Cluster size distribution of cell aggregates in culture

The growth patterns of established normal and cancer cell lines, cultured in monolayer and collagen gel, have been characterized using the cluster size distribution of cellular aggregates. HN-5 (cancer) cells exhibit, either in gel or in monolayer, power-law distributions at any time in culture, whereas for MDCK (“normal”) and Hep-2 (cancer) cells there is a transition from an exponential behavior to a power-law distribution after a transient time in culture. These results suggest that the transitions in growth regimes observed in MDCK and Hep-2 cell lines might be associated to changes in the control of replication or in the expression patterns of cell adhesion molecules of cell–cell and cell–matrix type related to intracellular signalling. These transitions are irreversible and seems to be an adaptative response to the growth constraints imposed by high cell population density or long permanence in culture.