Our present data demonstrate that miR-30a-3p acts as a tumor-suppressive miRNA in BC cells through controlling the following cell-cycle-related genes: ANLN, MKI67, CCNB1, NCAPG, ZWINT, E2F7, PDS5A, RIF1, BIRC5, MAD2L1, CACUL1, KIF23, UBE2S, EML4, SEPT10, CLTC, and PCNP. The gene discussed is KIF23; the disease is breast cancer.