MTNR1A and lip and oral cavity carcinoma: In OSCC, melatonin and MTNR1A were reported to exhibit growth-suppressive activity and found that the MTNR1A gene is usually downregulated or silenced through epigenetic regulation [18, 30, 31]; however, there have been no studies on the relationship between genetic regulation of the MTNR1A gene and oral cancer.