The most recent studies showed that knockdown of NNMT was able to inhibit the proliferation of KB cancer cells [24], renal carcinoma cells [25] and oral cancer cells [26], and NNMT expression was involved in maintaining cell proliferation by increasing the activity of Complex I (NADH:ubiquinone oxidoreductase) in SH-SY5Y neuroblastoma cells [27]. Here, NNMT is linked to lip and oral cavity carcinoma.