Mouse 4T1 breast tumor model.

The 4T1 mammary carcinoma is a transplantable tumor cell line that is highly tumorigenic and invasive and, unlike most tumor models, can spontaneously metastasize from the primary tumor in the mammary gland to multiple distant sites including lymph nodes, blood, liver, lung, brain, and bone The 4T1 tumor has several characteristics that make it a suitable experimental animal model for human mammary cancer. First, tumor cells are easily transplanted into the mammary gland so that the primary tumor grows in the anatomically correct site, as described in this unit. Second, as in human breast cancer, 4T1 metastatic disease develops spontaneously from the primary tumor. Also, the progressive spread of 4T1 metastases to the draining lymph nodes and other organs is very similar to that of human mammary cancer. In this unit, a protocol describes surgical removal of the primary tumor, so that metastatic disease can be studied in an animal setting comparable to the clinical situation where the primary tumor is surgically removed, and metastatic foci remain intact. Another advantage of 4T1 is its resistance to 6-thioguanine. This property enables precise quantitation of metastatic cells, even when they are disseminated and at sub-microscopic levels in distant organs, as described here.