In vitro growth characteristics associated with benign and metastatic variants of tumor cells.

Tumors show a wide range of growth rates in vivo. In general, nonmetastatic (benign) tumors appear to grow slowly, while metastasizing (malignant) tumors proliferate rapidly and contain a large number of dividing cells. In order to analyze if there is a direct relationship between metastatic potential and growth rate (without the influence of host factors), in vitro analyses are necessary. In vitro studies that compared monolayer doubling times and in vivo tumorigenicity rarely demonstrated a correlation between the two parameters. Differences in monolayer growth rates were observed among tumors, but the differences were unrelated to in vivo growth. In contrast, some tumor systems demonstrated a correlation between in vivo growth and/or malignant potential and growth properties observed during anchorage independent growth. Evidence is presented to show that in particular tumor systems, an analysis of colony size and colony morphology during growth in suspension can be used to study the relationship between malignant potential and growth properties.