Sun Gangyi, Shang Ziyi, Liu Wenjia
Department of Massage, The Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan 250000, China.
Treating Potential Diseases Branch, The Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan 250000, China.
J Oncol. 2021 Jul 27;2021:1642852. doi: 10.1155/2021/1642852. eCollection 2021.
Radiotherapy has been widely applied for the treatment of locally advanced and metastatic gastric adenocarcinoma (GAC). The aberrant expression of secreted phosphoprotein 1 (SPP1) is involved in radiosensitivity in a variety of cancers. The present study aims to characterize the clinical significance of SPP1 expression in GAC and its role and underlying mechanism of radiosensitivity.
The SPP1 expression in GAC tissues and pericarcinomatous tissues was determined by QRT-PCR and immunohistochemistry, and the SPP1 expression in GAC cell lines (BGC823, AGS, and SGC7901) and normal human gastric epithelial cell line (GES-1) was determined by western blot. -test, one-way ANOVA, Cox regression model, and Kaplan-Meier plotter were applied to further assess the association between SPP1 expression and the prognosis of the patients with GAC. After irradiation and transfection with si-SPP1 combined with or without Wnt/-catenin pathway inhibitor (XAV939), western blot, transwell, flow cytometry, and TOP-flash reporter assay were applied to detect DNA damage, invasion, apoptosis, cell cycle, and activation of Wnt/-catenin pathway, respectively.
SPP1 mRNA and protein levels in GAC tissues were both dramatically higher than those in pericarcinomatous tissues. SPP1 overexpression was positively associated with tumor size, nodal status, and histological grade of GAC patients. SPP1 overexpression, depth of invasion, and nodal status were independent prognostic factors for the patients. High SPP1 expression was negatively related to the overall survival in patients with GAC. We found that SPP1 knockdown enhanced the radiosensitivity of GAC cell lines (AGS and SGC7901). Increasing H2AX phosphorylation, apoptosis and G2/M phase arrest, and decreasing invasion were observed after the administration of si-SPP1 and irradiation. Radiosensitivity of SPP1 was mainly dependent on the Wnt/-catenin signal pathway. XAV939 could enhance these phenomena induced by irradiation combined with SPP1 knockdown.
This study demonstrates that SPP1 suppresses Wnt/-catenin signaling to enhance the radiosensitivity of GAC via inhibiting invasion and accelerating DNA damage, G2/M phase arrest, and apoptosis.
放射疗法已广泛应用于局部晚期和转移性胃腺癌（GAC）的治疗。分泌性磷蛋白1（SPP1）的异常表达与多种癌症的放射敏感性有关。本研究旨在探讨SPP1表达在GAC中的临床意义及其在放射敏感性中的作用和潜在机制。
采用实时定量聚合酶链反应（QRT-PCR）和免疫组织化学法检测GAC组织和癌旁组织中SPP1的表达，采用蛋白质免疫印迹法检测GAC细胞系（BGC823、AGS和SGC7901）及人正常胃上皮细胞系（GES-1）中SPP1的表达。采用t检验、单因素方差分析、Cox回归模型和Kaplan-Meier绘图法进一步评估SPP1表达与GAC患者预后的相关性。在照射并转染小干扰RNA（si-SPP1）联合或不联合Wnt/β-连环蛋白信号通路抑制剂（XAV939）后，分别采用蛋白质免疫印迹法、Transwell小室实验、流式细胞术和TOP-flash报告基因检测法检测DNA损伤、侵袭、凋亡、细胞周期及Wnt/β-连环蛋白信号通路的激活情况。
GAC组织中SPP1的mRNA和蛋白水平均显著高于癌旁组织。SPP1过表达与GAC患者的肿瘤大小、淋巴结状态及组织学分级呈正相关。SPP1过表达、浸润深度和淋巴结状态是患者的独立预后因素。GAC患者中高SPP1表达与总生存期呈负相关。我们发现敲低SPP1可增强GAC细胞系（AGS和SGC7901）的放射敏感性。给予si-SPP1并照射后，可观察到H2AX磷酸化增加、凋亡增加、G2/M期阻滞以及侵袭减少。SPP1的放射敏感性主要依赖于Wnt/β-连环蛋白信号通路。XAV939可增强照射联合敲低SPP1诱导的上述现象。
本研究表明，SPP1通过抑制侵袭、加速DNA损伤、G2/M期阻滞和凋亡来抑制Wnt/β-连环蛋白信号传导，从而增强GAC的放射敏感性。
