Monitoring of tumor growth and metastasis potential in MDA-MB-435s/tk-luc human breast cancer xenografts

Molecular imaging of reporter gene expression provides a rapid, sensitive and non-invasive monitoring of tumor behaviors. In this study, we reported the establishment of a novel animal model for longitudinal examination of tumor growth kinetics and metastatic spreading in vivo. The highly metastatic human breast carcinoma MDA-MB-435s cell line was engineered to stably express herpes simplex virus type 1 thymidine kinase (HSV-1-tk) and luciferase (luc). Both 131I-FIAU and D-luciferin were used as reporter probes. For orthotopic tumor formation, MDA-MB-435s/tk-luc cells were implanted into the first nipple of 6-week-old female NOD/SCID mice. For metastatic study, cells were injected via the lateral tail vein. Mice-bearing MDA-MB-435s/tk-luc tumors were scanned for tumor growth and metastatsis using Xenogen IVIS50 system. Gamma scintigraphy and whole-body autoradiography were also applied to confirm the tumor localization. The results of bioluminescence imaging as well as histopathological finding showed that tumors could be detected in femur, spine, ovary, lungs, kidney, adrenal gland, lymph nodes and muscle at 16 weeks post i.v. injection, and correlated photons could be quantified. This MDA-MB-435s/tk-luc human breast carcinoma-bearing mouse model combined with multimodalities of molecular imaging may facilitate studies on the molecular mechanisms of cancer invasion and metastasis.