DNA methylation in monozygotic twins discordant for acute lymphoblastic leukemia: a case report and systematic review

Acute lymphoblastic leukemia (ALL) is a prevalent malignant hematologic disease characterized by the abnormal proliferation and accumulation of immature lymphocytes in bone marrow and lymphoid tissues. In our study, Oxford Nanopore Technologies (ONT) sequencing was performed to investigate four types of methylation modifications-6 mA, CHG, CHH, and CpG-in a pair of monozygotic twins, where one twin has ALL and the other is healthy. The results showed the significant global hypomethylation of CpG sites and an increase in 6 mA, CHG, and CHH methylation in the twin diagnosed with ALL. Notably, the hypomethylation of CpG was particularly increased in the open sea, gene body, and 3'UTR regions, while 6 mA and CHG modifications exhibited high methylation levels in the gene body, TSS1500, TSS200, and 3'UTR regions. Additionally, CHH modifications showed high methylation across all genomic regions. Within the differential methylation loci (DML), we identified several genes related to tumorigenesis and progression (such as ZDHHC11, NBPF1, and TPTE). Furthermore, we systemically reviewed the literatures on leukemia and DNA methylation modifications, providing a comprehensive description of their correlation. In summary, these findings indicate that DNA methylation plays a crucial role in the onset and progression of ALL, offering valuable insights for future research into its impact on leukemia development.