More importantly, microarray analysis in four patients with primary lung adenocarcinoma who had low expression of USP15, revealed that 10 different genes (CCNE1, MMP9, SFN, UBE2C, CCR2, FAM83A, ETV4, MYO7A, MMP11, and GSDMB) that are associated with promoting lung cancer progression were significantly upregulated, whereas 10 different genes (FMO2, ZBTB16, FCN3, TCF21, SFTPA1B, HPGD, SOSTDC1, TMEM100, GDF10, and WIF1) known to suppress lung cancer were markedly downregulated. This evidence concerns the gene TCF21 and lung cancer.