ABCG2 and idiopathic pulmonary fibrosis: In particular, ABC transporter systems, the two-component regulatory system, biofilm formation, methane metabolism, aromatic compound degradation, amino acid biosynthesis (including alanine, tyrosine, valine and leucine), vitamin biosynthesis, biotin metabolism, and amino sugar and nucleotide sugar metabolism were enriched in the IPF group (Supplementary Figure 2).