| Background: Breast cancer is one of the most common malignant tumors in women. Recently,the attact rate of breast cancer rises yearly,and the age of onset is more younger now,the disease threatens seriously the health of women.Rhodiola rosea L has the function of caducity staving,radiation protection, anti-anoxiction, anti-fatigue, anti-tumor, immunity swelling and antivirus, etc. Salidroside is the primary function gene of Rhodiola. Apoptosis is a genetically programmed cell death which is regulated by apoptosis correlated genes. It plays an important role to maintain economy homeostasis.Recent studies have demonstrated that the process of tumorigenesis at cellular level is related to inhibition of celluar apoptosis and disorder of cell proliferation. With respect to apoptosis,tumorigenesis is correlated with inhibition of apoptosis mechanism, absence of cell death and disability of eliminating aberrant cell. Elevation of tumor cell survival contributes to tumorigenesis. Studies on molecular mechanism of apoptosis suggested that caspase family is a protease which directly results in cellular apoptosis and it is essential for cellular apoptosis mechanism network. Caspase-3 is a member of caspase family and it is crucial for protease responses.Caspase-3 is activated by its upstream proteases and directly hydrolyzes several substrates responsible for alteration of cellular biochemistry and morphology, which results in cellular apoptosis.Objective: The Rhodiola algida Var. tangutica was used in some tibetan medicinal prescriptions for tumor therapy, but little is known about the anticancer action of the Rhodiola algida Var. tangutica. The aim of this report is to investigate the antitumor activities of the aqueous extract of Rhodiola algida Var. tangutica and the mechanism of its action,thus to provide evidence and theoretical support for breast cancer therapy.Methods: The effective constituent of the the aqueous extract of Rhodiola algida Var. tangutica was analysed with the high efficiency liquid chromato-graphy. The survival rate of MCF-7 cells were evaluated by MTT test after being treated with the extract for 12, 24,48 h. The morphological change of cells was observed with optical microscope. The apoptotic influence of the extract on cells was researched with Annexin V-FITC/PI kit and flow cytometry. RT-PCR was performed to measure the expression level of caspase-3 gene in MCF-7 cells after treated with different concentration of the aqueous extract of Rhodiola algida Var. tangutica.Results: The main constituent of the aqueous extract contained the salidroside and tyrosol. The aqueous extract caused decrease in the survival of MCF-7 in 12 h. Treatment with the concentration from 90μg/mL to 450μg/mL reduced survival markedly, and the highest concentrations of the aqueous extract ( 450μg/mL) reduced it to almost 0 after 48 h of incubation. The results of optical microscope showed the vacuole and apoptotic body in MCF-7 cells. The FCM analysis showed that lower concentrations of the aqueous extract caused much apoptotic cells and higher concentrations led to much necrotic cells. The expression of Caspase-3 mRNA increased in the aqueous extract of Rhodiola algida group.Conclusion: The aqueous extract of Rhodiola algida Var. tangutica inhibits division of MCF-7 cells and the cytostatic and antiproliferative effect was related to apoptosis induction mechanism.
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