Fig. 1

Cancer cell proliferation. Green cells are normal cells and red cells are tumor cells. The proliferation activity of normal and tumor cells can be measured looking at the activation of a proliferation protein, which is driven by a complex network based on protein interactions. In a population of cells the proliferation activity can be described by means of probability density for the proliferation protein; e.g., phosphorylated form of the extracellular signal-regulated kinase (ERK). The plots at the bottom show an example of probability density of a proliferation indicator in tumor (red line) and normal cells (green line), respectively