Liaoning Provincial Core Lab of Glycobiology and Glycoengineering, Department of Biochemistry and Molecular Biology, College of Basic Medical Sciences, Dalian Medical University, Dalian, China.
Department of Oral Pathology, College of Stomatology, Dalian Medical University, Dalian, China.
J Cell Physiol. 2019 Apr;234(4):4504-4514. doi: 10.1002/jcp.27256. Epub 2018 Sep 24.
The transmembrane glycoprotein epithelial cell adhesion molecule (EpCAM) is overexpressed in most epithelial cancers including breast cancer, where it plays an important role in cancer progression. Previous study has demonstrated that knockdown of EpCAM inhibits breast cancer cell growth and metastasis via inhibition of the Ras/Raf/ERK signaling pathway and matrix metallopeptidase-9 (MMP-9). Although glycosylation is believed to be associated with the function of EpCAM, the contribution of N-glycosylation to this function remains unclear. We constructed the N-glycosylation mutation plasmid of EpCAM and used it to treat breast cancer cells. Loss of N-glycosylation at all three sites EpCAM had no effect on its level of expression or membrane localization. However, mutation at glycosylation sites significantly reduced the ability of EpCAM to promote epithelial to mesenchymal transition in breast cancer. N-glycosylation mutation of EpCAM led to decrease phosphorylation of Raf, ERK, and Akt, and inhibited the Ras/Raf/ERK and PI3K/Akt signaling pathways. Furthermore, we demonstrated that N-glycosylation mutation of EpCAM-mediated invasion and metastasis of breast carcinoma cells required the downregulation of MMP-9 via inhibition of these two signaling pathways. Our results identified the characteristics and function of EpCAM glycosylation. These data could illuminate molecular regulation of EpCAM by glycosylation and promote our understanding of the application of glycosylated EpCAM as a target for breast cancer therapy.
跨膜糖蛋白上皮细胞黏附分子（EpCAM）在大多数上皮性癌症中过度表达，包括乳腺癌，在乳腺癌中，它在癌症进展中发挥重要作用。先前的研究表明，通过抑制 Ras/Raf/ERK 信号通路和基质金属蛋白酶-9（MMP-9），EpCAM 的敲低可抑制乳腺癌细胞的生长和转移。尽管糖基化被认为与 EpCAM 的功能有关，但 N-糖基化对该功能的贡献仍不清楚。我们构建了 EpCAM 的 N-糖基化突变质粒，并将其用于治疗乳腺癌细胞。EpCAM 的三个位点的 N-糖基化缺失对其表达水平或膜定位没有影响。然而，糖基化位点的突变显著降低了 EpCAM 促进乳腺癌上皮间质转化的能力。EpCAM 的 N-糖基化突变导致 Raf、ERK 和 Akt 的磷酸化减少，并抑制了 Ras/Raf/ERK 和 PI3K/Akt 信号通路。此外，我们证明 EpCAM N-糖基化突变通过抑制这两个信号通路介导乳腺癌细胞的侵袭和转移，需要 MMP-9 的下调。我们的研究结果确定了 EpCAM 糖基化的特征和功能。这些数据可以阐明糖基化 EpCAM 的分子调控，并促进我们对糖基化 EpCAM 作为乳腺癌治疗靶点的应用的理解。
