Knockdown of FAK inhibits the invasion and metastasis of Tca‑8113 cells in vitro.

Tongue cancer originating on the surface of the tongue is most commonly squamous cell carcinoma, which has a higher invasive ability and a lower survival rate compared with other forms of tongue cancer. Notably, tongue squamous cell carcinomas metastasize into lymph nodes at early stages. Focal adhesion kinase (FAK) is an important protein tyrosine kinase involved in invasion and metastasis of cancer cells. In the present study, the role of FAK in the invasion and metastasis of tongue cancer was evaluated and the underlying mechanisms involved in this process were explored. FAK knockdown was performed using shRNA in the tongue cancer cell line, Tca‑8113, and the invasion and metastasis potentials were analyzed using wound healing and transwell assays, respectively. Cytoskeletal arrangement was detected by fluorescence using TRITC‑conjugated phalloidin staining. The activity of matrix metalloproteinase (MMP)‑2 and ‑9 was examined by gelatin zymography. Paxillin distribution was observed by immunofluorescence. The levels of E‑cadherin, N‑cadherin, MMP‑2 and ‑9, and c‑Jun N‑terminal kinase (JNK) was detected by western blot analysis. Wound healing and transwell assays demonstrated that FAK knockdown inhibited the invasion and metastasis of Tca‑8113 cells. Further analysis revealed that FAK knockdown caused the rearrangement of the cytoskeleton and decreased the activity of MMP‑2 and ‑9. Immunofluorescence analysis revealed that downregulation of FAK induced the relocalization of paxillin. Paxillin accumulated as dots and patches at the cell membrane in control cells. By contrast, in FAK knockdown cells, paxillin was distributed homogeneously in the cytoplasm. Western blot analysis revealed that FAK knockdown inhibited epithelial-mesenchymal transition (EMT) and decreased levels of MMP‑2 and ‑9, and p‑JNK. Knockdown of FAK inhibits the invasion and metastasis of Tca‑8113 by decreasing MMP‑2 and ‑9 activities and led to the rearrangement of the cytoskeleton and inhibited the EMT.