Melittin treatment suppressed malignant NSCLC progression through enhancing CTSB-mediated hyperautophagy

Melittin is preclinically investigated as anticancer agent in multiple tumor types. But its regulation role and regulatory mechanism regarding NSCLC is unknown. In our investigation, Proteomic test was employed to identify proteins that expressed abnormally in cancer cells and that with Melittin treatmented. The results showed CTSB was one of the Top proteins with different expression levels in the lysosomes of Melittin-treatmented cancer cells and showed an up-regulation trend. CTSB expression was increased in NSCLC cancer tissues compared to adjacent normal tissues, as demonstrated in lung cancer tissue chips experiment. However, Melittin treatment increased the CTSB level in lysosomes, which inhibited the malignant progression of NSCLC. We hypothesized that the relative homeostasis of CTSB in cancer cells was destroyed, and CTSB exerts its hydrolytic effect excessively, resulting in excessive autophagy of cancer cells, thus inhibiting the malignant progression of cancer cells. The direct combination of Melittin and CTSB was proposed by molecular docking technique, LiP-SMap was used to analyze the target genes and active components extracted from high-throughput sequencing proteomic data, and successfully verified that melittin was successfully demonstrated to directly target CTSB-binding. In vivo and in vitro studies have shown that Melittin treatment inhibits the malignant progression of A549 and HCC1833 cells and animal tumors, namely non-small cell lung cancer, by promoting CTSB-mediated hyperautophagy. CTSB-specific inhibitor CA-074 Me and autophagy inhibitor 3-MA treatment reversed the inhibit effect of Melittin to the malignant progression of NSCLC. Taken together, Melittin treatment inhibited malignant progression regarding NSCLC through enhancing CTSB-mediated hyperautophagy.