Yes-associated protein 1 exerts its tumor-promoting effects and increases cisplatin resistance in tongue squamous cell carcinoma cells by dysregulating Hippo signal pathway.

Tongue squamous cell carcinoma (TSCC) has been well-known for its high metastasis and poor prognosis, but the molecular mechanisms of TSCC pathogenesis and chemoresistance are still largely unknown. Thus, the present study aimed to identify the involvement of a classic Hippo/Yes-associated protein 1 (YAP1) pathway in regulating TSCC progression and cisplatin (DDP) resistance. DDP-resistant TSCC cell lines were established by gradual exposure to DDP. Through western blot analysis, the protein expression of Hippo/YAP1 axis in TSCC tissues and cell lines was detected separately. Then, YAP1 was inhibited or overexpressed in TSCC cells. Cell viability and drug resistance were evaluated by cell counting kit-8 method, colony formation assay and Trypan blue staining assay. Cell migration ability was measured by Transwell assay. The Hippo pathway was dysregulated, and YAP1 was upregulated and dephosphorylated in the TSCC tissues or DDP-resistant cell lines, compared with normal tissues or DDP-sensitive cells. YAP1 knockdown inhibited cell proliferation, colony formation ability and migration, whereas overexpression of YAP1 exacerbated these malignant characteristics. YAP1 knockdown increased DDP-sensitivity by reducing the RAD51-mediated DNA damage repair behavior under DDP intervention in the DDP-resistant TSCC cells. Conversely, YAP1 overexpression significantly increased DDP-resistance by enhancing the RAD51-mediated DNA damage repair behavior under DDP intervention in the DDP-sensitive TSCC cells. In a word, upregulation and dephosphorylation of YAP1 caused dysregulation of the tumor-inhibiting Hippo pathway, resulting in the aggressiveness and DDP resistance in TSCC.