Malignant transformation of mammalian cells in culture, including human cells.

Abstract

This overview of the malignant transformation of mammalian cells in culture, including human cells, describes the earliest evidence of spontaneous, virus-induced, and carcinogen-induced transformation. It discusses several systems developed to assay the carcinogen-induced transformation of highly selected infinite life span ("established") cell lines as well as finite life span diploid cells. Evidence is presented to support the multistep hypothesis of the process of malignant transformation, and the theoretical requirement for acquisition of an infinite, or greatly extended, life span in culture if a cell is to become malignant is explained in light of the multistep nature of the process. The use of oncogene transfection studies to analyze the number and kinds of changes involved is discussed, with emphasis on studies using human cells. Finally, the results of earlier studies on viral- and carcinogen-induced transformation of mammalian cells (or chicken cells) are reinterpreted in the light of more recent insights into the process of carcinogenesis.