Experimental study of inhibitory effects of diallyl trisulfide on the growth of human osteosarcoma Saos-2 cells by downregulating expression of glucose-regulated protein 78

BACKGROUND: Diallyl trisulfide (DATS) is a natural organic sulfur compound isolated from garlic that has good anticancer activity according to many previous reports. There are many studies pointing out that DATS can downregulate expression of the glucose-regulated protein 78 (GRP78), which is associated with poor prognosis and drug resistance in various types of human cancers. However, it remains unknown whether DATS has the same effect on human osteosarcoma cells. This study attempted to clarify the potential molecular mechanisms of the action of DATS in human osteosarcoma Saos-2 cells. METHODS: We used an inverted phase microscope and immunofluorescent staining to observe the morphological changes of Saos-2 cells after being cultured in different concentrations of DATS (0, 25, 50, and 100 μM) for 24 h, or for four time periods (24, 48, 72, and 96 h) in the same DATS concentration (50 μM). Quantitative real-time polymerase chain reaction and Western blot were used to detect the expression level of GRP78 mRNA and proteins in Saos-2 cells. GRP78 expression was suppressed in Saos-2 cells by utilizing small-interfering RNA, and the cells were subsequently used to study the anti-proliferative effects of DATS treatment. RESULTS: The expression level of GRP78 mRNA and proteins was significantly downregulated due to the increased concentration and effective times of DATS (P<0.05). In addition, there were significant associations between GRP78 silencing and cell proliferation (P<0.05) of DATS treatment. CONCLUSION: These results indicate that DATS inhibits the growth of human osteosarcoma Saos-2 cells by downregulating the expression of GRP78.