MiT基因家族相关融合基因转录调控mTORC1和自噬并驱动肾细胞癌代谢及增殖的机制研究

Microphthalmia-associated transcription factor family renal cell carcinoma (MiT RCC) is characterized by several different translocations, resulting in gene fusions of the TFE3 or TFEB gene, which were the only driver genes found in MiT RCC. As the genes fused 5' to TFE3/TFEB contribute strong promoters, oncogenic activation of TFE3/TFEB is driven by the fusions with a number of different gene partners. The potential linking mechanisms between TFE3/TFEB and carcinogenesis are yet to be determined. Recently, mTORC1 activation and the high level of cell autophagy function in MiT RCC have been identified by us. We further hypothesize that overexpression of TFE3/TFEB-related fusion genes activates mTOR pathway and induces high levels of autophagy. TFE3/TFEB-related fusion proteins have the ability to aggregate into the nucleus, making the transcriptional efficiency of fusion protein stronger than TFE3/TFEB protein. The interventions of autophagy and/or mTOR pathway may inhibit tumor progression, moreover, intervening both of autophagy and mTOR pathway may be more effective than intervening autophagy or mTOR pathway alone. We aim to elucidate the pathogenic mechanism of the TFE3/TFEB genes and the relationship among TFE3/TFEB, mTOR pathway, cell autophagy function, metabolism and proliferation. The findings may offer an important theoretical basis for the management and prevention of MiT RCC.

小眼畸形转录因子家族（MiT）易位性肾癌的特点是肿瘤都包含TFE3或TFEB基因（转录因子）的易位，并导致TFE3/TFEB过表达。TFE3/TFEB基因是迄今为止MiT家族易位性肾癌发现的唯一驱动基因，但其具体致病机制尚属未知。近期我们发现该类型肾癌存在mTORC1激活及高水平自噬现象，本项目提出过表达的TFE3/TFEB相关融合蛋白激活mTOR通路并诱导高水平自噬; TFE3/TFEB相关融合蛋白具有向核内聚集的能力，这使得其转录效能强于单纯TFE3/TFEB蛋白；干预抑制自噬和/或mTOR通路可抑制肿瘤生长，联合抑制自噬及mTOR通路的抗肿瘤效果或优于单独抑制。本研究拟阐述TFE3/TFEB相关融合基因过表达、mTOR通路、细胞自噬、营养代谢和肿瘤发生发展的关系及其影响肿瘤的机制，为MiT家族易位性肾癌的防治新靶点和干预措施提供理论依据。

小眼畸形转录因子家族（MiT）易位性肾癌的特点是肿瘤都包含TFE3或TFEB基因（转录因子）的易位，并导致TFE3/TFEB过表达。TFE3/TFEB基因是迄今为止MiT家族易位性肾癌发现的唯一驱动基因，但其具体致病机制尚属未知。我们发现ASPL-TFE3是tRCC在中国人群中最常见的融合类型(29/126,23.03%)。体内外实验均证实ASPL-TFE3定位于细胞核并增强肿瘤细胞的增殖能力。我们通过ChIP-seq与RNA-seq共分析，深入研究了ASPL-TFE3融合基因的转录调控回路，首次发现ASPL-TFE3融合蛋白可直接结合自噬相关基因的启动子区域，强力激活自噬通路。考虑到自噬与营养物质代谢之间的联系，我们进一步进行了非靶向代谢组学检测。发现ASPL-TFE3融合基因通过激活自噬通路，促进脂质及氨基酸等营养物质的利用，缓解肿瘤细胞的能量应激状态。并且，我们发现，在生理情况下，TFE3蛋白受mTOR通路调控入核，而在ASPL-TFE3易位性肾癌的情况下，ASPL-TFE3融合基因反向强力激活mTOR通路，mTOR与自噬通路的异常激活共同促进了肿瘤细胞的增殖。同时靶向自噬与mTOR信号通路表现出更强大的抑制肿瘤增殖作用。我们的结果说明：在tRCC中，ASPL-TFE3通过激活自噬调节物质代谢，同时靶向自噬和mTOR信号通路可能是ASPL-TFE3 tRCC的一种新的治疗策略。