SIRT1 and oral cavity squamous cell carcinoma: This assumption is supported by a previous study in which in vitro tumor-suppressive effects were found after upregulation of SIRT1 and apoptosis in human oral squamous cell carcinoma by dietary-derived betaine stimulation; selective SIRT1 inhibition, on the other hand, yielded an opposite effect, increasing proliferation of cultured carcinoma cells [62].