[Selection of highly metastatic lines from streptozotocin-induced mouse renal adenocarcinoma and their in vivo metastatic or in vitro invasive potential].

We selected highly metastatic lines from mouse renal adenocarcinoma (STZ-RCC) chemically induced with streptozotocin. At eight weeks after an intrasplenic injections (IS injection) of original STZ-RCC, this procedure yielded metastatic foci in the liver, which we transplanted serially in syngeneic mice (STZ-HM1). STZ-HM1 was then injected into the spleen of a syngeneic mouse, which provided a source for further cycles of hepatic metastasis selection. Three cycles of selection for hepatic metastasis yielded a high hepatic metastasis line (STZ-HM3). Intravenous injection of the parent line (original STZ-RCC) yielded metastatic foci in the lung eight weeks later, which we also transplanted serially in syngeneic mice (STZ-PM1). The repeated IS injection of the cells was clearly responsible for the increase in the frequency of hepatic metastasis and the number of its nodules. In particular, STZ-HM3 was revealed to have more metastatic nodules in the liver ranging from 293 to 432 (median; 368) in all five mice at eight weeks after IS injection. STZ-PM1 had a significantly higher rate of pulmonary metastasis and more pulmonary metastatic nodules after intravenous injection than the parent line. These results confirm that the parent line, STZ-RCC, has a heterogeneity in the metastatic phenotype. In vitro invasion assay for STZ-RCC, STZ-HM1, -HM2 and -HM3 demonstrated that in vitro invasive potential was paralleled with in vivo hepatic metastasis potential. The result suggests that the invasion potential revealed by in vitro invasion assay is important in metastasis formation.