中文摘要：

目的探讨乳酸菌培养上清液（1actobacilli supernatants，LS）处理乳腺癌细胞对顺铂（cisplatin，DDP）敏感性的影响及其机制。方法采用CCK．8和Westernblot检测不同浓度DDP（0、1、2、3、4、5μg／mL）和Ls（体积分数分别为1％、5％、10％、20％）对三阴性乳腺癌细胞MDA．MB-231增殖和Piwil2基因表达的影响；瞬时转染Piwil2siRNA沉默MDA-MB．231细胞中Piwil2基因表达，Westernblot检测其沉默效果，CCK-8检测Piwil2基因沉默后对MDA—MB-231细胞增殖的影响；2μg／mLDDP联合不同浓度LS（体积分数分别为1％、5％、10％、20％）作用MDA．MB．231细胞，观察细胞增殖抑制效应和Piwil2蛋白表达的改变。结果高浓度DDP（≥3μg／mL）可抑制MDA．MB-231细胞的增殖（P〈0．05），而低浓度DDP（≤2μg／mL）不能有效抑制细胞增殖；DDP以剂量依赖性方式上调Piwil2蛋白的表达；siRNA沉默Piwil2表达可恢复2μg／mLDDP对细胞增殖的抑制。与对照组（乳酸菌培养基，MRS）比较，LS以剂量依赖性方式下调Piwil2蛋白的表达，但并不影响细胞的增殖；与单用2μg／mLDDP比较，2μg／mLDDP联合20％LS处理可显著下调Piwil2蛋白的表达并抑制细胞增殖（P〈0．05）。结论三阴性乳腺癌细胞中Piwil2的高表达可导致细胞对顺铂敏感性的降低，乳酸菌培养上清液可通过下调Piwil2基因的表达增强三阴性乳腺癌细胞对顺铂的敏感性。

英文摘要：

Objective To assess the effect of Lactobacilli culture supernatant （LS） on the sensitivity of breast cancer cell line MDA-MB-231 to cisplatin （DDP） and investigate its underlying mechanism. Methods CCK8 assay and Western blotting were used to observe the proliferation and the expression of Piwil2, respectively, in triple-negative MDA-MB-231 cells treated with DDP（0, 1, 2, 3, 4 and 5 μg/mL） or LS （1%, 5%, 10% and 20%, V/V） for 24 h. In MDA-MB-231 cells transiently transfeeted with Piwil2 siRNA to silence the expression of Piwil2, the cell proliferation was detected with CCK8 assay. The expression of Piwil2 and cell proliferation were also observed in the MDA-MB-231 cells treated with 2 μg/mL DDP combined with LS （1%, 5%, 10% and 20% ,V/V） for 24 h. Results DDP at high doses（ ≥3 μg/mL）, but not at lower doses （ ≤2 μg/mL）, effectively inhibited the proliferation of MDA-MB-231 cells （P 〈 0.05 ）. Western blotting showed that DDP up-regulated the expression of Piwil2 in a dose-dependent manner, siRNA- mediated Piwil2 silencing restored the inhibitory effect of 2 μg/mL DDP on the proliferation of MDA-MB-231 ceils. Compared with the culture medium for Lactobacilli that did not contain Lactobacilli（ vehicle）, LS dose-dependently down-regulated the expression of Piwil2 without affecting the cell proliferation. Compared with DDP（2 μg/mL） treatment alone, DDP （ 2 μg/mL） combined with LS （ 20% ） significantly down-regulated Piwil2 expression and also inhibited the proliferation of MDA-MB-231 ceils （P 〈 0.05）. Conclusion High expression of Piwil2 may cause lowered sensitivity of tumor cells to DDP, and LS can enhance the sensitivity of MDA-MB-231 cells to DDP by down regulating Piwil2.