In order to detect molecular markers for the epidermal growth factor inhibitor 4-(3-chloro-benzyl)- 6,7-dimethoxy-quinazoline (tyrphostin), we investigated the kinetics of p120-catenin and periplakin in the human buccal mucosa squamous cancer cell line BICR 10 treated with 3 nM tyrphostin. Growth of BICR 10 cells was inhibited by treatment with tyrphostin. Although changes were not observed in the expression of EGFR and p120-catenin, expression of Akt, Src and periplakin in BICR 10 treated with 3 nM tyrphostin tended to decrease. In addition, phosphorylation of EGFR, Akt and Src was inhibited by treatment with tyrphostin. On immunocytochemical staining, immunoreactions with phosphorylated EGFR, phosphorylated Akt and phosphorylated p120-catenin were weak in BICR 10 treated with tyrphostin. There was a slight immunocy to chemical reaction to periplakin in BICR 10 cells induced by tyrphostin. In conclusion, the decrease in phosphorylation in EGFR and p120-catenin by tyrphostin, following the decrease in Src or Akt phosphorylation, may inhibit expression of several growth factors associated with the proliferation and migration of cancer cells.