Fig. 1.

Effect of treatment on population dynamics within heterogenous tumors. (A) In heterogeneous tumor population dynamics of competition (top) and cooperation (bottom) are at work. (B) Should treatment differentially affect the distinct populations within a tumor, the outcomes become increasingly difficult to predict. Panels show the basic scenarios with the following stipulations: Red and Orange populations cooperate as do Blue and Green. However, Red/Orange compete with Blue/Green. Post treatment, a net decrease in tumor size could result from scenarios including treatment equally affecting all populations in question and treatment mostly affecting more aggressive populations (Red/Orange) as shown in B, top panel. Note this does not preclude the evolution of additional clones (see Purple population). No net change in tumor size (B, middle panel) may result from increased sensitivity to treatment of either Orange (top middle panel) or Red (bottom middle panel). Net increase in tumor size (bottom panel) could result from more sensitivity to treatment of the Green (top of bottom panel) or Blue (bottom of bottom panel) populations.