Characterization of the heterogeneity of R3327 rat prostatic tumors derived from single-cell clones

Prostatic adenocarcinoma is characterized by cellular diversity, which is well demonstrated in the Dunning R3327 rat prostatic adenocarcinoma. This heterogeneity may arise from epigenetic influences, ie, cellular adaptation or selection, and/or from genetic changes. To investigate the question of genetic instability, four tissue culture cell lines were derived from single cells isolated from the uncloned late (UCL) passage of the Dunning R3327H prostate cell culture. Each of these clonally derived tissue cultures was injected into castrated and intact young adult male rats for tumor production. Uncloned early (UCE) and UCL passage tissue cultures were also propagated as solid tumors. Tumors and the cultures from which they were derived were examined for evidence of phenotypic and genetic changes using morphological and cytometric methods. Transmission and scanning electron microscopy revealed only slight differences among the cell cultures. A single population of diploid cells was demonstrated in each of the cell cultures by propidium iodide staining and subsequent flow cytometric measurement of DNA content/nucleus. Tumors of unicellular as well as multicellular origin exhibited extreme heterogeneity of histological features, both among animals as well as within a single tumor. Tumors were surveyed and tissue types were characterized and cataloged. Clone 3 was generally better differentiated than the others; tumors from castrated animals were better differentiated than those from intact animals. Flow cytometry revealed multiple hyperdiploid cell populations that were variable from one sample to another. We concluded that changes in genotype as well as phenotype occurred in the tumors derived from single cells. Some of these changes may have occurred in the cells while still in culture.