Cytometric analysis of neoplastic transformation of vertebrate cell populations.

Two parameters of neoplastic transformation in spontaneously transforming fibroblasts were examined. One parameter, the predilection for rounding of cells at metaphase, was studied using time-lapse cinephotomicrography and fixed, stained preparations. Ten different cell lines were assayed, including established lines of hamster, rat, and mouse cells, and six rodent cultures of known neoplastic potential as determined by animal injection and tumor production. There was a close correlation between the assumption by cells of a spherical shape at metaphase and their ability to form tumors on injection in syngeneic hosts. The projected area of adherent cells 24 hr after plating over a coverglass was used to assay the transition of these rodent cell populations in culture from nonneoplastic to neoplastic. As the cell population became neoplastic, there was a significant decrease in the mean projected area of the cells. Furthermore, as the cell cultures became capable of producing tumors, the projected area profile of the population shifted proportionally to smaller area classes.