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. Author manuscript; available in PMC: 2009 Jul 7.
Published in final edited form as: J Theor Biol. 2008 Feb 21;253(1):98–117. doi: 10.1016/j.jtbi.2008.02.016

Figure 1.

Figure 1

Cell-cycle model incorporated in the spheroid growth model. The entire spheroid volume was assumed to be comprised of either dead cells or cells in the different phases of the cell cycle: G0, G1, S, G2 and M. Each line signifies a transition from of one cell-cycle phase to another. In good nutrient conditions cells will proliferate by traversing from G1 to S to G2 to M to G1. In the final transition from M to G1 phase cells replicate. In good nutrient conditions quiescent G0 cells can become proliferating by entering the G1 phase. In moderately poor nutrient conditions G1 cells will traverse to the quiescent, G0 phase. In acutely poor nutrient conditions (or in the presence of a cytotoxic drug) cells from all cell-cycle phases will die.