Focal adhesion kinase and Src expression in premalignant and malignant skin lesions

Focal adhesion kinase (FAK) and Src are non‐receptor tyrosine kinases. FAK and Src play a critical role in inducing malignant transformation in tumor cells. We performed immunohistochemical staining for total and phosphorylated forms of FAK and Src, to evaluate the role of FAK and Src in the development of premalignant and malignant skin lesions. A total of 59 facial skin samples (30 actinic keratoses, 10 Bowen's diseases, 13 squamous cell carcinomas and six perilesional skins) were immunohistochemically stained for Ki‐67, total (t) and phosphorylated (p) form of FAK and Src. Cells positive for t‐Src, p‐Src‐y530, t‐FAK and pFAK‐s722 were detected in premalignant intra‐epithelial lesions (PELs) and squamous cell carcinomas (SCCs), but not in the perilesional skin. There was a tendency towards high correlation between Ki‐67 and t‐FAK or pFAK‐s722, suggestive of the active role of FAK in cell proliferation. However, our findings of higher t‐Src and p‐Src‐y530 positive cells in PELs, as compared to SCCs (with higher Ki‐67 level), are suggestive of the other role of Src in tumor formation and progression, which requires further investigation.