SOX4/CXCR7通路在乳腺癌转移中的作用研究

Metastasis is the major cause of death for breast cancer patients. Increasing evidence suggests that transcription factor SOX4 is involved in metastasis in many malignant tumors including breast cancer. In our previous study, we overexpressed SOX4 by lentivirus in two breast cancer cell lines (MDA-231/SOX4,SUM149/SOX4) and found that overexpression of SOX4 enhanced the ability of migration and invasion. We also demonstrated that expression of CXCR7 was significantly increased in both SOX4 overexpressing cells and assumed SOX4 may promote cancer metastasis by upregulating CXCR7. This project aims to further clarify the connection of SOX4 and CXCR7 as well as up- and down-stream genes based on the existing work, and systematically investigate the mechanism of SOX4/CXCR7 pathway in breast cancer metastasis. We will detect the expression of SOX4 and CXCR7 in breast cancer tissues and analyse their relationship with other metastasis-related genes and clinical pathological characteristics. Finally, we will attempt to abolish the increased migration and invasion ability associated with SOX4 overexpression by blocking this pathway and it may provide a potential target for the clinical prevention and treatment of breast cancer metastasis.

远处转移是乳腺癌患者最主要的死亡原因，越来越多的证据表明转录因子SOX4与包含乳腺癌在内的多种肿瘤的转移相关。本课题组前期研究中利用慢病毒感染获得两株过表达SOX4的乳腺癌细胞系（MDA-231/SOX4,SUM149/SOX4），发现其迁移、侵袭能力明显增高的同时趋化因子受体CXCR7的表达均升高，进而推测SOX4可能通过上调CXCR7的表达促进肿瘤转移。本项目拟在已有的工作基础上通过体内外实验进一步明确SOX4/CXCR7及其上下游基因之间的调控关系，系统阐述此通路在乳腺癌转移中的作用机制；检测SOX4/CXCR7在乳腺癌组织中的表达情况，分析其与临床病理特征及其他转移相关基因的关系；尝试通过阻断此通路抑制SOX4相关的细胞迁移侵袭能力改变，为临床预防、治疗此类乳腺癌转移提供新的靶点。

远处转移是乳腺癌患者最主要的死亡原因，越来越多的证据表明转录因子SOX4与包含乳腺癌在内的多种肿瘤的转移相关。本项目用慢病毒感染细胞分别获得过表达SOX4和SOX4表达下调的乳腺癌细胞株，体外Transwell实验发现过表达SOX4细胞的迁移、侵袭能力显著提高，在部分乳腺癌细胞中SOX4还能促进细胞生长。利用活体动物荧光成像的方法观察荷瘤小鼠发现过表达SOX4的肿瘤发生转移更早，且发生转移的比例更高。在发现这些生物学现象的基础上我们深入探究其可能的作用机制，我们观察到过表达SOX4的细胞发生上皮间质化（EMT）的形态学改变和相应分子表达水平改变，推测SOX4 可能通过上调间质特征的分子，下调上皮特征的分子，使细胞向间质转化，从而提高细胞迁移、侵袭能力。通过基因芯片筛选我们发现SOX4过表达细胞中趋化因子受体CXCR7表达明显上调，real-timePCR也证实了这一变化。利用染色质免疫共沉淀（ChIP）的方法我们证实细胞内SOX4能与CXCR7的启动子结合，同时，抑制CXCR7的小分子化合物CCX771能消除SOX4相关的迁移、侵袭能力的改变。这说明CXCR7很可能是SOX4的下游靶基因，SOX4通过调控CXCR7促进乳腺癌转移，在目前还没有针对SOX4的特异性药物的情况下，针对CXCR7的治疗可能可以取得较好的疗效。体内外实验均证明上调SOX4表达后细胞对紫杉醇敏感性增高，提示对SOX4高表达患者应用紫杉醇化疗可能会有较大获益。对临床乳腺癌标本的免疫组化检测发现在肿瘤较大（>2cm）、存在淋巴结转移的乳腺癌组织和淋巴结转移组织中SOX4普遍高表达同时伴随CXCR7高表达。本研究为临床预防、治疗此类乳腺癌转移提供了新的靶点。