乳腺癌形成是癌症相关死亡的第二大原因，现有化疗手段的不足促使我们开发一种新型的治疗方法，针对其分子信号通路。哺乳动物雷帕霉素靶蛋白(mTOR)的高度活化在侵袭性乳腺癌的发展中起着关键作用，是潜在的治疗靶点。本实验旨在探究mTOR特异性siRNA对mTOR基因的治疗效果，评估其在体外抑制乳腺癌方面的熟练度，并确定潜在的分子机制。特异性siRNA针对mTOR转染到MDA-MB-231细胞中，通过qRT-PCR和Western blot分析验证了mTOR的下调。细胞增殖通过MTT检测和共聚焦显微镜分析。流式细胞术研究了细胞凋亡，分别估计S6K、GSK-3β和caspase 3的表达。进一步确定了mTOR阻滞对细胞周期进展的影响。将mTOR-siRNA转染到MDA-MB-231细胞中后，检测了细胞的存活和凋亡，结果表明，在临床相关浓度下，mTOR-siRNA抑制了细胞的生长和增殖并促进了凋亡，这是由于mTOR的抑制引起的。这导致了mTOR下游S6K的下调和GSK-3β的上调。caspase 3的升高表示凋亡活性是通过caspase依赖型路径介导的。此外，mTOR的下调导致细胞周期在G0/G1阶段停滞，这在流式细胞术研究中观察到。通过这些结果，我们可以得出结论，mTOR-siRNA通过S6K-GSK-3β-caspase 3介导的凋亡和诱导细胞周期阻滞发挥了直接的“抗乳腺癌”活性。版权所有？Bentham Science Publishers；如有任何查询，请发送电子邮件至epub@benthamscience.net。

Mammary carcinogenesis, being ranked second in cancer-related mortality and the inadequacy of existing chemotherapy advocates the development of a novel treatment approach targeting its molecular signalling. Hyperactivation of mammalian target of rapamycin (mTOR) has a critical role in developing invasive mammary cancer and it can be a potential target.This experiment was to explore the efficacy of mTOR-specific siRNA on therapeutic targeting of the mTOR gene, assess its proficiency in suppressing in vitro breast cancer and determine underlying molecular mechanisms.Specific siRNA targeting mTOR was transfected into MDA-MB-231 cells and mTOR downregulation was validated through qRT-PCR and western blot analysis. Cell proliferation was analysed by MTT assay and confocal microscopy. Apoptosis was studied through flow cytometry and S6K, GSK-3β and caspase 3 expression were estimated. Further, the effect of mTOR blockade on cell cycle progression was determined.Following transfection of mTOR-siRNA into the MDA-MB-231 cells, cell viability and apoptosis were examined which indicates that clinically relevant concentration of mTOR-siRNA inhibited cell growth and proliferation and promote apoptosis, resulting from the suppression of mTOR. This leads to the downregulation of mTOR downstream S6K and upregulation of GSK-3β. An increased level of caspase 3 symbolises that the apoptotic activity is mediated through caspase-dependent pathway. Further, mTOR downregulation causes cell cycle arrest in G0/G1 phase as observed in the flow cytometry study.With these results, we can conclude that mTOR-siRNA exerts direct 'anti-breast cancer' activity propagated by the S6K-GSK-3β- caspase 3 mediated apoptosis and by inducing cell cycle arrest.Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.