Western blotting analysis showed that MEN1 shRNA-knockdown (KD) noticeably inhibited the expression of both the precursor (p) and mature (m) forms of CTSB and CTSE in the lung cancer cell lines (A549 and NCI-H157) and the immortalized bronchial epithelial cell line (16-HBE) (Supplementary Fig. S1B). This evidence concerns the gene CTSB and lung cancer.