KDM4A and breast cancer: Mammary epithelial cells MCF-10A and human breast cancer cell lines BT474, SKBr-3, ZR-75-30, and MCF7 are cultured, and the mRNA expressions of hsa_circ_000 1429, miR-205, and KDM4A are detected by qRT-PCR; hsa_circ_000 1429 binds to miR-205, and miR-205 targets KDM4A.