Selection and characterization of pulmonary colonizing cells from cultured mouse mammary carcinoma cells

Pulmonary colonizing cells were selected by an in vivo-in vitro selection method from cultured mouse mammary carcinoma FM3A cells. When 10(6) parent cells (P-O) were injected iv into syngeneic C3H/He mice, no tumor nodules were reduced. However, when the selected variant cells (P-15) were injected iv, tumor nodules formed predominantly in the lungs within 2 weeks. Mice inoculated iv with 10(6) P-15 cells began to die on day 22, but mice inoculated with P-O cells survived for more than 6 months. When injected sc into C3H/He mice, P-O cells were as tumorigenic as P-15 cells to the syngeneic mice. There was no significant difference between P-O and P-15 cells in their proliferation in vitro or in the inducibility of alkaline phosphatase activity. During successive selection of colonizing variants, the proportion of adherent cells increased. Adherent P-15 cells had a higher colonizing potential than nonadherent P-15 cells. The correlation of the adhesive property of the cells and their colonizing potential is discussed.