Theoretical considerations and practical concerns regarding the use of continuous cell lines in the production of biologics

The origin and history of continuous cell lines are discussed briefly in the context of their biological relationship to diploid and tumorigenic cells. The question of the potential tumorigenicity of continuous cell lines is examined from the points of view of the theoretical risks involved in the use of these cells for the production of biological products, and of practical approaches to risk assessment. Animal and in vitro tumorigenicity test systems are discussed, and published data on the transfer of tumorigenic properties by DNA are reviewed. Both animal and human experience with vaccines produced in tumor cells is discussed in relation to cancer risk. When the theoretical risks of using continuous cell lines as substrates to produce biological products are balanced against the available data, it would appear reasonable to proceed with the use of such cell lines for the development of biologics because the benefits of those products appear to exceed by far the potential risks associated with the use of these cell substrates.