Molecular growth requirements of single mammalian cells. III. Quantitative colonial growth of single S3 cells in a medium containing synthetic small molecular constituents and two purified protein fractions.

Two purified serum protein fractions, fetuin and serum albumin, will replace whole or dialyzed serum in supporting the growth of single S3 HeLa cells in an otherwise chemically defined nutrient solution. In the serum-free medium, single S3 cells will form macroscopic colonies with essentially 100 per cent efficiency. The generation time of S3 cells in the serum-free medium is approximately 50 per cent greater than that observed in an optimal, serum-containing medium. All components of the serum-free medium are available commercially, except fetuin, which can easily be prepared in substantial quantities. The problem of the purity of the protein preparations and of their possible roles in promoting cell growth is discussed.