Development of an in vitro clonogenic assay for the R3327 rat prostatic adenocarcinoma permits comparison of the proliferative potential of the R3327, R3327A, and R3327AT tumors.

The R3327 class of rat prostate tumors consists of both the androgen-dependent R3327 adenocarcinoma and androgen-independent sublines, the R3327At spindle cell tumor, and the R3327A, a squamous cell carcinoma. We have developed in vitro clonogenic cell assays to measure and compare systematically the proliferative potential of these tumors following various monodispersion techniques. Linear relationships between the number of monodispersed tumor cells cultured at low cell density and the number of colonies formed 10 days later establish these assays as the first quantitative cellular approach to those proliferative subpopulations ultimately responsible for the growth of these tumors. We have chosen the name colony forming cell-prostatic adenocarcinoma (CFC-PA) to refer to the members of the proliferative subpopulation of the R3327 tumor. An ultrastructural comparison of R3327 adenocarcinoma tissue sections with the cells produced during culture provides evidence that the cells of the proliferative subpopulation may be derived from the acinar epithelium of the tumor.