EGFR and lung adenocarcinoma: To exclude the possibility that the delayed EGFR degradation in CTSS-inhibited cells was merely restricted to OEC-M1 and MDA-MB-231 cells, several human cancer cell lines, including human lung adenocarcinoma A549, human non-small cell lung carcinoma PC9, human pancreatic carcinoma Panc1, and human colon adenocarcinoma HT29, were examined.