The RNA sequence data from the TCGA demonstrated that the expression of CTSW, CTSH, CTSO and CTSS was downregulated in lung cancer tissues; notably, only CTSV was found upregulated in lung cancer tissues (n=1037), approximately 2.6-fold higher than that in normal tissues (n=108) (Figures 1A, B), and no significant changes were observed in the remaining cathepsin family members. Here, CTSO is linked to lung carcinoma.