Another study of the COPDGene dataset[22] using a two-step pathway enrichment approach found that the purine metabolism, mineral absorption, arginine biosynthesis, aminoacyl-tRNA biosynthesis, ABC transporters and glycine, serine and threonine metabolism pathways were all associated with various measures of lung function and increased COPD exacerbations[37]. Here, ABCG2 is linked to chronic obstructive pulmonary disease.