SOX1调控鼻咽癌干细胞维持及自我更新的分子机制研究

Self-renewal of cancer stem cell is the vital reason for tumor recurrence, radio- and chemo-resistance. Our previous study (Mol Cancer 2014) has showed that SOX1 suppressed the proliferation of nasopharyngeal carcinoma (NPC) cells, and reduced the stemness of NPC stem cells. SOX1 down-regulated the protein level of β-catenin and regulated the transcription of its downstream molecular. So far, the molecular mechanism of SOX1-regulated the maintaining and self-renewal of cancer stem cells (CSCs) has not been elucidated yet. In this project, the role of SOX1 in regulating the maintaining and self-renewal of NPC CSCs will be investigated by sphere formation, serial transplantation and limiting dilution assay in vivo. Besides, the changes of Wnt/β-catenin, Notch and Hh signaling pathways will be measured. The CHIP-seq, luciferase and Co-IP assays will be conducted to determine the target genes by which SOX1 regulating the NPC CSCs. Additionally, the effects of targeting SOX1 and related genes in radio- and chemical- resistance of NPC cells will also be evaluated. Finally, pathological analysis is designed to determine the correlation among the SOX1 and target genes expressions, stage, recurrence as well as prognosis of NPC. This study will provide new targets for the treatment of NPC which improves the effectiveness of cancer therapy.

肿瘤干细胞的自我更新是肿瘤复发、放化疗抵抗的重要原因。申请人前期研究表明，SOX1能抑制鼻咽癌细胞的增殖，并减弱鼻咽癌干细胞的干性，且SOX1能下调β-catenin蛋白水平及影响其下游分子转录（Mol Cancer 2014）。目前SOX1调控肿瘤干细胞的维持及自我更新的分子机制尚未阐明。本课题拟采用微球体形成、体内多次成瘤及极限稀释成瘤等方法探讨SOX1在调控鼻咽癌干细胞维持和自我更新中的作用；通过检测Wnt/β-catenin、Notch及Hh等相关信号通路的变化，CHIP-seq、荧光素酶试验、免疫共沉淀等明确SOX1调控鼻咽癌干细胞维持和自我更新的靶基因；探讨靶向SOX1及靶基因对鼻咽癌细胞放化疗抵抗的影响，并结合病理分析SOX1及靶基因表达水平与鼻咽癌分期、复发及预后的相关性。本研究将为鼻咽癌的治疗提供新的靶点以提高治疗的有效性。

肿瘤干细胞的自我更新是肿瘤复发、放化疗抵抗的重要原因。靶向肿瘤干细胞，诱导肿瘤细胞分化，成为肿瘤治疗重要的手段和切入点。项目前期研究发现SOX1能够抑制鼻咽癌细胞的干性。为进一步探索SOX1对鼻咽癌细胞干性的调控作用，在本项目课题中，我们利用可诱导SOX1表达的鼻咽癌细胞系，证实SOX1抑制鼻咽癌细胞增殖、促进细胞衰老的作用。过表达SOX1的鼻咽癌细胞形态学上呈分化状态，克隆形成能力的减弱以及上皮-间质转化 (Epithelial–Mesenchymal Transition，EMT) 上皮标志物表达的上升，均提示SOX1能够促进鼻咽癌细胞的分化。我们发现过表达SOX1影响了一系列与细胞分泌相关通路的活性，进一步发现胞外分泌代谢物中维生素A的量变化最为显著。本课题组此前已发表研究 (Nature Communications 2014, 5, 3661) 证实维生素A可通过诱导鼻咽癌细胞的分化抑制鼻咽癌细胞的恶性表型。此外，我们进一步研究发现SOX1通过转录抑制作用下调鼻咽癌细胞中葡萄糖醛酸转移酶UGT1A及UGT1A6的表达。细胞产生的维生素A的分泌受自身葡萄糖醛酸化的调控，UGT1A及UGT1A6的下调则促进维生素A向胞外的分泌，进而对周围的肿瘤细胞产生影响。本课题发现SOX1可能通过调控鼻咽癌细胞的代谢重编程，进而抑制干细胞的自我更新并促进分化，为进一步探索靶向维生素A代谢在鼻咽癌治疗中的应用前景提供理论依据。