Relation of Spontaneous Transformation in Cell Culture to Adaptive Growth and Clonal Heterogeneity

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 87; no. 1; pp. 482 - 486
• Main Authors: Rubin, Andrew L., Yao, Adam, Rubin, Harry
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-01-1990; National Acad Sciences
• Subjects: 3T3 cells; Animal cells; Animals; Biological and medical sciences; Cell culture techniques; Cell cycle, cell proliferation; Cell Division; Cell growth; Cell physiology; Cell Transformation, Neoplastic; Cells; Cells, Cultured; Clone Cells; Cultured cells; Fundamental and applied biological sciences. Psychology; Kinetics; Mice; Mice, Inbred Strains; Molecular and cellular biology; NIH 3T3 cells; Population density; Population dynamics; Population growth; Time Factors; Cell proliferation; Cell cloning; Cell culture; Embryo; Growth rate; Rodentia; Environmental factor; 3T3-Cell line; Cell density; Vertebrata; Mammalia; Mouse; Growth stress; Morphological analysis; Cell cycle; Kinetics
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.87.1.482

Cell transformation in culture is marked by the appearance of morphologically altered cells that continue to multiply to form discrete foci in confluent sheets when the surrounding cells are inhibited. These foci occur spontaneously in early-passage NIH 3T3 cells grown to confluency in 10% calf serum (CS) but are not seen in cultures grown to confluency in 2% CS. However, repeated passage of the cells at low density in 2% CS gives rise to an adapted population that grows to increasingly higher saturation densities and produces large numbers of foci in 2% CS. The increased saturation density of the adapted population in 2% CS is retained upon repeated passage in 10% CS, but the number and size of the foci produced in 2% CS gradually decrease under this regime. Clonal analysis confirms that the focus-forming potential of most if not all of the cells in a population increases in response to a continuously applied growth constraint, although only a small fraction of the population may actually form foci in a given assay. The acquired capacity for focus formation varies widely in clones derived from the adapted population and changes in diverse ways upon further passage of the clones. We propose that the adaptive changes result from progressive selection of successive phenotypic variations in growth capacity that occur spontaneously. The process designated progressive state selection resolves the apparent dichotomy between spontaneous mutation with selection on the one hand and induction on the other, by introducing selection among fluctuating states or metabolic patterns rather than among genetically altered cells.