目的·分析大肠埃希菌外膜囊泡（Escherichia coli outer membrane vesicle，E.coli-OMV）在体外对小鼠4T1乳腺癌细胞增殖的影响，在体内对BALB/c-4T1荷瘤小鼠肿瘤生长的抑制作用。方法·从E.coli的培养上清液中收集OMV并进行表征。采用荧光标记追踪法检测E.coli-OMV被4T1细胞摄入的情况。采用CCK-8法测定E.coli-OMV对4T1细胞增殖的影响。采用流式细胞术检测E.coli-OMV对4T1细胞周期的影响。利用皮下接种法建立BALB/c-4T1荷瘤小鼠模型，而后将小鼠分为E.coli-OMV组与对照（Control）组（每组10只）；前者于每2 d注射0.25 mg/kg E.coli-OMV，后者则注射等剂量的PBS。观察2组小鼠的体质量、40 d生存率、肿瘤体积及质量变化，采用苏木精-伊红染色（hematoxylin-eosin staining，H-E染色）评价肿瘤组织的病理学形态，采用免疫组织化学染色法观察肿瘤组织中增殖细胞核抗原（proliferating cell nuclear antigen，PCNA）与细胞周期蛋白D1（CyclinD1）的表达情况。结果·E.coli-OMV是粒径为（216.00±18.30）nm的球形膜囊结构，可表达E.coli外膜蛋白A（outer membrane protein A，OmpA）与OmpC。荧光显微镜的观察结果显示4T1细胞可摄入E.coli-OMV。CCK-8法的结果显示，E.coli-OMV对4T1细胞的抑制作用与时间-剂量呈正相关。流式细胞术的结果显示，E.coli-OMV将4T1细胞的生长周期阻滞于G₀/G₁期。体内实验显示，与Control组相比，E.coli-OMV组小鼠的体质量在初期注射后稍有下降（P=0.031），而后出现回升；其40 d生存率增加（P=0.037）；该组小鼠肿瘤的体积、质量的增长量均较少（P=0.041，P=0.004），其肿瘤体积抑制率达29.69%、肿瘤质量抑制率达49.81%。H-E染色的结果显示，E.coli-OMV组小鼠肿瘤组织细胞核分裂象较Control组减少（P=0.038）。免疫组织化学染色的结果显示，E.coli-OMV组小鼠肿瘤组织中的PCNA及CyclinD1阳性表达较Control组减少（P=0.031，P=0.002）。结论·体外研究与体内研究均表明，E.coli-OMV可对4T1细胞的增殖产生明显的抑制作用。

Objective ·To analyze the effect of Escherichia coli outer membrane vesicle (E.coli-OMV) on the proliferation of 4T1 breast cancer cells in vitro and the inhibition of tumor growth in BALB/c-4T1 tumor-bearing mice in vivo. Methods ·OMVs were collected from the culture supernatant of E.coli and characterized. The uptake of E.coli-OMV by 4T1 cells was detected by fluorescent label tracking method. The effect of E.coli-OMV on 4T1 cell proliferation was detected by CCK-8 method. The effect of E.coli-OMV on 4T1 cell cycle was detected by flow cytometry. The BALB/c-4T1 tumor-bearing mouse models were established by subcutaneous inoculation, and the mice were divided into E.coli-OMV group and Control group, with 10 mice in each group. The mice in the E.coli-OMV group were injected with 0.25 mg/kg E.coli-OMV every 2 d, while the mice in the Control group were injected with equal doses of PBS. The changes in body weight, 40 d survival rate, tumor volume and tumor weight of the two groups of tumor-bearing mice were observed. The pathological morphology of the tumor tissues was evaluated by hematoxylin-eosin staining (H-E staining). The expression of proliferating cell nuclear antigen (PCNA) and CyclinD1 in tumor tissues was observed by immunohistochemical staining. Results ·E.coli-OMVwas spherical membrane vesicle structure with a particle size of (216.00±18.30) nm, which expressed E.coli outer membrane protein A (OmpA) and OmpC. Fluorescence microscopy results showed that 4T1 cells could intake E.coli-OMV. CCK-8 results showed that the inhibitory effect of E.coli-OMV on 4T1 cells was positively correlated with time-dose. Flow cytometry results showed that E.coli-OMV arrested the growth cycle of 4T1 cells in G₀/G₁ phase. In vivo experiments showed that compared with the Control group, body weight of mice in the E.coli-OMV group decreased slightly after the initial injection (P=0.031), and then recovered, while 40 d survival rate increased (P=0.037). The growth of tumor volume and weight of mice in E.coli-OMV group were lower than those in the Control group (P=0.041, P=0.004). Its tumor volume inhibition rate reached 29.69%, and tumor weight inhibition rate reached 49.81%. The results of H-E staining showed that nuclear splitting images of tumor tissues of mice in the E.coli-OMV group decreased compared to the Control group (P=0.038). The results of immunohistochemical staining showed that the positive expression of PCNA and CyclinD1 in the tumor tissues of mice in the E.coli-OMV group decreased compared to the Control group (P=0.031, P=0.002). Conclusion ·Both in vitro and in vivo studies show that E.coli-OMV can significantly inhibit the proliferation of 4T1 cells.