DKK1 and lung cancer: The other studies also indicated the role of DKK1 as a novel serologic and prognostic biomarker due to its increased serum concentrations in various cancers, including gynecological cancer (34), prostate cancer (35), hepatocellular carcinoma (36), bladder cancer (37), lung cancer (38), multiple myeloma (39), and osteosarcoma (40).These data implied that DKK1 could be a novel diagnostic and prognostic biomarker and a promising therapeutic target for many cancers.