<p>(A) Heterogeneous EGFR activity in a lung squamous cell carcinoma. Representative image of red foci showing EGFR:GRB2 proximity. Tumor cells (green) are stained with a cytokeratin antibody demarcating epithelial origin. Nuclei (blue) are stained with DAPI. Image was acquired at 200x. (B) HGF distribution. The Eq (<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002930#pbio.2002930.e006" target="_blank">3</a>) was solved assuming the following parameters: <i>γ</i> = 1.0, diffusion rate <i>D</i> = 0.04, and decay rate <i>λ</i> = 0.001. To be consistent with the choice of parameter in the pathway model (Eq [<a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002930#pbio.2002930.e001" target="_blank">1</a>]), we use a scaling factor <i>ω</i> (<i>ω</i> ≡ 10) (i.e., HGF input in the pathway model <i>x</i><sub>2</sub> = <i>ωH</i>(<i>x</i>,<i>t</i>), <i>H</i>(<i>x</i>,<i>t</i>): solution obtained using the assumed parameters). (C) First, an initial randomized configuration of cells (domain size: 50 cells × 38 cells). Color represents different in silico cells. Second, a snapshot of <i>RAS_m</i> inhibitor simulation (day 180). (D) Simulated protein activity after 180 days of <i>RAS_m</i> inhibition. The activities of MET, EGFR, RAS_w, and RAF are heterogeneous (yellow to blue color), while those of AKT, MEK, ERK, and RSK are less heterogeneous (blue color). (E) Comparison of combination therapies for 400 days. First, a snapshot of simulation (day 400) after a sequential therapy of <i>RAS_m</i>i for the first 200 days and then RAFi for the rest 200 days (200 days of <i>RAS_m</i>i → 200 days of RAFi). Color represents different in silico cells. Second, a snapshot of simulation (day 400) after a sequential therapy of RAFi for the first 200 days, then <i>RAS_m</i>i for the remaining 200 days (200 days of RAFi → 200 days of <i>RAS_m</i>i). Third: the number of cells over time during the two sequential therapies of <i>RAS_m</i>i and RAFi (blue: <i>RAS_m</i>i → RAFi, red: RAFi → <i>RAS_m</i>i) and a concurrent therapy of the two (green: <i>RAS_m</i>i/RAFi). The numerical data used in Fig 7 are included in the sixth sheet <a href="http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.2002930#pbio.2002930.s013" target="_blank">S1 Data</a>. AKT (PKB), protein kinase B; DAPI, 4',6-diamidino-2-phenylindole; EGFR, epidermal growth factor receptor; ERK, extracellular receptor kinase; GRB2, growth factor receptor bound protein 2; HGF, hepatocycte growth factor; MEK, mitogen-activated protein kinase kinase; MET (c-MET), tyrosine-protein kinase Met or hepatocyte growth factor receptor (HGFR); RAF, rapidly accelerated fibrosarcoma; RAS, rat sarcoma; RSK, ribosomal S6 kinase.</p
