Objective · To investigate the effect of toosendanin (TSN) on the growth and invasion of gastric cancer cells BGC-823 by regulating circDLST expression. Methods · After gastric cancer cells BGC-823 were exposed to different concentrations of TSN (0, 0.5, 1.0, and 2.0 μmol/L) for 24 h, quantitative PCR was used to detect the expression of circDLST. BGC-823 cells were transfected with the circDLST overexpression lentiviral vector or its control vector (CON), and then treated with 0.5 μmol/L TSN or PBS. So the cells were divided into circDLST+TSN group, CON+TSN group and CON+PBS group. The viability and invasive potential of BGC-823 cells were observed by MTT proliferation test and Transwell invasion assay. The subcutaneous transplanted tumor models were established by using circDLST-transfected cell line BGC-823 or the control cell line in nude mice, and then 200 μg/kg TSN or the same volume of PBS was injected intraperitoneally every day. So the mice were divided into circDLST+TSN group, CON+TSN group and CON+PBS group. Results · Compared with the control group (0 μmol/L), all 3 concentrations of TSN decreased the expression levels of circDLST in a concentration dependent manner (P<0.01). TSN could significantly reduce the cell viability, cell invasion and subcutaneous xenograft tumor growth (P=0.000), while circDLST overexpression reversed the inhibitory effect of TSN (P<0.01). Conclusion · TSN may inhibit the growth and invasion of gastric cancer cells BGC-823 by downregulating circDLST expression.