Microcirculation and metastasis in a new mouse mammary tumor model system.

Two new metastatic mouse mammary tumor transplant lines have been established in nude mice. The Met-1 line, with the polyoma virus middle T (PyV-MT) transgene, metastasized with 100% efficiency. The Db-7 line, expressing a PyV-MT transgene mutated at positions 315 and 322, metastasized with 8.8% efficiency. Histology and computer-assisted intravital microscopy demonstrated that internal microcirculation in Met-1 was more complex than Db-7; Met-1 exhibited higher microvessel density and tortuosity (P < 0.0001). These indices of microvascular complexity correlated with the higher Met-1 metastatic rate (P < 0.0001). These two transplantable lines will be useful for investigating the complex relationship between angiogenesis and metastasis.