LSD1调控TCF-4/CD47/SIRPα轴介导胃癌免疫逃逸的机制及小分子干预研究

The dynamic interaction between tumor cells and immune cells promotes the malignant progression of tumors. The recognition between CD47 and SIRPα is a key factor to help tumor cells evade the attack from macrophages. However, up to now the regulation mechanism of CD47 expression of tumor cells remains not entirely clear. It has been reported that high expression of histone lysine demethylase LSD1 in most tumor tissues could induce tumor immune escape. Our previous studies showed that knocking out LSD1 could inhibite the expression of CD47, suppress the transcriptional activity of TCF-4, reverse the TAM type M2 polarization and enhance the phagocytic function of TAM in gastric cancer cells in gastric cancer cells which could be also induced by LSD1 inhibitors. It is suggested that LSD1 may induce immune escape of gastric cancer by regulating TCF-4/CD47 signaling pathway. By the unique LSD1 inhibitor compound library and a series of technologies including gene editing, Co-IP and ChIP technologies this project would intend to further clarify the mechanism of LSD1 regulating CD47 expression, determine the relationship between LSD1/CD47/SIRPα axis and immune escape, and evaluate the antitumor effect of CD47 antibody and LSD1 inhibitors in alone or in combination. The expected results of this project will not only lay a theoretical foundation for the development of LSD1 inhibitors, but also provide new ideas for tumor immunotherapy.

肿瘤细胞表面的CD47与SIRPα识别是肿瘤逃避巨噬细胞吞噬的关键信号，明确CD47的表达机制并阻断该识别信号将能抑制肿瘤恶性进展。然而CD47表达的调控机制尚未完全清楚。组蛋白赖氨酸去甲基化酶1（LSD1）在多数肿瘤中高表达与肿瘤免疫逃逸密切相关。我们近期研究发现，在胃癌细胞中敲除LSD1或加入LSD1抑制剂能降低CD47的表达、抑制TCF-4转录活性、逆转胃癌肿瘤相关巨噬细胞（TAM）类M2型极化及增强TAM的吞噬功能，提示LSD1可能通过调控TCF-4/CD47通路改变胃癌免疫逃逸。本项目将利用独有的LSD1抑制剂化合物库，借助基因编辑、Co-IP及ChIP等技术深入阐明LSD1如何调控CD47表达并通过CD47/SIRPα轴促进胃癌免疫逃逸，评估CD47抗体与LSD1抑制剂及二者联用体内抗肿瘤疗效。本项目预期结果将为LSD1抑制剂的研发奠定理论基础，同时也为肿瘤免疫治疗提供新思路。

肿瘤细胞表面的CD47与SIRPα识别是肿瘤逃避巨噬细胞吞噬的关键信号，明确CD47的表达机制并阻断该识别信号将能抑制肿瘤恶性进展。然而CD47表达的调控机制尚未完全清楚。组蛋白赖氨酸去甲基化酶1（LSD1）在多数肿瘤中高表达与肿瘤免疫逃逸密切相关。本项目研究发现，在胃癌细胞中敲除LSD1或加入LSD1抑制剂能降低CD47的表达。据报道TCF-4能调控CD47的表达，结合本项目研究结果，敲除或抑制LSD1能显著抑制TCF-4的表达和TCF-4的转录活性，并且CO-IP实验发现TCF-4可与LSD1形成蛋白复合物，抑制LSD1可促进TCF-4与LSD1的解离，抑制其转录活性，降低CD47表达，该结果说明LSD1通过TCF-4调控CD47的表达。此外，本项目还发现敲除或抑制胃癌细胞中的LSD1后，可逆转胃癌肿瘤相关巨噬细胞（TAM）类M2型极化、增强TAM的肿瘤杀伤能力和吞噬功能，并发现该生物学效应是敲除或抑制LSD1后胃癌细胞分泌干扰素作用于IFN受体进而激活了TAM中的IFN/STAT1/NF-κB通路实现的。值得注意的是，本项目利用独有的LSD1抑制剂化合物库，从中筛选出最具有免疫调节潜力的新型LSD1小分子抑制剂1093，该化合物可显著抑制CD47的表达、逆转TAM类M2型极化、并增强TAM的吞噬功能。最后，体内研究结果显示，LSD1抑制剂和CD47抗体二者单独或联用均具有显著的抗肿瘤疗效，但二者联合使用的抗肿瘤疗效更佳。本项目的研究结果，不仅揭示了LSD1通过调控CD47/SIRPα轴介导胃癌免疫逃逸的分子机制，还进一步明确了LSD1抑制剂单用或者和CD47抗体联用的药理学效应，将为LSD1抑制剂的研发奠定理论基础，同时也为胃癌肿瘤免疫治疗提供新思路。