Hu Wan-Ting, Yeh Chi-Chuan, Liu Shin-Yun, Huang Min-Chuan, Lai I-Rue
Graduate Institute of Anatomy and Cell Biology, College of Medicine, National Taiwan University Taipei, Taiwan.
Department of Surgery, National Taiwan University Hospital Taipei, Taiwan.
Am J Cancer Res. 2018 Sep 1;8(9):1739-1751. eCollection 2018.
Aberrant glycosylation affects the malignant progression of cancers. Here, we report that N-acetyl-galactosaminyltransferase 2 (GALNT2), an enzyme that initiates the mucin type-O glycosylation, suppresses malignant phenotypes in gastric adenocarcinoma (GCA) cells by modifying epidermal growth factor receptor (EGFR) activity. GALNT2 was knocked down using siRNA in AGS and MKN28 cells. The expression of phosphorylated EGFR (pEGFR), phosphorylated Akt (pAkt) and Tn antigen were detected by western blotting. Proliferation, migration and invasion of cells with/without GLANT2-knockdown were assessed. Expression of pEGFR in the resected gastric cancer tissue was analyzed by Immunohistochemical staining, and was correlated with clinicopathological factors. The results showed that GALNT2 knockdown enhanced phosphorylation of EGFR and decreased expression of the Tn antigen on EGFR. Inhibiting EGFR activity with Gefitinib decreased the migration/invasion abilities and reversed the increase pAkt caused by GALNT2 knockdown in GCA cells. The addition of MK2206 (Akt inhibitor) mitigated the migration and invasion abilities of the GALNT2-knockdown cells. Patients with increased expressions of pEGFR in their cancer tissues were associated more metastasis, advanced stage and recurrence after surgical resection. Our results indicate that GALNT2 suppresses the malignant potential of GCA cells through the EGFR-Akt signaling pathway. The significance of O-glycosylation in receptor tyrosine kinases activities and GCA progression deserve further studies.
异常糖基化影响癌症的恶性进展。在此，我们报告N-乙酰半乳糖胺基转移酶2（GALNT2），一种启动粘蛋白型O-糖基化的酶，通过调节表皮生长因子受体（EGFR）活性来抑制胃腺癌（GCA）细胞的恶性表型。在AGS和MKN28细胞中使用小干扰RNA敲低GALNT2。通过蛋白质印迹法检测磷酸化EGFR（pEGFR）、磷酸化Akt（pAkt）和Tn抗原的表达。评估有无GALNT2敲低的细胞的增殖、迁移和侵袭能力。通过免疫组织化学染色分析切除的胃癌组织中pEGFR的表达，并与临床病理因素相关联。结果显示，GALNT2敲低增强了EGFR的磷酸化并降低了EGFR上Tn抗原的表达。用吉非替尼抑制EGFR活性降低了迁移/侵袭能力，并逆转了GCA细胞中由GALNT2敲低引起的pAkt增加。添加MK2206（Akt抑制剂）减轻了GALNT2敲低细胞的迁移和侵袭能力。癌组织中pEGFR表达增加的患者与更多转移、晚期和手术切除后的复发相关。我们的结果表明，GALNT2通过EGFR-Akt信号通路抑制GCA细胞的恶性潜能。O-糖基化在受体酪氨酸激酶活性和GCA进展中的意义值得进一步研究。
