In Vitro Transformation Assays Using Diploid Syrian Hamster Embryo Cell Strains

Abstract

Freshly prepared, diploid Syrian hamster embryo (SHE) cells, when plated at low density, will form colonies against a background of lethally irradiated homologous feeder cells (1, 3, 5, 8–10). These colonies exhibit a variety of cellular morphologies, but consist of highly ordered populations sometimes exhibiting contact inhibition and usually little or no evidence of perimarginal cellular crossing-over. In contrast, cells treated in vitro with chemical carcinogens may give rise to colony morphologies exhibiting evidence of cellular disorder, including significant perimarginal cell criss-crossing, characteristic of the transformed phenotype (1, 9). This morphological phenotype may occur in untreated cultures, but with extremely low frequency, and has been shown to be associated with the expression of malignant properties by carcinogen-transformed colony isolates (4, 6, 8). These observations form the basis for an assay system that has been applied to investigations into the mechanism of neoplastic transformation as well as the evaluation of chemicals for their genotoxic potential. The following sections describe the methodologies employed in these studies and are intended to provide investigators unfamiliar with cell transformation with the SHE assay’s basic technical framework in relation to the 3T3 and 10T1/2 assays.