PTPA and esophageal squamous cell carcinoma: For example, NNMT‐mediated decrease in SAM level can attenuate PP2A methylation to inhibit PP2A activity, or reduce histone methylation to suppress E‐cadherin expression, resulting in increased growth or metastasis of cancer cells in breast cancer, esophageal squamous cell carcinoma or glioblastoma.[7, 17, 26] NNMT‐catalyzed production of 1‐MNA was found to promote cell cycle progression in breast cancer by inhibiting UBC12/Cullin‐1‐mediated p27 degradation.[27] However, how NNMT is upregulated in cancer remains unclear.