* Department of Anatomy, Mahidol University, Bangkok, Thailand.
† Department of Biochemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.
Am J Chin Med. 2017;45(3):615-633. doi: 10.1142/S0192415X17500367. Epub 2017 Apr 6.
Cholangiocarcinoma (CCA) is increasing in incidence worldwide and is resistant to chemotherapeutic agents, making treatment of CCA a major challenge. Previous studies reported that natural sulfated polysaccharides (SPs) disrupted growth factor receptor activation in cancer cells. The present study, therefore, aimed at investigating the antiproliferation effect of sulfated galactans (SG) isolated from the red seaweed Gracilaria fisheri (G. fisheri) on CCA cell lines. Direct binding activity of SG to CCA cells, epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) were determined. The effect of SG on proliferation of CCA cells was investigated. Cell cycle analyses and expression of signaling molecules associated with proliferation were also determined. The results demonstrated that SG bound directly to EGFR. SG inhibited proliferation of various CCA cell lines by inhibiting EGFR and extracellular signal-regulated kinases (ERK) phosphorylation, and inhibited EGF-induced increased cell proliferation. Cell cycle analyses showed that SG induced cell cycle arrest at the G/G phase, down-regulated cell cycle genes and proteins (cyclin-D, cyclin-E, cdk-4, cdk-2), and up-regulated the tumor suppressor protein P53 and the cyclin-dependent kinase inhibitor P21. Taken together, these data demonstrate that SG from G. fisheri inhibited proliferation of CCA cells, and its mechanism of inhibition is mediated, to some extent, by inhibitory effects on EGFR activation and EGFR/ERK signaling pathway. SG presents a potential EGFR targeted molecule, which may be further clinically developed in a combination therapy for CCA treatment.
胆管癌（CCA）的发病率在全球范围内呈上升趋势，并且对化疗药物具有抗性，因此治疗 CCA 是一个主要挑战。先前的研究报告称，天然硫酸化多糖（SPs）会破坏癌细胞中生长因子受体的激活。因此，本研究旨在研究从红海藻石花菜（G. fisheri）中分离出的硫酸化半乳糖（SG）对 CCA 细胞系的抗增殖作用。测定了 SG 与 CCA 细胞、表皮生长因子（EGF）和表皮生长因子受体（EGFR）的直接结合活性。研究了 SG 对 CCA 细胞增殖的影响。还测定了与增殖相关的信号分子的细胞周期分析和表达。结果表明，SG 直接与 EGFR 结合。SG 通过抑制 EGFR 和细胞外信号调节激酶（ERK）磷酸化来抑制各种 CCA 细胞系的增殖，并抑制 EGF 诱导的细胞增殖增加。细胞周期分析表明，SG 诱导细胞周期停滞在 G1/G0 期，下调细胞周期基因和蛋白（细胞周期蛋白-D、细胞周期蛋白-E、cdk-4、cdk-2），并上调肿瘤抑制蛋白 P53 和细胞周期蛋白依赖性激酶抑制剂 P21。总之，这些数据表明，G. fisheri 的 SG 抑制了 CCA 细胞的增殖，其抑制机制在某种程度上是通过抑制 EGFR 激活和 EGFR/ERK 信号通路来介导的。SG 呈现出一种潜在的 EGFR 靶向分子，可进一步在 CCA 治疗的联合治疗中进行临床开发。
