Figure 3.

Robustness of networks and its effect on the development of drug resistance in cancer. (A) (Left) Representation of network plasticity. High connectivity of nodes allows communication to be maintained even after removal of edges (states 1–3). (Right) Representation of network redundancy. The degree of communication between nodes A and B is not affected even after removal of a direct path, given the existence of redundant, equivalent paths of communication. Plasticity and redundancy define the robustness of a network. (B) Robustness allows the action of drugs to be overcome. Initially, signal transduction occurred from the top to the bottom node through the yellow, upregulated nodes and solid edges, with a parallel, inactivated pathway having little contribution (grey nodes, solid edges). After drug inhibition of the active pathway, the parallel pathway can be activated and restore signalling, leading to drug resistance. Given the high robustness of unicellular network regions, the development of resistance and the ability to withstand genetic changes would preferably occur in these regions.