Growth and metastasis of hypermotile, hyperinvasive cancer cells selected in vitro by rapid locomotion under various conditions.

Cancer cells selected from a cultured murine fibrosarcoma by rapid migration through micropore membranes moved considerably faster through such membranes and invaded biological tissues much more efficiently than did the unselected parent cells. The present data show that populations of cells selected by unstimulated migration or by haptotaxis to laminin moved not only faster, but also in larger numbers than the parent cells. However, the selected cells were far less efficient than the parent cells in forming spontaneous lung metastases in syngeneic mice, although all cell lines were 100 per cent tumorigenic. Analysis of paired data within each group showed no relationship between the primary tumor size at any observation time and the number of lung metastases finally formed. Therefore, although the parent cell line produced primary tumors growing slightly more rapidly than did the various lines of hypermotile cells, this was probably not the main cause of the difference in spontaneous metastasis formation between the groups. Lung colonization experiments performed by intravenous injection of cells could not explain the spontaneous metastasis results. In vitro, the cells selected by rapid haptotaxis to laminin grew considerably better than the other cells in 0.1 per cent fetal bovine serum, but there were no, or only minor, differences in higher serum concentrations. Combined, these results indicate that small subpopulations of cells selected by extreme efficiency in one step of the metastasis process may be so specialized that they perform poorly in other steps. Therefore, the results do not disprove the concept that tumor cell migration plays an important part in metastasis.