Female Balb/c mice at 6–8 weeks of age were separated randomly into several groups. In all, 5 × 104 4T1-luci cells/100ul were inoculated s.c into each mouse at right axilla. After 5-7 days, palpable tumors were seen. After 20-30 days, it will have lung metastasis.
you can use Balb/C cell line expressing green flourecent protein (GFP) like 66 cl-4-GFP. this cell line will help you to track cancer cells metastasis.