β-elemene increases the sensitivity of gastric cancer cells to TRAIL by promoting the formation of DISC in lipid rafts

β-Elemene, an anti-cancer drug extracted from traditional Chinese medicinal herb, showed anti-tumor effects on gastric cancer cells. Our previous studies reported gastric cancer cells are insensitive to TRAIL. However, whether β-elemene could enhance anti-cancer effects of TRAIL on gastric cancer cells is unknown. In our present study, β-elemene prevented gastric cancer cell viability in dose-dependent manner, and when combined with TRAIL, obviously inhibited proliferation and promoted apoptosis in gastric cancer cells. Compared to β-elemene or TRAIL alone, treatment with β-elemene and TRAIL obviously promoted DR5 clustering as well as translocation of Caspase-8, DR5 and FADD into lipid rafts. This led to cleavage of Caspase-8 and the formation of death-inducing signaling complex (DISC) in lipid rafts. The cholesterol-sequestering agent nystatin partially reversed DR5 clustering and DISC formation, preventing apoptosis triggered by the combination of β-elemene and TRAIL. Our results suggest that β-elemene increases the sensitivity of gastric cancer cells to TRAIL partially by promoting the formation of DISC in lipid rafts.