DPP4 and lung cancer: The top 10 proteins (MIG6, GAPDH, NDRG1_pT346, BRD4, CD26, TFRC, INPP4B, GSK3ALPHABETA, IGFBP2, and DUSP4) were screened by applying the WBFS algorithm, and they can be regarded as the candidate biomarkers that are most closely associated with the classification of lung cancer subtypes.