Figure 1a shows the basic susceptibility of unsensitized IGROV-1 cells to erlotinib (E), gefitinib (G), and vandetanib (V). Addition of cetuximab did not reduce cell viability further (striped columns). Sensitization of IGROV-1 cells (sE, sG, sV) with anti-EGFR TKIs for 7 days (Figure 1b) and 6 weeks (Figure 1c) resulted in a significantly increased resistance of the cancer cells to TKI treatment over time (compare white columns in Figure 1a–c). This evidence concerns the gene EGFR and cancer.