Abstract
Epigenetic modifications, particularly DNA methylation, play a critical role in the metastatic progression of breast cancer. This study investigates the role of DNA methyltransferase 1 (DNMT1) in regulating the methylation of RASSF1A and its contribution to breast cancer brain metastasis. Using single-cell transcriptome sequencing of CTCs derived from in situ breast cancer models, DNMT1 was identified as a key promoter of tumor cell viability, migration, and invasion. RASSF1A was further validated as a direct target of DNMT1-mediated methylation. This regulatory interaction was confirmed through DNA methylation sequencing, methylation-specific PCR, and chromatin immunoprecipitation assays. These findings highlight the pivotal role of DNMT1-driven RASSF1A methylation in facilitating breast cancer metastasis to the brain, and suggest that targeting DNMT1 may represent a promising therapeutic approach for managing metastatic breast cancer.