Elston Marianne S, Gill Anthony J, Conaglen John V, Clarkson Adele, Shaw Janet M, Law Andrew J J, Cook Raymond J, Little Nicholas S, Clifton-Bligh Roderick J, Robinson Bruce G, McDonald Kerrie L
Cancer Genetics Unit, Kolling Institute of Medical Research, Royal North Shore Hospital, St. Leonards, New South Wales 2065, Australia.
Endocrinology. 2008 Mar;149(3):1235-42. doi: 10.1210/en.2007-0542. Epub 2007 Dec 13.
The etiology of sporadic pituitary tumors is currently unknown. The Wnt pathways have been implicated in the pathogenesis of a variety of human tumors, but the role of these pathways in pituitary tumors is unclear. Microarray analysis using the Affymetrix HG U133 plus 2.0 GeneChips identified four secreted frizzled-related protein (sFRP) family members of Wnt pathway inhibitors that were differentially expressed in both nonfunctioning and clinically functioning pituitary tumors (n = 20) compared with normal pituitary controls (n = 3). Reduced tumor expression of Wnt inhibitory factor-1 (WIF1), sFRP2, and sFRP4 mRNA was confirmed by real-time quantitative RT-PCR (P <0.001 and P = 0.002 and 0.013, respectively) in all pituitary subtypes. Hypermethylation of the WIF1 promoter was present in 88% of the pituitary tumors (n = 41). Seventy-six percent of pituitary tumors demonstrated absent or weak cytoplasmic WIF1 staining by immunohistochemistry (n = 41), although preserved staining was seen in some functioning tumors, with strong staining in 92% of normal pituitary controls (n = 13). The Wnt pathway target gene cyclin D1 was found to be up-regulated specifically in the nonfunctioning pituitary tumors compared with controls at both mRNA and protein level, supportive of activation of the Wnt-beta-catenin pathway. Nuclear accumulation of beta-catenin, however, was not observed in any pituitary tumors (n = 70). By transfecting GH3 cells with WIF1, decreased cell proliferation and colony formation was observed compared with empty vector controls. In conclusion, our data suggest that WIF1 may be a tumor suppressor, specifically in nonfunctioning pituitary tumors, and that the Wnt pathways are important in pituitary tumorigenesis.
散发性垂体瘤的病因目前尚不清楚。Wnt信号通路与多种人类肿瘤的发病机制有关，但这些通路在垂体瘤中的作用尚不清楚。使用Affymetrix HG U133 plus 2.0基因芯片进行的微阵列分析确定了Wnt信号通路抑制剂的四个分泌型卷曲相关蛋白（sFRP）家族成员，与正常垂体对照（n = 3）相比，它们在无功能和有临床功能的垂体瘤（n = 20）中差异表达。通过实时定量RT-PCR在所有垂体亚型中证实Wnt抑制因子-1（WIF1）、sFRP2和sFRP4 mRNA的肿瘤表达降低（分别为P <0.001、P = 0.002和0.013）。88%的垂体瘤（n = 41）存在WIF1启动子的高甲基化。76%的垂体瘤通过免疫组织化学显示细胞质WIF1染色缺失或弱阳性（n = 41），尽管在一些有功能的肿瘤中可见保留的染色，在92%的正常垂体对照（n = 13）中染色强。与对照相比，发现Wnt信号通路靶基因细胞周期蛋白D1在无功能垂体瘤的mRNA和蛋白质水平均特异性上调，支持Wnt-β-连环蛋白信号通路的激活。然而，在任何垂体瘤（n = 70）中均未观察到β-连环蛋白的核积累。通过用WIF1转染GH3细胞，与空载体对照相比，观察到细胞增殖和集落形成减少。总之，我们的数据表明WIF1可能是一种肿瘤抑制因子，特别是在无功能垂体瘤中，并且Wnt信号通路在垂体瘤发生中很重要。
