Western blot of expression levels of intracellular kinases in colorectal cancer cells after 2 h exposure to trifluorothymidine (TFT) alone, erlotinib (E) alone, or in simultaneous combination (T + E) with or without epidermal growth factor (EGF) to stimulate EGF receptor (EGFR)‐related signaling. The blots are representative of two or three independent experiments. Colo320 cells did not show any detectable expression of phosphorylated (p‐)EGFR or phosphorylated MAPK. E → T + E, cells preincubated with E, followed by T + E combination; T → T + E, cells preincubated with TFT, followed by T + E combination.