CXCR7-TAGLN2相互作用调控PTC侵袭转移的作用机制研究

Papillary thyroid cancer is the most common endocrine tumor, prone to cervical lymph node metastasis. The metastasis-related mechanism was not been fully studied in PTC. Chemokine receptor (CXCR7) was associated with the invasion and metastasis of many kinds of tumors, and silencing CXCR7 inhibit the growth and metastasis of PTC cells. Actin binding protein TAGLN2 was not only highly expressed in PTC tissues, but also related to invadopodia formation. Overexpression of CXCR7 upregulated the expression of TAGLN2, and promoted the invasion and metastasis of PTC. To elucidate the molecular mechanism of the invadopodia formation induced by CXCR7-TAGLN2 interaction in regulating the invasion and metastasis of PTC, this study is intended to explore the relationship between CXCR7 and TAGLN2 expression in PTC tissues, the interaction between CXCR7 and TAGLN2 protein, as well as the effect of cotransfection of CXCR7 and TAGLN2 genes on cell function, invadopodia activity and the expression of related protein molecules in PTC cells. In addition, we will observe the influence of co-transfection of CXCR7 and TAGLN2 genes on the malignant biological behavior of PTC by building PTC models in nude mice, and search for novel intervention target for anti-metastasis therapy of PTC.

甲状腺乳头状癌（papillary thyroid cancer,PTC）是最常见的内分泌肿瘤，易淋巴结转移。PTC转移相关机制尚未得到充分研究。趋化因子受体CXCR7与多种肿瘤的侵袭及转移相关。沉默CXCR7抑制PTC细胞生长及转移。肌动蛋白结合蛋白TAGLN2在PTC癌组织中高表达，且与侵袭性伪足形成相关。过表达CXCR7上调TAGLN2的表达，促进PTC侵袭及转移。本研究拟通过探讨PTC组织中CXCR7与TAGLN2表达相关性、细胞中CXCR7与TAGLN2蛋白互作关系及共转染CXCR7及TAGLN2基因对PTC细胞功能、侵袭性伪足活性及相关蛋白分子表达的影响，阐明CXCR7-TAGLN2互作影响侵袭性伪足形成从而调节PTC侵袭转移的分子机制。本课题还将构建PTC裸鼠模型，观察共转染CXCR7及TAGLN2基因对PTC恶性生物学行为的影响，为临床PTC抗转移治疗寻找新的干预靶点。

甲状腺乳头状癌（papillary thyroid cancer，PTC）复发与淋巴转移是影响患者生存预后的重要因素。前期研究证实趋化因子受体CXCR7在PTC侵袭转移中发挥重要作用。进一步研究显示CXCR7过表达使TAGLN2明显上调。TAGLN2(Transgelin-2,转胶蛋白2)是一种重要的肌动蛋白结合蛋白，通过与肌动蛋白结合，参与细胞骨架重构。前期研究发现TAGLN2在PTC发生发展中发挥促癌作用。本次实验中，IHC检测73例PTC样本及24例结节性甲状腺肿组织样本中TALGN2、CXCR7的表达，发现两者在PTC癌组织中均高表达，且均与淋巴转移密切相关；两者的表达呈正相关。培养PTC细胞系，通过CO-IP及免疫荧光共定位发现胞内TAGLN2与CXCR7蛋白存在相互作用。进一步通过共转染，发现过表达CXCR7可以减弱沉默TAGLN2对PTC细胞迁移侵袭的抑制作用。肿瘤转移离不开MMPs介导的ECM的降解。前期通过免疫沉淀-质谱联用筛选PTC中TAGLN2的互作蛋白，发现 TAGLN2与侵袭性伪足的关键成分蛋白Arp2 (Actin-related protein 2)及Arp3(Actin-related protein 3)相互作用，说明侵袭性伪足可能参与TAGLN2介导的PTC侵袭转移过程。最后，本实验对转移相关蛋白MMP-2、MMP-9，侵袭性伪足相关蛋白MMP-14、cortactin、WASL及关键信号通路分子RhoA、ROCK1/2、Src/p-Src、PI3K/p-PI3K的表达进行检测，发现沉默TAGLN2后，MMP-9、WASL、RhoA、p-Src、p-PI3K表达下调，过表达CXCR7共转染后，这些蛋白的表达回升；而MMP-2、cortactin、ROCK1/2、Src及PI3K蛋白表达无变化。表明CXCR7可能通过Src-PI3K信号轴介导TAGLN2上调，协同MMP-9分泌降解ECM及侵袭性伪足的形成，最终促进PTC侵袭转移。为PTC抗转移治疗提供参考。