PTEN and oral cavity squamous cell carcinoma: PTEN, a known suppressor of the PI3K/AKT signaling pathway, was discovered to be downregulated by FAP in oral squamous cell carcinoma (OSCC) cells, and knockdown of FAP inhibited the growth and metastasis of OSCC cells in vitro and in vivo; therefore, it is suggested that FAP-mediated inhibition of PTEN activates the PI3K/AKT/GSK-3β pathway and that FAP acts as an oncogene [51].