转移相关蛋白CPE△N在肺腺癌中的表达及相关分子机制研究

Lung cancer is one of the malignant tumors with the highest morbidity and mortality rates. There are no ideal molecular diagnostic tools that can predict metastasis and recurrence of lung cancer. CPE△N has recently been identified as a metastasis-associated protein. Our previous studies have shown that expression of CPE△N can be detected in 60% of lung adenocarcinoma samples. Among lung adenocarcinoma patients, recurrence rate and metastasis rate of CPE△N positive group was significantly higher than the rates of CPE△N negative group. Inhibition of CPE△N expression in highly metastatic lung cancer cell lines resulted in significantly decreased cell infiltration capacity. We also proved that CPE△N contributes to the activation of the Wnt signaling pathway. Interestingly, we found T-CPE, a new CPE variant, in lung cancer samples. The biological functions of T-CPE need to be clarified. In this study, we plan to further expand the number of samples, and verify whether CPE△N and T-CPE can be used as molecular markers to predict recurrence, metastasis, or poor prognosis of lung adenocarcinoma patients. We will also further clarify possible molecular mechanisms that involved in the regulation of Wnt signaling pathway by CPE△N and T-CPE. Our study might lead to the discovery of new molecular markers to predict recurrence or metastasis of lung adenocarcinoma patients. These finding could be a key guide in individualizing their cancer care to improve outcome.

肺癌是发病率和死亡率最高的恶性肿瘤，目前还没有合适的分子诊断工具可以预测肺癌的转移复发。CPE△是最近被鉴定出来的一个转移相关蛋白，本室的前期研究表明，在60%的肺腺癌组织中可以检测到CPE△N表达，CPE△N表达组病例的复发转移率显著高于CPE△N非表达组。在高转移肺癌细胞株中抑制CPE△N表达，细胞的浸润能力显著下降，CPE△N能够促进Wnt通路的活化。此外，在肺癌中我们还发现了一个新的CPE异构体T-CPE，其生物学功能尚不清楚。本研究拟扩大样本量，进一步确证CPE△N和T-CPE表达与肺腺癌复发、转移及预后不良的相关性。并采用报告基因、Real-time PCR、Western Blot及细胞侵袭等技术探明CPE△N、T-CPE参与Wnt信号调控的可能分子机制。我们的研究结果可能为肺癌转移复发找到新的标志分子，并有助于医生对患者分层，推进治疗的个性化进程。

CPEΔN是一个肿瘤转移相关蛋白。在这项研究中，我们证实在62.1%的肺腺癌组织中存在CPE和CPE△N的共表达（59/95）；而癌旁组织主要表达CPE,只有5.26%的病例表达CPE△N（5/95）。CPE△N的表达和淋巴结转移（p=0.026）具有相关性。CPE△N表达组患者术后3年复发、转移率显著高于CPE△N非表达组（p=0.009）。高表达CPEΔN可以加速肺癌细胞的浸润和转移。CPEΔN可以从mRNA和蛋白水平上抑制粘附相关蛋白E-cadherin的表达,恢复E-cadherin的表达，可以部分拮抗肺癌细胞的侵袭。免疫共沉淀和GST pull down实验证实CPEΔN可以和组蛋白去乙酰化酶HDAC1、HDAC3、Snail及甲基转移酶EZH2形成复合体。去乙酰化酶抑制剂TSA处理肺癌细胞或敲低Snail的表达，用可以削弱EZH2的募集，而HDAC3抑制剂RGFP966不影响CPEΔN和EZH2的结合。通过染色质免疫沉淀实验证实CPEΔN能够结合在E-cadherin启动子区的第2和第3个E-box盒上，过表达CPEΔN可以降低E-cadherin启动子区H3K27的乙酰化，增加H3K27的三甲基化修饰。这些研究数据支持，CPEΔN/HDAC1/HDAC3/Snail/EZH2可以形成转录抑制复合体，通过调节启动子区的表观修饰进而调节E-cadherin基因的转录。这是第一次证实定位在细胞核中的CPEΔN可以参与转录调控，这个研究结果能够从一个全新的角度诠释CPEΔN促进肿瘤转移的潜在分子机制。