As Cyclin D3 was related with DFS of BC patients and it showed that Cyclin D3 was highly expressed in the high metastasis BC cell lines, such as MDA-MB231 and its high lung and bone metastatic subtypes (HM and BO), transwell assay was carried out to further examine the role of Cyclin D3 in BC metastasis. The gene discussed is CCND3; the disease is breast cancer.