Jung Soon-Young, Lee Hyun Kyoung, Kim Hyungmin, Kim Seulki, Kim Jung Soo, Kang Jeong Gu, Kuh Hyo-Jeong, Yoo Jong Shin, Ko Jeong-Heon, Lee Jeong-Hwa
Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul, 06591, South Korea; Institute for Aging and Metabolic Diseases, College of Medicine, The Catholic University of Korea, Seoul, 06591, South Korea.
Research Center of Bioconvergence Analysis, Korea Basic Science Institute, Cheongju, 28119, South Korea.
Biochem Biophys Res Commun. 2021 Oct 20;575:78-84. doi: 10.1016/j.bbrc.2021.08.055. Epub 2021 Aug 25.
Alterations in sialylation of terminal residues of glycoproteins have been implicated in forming tumor-associated glycans. ST6GALNAC transfers sialyl moiety to N-acetylgalactosamine residue via α2,6 linkage. Although the oncogenic characteristics of ST6GALNACI or II have been demonstrated in various cancer cells, the impact of ST6GALNACIII on tumor progression remains undefined. In this study, we evaluated the effect of ST6GALNACIII knockdown on the growth of A549 non-small cell lung cancer cells. ST6GALNACIII depletion resulted in significant retardation in growth of A549 cells under various culture conditions, including collagen-supported 3D culture and anchorage-independent soft agar culture conditions. Liquid chromatography with tandem mass spectrometry revealed that two glycopeptides of transferrin receptor protein 1 (TFR1) containing N-acetylhexosamine-sialic acid were not detected in ST6GALNACIII-depleted A549 cells compared with control cells. Subsequent lectin binding assay, western blotting, and real-time RT-PCR indicated that TFR1 sialylation was not significantly changed, but TFR1 protein and mRNA expressions were decreased after ST6GALNACIII knockdown. However, cell growth retardation by ST6GALNACIII knockdown was partially rescued by TFR1 overexpression. Additionally, TFR1 mRNA degradation was accelerated following ST6GALNACIII knockdown with concomitant reduction in mRNA levels of iron regulatory protein 1 and 2, the upstream regulators of TFR1 mRNA stability. Therefore, our results indicated an important role of ST6GALNACIII in promoting A549 cell growth through quantitative regulation of TFR1 expression and provided therapeutic implications for ST6GALNACIII targeting in tumor growth suppression in vivo.
糖蛋白末端残基的唾液酸化改变与肿瘤相关聚糖的形成有关。ST6GALNAC通过α2,6连接将唾液酸部分转移至N-乙酰半乳糖胺残基上。尽管ST6GALNACI或II的致癌特性已在多种癌细胞中得到证实，但ST6GALNACIII对肿瘤进展的影响仍不明确。在本研究中，我们评估了敲低ST6GALNACIII对A549非小细胞肺癌细胞生长的影响。在包括胶原支持的3D培养和非贴壁软琼脂培养条件在内的各种培养条件下，敲低ST6GALNACIII导致A549细胞生长显著迟缓。液相色谱-串联质谱分析显示，与对照细胞相比，在敲低ST6GALNACIII的A549细胞中未检测到两种含有N-乙酰己糖胺-唾液酸的转铁蛋白受体蛋白1（TFR1）糖肽。随后的凝集素结合试验、蛋白质印迹法和实时RT-PCR表明，TFR1的唾液酸化没有显著变化，但敲低ST6GALNACIII后TFR1蛋白和mRNA表达降低。然而，TFR1过表达部分挽救了敲低ST6GALNACIII引起的细胞生长迟缓。此外，敲低ST6GALNACIII后TFR1 mRNA降解加速，同时TFR1 mRNA稳定性的上游调节因子铁调节蛋白1和2的mRNA水平降低。因此，我们的结果表明ST6GALNACIII在通过定量调节TFR1表达促进A549细胞生长中起重要作用，并为体内靶向ST6GALNACIII抑制肿瘤生长提供了治疗意义。
