The Breast Cancer Biology Program, Barbara Ann Karmanos Cancer Institute; Department of Oncology and Pathology, Wayne State University School of Medicine, HWCRC, Room 840.2, 4100 John R Street, Detroit, MI 48201, USA.
Cancer Res. 2011 Jul 15;71(14):4846-56. doi: 10.1158/0008-5472.CAN-11-0414. Epub 2011 Jul 12.
In this study, we have showed that GCNT2, a gene-encoding glucosaminyl (N-acetyl) transferase 2, I-branching enzyme, is overexpressed in highly metastatic breast cancer cell lines of human and mouse origin and basal-like breast tumor samples. GCNT2 expression is also significantly correlated to the metastatic phenotype in breast tumor samples. Functional studies showed that ectopic expression of GCNT2 enhances cell detachment, adhesion to endothelial cells, cell migration and invasion in vitro, and lung metastasis of breast cancer cells in vivo. Knockdown of GCNT2 expression decreases cell migration and invasion in vitro and lung metastasis in vivo. We have further shown the involvement of GCNT2 in the epithelial-to-mesenchymal transition (EMT). Specifically, the expression of E-cadherin is significantly changed upon GCNT2 expression at the protein level but not at the RNA level. Moreover, we have shown that GCNT2 is a direct target of the TGF-β-smad pathway and that change in GCNT2 expression modulates EMT induced by TGF-β1 treatment. Finally, we have shown that diminution of the glycosyltransferase activity of I-branching β-1, 6-N-acetylglucosaminyl transferase 2 (GCNT2) abrogates its cell migration and invasion-promoting function and synergistic effect with TGF-β to induce EMT. Our study for the first time showed that GCNT2 is a novel gene contributing to breast cancer metastasis with preferential expression in basal-like breast cancer. Moreover, we discovered that involvement of GCNT2 in EMT and TGF-β signaling, and further glycosylation modification of E-cadherin by GCNT2, are the underlying integrative mechanisms for breast cancer metastasis, implying that blocking TGF-β/GCNT2 signaling is a promising approach for targeting metastatic breast cancer.
在这项研究中，我们表明，编码糖基转移酶 2（Glucosaminyl（N-乙酰）转移酶 2，I-分支酶）的基因 GCNT2 在人源和鼠源高转移性乳腺癌细胞系以及基底样乳腺癌肿瘤样本中过度表达。GCNT2 表达也与乳腺癌肿瘤样本中的转移表型显著相关。功能研究表明，GCNT2 的异位表达增强了细胞体外分离、与内皮细胞的黏附、细胞迁移和侵袭，以及乳腺癌细胞体内肺转移。GCNT2 表达的敲低降低了细胞体外迁移和侵袭以及体内肺转移。我们进一步表明 GCNT2 参与上皮间质转化（EMT）。具体而言，GCNT2 表达在蛋白水平而非 RNA 水平上显著改变 E-钙粘蛋白的表达。此外，我们表明 GCNT2 是 TGF-β-smad 途径的直接靶标，并且 GCNT2 表达的变化调节 TGF-β1 处理诱导的 EMT。最后，我们表明，分支β-1,6-N-乙酰葡萄糖胺基转移酶 2（GCNT2）的糖基转移酶活性的减弱会破坏其促进细胞迁移和侵袭的功能，并与 TGF-β 协同诱导 EMT。我们的研究首次表明，GCNT2 是促进乳腺癌转移的新基因，在基底样乳腺癌中优先表达。此外，我们发现 GCNT2 参与 EMT 和 TGF-β 信号通路，以及 GCNT2 对 E-钙粘蛋白的进一步糖基化修饰，是乳腺癌转移的潜在整合机制，这意味着阻断 TGF-β/GCNT2 信号通路是靶向转移性乳腺癌的一种有前途的方法。
