Abstract
BackgroundCasticin is one of the main active components obtained from Fructus Viticis and has been reported to exert anti-carcinogenic activity on a variety of cancer cells but the precise mechanism underlying this activity remains unclear.Materials and MethodsApoptotic activities of casticin (1.0 µmol/l) and TRAIL (25, 50 ng/ml) alone or in combination in the gastric cancer cell lines BGC-823, SGC-7901 and MGC-803 were detected by the use of a cell apoptosis ELISA detection kit, flow cytometry (FCM) with propidium iodide (PI) staining and activities of caspase-3, -8 and -9 by ELISA and cleavage of polyADP-ribose polymerase (PARP) protein using western blot analysis. Death receptors (DR) expression levels were evaluated using FCM analysis and western blotting. 2′, 7′-dichlorofluorescein diacetate (DCFH-DA) was used as a probe to measure the increase in reactive oxygen species (ROS) levels in cells. Multiple interventions, such as siRNA transfection and pharmacological inhibitors were used to explore the mechanisms of these actions.ResultsSubtoxic concentrations of casticin significantly potentiated TRAIL-induced cytotoxicity and apoptosis in BGC-823, SGC-7901 and MGC-803 cells. Casticin dramatically upregulated DR5 receptor expression but had no effects on DR4 or decoy receptors. Deletion of DR5 by siRNA significantly reduced the apoptosis induced by the co-application of TRAIL and casticin. Gene silencing of the CCAAT/enhancer binding protein homologous protein (CHOP) and pretreatment with salubrinal, an endoplasmic reticulum (ER) stress inhibitor, attenuated casticin-induced DR5 receptor expression, and apoptosis and ROS production. Casticin downregulated the expression levels of the cell survival proteins cFLIP, Bcl-2, XIAP, and survivin. In addition, casticin also induced the expressions of DR5 protein in other gastric cancer cells (SGC-7901 and MGC-803).Conclusion/SignificanceCasticin enhances TRAIL-induced apoptosis through the downregulation of cell survival proteins and the upregulation of DR5 receptors through actions on the ROS-ER stress-CHOP pathway.
Highlights
Fructus Viticis (Manjingzi is the Chinese name) namely fruit of Vitex trifolia L. that is a traditional Chinese medicine used as an anti-inflammatory agent
Because we found that the combined treatment with casticin and tumor necrosis factor-a-related apoptosis-inducing ligand (TRAIL) strongly induced cytotoxicity in gastric cancer cells, we examined the effect of the treatment on the immortalized human gastric mucosa epithelial cell line GES-1
We investigated the ability of casticin, a polymethoxyflavone derived from Fructus Viticis, to modulate TRAIL signaling in gastric cancer cells, and our findings suggest that casticin potentiates TRAIL-induced apoptosis in gastric cancer BGC-823, SGC-7901 and MGC-803 cells by (1) inducing DR5 expression and (2) downregulatin of cell survival proteins linked to tumor cell resistance to TRAIL
Summary
Fructus Viticis (Manjingzi is the Chinese name) namely fruit of Vitex trifolia L. (family Verbenaceae) that is a traditional Chinese medicine used as an anti-inflammatory agent. Casticin is one of the active components derived from Fructus Viticis [1]. ER stress is induced when unfolded proteins accumulate in the ER lumen [16]. It seems that this response can activate specific apoptotic pathways to eliminate severely damaged cells, in which protein folding defects cannot be resolved [17,18]. Whether casticin induces DR5 expression in gastric cancer cells and if so, the nature of the molecular mechanism involved is unknown. Casticin is one of the main active components obtained from Fructus Viticis and has been reported to exert anti-carcinogenic activity on a variety of cancer cells but the precise mechanism underlying this activity remains unclear
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