4T1

4T1 is a 6-thioguanine-resistant cell line obtained from the 410.4 tumor strain without mutagenesis screening. When injected into BALB/c mice, 4T1 cells spontaneously produce highly metastatic tumors that can metastasize to the lungs, liver, lymph nodes, and brain, while forming primary foci at the injection site. Induction of metastasis does not require removal of the primary foci. The growth and metastatic characteristics of 4T1 cells in BALB/c mice closely resemble those of breast cancer in humans, making this tumor an animal model for human stage VI breast cancer. The kinetics of tumor metastasis induced by 4T1 cells are similar in both post-surgery and non-surgery settings, making it a suitable model for both scenarios. Compared to other tumor models, due to the anti-6-thioguanine resistance of 4T1 cells, even small metastatic cell clusters (as few as one) can be detected in many distant organs, eliminating the need to count lymph nodes or weigh organs.