Rap1 stabilizes beta-catenin and enhances beta-catenin-dependent transcription and invasion in squamous cell carcinoma of the head and neck.
Rap1 stabilizes beta-catenin and enhances beta-catenin-dependent transcription and invasion in squamous cell carcinoma of the head and neck.
复制标题
Rap1 可稳定 β-连环蛋白并增强头颈部鳞状细胞癌中 β-连环蛋白依赖性转录和侵袭。
DOI：
10.1158/1078-0432.ccr-09-1122
复制
发表时间：
2010-01-01
期刊：
影响因子：
--
通讯作者：
D'Silva NJ
中科院分区：
文献类型：
--
作者：
Goto M;Mitra RS;Liu M;Lee J;Henson BS;Carey T;Bradford C;Prince M;Wang CY;Fearon ER;D'Silva NJ
在头颈部鳞状细胞癌（HNSCC）细胞中，Rap 1穿梭于细胞核和细胞质之间。先前的研究结果表明，Rap 1可能在某些情况下调节β-catenin非依赖性Wnt通路，但Rap 1在β-catenin依赖性Wnt信号传导中的作用仍不明确。我们观察到β-catenin在体外与活性Rap 1结合，Rap 1激活β-catenin-TCF（T细胞因子）依赖的转录。免疫荧光研究表明Rap 1的异位表达增加了β-catenin的核转位。活性Rap 1的过表达促进了β-连环蛋白介导的转录的增加，而这种转录被显性负性TCF 4所消除。相反，siRNA介导的内源性Rap 1表达抑制β-catenin/TCF介导的转录以及HNSCC的侵袭。抑制Rap 1表达可下调β-catenin/TCF的转录靶点MMP 7的表达。在用β-catenin稳定转染或用氯化锂或Wnt 3A处理以稳定内源性β-catenin的HNSCC细胞中，Rap 1表达的抑制导致β-catenin游离池的减少。对HNSCC患者组织的免疫组织化学研究表明，β-连环蛋白强度的增加与较高的肿瘤分期相关。此外，发现活性Rap 1对肿瘤N期的预后影响依赖于胞浆β-catenin表达（p<0.013）。当β-catenin高时，rap 1GTP强度越高，N分期越晚。研究结果表明，Rap 1增强β-catenin的稳定性和核定位。除了表明Rap 1在调节β-连环蛋白和β-连环蛋白依赖性进展为更晚期N期病变方面具有重要作用外，这些数据还强调Rap 1是HNSCC的潜在治疗靶点。
In head and neck squamous cell carcinoma (HNSCC) cells, Rap1 shuttles between the nucleus and cytoplasm. Prior findings suggested that Rap1 may modulate the β-catenin-independent Wnt pathway in some settings, but the role of Rap1 in β-catenin-dependent Wnt signaling remains undefined. We observed that β-catenin bound to active Rap1 in vitro and Rap1 activated β-catenin-TCF (T cell factor)-dependent transcription. Immunofluorescence studies showed that ectopic expression of Rap1 increased nuclear translocation of β-catenin. Overexpression of active Rap1 facilitated an increase in β-catenin-mediated transcription that was abrogated by dominant negative TCF4. Conversely, siRNA-mediated inhibition of endogenous Rap1 expression inhibited β-catenin/TCF-mediated transcription as well as invasion of HNSCC. Furthermore, inhibition of Rap1 expression downregulated the expresesion of MMP7, a transcriptional target of β-catenin/TCF. In HNSCC cells stably transfected with β-catenin or treated with lithium chloride or Wnt3A to stabilize endogenous β-catenin, inhibition of Rap1 expression led to decreases in the free pool of β-catenin. Immunohistochemical studies of tissue from HNSCC patients revealed that increased β-catenin intensity correlated with higher tumor stage. Furthermore, the prognostic effect of active Rap1 on tumor N-stage was found to depend on cytosolic β-catenin expression (p<0.013). When β-catenin is high, higher rap1GTP intensity is associated with more advanced N stage. The findings suggest that Rap1 enhances β-catenin stability and nuclear localization. In addition to indicating that Rap1 has a significant role in regulating β-catenin and β-catenin-dependent progression to more advanced N-stage lesions, these data highlight Rap1 as a potential therapeutic target in HNSCC.