应激微环境与p53氧化还原修饰对肝肿瘤细胞能量代谢平衡的调控作用研究

Tumor cells have specific energy metabolism and redox status in order to meet their rapid growth. The recent researches have shown that p53 has a new role in regulating energy metabolism, but its mechanism is still unclear. Our previous project which was funded by the Key Program of National Natural Science Foundation of China has proved that the tumor cells can be regulated by ROS, and the tumor cells' growth relies on a certain level of ROS. It is known that ROS and p53 have an intimate relationship. ROS can oxidize and modify p53, however it is unknown whether they interact and cooperate with each other to participate in regulating the balance of energy metabolism. According to our previous works that different species of ROS have different impacts on tumor cells' growth, and combining with the latest results published on "SCIENCE" that ROS can oxidize and modify the key enzyme involved in the metabolic pathway, it suggests that ROS may regulate p53 by oxidative modification and thus regulate the energy metabolism balance of tumor. Understanding its mechanism will have important significance not only in theory but also in cancer prevention and treatment. Therefore, we plan to establish the various cell lines and different endogenously and exogenously redox microenvironments, we will explore the internal relationships between ROS stress and p53 modification and its new regulatory function by using multi-disciplinary methods including molecular biology and ESR spectrum techniques. We hope to find the sensitive regulatory points to balance the energy metabolism of tumor.

肿瘤因快速生长需求而具特异的能量代谢及氧化还原状态。近期研究发现p53具有调节能量代谢的新功能，但其机制尚不明。课题组原承担的国家自然科学基金重点项目已证实，肿瘤细胞生长可被活性氧（ROS）调控并具依赖性，并知ROS与p53关系密切，包括可氧化修饰p53，但它们之间相互作用及是否协同参于能量代谢平衡的调节尚不清楚。根据原来的工作基础，发现不同活性氧对肿瘤细胞生长可产生不同效果，结合"SCIENCE"最新报道活性氧可以氧化修饰代谢通路的关键酶蛋白，启示特定活性氧也可能通过对p53氧化修饰而调控肿瘤的能量代谢平衡。如能阐明其机制，不仅理论上有重要价值，对肿瘤防治也将具有深远意义。故拟建立不同转染细胞株及内外源不同氧化还原微环境，采用分子生物学及ESR波谱技术等多学科手段，深入探究活性氧应激与p53修饰和新调节功能之间的内在联系，以能找到对肿瘤能量代谢平衡的敏感调控点。

肿瘤因快速生长需求而具特异的能量代谢及氧化还原状态，但氧化还原状态对肿瘤能量代谢的调节尚不清楚，其机制尚不明确。本课题发现，肿瘤细胞与正常细胞具有不同的氧化还原微环境和不同的氧化还原稳态阈值，所以对外源相同的应激会有差异化甚而相反的应答。肿瘤耐缺氧能力大大高于正常细胞，在缺氧应激状态下，正常细胞主要依赖有氧氧化补偿能量，肿瘤细胞则主要依赖糖酵解。ROS或可通过调节肿瘤细胞p53/TIGAR、p53/SCO2通路及糖酵解关键酶活性促进Warburg效应与肿瘤耐缺氧能力。然而，在缺氧癌细胞中，线粒体的功能依然维持，从而维持更稳定的ATP/ADP比值。在缺氧下，肿瘤细胞能够快速转化缺氧诱导的O2·-生成H2O2，H2O2进一步被相对更强的抗氧化系统分解，导致肿瘤细胞增加的ROS水平相比正常细胞更少。中等强度的ROS可导致肿瘤细胞适当程度的自噬，自噬清除了受损的线粒体，并提供营养促进线粒体融合，从而保护线粒体并促进肿瘤缺氧耐受。有功能的线粒体可以使肿瘤细胞灵活地在糖酵解和氧化磷酸化之间切换以满足肿瘤生长期间缺氧/再复氧循环过程中的不同生理需求。因此活性氧不仅参与糖酵解也参与调节包括有氧氧化在内的肿瘤总体能量代谢的平衡。除此之外，我们还发现适量ROS可以通过上调戊糖途径重新编程葡萄糖代谢。低浓度ROS可以协同Grxs介导的AMPK-α催化亚基上的S-谷胱甘肽化活化AMPK以改善葡萄糖转运和降解，同时抑制糖原合成和保持氧化还原平衡。我们的结果提示：基于不同细胞具有氧化还原阈值，根据体内实际氧化还原水平使用不同浓度的ROS或抗氧化剂可以精准的治疗肿瘤及糖代谢紊乱。