In order to determine the function of miR-29a in regulating breast cancer in vivo, we stably overexpressed miR-29a in MDA-MB-231 or MCF-10A-Src cells, labeled with GFP, and transplanted into immunodeficient nude mice, followed by analyses of mammary tumor growth, CTC in blood and metastasis in the lung (Fig. 4A). This evidence concerns the gene SRC and breast cancer.