Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations.Recent studies revealed that abnormal gene expression induced by epigenetic changes,including aberrant promoter methylation and histone modification,plays a critical role in human breast carcinogenesis.Silencing of tumor suppressor genes(TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression,thus directly contributing to breast tumorigenesis.Usually,aberrant promoter methylation of TSGs,which can be reversed by pharmacological reagents,occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer.In this review,we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast cancer. Breast cancer is a complex disease driven by multiple factors including both genetic and epigenetic alterations. Recent studies revealed that abnormal gene expression induced by epigenetic changes, including aberrant promoter methylation and histone modification, plays a critical role in human breast carcinogenesis. Silencing of tumor suppressor genes (TSGs) by promoter CpG methylation facilitates cells growth and survival advantages and further results in tumor initiation and progression, thus directly contributing to breast tumorigenesis. Usually, aberrant promoter methylation of TSGs, which can be reversed by pharmacological reagents, occurs at the early stage of tumorigenesis and therefore may serve as a potential tumor marker for early diagnosis and therapeutic targeting of breast cancer. In this review, we summarize the epigenetic changes of multiple TSGs involved in breast pathogenesis and their potential clinical applications as tumor markers for early detection and treatment of breast can cer.