癌睾抗原CT45A1促进肺癌细胞侵袭和转移的作用及其机制

Cancer/testis antigens (CTA) play an important role in carcinogenesis. We recently reported that CTA member CT45A1 promoted EMT, invasion and metastasis of breast cancer. Our preliminary research results showed that CT45A1 overexpression in lung cancer cases was closely associated with the poor prognosis of the patients, and that CT45A1 also enhanced the migration and invasion of lung cancer cells, and promoted transcription of key tumor metastatic genes, such as CXCR4；however，the mechanisms are largely unknown. In this research project, we aim to elucidate the mechanisms of CT45A1-enhanced lung cancer cell invasion and metastasis at molecular, cellular, and in vivo three levels as follows: (1) at the molecular level, we will reveal the mechanisms of CT45A1 to promote the transcription of CXCR4 and EGFR genes, analyze the 3-dimentional crystal structure of CT45A1 protein-CXCR4 promoter complex and its function; we will also study the interaction between CT45A1 and the transcription factors, and elucidate the molecular mechanisms of CT45A1 acting as a gene transcriptional activator to boost transcription of CXCR4 and EGFR genes. (2) At the levels of cells, animals, and lung cancer patients, we will reveal the role and mechanism of CT45A1 to enhance the invasion and spread of lung cancer cells in the lung tissue, and metastasis of CT45A1-induced CXCR4-overexpressing lung cancer cells to the bone and brain tissues. This project will provide new thoughts for elucidating the mechanisms of lung cancer invasion and metastasis, and to solving the difficult problems in lung cancer therapy.

癌睾抗原（CTAs）在肿瘤发生中起重要作用。近来，我们报道了CTAs 成员CT45A1促进乳腺癌细胞EMT、侵袭和转移。预研结果显示，CT45A1在肺癌患者高表达与病人预后差密切相关，也能增强肺癌细胞迁移和侵袭能力，及促进CXCR4等肿瘤转移关键基因转录，但其作用机制不明。本项目将在分子、细胞和体内三个层次，研究CT45A1促进肺细胞癌侵袭和转移的作用及其机制：（1）在分子水平，揭示CT45A1促进CXCR4和 EGFR基因转录的机理，解析CT45A1蛋白-CXCR4启动子复合物的三维晶体结构和功能，并研究CT45A1与转录因子相互作用，作为基因转录激活物，促进CXCR4和EGFR基因转录的分子机制。（2）在细胞水平、动物体内和肺癌病人，研究CT45A1增强肺癌细胞在肺组织侵袭和扩散，及促进肺癌细胞向骨和脑组织转移机理。以期能为阐明肺癌细胞侵袭和转移机制，及解决肺癌治疗难题提供新思路。

本项目在细胞水平上，CT45A1基因高表达使肺癌细胞移动性和侵袭能力分别增加4.3倍和2.9倍；反之，CT45A1基因沉默后，肺癌细胞移动性和侵袭能力则分别降低4.4倍和2.8倍。.动物实验揭示，肺癌细胞CT45A1基因高表达使荷瘤小鼠肿瘤重量增加10.2倍，并引起肺癌转移；而CT45A1基因沉默的荷瘤小鼠未见肿瘤转移。这些结果表明CT45A1增强肺癌细胞致瘤性、侵袭和转移。.分子水平上我们发现，CT45A1蛋白能直接结合于29种致瘤基因的启动子区域的共识核苷酸序列CGCCCC，其结合的亲和常数高达0.2-2.7 nM。此外，CT45A1蛋白还能与RNA转录酶II (Pol-II)和多种致瘤性转录因子及其激活物相互作用，包括SP1、β-catenin、ATF3等，驱动862个基因转录，其中包括6个癌基因和101个促瘤基因，并激活SRC和STAT3等信号通路，导致肺癌细胞恶性演化和转移。生物信息分析也显示，CT45A1蛋白能与500多个基因的启动子核苷酸CGCCCC相结合，为我们的结果提供佐证。.CT45A1蛋白选择性地结合于多种致瘤基因启动子共识核苷酸序列，形成基因转录启动调控物，提供一个抛锚点，招募Pol-II、多种转录因子、转录激活物富集在该启动子部位，同时驱动多个致瘤基因转录，增强肺癌细胞生长、侵袭和转移。.据此，我们提出了一个新的科学假设：即，肿瘤细胞内存在选择性地驱动多个癌基因转录的致瘤性基因转录机器（Oncogenic gene transcription machinery）。该机器是由致瘤基因的启动子，转录启动因子、转录因子、转录激活物、Pol-II等蛋白动态组装而成，能同时驱动多个致瘤基因转录，从而诱导细胞恶性演变。这些新发现和新设想为肺癌恶性演变和转移机制提供了新见解，也为将来解决肺癌等恶性肿瘤转移难题提供了新思路，具有重要科学意义和潜在临床应用价值。