ObjectiveTo study the tumor growth and pulmonary metastasis in mice transplanted with different number of luciferase-labeled mouse breast cancer cells, and to provide important information for drug screening and cancer mechanism research. MethodsThe vector containing luciferase gene was constructed and transfected into mouse breast tumor cell line 4T1 cells and selected with G418 to obtain stable Luc-expressing clones. The cells in logarithmic phase was collected and diluted to 1×10⁸,5×10⁷,2×10⁷ and 1×10⁷ cells/mL. Then 0.1 mL cell suspension was inoculated into the second mammary fat pad on the right side of normal BALB/c mice to establish the tumor models. Their tumorigenesis and metastasis were analyzed in vivo.ResultsThe stable Luc-expressing cell lines were obtained which had no obvious difference with parental cells in tumorigenicity. The whole-body optical imaging found that tumor could be formed after the cells were inoculated orthotopically. After 28 days, the tumor sizes were similar among the four concentrations, while there were two mice each died at 5×10⁶ and 1×10⁷ cells concentrations. After 31 days, the tumor metastasis showed different degree among the four concentrations. The metastasis became more seriously with time passed. However, after 42 days, deaths of mice occurred in succession.ConclusionsThe number of 1×10⁶ cells is the best concentration, not only induces obvious pulmonary metastasis but also shows a survival time longer than 45 days, compared with that induced at other higher concentrations. 