PTK2 and cancer: In studies related to the transformation of normal stem cells into tumor stem cells (CSCs) without genetic manipulation, fibroblast growth factor 2 (FGF2) was found to induce normal stem cells to acquire stemness expression of tumor stem cells and initiate cancer; this process was found to be associated with integrin/FAK/PI3K/AKT signaling pathway activation (Sheta et al., 2021).