Abstract: OBJECTIVE To evaluate the effects and mechanism of C₂₁ sterols in Marsdeniae Tenacissimae Caulis extract on inhibition of proliferation and induction of apoptosis of low invasion and lung hypermetastasis in salivary adenoid cystic carcinomacv cell line SACC-83 and SACC-LM, respectively. METHODS SACC-83 and SACC-LM cells were treated with C₂₁ sterols at different doses (5, 10, 20, 40, 60, 80, 100 μmol·L^-1) for 48 h, then the cell viability was measured by MTT assay, and calculated the value of IC₂₀ and IC₅₀ for drug. The capacity of clone formation of cells were detected by clone formation assay. The apoptotic of SACC-83 and SACC-LM cells were determined by flow cytometry. The expression levels of Bcl-2, Bax and caspase-3 mRNA and proteins in SACC-83 and SACC-LM cells were examined by q-PCR and Western blot method. RESULTS C₂₁ sterols at different doses decreased the viability and inhibited proliferation of SACC-83 and SACC-LM cells, and the concentration of IC₂₀ was 7.49 μmol·L^-1, and IC₅₀ was 38.34 μmol·L^-1 for SACC-83 cells. In addition, the concentration of IC₂₀ was 9.30 μmol·L^-1, and IC₅₀ was 46.04 μmol·L^-1 for SACC-LM cells. The apoptotic rate of SACC-83 and SACC-LM cells under concentration of IC₂₀ with C₂₁ sterols was significantly increased(P<0.05, P<0.01). The q-PCR and Western blot results showed that the expression level of Bcl-2 in the SACC-83 and SACC-LM cells was decreased significantly(P<0.01), and the expression level of Bax and Caspase-3 were increased significantly (P<0.05). CONCLUSION C₂₁ sterols in Marsdeniae Tenacissimae Caulis extract can depress the proliferation and promote apoptosis of SACC-83 and SACC-LM cells, which mechanism may be related to decreasing the Bcl-2 level, and increasing the Bax and Caspase-3 level.