Xiao Xiaomin, Xiao Yingying, Wen Ruiling, Zhang Yuhua, Li Xiaoxia, Wang Haoli, Huang Jianqiong, Liu Jiahua, Long Tiandi, Tang Jun
KingMed Diagnostics and KingMed School of Laboratory Medicine, Guangzhou Medical University, Guangzhou, P.R. China.
Oncol Rep. 2015 Nov;34(5):2259-66. doi: 10.3892/or.2015.4221. Epub 2015 Aug 21.
The secreted frizzled-related protein 2 (SFRP2) plays a pivotal role in the Wnt pathway, however, it functions as an agonist or an antagonist is still controversial. We profiled SFRP2 expression in several lung cancer cell lines, and found that A549 and 95-D exhibited the lowest and the highest level of SFRP2, respectively. Then we employed the SFRP2-overexpressing plasmid and siRNA to transfect A549 and 95-D cells, respectively. Through MTT assays, we found that SFRP2 knockdown inhibited cell proliferation, and halted the 95-D cells in G1 phase of the cell cycle by downregulation of CCND1 and CDK4, indicating that SFRP2 has the ability of promoting lung cancer cell proliferation. We further checked the cell properties of migration and invasion, using wound scratch assay and Transwell assays. The data showed decreased migrated and invasive 95-D cells after SFRP2 knockdown, and the observations were the opposite in the overexpressing model, implying that SFRP2 promoted lung cancer cell invasion. Moreover, the canonical Wnt pathway was also studied through detection of β-catenin by western blotting. In the SFRP2 overexpressing model, A549 cells presented stronger expression of β-catenin compared with controls, while it was the opposite in 95-D cells. These results suggested that SFRP2 serves as a Wnt agonist in lung cancer cells. Together, the findings of this study implied that SFRP2 is not only an agonist of Wnt pathway, but also a cancer promoting protein for lung cancer, indicating SFRP2 as a promising therapeutic target for lung cancer treatment.
分泌型卷曲相关蛋白2（SFRP2）在Wnt信号通路中起关键作用，然而，其作为激动剂还是拮抗剂发挥作用仍存在争议。我们分析了几种肺癌细胞系中SFRP2的表达情况，发现A549和95-D细胞系分别呈现出最低和最高水平的SFRP2。然后我们分别用SFRP2过表达质粒和小干扰RNA（siRNA）转染A549和95-D细胞。通过MTT实验，我们发现敲低SFRP2可抑制细胞增殖，并通过下调细胞周期蛋白D1（CCND1）和细胞周期蛋白依赖性激酶4（CDK4）使95-D细胞停滞在细胞周期的G1期，这表明SFRP2具有促进肺癌细胞增殖的能力。我们进一步通过划痕实验和Transwell实验检测细胞的迁移和侵袭特性。数据显示，敲低SFRP2后95-D细胞的迁移和侵袭能力下降，而过表达模型中的观察结果则相反，这意味着SFRP2促进肺癌细胞侵袭。此外，我们还通过蛋白质免疫印迹法检测β-连环蛋白，对经典Wnt信号通路进行了研究。在SFRP2过表达模型中，与对照组相比，A549细胞中β-连环蛋白的表达更强，而在95-D细胞中情况则相反。这些结果表明SFRP2在肺癌细胞中作为Wnt激动剂发挥作用。综上所述，本研究结果表明SFRP2不仅是Wnt信号通路的激动剂，也是一种促进肺癌发生的蛋白，提示SFRP2有望成为肺癌治疗的靶点。
