【作者】 张哲；

【导师】 吴亚群； 覃吉超； 易继林；

【作者基本信息】 华中科技大学 ， 外科学， 2017， 博士

【摘要】 肿瘤干细胞(cancer sterm cells,CSCs)与结直肠癌的侵袭转移密切相关,但是肿瘤中CSCs增多的机制及细胞来源并不清楚。肿瘤相关成纤维细胞(Carcinoma-associated fibroblasts,CAFs)与结直肠肿瘤的转移和复发有关,清除组织内的CAFs可以明显降低肿瘤细胞侵袭转移能力。本研究旨在探索CAFs在诱导结直肠癌细胞去分化为肿瘤干细胞和促进肿瘤细胞的侵袭转移能力中的作用。首先,我们证明,与CAFs共培养可以明显的改变结直肠癌细胞的形态并显著的增强肿瘤细胞的侵袭、转移及粘附能力,并使得肿瘤细胞获得“干性”,而且这已系列现象是通过旁分泌的方式实现的;其次我们发现,CAFs分泌的效应成分为外泌体(exosome),它在体内外均可增强肿瘤细胞侵袭转移能力并使其去分化为肿瘤干细胞,而抑制exosome的分泌即可阻断这已效应。随后,我们用肿瘤干细胞表面标志物CD133对结直肠癌细胞进行分选,并用CAFs分泌的exosome处理分选后的细胞。结果发现,exosome可促进已分化的肿瘤细胞(CD133/lo)去分化为肿瘤干细胞,且可维持CSCs(CD133+/hi)的干细胞表型,同时exosome促进了 CSCs(CD133+/hi)发生EMT从而增强了肿瘤细胞的侵袭转移。我们进已步通过MicroArray测序分析发现CAFs来源的exosome中高表达miRNA21-5p,经过GO/KEGG/TargetScan数据库预测miR21-5p通过调控YAP1蛋白从而增加肿瘤中CSCs的比例,并促进肿瘤细胞的侵袭转移。我们的研究结果提示,对于肿瘤的治疗不仅要针对CSCs,还需阻断CAFs的分泌作用才能使患者在治疗中得到更大的受益。更多还原

【Abstract】 Cancer stem cells are closely related to invasion and metastasis of colorectal cancers,while the exact mechanism of the increasing number and cell-of-origin of CSCs remains unclear.Carcinoma-associated fibroblasts(CAFs)are associated with metastasis and recurrence of colorectal cancers.Tumor invasion and metastasis can be significantly inhibited by elimination of CAFs.Our study investigated the role of CAFs in inducing dedifferentiation of colorectal cancer cells into CSCs and promoting tumor cell invasion and metastasis.We first demonstrated that co-culture with CAFs could alter the morphology of colorectal cancer cells and enhance the invasion,metastasis and ahesion ability and cell sternness of tumor cells in a paracrine manner.These paracrine effects of CAFs on tumor cells were through exosomes.Exosomes derived from CAFs promoted tumor invasion and metastaisis and increased the number of CSCs both in vitro and in vivo.Inhibiting exosomes secretion blocked the effects.Then we sorted colorectal cancer cells with CSCs surface marker,CD133 into CSCs(CD133-/lo)and non-CSCs(CD133+/hi)and treated them with CAFs-exosomes.CAFs-exosomes induced dedifferentiation of CD133-/lo into CSCs and sustained stem cell phenotype of CD133+/hi.They also promoted endothelial interstitial transformation(EMT)of CSCs,thus enhanced tumor invasion and metastasis.We further identified a highly expressed microRNA,miRNA21-5p in CAFs-exosomes by MicroArray.GO,KEGG and TargetScan databases analyses indicated that miRNA21-5p may exert effects on cancer cells through regulating YAP1.Our findings revealed the important role of exosomes in cancer therapy.Inhibiting exosomes secretion of CAFs in tumor treatment will bring more benefits for patients.更多还原