We found that gefitinib has a significant impact on the growth of BTC lines in vitro (Fig. 6B) as well as on tumor growth in vivo (Fig. 1F), with the cell culture result substantiating the conclusion that Egfr signaling is involved in stimulating the cancer cells in a cell autonomous manner, consistent with the phenotype of Tgf-α mutant RT2 mice. This evidence concerns the gene EGFR and cancer.