Figure 4.

  Differences in IL‐6 production characteristics significantly alter population dynamics in the two cell types. (a) The rate parameter p(s) saturates beyond a threshold signal concentration [eqn (5)]. (b) The signal concentration at the centre of the tumour, i.e. s(0,t) is highly dependent on the paracrine signal sources for ER‐α‐positive cells. This has significant impact on differences in the evolution of the proliferation rates of (c) ER‐α‐negative and (d) positive cell types so that the population dynamics of (e) the ER‐α‐negative cells are less responsive to paracrine signal sources than of (f) ER‐α‐positive cells. The results have been generated using the same values for all parameters that relate the dependence of p(s) to the local IL‐6 concentration for the two cell types.