NNMT and oral cavity squamous cell carcinoma: High NNMT expression at mRNA or protein level was also reported in oral squamous cell carcinoma (OSCC) [58], gastric cancer [59], ovarian cancer [60], and even in cancer-associated fibroblasts (CAFs) of high-grade serous carcinoma (HGSC) [61], suggesting that high NNMT expression is needed for tumor progression in above-mentioned tumors.