However, a few studies have classified SIRT1 as a negative regulator of tumor progression, as SIRT1 upregulation inhibited the migration and metastasis of oral squamous cell carcinoma cells through the deacetylation of SMAD4, which suppressed the effects of Transforming Growth Factor beta (TGF-β) signaling [12]. This evidence concerns the gene SIRT1 and oral cavity squamous cell carcinoma.