淋巴细胞特异性转录因子SpiB在小细胞肺癌中的功能和调控研究

Compared with NSCLC, SCLC generally has a more rapid doubling time, a higher growth fraction, and earlier development of widespread metastases. To understand the molecular mechanism of cancer distal metastasis, we examined gene expression profiling in SCLC using RNA-Seq and found that SCLC expresses a series of transcription factors normally restricted to lymphoid cells, including SpiB. Overexpression of SpiB significantly increased the lung metastasis of LLC1 and promoted the expression of invasion-related genes, such as MMP9 and PLGF. These data suggest that SpiB might be a signature of SCLC and its ectopic expression increase the malignancy. Here, the objective of this project is to focus on the function and regulation of SpiB in tumor metastasis using multiple techniques including orthotopic nude mouse models, 3C, immunohistochemistry, RNA interference and ChIP. Specifically, we will dissect the connection between SpiB expression level and distal metastasis of lung cancer through tissue microarray, and the role of ectopic expression of SpiB in tumor invasion and tumor cells transendothelial migration. The results will shed a light in understanding the molecular mechanism of tumor cell metastasis and may provide a new target for the tumor treatment.

与非小细胞肺癌相比，小细胞肺癌转移快，恶性程度高。利用RNA-Seq我们发现小细胞肺癌细胞表达一系列生理状态下仅表达于造血细胞中的转录因子包括SpiB。在不表达SpiB的鼠肺癌细胞LLC1中导入该蛋白之后进行小鼠皮下注射，其肺转移能力较对照组显著增强，并能上调MMP9、PLGF等肿瘤侵袭相关基因的表达，表明这一淋巴细胞特异性的转录因子能够促进实体肿瘤的转移，提示SpiB的异位表达很可能是小细胞肺癌具有高转移特性的关键因素之一。本项目将利用裸鼠肺内注射模型、3C、ChIP等技术研究SpiB是否通过上调MMP9和PLGF来促进小细胞肺癌的转移以及调控这些基因表达的表观遗传机制，并利用临床肺癌组织芯片研究SpiB的异位表达与临床肺癌转移的相关性，研究结果将丰富人们对于实体肿瘤转移的分子机制的理解，为实体肿瘤的治疗提供新的思路。

单个或小簇癌细胞断开与邻近上皮细胞的连接，脱离原位癌细胞片层结构，是转移早期的重要事件。Spi-B是淋巴细胞特异性转录因子，生理状态下仅表达于B淋巴细胞、祖T淋巴细胞、浆细胞样树突状细胞以及肠道M细胞。我们的研究发现转录因子Spi-B异位表达于人肺癌组织中，其主要定位于癌巢中具有间质样特性的浸润能力高的肿瘤细胞中，对这些肿瘤细胞维持间质特性具有重要作用；增加的Spi-B表达与肿瘤的TNM分期、淋巴结转移以及较差的预后正相关。Spi-B能够通过介导CLDN2上游抑制子与启动子的相互作用进而下调该基因，同时上调金属蛋白酶MMP9，使得肿瘤细胞间连接断开，肿瘤细胞能够从原发灶的片层结构中脱离，同时使得肿瘤细胞能够降解基质，以便侵袭转移。这一研究表明Spi-B在肺癌细胞中异位表达，赋予了肺癌细胞低粘附性以及侵袭特性，该发现将淋巴细胞调控网络与实体肿瘤转移联系起来，并提示Spi-B可能成为肺癌预后和治疗的潜在靶点。