PPM1D and gastric cancer: NAPRT promoter hypermethylation in cancer is frequently associated with mutations in the protein phosphatase Mg2+/Mn2+-dependent 1D (PPM1D) or isocitrate dehydrogenase 1 (IDH1) genes, as well as with the epithelial-mesenchymal transition (EMT)-subtype of gastric cancer [36,37,38].