大肠癌细胞来源的低水平EpCAM胞外囊泡促进大肠癌肝转移的作用及机制研究

Hepatic metastasis of colorectal cancer is the leading cause of death in colorectal cancer patients. New research shows that extracellular vesicles derived from cancer cells play a vital role in the formation of pre-metastatic niches, but the effects and mechanisms of extracellular vesicles derived from colorectal cancer cells to colorectal cancer of hepatic metastasis colorectal cancer are not clear. Our previous research shows that colorectal cancer cells derived extracellular vesicles with low EpCAM can migrate from intestinal tract to liver. And our prophase data suggests that highly metastatic colorectal cancer cells produce extracellular vesicles with lower EpCAM than tumor with low metastatic capacity, the EpCAM level in extracellular vesicles from serum of metastatic colorectal cancer patients is lower than in that of primary cancer patients，and EpCAM level in extracellular vesicles from colorectal cancer tissue is lower than that of distal normal colon tissues. We hypothesized that colorectal cancer cells derived extracellular vesicles with low EpCAM could promote hepatic metastasis of colorectal cancer. Therefore, we sought to study the relationship between EpCAM level of colorectal cancer patients serum derived extracellular vesicles with clinical stages and prognosis of colorectal cancer. Then we investigate the effect of colorectal cancer cells derived extracellular vesicles with low EpCAM on hepatic metastasis of colorectal cancer. And the related mechanisms will also be investigated that low EpCAM affect the distribution of colorectal cancer cells derived extracellular vesicles in liver, thus modify the liver microenvironment. In conclusion, our study will elucidate the effect of colorectal cancer cells derived extracellular vesicles with low EpCAM on hepatic metastasis of colorectal cancer and the mechanisms, which may provide new experimental basis for clinical intervention for hepatic metastasis of colorectal cancer.

大肠癌肝转移是大肠癌病人死亡的主要原因之一。肿瘤细胞来源的胞外囊泡在肿瘤前转移灶形成中发挥重要作用，但在大肠癌肝转移中的作用和机制并不清楚。我们以前的研究发现大肠癌细胞来源的低水平EpCAM胞外囊泡具有肠道外转移的特性，前期工作发现高转移大肠癌细胞分泌低水EpCAM胞外囊泡，临床分级高的大肠癌组织来源的胞外囊泡EpCAM水平低。我们提出科学假说，癌细胞来源的低水平EpCAM胞外囊泡促进大肠癌肝转移。为此，我们首先检测大肠癌患者血清胞外囊泡EpCAM水平与临床分级、预后等的关系；接着研究大肠癌细胞来源的低水平EpCAM胞外囊泡对大肠癌肝转移的作用；最后研究低水平EpCAM胞外囊泡在肝脏中的分布和对肝脏微环境的影响等相关机制。我们的研究将明确胞外囊泡EpCAM在大肠癌肝转移中的作用和机制，有望为临床干预肿瘤转移提供新的实验基础。

本项目研究了不同来源的胞外囊泡（EVs）对免疫微环境的调控作用，EVs通过携带TGF-β1、HLA-E等免疫调节分子分别调节Treg、NK等免疫细胞的功能，从而发挥调控肿瘤细胞生长、调节血管新生和胚胎生长等效应。. 绝经后服用雌激素补充剂的女性患晚期结直肠癌的风险较低，但其潜在机制尚不清楚。我们建立了双侧切除卵巢的雌激素剥夺小鼠模型，与假手术组相比，无卵巢小鼠的MC38肿瘤生长增强，而补充E2可取消这一作用。在无卵巢小鼠的MC38肿瘤中，PD-L1+ M2样巨噬细胞、Treg细胞和髓源性抑制细胞(MDSC)数量显著增加，细胞毒性CD8+ T细胞数量下降，而补充E2可以逆转。MC38细胞来源的EVs(MC38-EVs)参与了免疫抑制肿瘤微环境的建立，而E2处理的MC38细胞来源的EVs(E2-MC38-EVs)则没有这一作用。E2-MC38-EVs中TGF-β1水平较低，体外诱导Treg细胞的能力较弱。本研究证实了雌激素通过调控MC38-EVs介导的肿瘤免疫微环境抑制MC38肿瘤生长的作用，为绝经期女性是否服用雌激素补充剂提供了理论依据。.此外，负责人注意到，妊娠提供了研究EVs的绝佳模型：怀孕开始和结束的时间确定，可在整个妊娠过程中追踪EVs；胎盘有特定的标记物，可方便地把胎盘EVs与其他EVs区分开来；胎盘在妊娠结束时常作为医疗垃圾丢弃，可回收用于研究。研究发现早期胎盘滋养细胞来源的EVs（T-EVs）通过HLA-E促进蜕膜NK细胞的糖酵解和氧化磷酸化从而促进VEGFα和IFN-γ的分泌，其中蜕膜NK细胞的氧化磷酸化增强与mTORC1有关。在小鼠体内也证实了T-EVs通过Qa-1(HLA-E的小鼠同源物)调节蜕膜NK细胞分泌功能维持妊娠。该研究阐述了T-EVs通过HLA-E调控子宫NK细胞功能维持妊娠的新机制，并提示了T-EVs作为治疗复发性流产的生物制剂的潜力。