declare.

*signifies non-member of ASH