Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
Department of Pharmacology, Shanxi Medical University, Taiyuan 030001, China.
Cell Signal. 2020 Dec;76:109810. doi: 10.1016/j.cellsig.2020.109810. Epub 2020 Oct 15.
Induction of epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) characteristics underlie the development of metastasis, chemoresistance, and tumor recurrence in breast cancer. Downregulation of cytokeratin 18 (CK18) is a critical molecular event of EMT; however, its importance in the induction of EMT and CSC features has not been defined to date. This study aimed to investigate the biological significance and underlying molecular mechanisms of CK18 in inducing EMT phenotype and stemness properties of breast cancer cells. Three breast cancer cell lines (i.e., non-metastatic MCF-7, highly metastatic MDA-MB-231, and mitoxantrone (MX)-selected resistant MCF-7/MX cells) and two CK18-knockdown stable cell clones (MCF-7-shCK18-7D and 3C) were used to determine the association between CK18 and EMT and stemness. CK18 expression was extremely low in highly metastatic, resistant, and transforming growth factor (TGF)-β1/tumor necrosis factor (TNF)-α-treated breast cancer cells with mesenchymal phenotype and increased expression of CSC markers. Depletion of CK18 promoted partial EMT and the acquisition of stemness properties in breast cancer MCF-7 cells. Mechanistically, CK18 interference in MCF-7 cells activated the Wnt/β-catenin signaling, resulting in the up-regulation of epithelial cell adhesion molecule (EpCAM). Consistently, the stemness properties and metastasis can be attenuated by further knockdown of EpCAM in CK18-depleted cells. In conclusion, downregulation of CK18 promotes partial EMT and enhances breast cancer stemness by increasing EpCAM expression partly via the Wnt/β-catenin pathway. These findings indicate that CK18 may serve as a potential treatment target for advanced breast cancer.
上皮-间充质转化 (EMT) 和癌症干细胞 (CSC) 特征的诱导是乳腺癌转移、化疗耐药和肿瘤复发的基础。细胞角蛋白 18 (CK18) 的下调是 EMT 的一个关键分子事件；然而，其在 EMT 和 CSC 特征诱导中的重要性迄今尚未确定。本研究旨在探讨 CK18 在诱导乳腺癌细胞 EMT 表型和干细胞特性中的生物学意义和潜在分子机制。使用三种乳腺癌细胞系（即非转移性 MCF-7、高转移性 MDA-MB-231 和米托蒽醌 (MX) 选择耐药 MCF-7/MX 细胞）和两个 CK18 敲低稳定细胞克隆（MCF-7-shCK18-7D 和 3C）来确定 CK18 与 EMT 和干细胞之间的关联。具有间充质表型和 CSC 标志物高表达的高转移性、耐药和转化生长因子 (TGF)-β1/肿瘤坏死因子 (TNF)-α 处理的乳腺癌细胞中 CK18 表达极低。CK18 的耗竭促进了乳腺癌 MCF-7 细胞的部分 EMT 和干细胞特性的获得。从机制上讲，MCF-7 细胞中 CK18 的干扰激活了 Wnt/β-连环蛋白信号通路，导致上皮细胞黏附分子 (EpCAM) 的上调。一致地，CK18 耗尽细胞中 EpCAM 的进一步敲低可减弱干细胞特性和转移。总之，CK18 的下调通过增加 EpCAM 表达部分通过 Wnt/β-连环蛋白通路促进部分 EMT 并增强乳腺癌干细胞特性。这些发现表明 CK18 可能成为晚期乳腺癌的潜在治疗靶点。
