PNMT and idiopathic pulmonary fibrosis: Then, we used two machine-learning methods, least absolute shrinkage and selection operator (LASSO) regression and support vector machine recursive feature elimination (SVM-RFE), to identify six IPF signature genes as key DEMRGs: ENPP3, ENTPD1, PDE7B, GPX3, PNMT, and POLR3H.