PTK2 and breast carcinoma: A direct link between FAK and breast tumorigenesis in vivo was also ascertained employing a tetracycline-inducible (Tet-ON) system of MCF-7 breast cancer cells stably transfected with expression vectors of FAK wild-type (WT), a dominant-negative construct and a C-terminal domain of FAK (FAK-CD) [77].