E2F1 and breast cancer: For instance, exosomal miRNA-205 could promote chemoresistance and tumorigenesis through E2F1 in breast cancer, and targeting exosomal miRNA-205 may be a treatment strategy to reduce cancer chemoresistance [17]; One study reported that five plasma miRNAs (let-7b-5p, miR-122-5p, miR-146b-5p, miR-210-3p and miR-215-5p) could serve as promising biomarkers for breast cancer detection [18].