Fig. 1

Oncogenic mutations will rarely be advantageous within a population of healthy well-adapted stem cells residing in a healthy niche, leading to loss of the oncogenic clone over time (top). But following aging or damage-induced reductions in stem pool fitness, together with damage or degradation of the niche, oncogenic events that improve fitness should provide selective advantages, leading to expansion of the oncogenic clone over time (bottom). Cellular competition is denoted with arrows, with darker arrows indicating greater competition