PTK2 and esophageal squamous cell carcinoma: To further examine the importance of TM4SF1/integrin α6/FAK signaling axis on ESCC metastasis, nude mice were also intravenously injected with Con, TM4SF1-knockdown or related TM4SF1-rescue, integrin α6-overexpression, and TM4SF1-rescue plus integrin α6-overexpression KYSE-410 cells via tail veins.