缺氧肿瘤微环境在促进CD133+CXCR4-结肠癌细胞上皮间质转化中的作用及机制研究

Cancer stem cells (CSCs) consist of two subpopulations, namely stationary CSCs and migratory CSCs, and migratory CSCs show EMT phenotype. However, the mechanism regulating this transition has not been uncovered. Tumor cells under hypoxia undergo EMT. Previously, we found that compared with CD133+CXCR4- cells, CD133+CXCR4+ cells show EMT phenotype and contribute to hepatic metastasis of colorectal cancer. And hypoxia treatment could induce CD133+CXCR4- cells to undergo EMT with higher invasive ability. In this project, we will isolate CD133+CXCR4- cells to investigate the role of hypoxia in its transition to CD133+CXCR4+ cells via EMT. Hypoxia is one of the most outstanding factors for autophagy activation, we will also determine the role of autophagy in this process by regulating its level with autophagy inhibitor or activator. And we aim to further check out whether the above effect is mediated by autophagic degradation of E-cadherin, the important regulator of EMT. Finally, the expression level of LC3B and E-cadherin will be investigated to analyze the association between them as well as the association between LC3B and prognosis. This project will provide experimental evidence for new therapeutic regimen of inhibiting autophagy.

肿瘤干细胞（CSC）存在静止和转移CSC两个亚群，转移CSC具有上皮间质转化（EMT）表型，但调控机制不清楚。缺氧可促进肿瘤细胞发生EMT。前期发现与CD133+CXCR4-细胞相比，CD133+CXCR4+细胞具有EMT表型并促进结肠癌侵袭转移；缺氧可促进CD133+CXCR4-细胞发生EMT，侵袭性增强。本研究拟分选CD133+CXCR4-结肠癌细胞，体内外观察缺氧条件下CD133+CXCR4-细胞EMT表型和CXCR4表达的改变，明确缺氧在促进CD133+CXCR4-细胞发生EMT并向CD133+CXCR4+细胞转化中的作用。缺氧可激活自噬，自噬与侵袭转移相关。本研究将通过调控自噬，探讨自噬在缺氧这一促进转化中的作用；并研究是否通过自噬性降解E-cadherin实现的；在临床标本分析LC3B和E-cadherin表达相关性及与预后的相关性。本课题将为以自噬为靶点的肿瘤治疗提供理论依据

肿瘤干细胞（Cancer stem cells，CSCs）与肿瘤的侵袭转移密切相关。肿瘤微环境可以促进肿瘤细胞的侵袭转移能力，缺氧，炎症是肿瘤微环境的重要特征。上皮间质转化（Epithelial-mesenchymal transition，EMT）是肿瘤细胞侵袭转移的重要机制。我们前期研究发现与CD133+CXCR4-细胞相比，CD133+CXCR4+细胞具有EMT表型并促进结肠癌侵袭转移；缺氧可促进CD133+CXCR4-细胞发生EMT，侵袭性增强。本研究拟在前期基础上进一步明确肿瘤微环境在促进CD133+CXCR4-细胞发生EMT并向CD133+CXCR4+细胞转化中的作用及其作用机制。本项目已明确肿瘤微环境中缺氧等因素对肿瘤细胞EMT及侵袭转移的影响，并发现CXCR4高表达与结肠癌细胞EMT发生及侵袭转移密切相关，完成了预期研究目标。此外，我们课题组发现肿瘤微环境中重要促炎因子脂多糖（LPS），即肠道来源的LPS水平，在肠道受损，肠粘膜被破坏时往往异常增高，并被证实在结肠癌的发展中发挥重要作用。我们的研究证实LPS可以诱导结肠癌细胞发生EMT，促进其侵袭转移，并证实了SDF-1/CXCR4趋化轴参与了LPS诱导的结肠癌细胞肝转移。此外，我们的研究亦证实了SDF-1/CXCR4趋化轴在间充质干细胞的迁移过程中发挥重要作用。肿瘤干细胞与肿瘤的侵袭转移密切相关，我们发现肿瘤微环境中LPS可以维持肿瘤干细胞的干性特征，并与肿瘤的侵袭转移密切相关。上述研究结果目前已发表SCI论文4篇，总影响因子为18.118分，并培养了2名硕士研究生。不但完成了项目的预期研究成果，还延伸做了相关的肿瘤干细胞对肿瘤发生侵袭转移的影响，证实了SDF-1/CXCR4趋化轴在肿瘤侵袭转移中的重要作用，这些研究结果进一步阐明了肿瘤微环境及肿瘤干细胞影响肿瘤发生转移的本质，为临床结肠癌病人寻找新的治疗靶点提供了一定的理论基础。