Cells Out of Control

Cancer is not a stage in the orderly evolution of a i complex organism it is an organismic catastrophe. 

Transformed Cells Are Closely Related to Cancer Cells 

In the 1950s, systematic methods were developed for taking cells directly from the tissues of whole animals and inducing them to grow as single cells in liquid culture. 

Typically, continuous cell lines grow in culture only on a solid support or anchor (the surface of a petri dish, for example) and in the presence of relatively high concentrations of nutrients. Even then, they divide only as long as the culture is sparse. When the cell density increases beyond a critical point, the growth rate decreases sharply in fact, the cells of some continuous lines stop dividing altogether once they have formed a confluent monolayer. 

At the density that normally halts growth, rare transformed cells continue to multiply and may reach cell densities up to 20 times higher than those of untransformed cells. By picking and subculturing such transformed cells, it is possible to establish clonal lines of transformants and to ask in what ways such cells differ from their untransformed progenitors. 

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