NRF2信号通路通过调控氧化应激及能量代谢介导ALDH1A3阳性坏死型胰腺癌侵袭转移的研究

Early metastasis is the major reason for cancer-related death in pancreatic ductal adenocarcinoma (PDAC). Using a set of transgenic mouse models, we have previously identified and characterized a highly metastatic subtype of PDAC driven by the MEK/mTOR signalling axis. Molecular analyses uncovered that MEK/mTOR directly controls the expression of ALDH1A3 (as the specific marker of this subtype), which may promote the tumor growth and metastasis via its effects on cellular glycolysis. However, our previous data show that PDAC cells underwent metastasis actually maintain the high ALDH1A3 expression albeit the transiently damped mTOR activity and tumor growth. Certainly, the unilateral signal axis-MEK/mTOR/ALDH1A3 is not sufficient to explain the underlying biological complexity. Here, it has been shown previously that ALDH1A3 responds to oxidative stress and is a component of the antioxidant transcription factor NRF2. Thus, we proposal a novel concept under which the ALDH1A3 expression is controlled by both NRF2 and MEK/mTOR signals depending on the biological contexts. In the current proposal, we aim to exploit the functional role of NRF2/ALDH1A3 in the development of metastatic PDAC subtype using human samples and a set of in vitro and in vivo assays.

胰腺导管腺癌早期远处转移是导致患者肿瘤相关死亡的主要因素。本课题组新近首次发现并鉴定出一类具有高转移潜能的胰腺癌分子亚型，其病理表现为组织坏死，同时由于其高表达ALDH1A3分子, 故将该亚型命名为ALDH1A3阳性坏死型胰腺癌。前期研究证实ALDH1A3的表达直接受生长通路MEK/mTOR的控制，且该通路通过促进糖酵解导致该亚型细胞的增殖。然而该单一控制模型无法解释该亚型在当生长暂时受抑时，表现出的高转移潜能和ALDH1A3的稳定表达。已有研究证实ALDH1A3可同时受另一个关键蛋白NRF2的调控并起着抗氧化氧化应激的作用。因此，本课题组修正性的提出ALDHA3在该亚型中的表达同时受NRF2和MEK/mTOR双信号通路的协调调控的概念。本课题将通过人体标本、细胞、转基因小鼠多层次探索NRF2信号通路调控的氧化应激及能量代谢对ALDH1A3阳性坏死型胰腺癌侵袭转移的作用及机制。

胰腺导管腺癌早期远处转移是导致患者肿瘤相关死亡的主要因素。本课题组发现并鉴定出一类具有高转移潜能的胰腺癌亚型，由于其高表达ALDH1A3分子，病理表现为组织坏死，故将该亚型命名为ALDH1A3阳性坏死型胰腺癌。然而在PDAC中，ALDH1A3调控了何种通路，以及其与肿瘤细胞增殖和（或）转移活动的关系，目前尚不清楚。我们通过收集PDAC患者的标本和生存信息评估ALDH1A3的表达量和高表达ALDH1A3的PDAC患者的预后。通过一系列体内和体外实验评估ALDH1A3对于PDAC的增殖、侵袭和迁移能力的影响；同时行乳酸生成实验、Seahorse细胞能量代谢实验、活性氧检测实验、ATP/ADP实验等评估细胞的氧化应激和能量代谢改变；转录组测序评估与ALDH1A3显著相关的通路和基因；构建条件性敲入和敲除Aldh1a3的小鼠以评估Aldh1a3对于PDAC表型的影响。通过以上工作，我们明确了ALDH1A3阳性的PDAC亚型具有更高的侵袭转移潜能，并且与胰腺癌患者的预后密切相关。通过转录组测序，我们发现ALDH1A3能显著引起HK2、PKM2等糖酵解关键酶的显著升高，并进一步促进肿瘤细胞糖酵解。而转录因子PPARγ可能在ALDH1A3介导糖酵解过程中发挥重要作用。同时，我们排除了ALDH1A3与氧化应激、转录因子NRF2之间的调控关系，明确了ALDH1A3增强PDAC细胞恶性表型的机制与能量代谢之间紧密相关。这些研究成果为治疗ALDH1A3阳性PDAC亚型提供了潜在的靶点治疗药物。