Apart from the well-established effects on cellular metastasis, FAK has been shown to regulate the self-renewal and tumor-initiating capabilities of CSCs in many types of cancer, such as in breast cancer [21,22], Ductal Carcinoma In Situ [34], mesothelioma [35], liver cancer [24], and squamous cell carcinomas [36]. This evidence concerns the gene PTK2 and breast cancer.