To explore the specific molecular mechanisms by which MAP2K4 functions as a breast cancer oncogene, we conducted Western blot analyses to analyze key regulators of the cell cycle and found that MAP2K4 overexpression upregulated cell cycle-related genes including p-PI3K, p-AKT, c-JUN, c-Myc, and Cyclin D1(CCND1) in both MCF-7 and MDA-MB-231 cells. The gene discussed is CCND1; the disease is breast cancer.