芳香烃受体AhR在肿瘤放射抵抗细胞中靶向干细胞样基因的研究

Radiotherapy do not improve much up to now as a key therapy strategy for cancer. A certain proportion of irradiation-resistant cells in cancer tissues leads to the failure treatment, the mechanisms for this remain unknown. We previously established several cell lines with irradiation-resistant properties that contained stem-like. Moreover, we found that Aryl hydrocarbon receptor (AhR) was highly expressed in these irradiation-resistance cells, meanwhile, AhR was recruited to the promoters of stem-like genes including ATP-binding cassette transporter G2 (ABCG2). On the basis of these, we will address the potential interaction and motifs between AhRa and UCHL3 (Ubiquitin C-terminal hydrolase-L3), and confirm the interaction between AhR and UCHL3 will cooperatively regulate stem-like genes such as ABCG2, in turn, up-regulating stem-like genes. Several oncometabolites including TCA intermediates could promote AhR signaling pathway, in turn, induce stem-like in the irradiation resistante cells. The intermediates promote tumor migration and invasion through EMT. Therefore, the proposal makes a new connection among tumor cancer reprograming, migration and invasion as well as metabolic reprograming, also provide new evidence in tumor irradiation resistance.

放疗作为肿瘤的主要治疗手段， 疗效至今无明显改善。放疗失败的主要原因是肿瘤组织中存在一定比例的放疗抵抗细胞，肿瘤放射抵抗的分子机制目前仍不清楚。我们前期建立了一批具有放射抵抗的细胞系，发现这些细胞系的干细胞样水平增加，且芳香烃受体AhR在肿瘤放射抵抗细胞系中表达上调，并靶向ABCG2等干细胞功能标志分子。此外，肿瘤放射抵抗细胞系中代谢中间产物含量也明显增加。 基于此，我们拟从放射抵抗的角度探讨放射抵抗细胞系中AhR与泛素水解酶UCHL3相互作用及其功能域，并且确定这种相互作用可协同调控ABCG2等干细胞样基因，上调ABCG2等干细胞样基因的表达水平，同时中间代谢产物激活AhR信号通路促进放射抵抗细胞系的干细胞样形成，最终通过EMT而促进肿瘤侵袭与转移，从而在肿瘤干细胞重编程、侵袭与转移及代谢重编程之间建立了新的联系，为肿瘤放疗抵抗提供了新的实验依据。

肿瘤细胞可以表现出类干细胞的特性，肿瘤中调控干性功能的通路通常很活跃。肺癌是发病率和死亡率最高的恶性肿瘤，探讨其发生发展机制，研发新的抗肿瘤分子靶向药物意义重大。本项目从放疗抵抗着手探讨了芳香烃受体AhR与去泛素化酶UCHL3相互作用，协同调控ABCG2等干性相关基因，维持肿瘤的干细胞样表型。. 通过本项目的实施，发现了芳香烃受体AhR在肺癌中存在差异表达，且体外生物学功能实验显示，AhR在肺癌中具有可促进细胞增殖、侵袭转移、放化疗抵抗以及维持肿瘤细胞干细胞样表型的促癌作用。还确定了AhR在肿瘤放射抵抗细胞系中表达上调，并可靶向ABCG2等干细胞功能标志分子。代谢中间产物可激活AhR信号通路，并促进放射抵抗细胞EMT相关分子上调从而导致肿瘤的侵袭与转移。采用Co-IP和Chip等实验发现，AhR与泛素水解酶UCHL3存在相互作用，以去泛素化酶依赖模式水解与AhR结合的泛素肽段，稳定AhR蛋白从而上调ABCG2、KLF4和c-Myc等干细胞样基因的表达水平。在此基础上，进一步将UCHL3缺失或利用UCHL3抑制剂TCID使其活性丧失，发现可抑制肺癌细胞干细胞样表型和降低肺癌的恶性演进。. 上述研究强调了AhR在肿瘤放疗抵抗中所起到的重要作用，并揭示了UCHL3可作为稳定AhR蛋白的关键DUB分子，在肿瘤发生发展中的作用以及促进肺癌细胞干细胞样表型的分子机制，为肿瘤的放疗抵抗以及抗癌药物新靶点的开发提供了新的理论和实验依据。