目的：研究来自桔梗的天然单体化合物桔梗皂苷D（platycodin D, PD）对高转移性乳腺癌细胞MDA-MB-231凋亡的影响，初步探索其可能的作用机制。方法：以不同浓度（0、2.5、5、10 μmol/L）PD处理乳腺癌MDA-MB-231细胞后，采用MTT法检测细胞增殖率并计算IC50值，流式细胞术检测细胞凋亡情况，Western blotting检测凋亡相关蛋白的表达水平。结果： PD呈剂量依赖性显著抑制MDA-MB-231细胞的增殖(P<0.01），作用72 h 的IC50值为（7.30±2.67）μmol/L。与对照组相比，10 μmol/L的PD可显著促进MDA-MB-231细胞的凋亡（P＜0.05）。PD激活了caspase家族蛋白，上调有活性的cleaved caspase-3、cleaved caspase-8和cleaved caspase-9的表达，下调无活性的caspase-8和caspase-9的表达；PD同时减少Bcl-2的表达，增加Bax的表达，使Bcl-2/Bax的比值降低。研究还发现PD使突变型P53蛋白的表达减少、E2F1的表达增加。结论： PD抑制乳腺癌细胞增殖具有明显的抗肿瘤效应，而诱导凋亡的发生可能是其发挥抗肿瘤效应的机制之一。

Objective:This study was designed to estimate the role of platycodin D (PD), a natural monomeric compound derived from platycodin grandiflorum, in apoptosis of highly metastatic breast cancer cell line MDA-MB-231 and to primarily explore the possible mechanisms. Methods: MDA-MB-231 cells were treated with different concentrations of PD (0, 2.5, 5, 10 μmol/L), cell proliferation rate was detected by MTT and IC50 value was calculated; cell apoptosis was evaluated by Flow cytometry, and the expressions of apoptosis-related proteins were assessed by Western blotting. Results: PD significantly inhibited MDA-MB-231 cell proliferation (P＜0.01) in a dose-dependent manner with a IC50 value of (7.30±2.67) μmol/L at 72 h. Compared with control group, 10 μmol/L PD could significantly promote the apoptosis of MDA-MB-231 cells (P<0.05). PD increased the caspase protein activity by up-regulating active cleaved caspase-3, -8 and -9 and down-regulating inactive caspase-8 and -9. PD also decreased the expression level of Bcl-2 and increased Bax expression, resulting in the decrease of Bcl-2/Bax ratio in MDA-MB-231 cells. The protein expression of mutant P53 was down-regulated after treated with PD; otherwise, the expression of E2F1 was up-regulated. Conclusion：PD had an obvious anticancer effect by inhibiting breast cancer cell proliferation, and inducing apoptosis might be a potential mechanism of anti-cancer effects.

国家自然科学基金资助项目（No.81171991）