CELL DENSITY DEPENDENCE OF FOCUS FORMATION IN C3H-10T1-2 TRANSFORMATION ASSAY

Abstract

Some of the dynamics of neoplastic transformation in vitro were studied with the use of benzo(a)pyrene [BP] as the carcinogen in the C3H/10T1/2 [mouse embryo fibroblast] morphological transformation assay. Experiments that involved the dispersion of cells into new culture dishes at various times after carcinogen treatment showed that no change in the fraction of potentially transformed cells occurs while cultures grow to form a confluent monolayer, little or no change in the fraction of potentially transformed cells occurs for .apprx. 3 wk after confluence is attained and this fraction increases rapidly 7 wk after BP treatment. When confluent BP treated cultures are dispersed in new culture dishes prior to the onset of growth toward focus formation, the formation of transformed foci is suppressed at high cell densities of seeding. This phenomenon is independent of the total number of divisions undergone by cells after treatment. Phenotypic expression of morphological transformation is dependent on colony interactions in he C3H/10T1/2 system, which are not yet understood, but which are independent of time posttreatment expressed in cell generations or absolute time.