Abstract
BACKGROUND Ricin protein derived from Ricinus communis seeds is known to have a high toxicity to humans and animals. Several studies revealed that ricin, belonging to ribosome inactivating protein-I, has cytotoxic properties against various types of cancer cell lines. MATERIAL AND METHODS Crude ricin (CR) from the seeds of R. communis was investigated for its cytotoxicity on the A549 cancer cell lines using the MTS assay, and the cell death mechanism was explored using flow cytometry and Western blot methods. The cell migration was measured using a scratch/wound-healing method and the autophagy activity was explored using Western blotting. RESULTS CR showed cytotoxicity against A549 cancer cell lines, with an IC₅&sub0; of 40.94 ppm. CR induced apoptosis and necrosis, but apoptosis occurred more frequently than necrosis. Apoptosis induced by CR was mediated by the activation of caspase-9 and caspase-3. CR inhibited cell migration in a concentration- and time-dependent manner, with the highest effect occurred at the concentration of 1.0 ppm. The autophagic experiment showed that CR inhibited autophagy in A549 lung cancer cells by decreasing Beclin-1 levels while increasing Atg5 levels in a concentration-dependent manner and CR decreased LC3-II level while increasing p62 level. Cisplatin treatment also inhibited autophagy as it exhibited the same effect on those autophagic proteins as CR. CONCLUSIONS Our findings suggest that CR might be a potential candidate for anticancer drugs, but further study is needed to verify its anticancer properties.