Factors affecting SC fate. (A) Cells with various kinetic parameters were simulated under different levels of intercellular communication. Three different effects are depicted at steady state. (a) Under a relatively high intercellular communication, K1 = K2 = K3 = 6, K4 = ... = 0, in about half of the cases all SCs transiently replicate and differentiate into end cells, and in about half of the cases SCs uncontrollably proliferate; (b) Under a lower intercellular communication, K1 = 6, K2 = ... = 0, most of the cases evolve to SC immortalization. (c) An even lower intercellular communication, K1 = K2 = K3 = 1, K4 = ... = 0, or K1 = 1, K2 = ... = 0, preserves all SCs in the proliferative state (note two overlapping curves). (B) Effect of cell kinetic parameters in environments of high intercellular intensity. Transient SC proliferation and transition to differentiation is dominant when F, Ψ, T obey condition (a) in Table 1. Intermediate probability of full differentiation is obtained under case (b) in Table 1. Immortalization is always obtained under case (c) in Table 1. (C) Proportion of immortalized SCs as a function of initial SC density. The parameters Φ, Ψ, Θ obey case (a) in Table I (open squares), case (b) (filled squares), case (c)(circles).