Surgically-Induced Multi-organ Metastasis in an Orthotopic Syngeneic Imageable Model of 4T1 Murine Breast Cancer.

Anticancer research

PubMedID: 26254353

Zhang Y, Zhang N, Hoffman RM, Zhao M. Surgically-Induced Multi-organ Metastasis in an Orthotopic Syngeneic Imageable Model of 4T1 Murine Breast Cancer. Anticancer Res. 2015;35(9):4641-6.
BACKGROUND/AIM
Murine models of breast cancer with a metastatic pattern similar to clinical breast cancer in humans would be useful for drug discovery and mechanistic studies. The 4T1 mouse breast cancer cell line was developed by Miller et al. in the early 1980s to study tumor metastatic heterogeneity. The aim of the present study was to develop a multi-organ-metastasis imageable model of 4T1.

MATERIALS AND METHODS
A stable 4T1 clone highly-expressing red fluorescent protein (RFP) was injected orthotopically into the right second mammary fat pad of BALB/c mice. The primary tumor was resected on day 18 after tumor implantation, when the average tumor volume reached approximately 500-600 mm(3).

RESULTS
When the post-surgical mice were sacrificed 6-8 weeks after cell implantation, metastases were found in the lung in 91%; in the lymph nodes in 100%, including axillary nodes; in the brain in 25%; and in bone in 42% of the mice. The metastases were readily visualized by fluorescence imaging. Detailed fluorescence analysis visualized extensive metastasis in the thoracic cavity and the lymphatic system. Large metastatic nodules in the lung involved most of the pulmonary parenchyma in all lobes. In the liver, fluorescent macroscopic metastatic nodules were found under the capsule. Bone metastases were found mainly in the spine and thigh bone.

CONCLUSION
Metastasis appeared to be enhanced by resection of the primary tumor. The metastatic pattern in the model thus reflected the clinical metastatic pattern of breast cancer and should be of use for discovery and evaluation of novel therapeutics.