Let －7c 通过阻断雌激素激活的 Wnt 信号通路活性而抑制乳腺癌干细胞的自我更新能力

目的：探究 Let －7c 是否能通过 Wnt 信号通路调控乳腺癌干细胞自我更新能力。方法：分析乳腺癌临床样本中 Let －7家族成员的表达情况，检测 Let －7与 ERα的相关性，进一步探讨 Let －7c 与 Wnt 通路活性分子表达的相关性；在细胞试验中，通过 ALDH 流式细胞仪分选法及微成球实验分选乳腺癌干细胞；采用免疫印迹、荧光素酶报告试验及免疫荧光实验，验证 Let －7c 与 ERα－3＇UTR 是否能直接结合。结果：Let －7家族成员在乳腺癌组织中高表达，并且 Let －7b 和 Let －7c 的表达与患者临床预后显著相关；Let －7c 表达与ERα表达呈负相关，Let －7c 表达与 Wnt 信号通路活性分子呈负相关；Let －7c 能够抑制雌激素受体阳性乳腺癌干细胞自我更新能力；Let －7c 能够直接结合到 ERα－3＇UTR 上，进而抑制 ERα的表达和雌激素激活的Wnt 信号通路。结论：我们的研究首次证实了 Let －7c 通过抑制雌激素激活的 Wnt 通路活性，而对肿瘤干细胞的自我更新能力产生抑制作用。

Let -7c suppresses the activity of estrogen induced Wnt signaling and represses the self-renewal ability of breast cancer stem cells

Objective:To study the effects of Let -7 on Wnt signaling pathway in breast cancer stem cells.Meth-ods:We first checked the expression levels of Let -7 family in clinical tissues,and then detected the correlation be-tween Let -7c and ERαexpression.Further,the relationship among Let -7c and Wnt signaling was examined in clin-ical tissues.Through Western blot,luc -assay and immunofluorescence staining,we then explored the roles of Let -7c in breast cancer stem cells(BCSCs),and tested whether Let -7 can directly regulate the expression of ERαand Wnt signal.Using Lentivirus -mediated RNA interference technology,we detected that whether regulated ERα.Results:We found that higher expression levels of Let -7b and Let -7c indicate better clinical prognosis(P <0.01).Further, we found that only Let -7c was inversely correlated with ERαexpression.Besides,Let -7c repressed estrogen in-duced self -renewal of stem cells.We confirmed that Let -7 decreased ERαby degrading the mRNA,and also,en-forced Let -7c inhibited the activity of estrogen induction of Wnt signaling pathway.Conclusion:Let -7c inhibited estrogen induced Wnt activity through decreasing ERαexpression level.