miRNAs在XIAP介导的乳腺癌细胞自噬和凋亡"平衡性" 调控中作用及其机制的研究

Autophagy and apoptosis are different processes of cell activities. However, recent studies revealed that same genes and pathways were shared in progression of autophagy and apoptosis, suggesting that undefined connection may be involved in these processes. Our previous study demonstrated that X-linked inhibitor of apoptosis (XIAP), a well characterized regulator of apoptosis, had a novel role in autophagy inhibition among physiological and cancerous processes. Then, we would like to ask how XIAP balance these two functions of apoptosis and autophagy and what kind of effect was in the XIAP-regulated autophagy on cell behaviors. To investigate it, we further used the breast cancer cell as a model and scaned and then verified 2 miRNAs which specificly down-regulated XIAP expression. Intresetingly, we further revealed that differnt miRNAs which targets XIAP had different effects of apoptosis and autophagy induction. Thus, we presume that miRNAs might play important roles in the conversion of XIAP-regulated processes of autophagy and apoptosis, and then in the behavior of breast cancer cells. In this study, we will explore the molecular machnisms invovled the effects of anti-apoptosis and anti-autophagy of XIAP mediated by differet miRNAs.And we further investigate the role of this balance in the sensitivity of breast cancer chemotherapy. The other is investigating the impact of miRNAs-XIAP-autopthagy pathway in the behaviors of breast cancer cells and its mechanisam. From this study, we would like to somehow understand the regulation of autophagy and the relationship between autophagy and apoptosis.

从理论角度，细胞自噬和凋亡属于两种不同的生物学进程，但在实际研究中，两者似乎又有着千丝万缕的联系，机制尚不明了。 研究前期发现：已知的凋亡抑制因子XIAP具有新的功能-参与细胞的自噬调控，提示其可能是自噬与凋亡对话的交点之一。那么XIAP在自噬和凋亡两种不同功能中如何"平衡"？对细胞行为有何影响？前期进一步以乳腺癌细胞为模型，通过芯片筛选并验证了两个调控XIAP的miRNAs，进一步发现这两个miRNAs对自噬和凋亡的调控具有截然不同的功能。据此推测：miRNAs可能在XIAP介导的自噬和凋亡功能的"平衡性"调控中发挥了作用。 为此，拟开展以下工作：①探索miRNAs参与XIAP介导的细胞自噬和凋亡调控"平衡性"的分子机制，验证该途径对乳腺癌化疗敏感性作用；②观察miRNAs-XIAP-自噬通路对乳腺癌细胞生物学行为的影响及机制。以期进一步认识自噬的调节机制及其与细胞凋亡之间的的关系。

XIAP在促进细胞存活和维持细胞内稳态方面发挥了重要作用。在恶性肿瘤中XIAP呈高表达状态，并且与恶性行为、不良预后和治疗耐药等方面密切相关。但XIAP在肿瘤的发挥重要的分子机制尚未明了。在本研究中，我们首先在临床乳腺和结肠样本和细胞系中发现XIAP和p62表达呈负相关，并且两者的表达率决定了肿瘤细胞的表型；进一步，我们发现XIAP可以和p62直接相关作用，并且敲除XIAP可以促进p62表达；XIAP可以作为p62的泛素化E3连接酶，从而通过泛素-蛋白酶途径降解p62；在体外和体内实验中，XIAP均可以通过抑制p62表达促进肿瘤细胞增殖和生长。下一步，本研究探索了XIAP抑制乳腺癌细胞自噬的分子机制。从miRNA调控的角度，我们发现miR-23a可以直接靶向XIAP，调控XIAP介导的乳腺癌细胞自噬，从而促进细胞生长和迁移。研究显示：非编码的基因3’UTR通过调控miRNA从而发挥生物学功能。在体外实验和体内实验中，我们发现外源性表达XIAP的3’UTR可以促进乳腺癌细胞的生长、克隆形成、迁移和侵袭，并抑制凋亡；miR-29a-5p 是XIAP和FSCN1的共同靶向miRNA，XIAP的3’UTR可以作为一个ceRNA竞争性结合miR-29a-5p，从而释放其对FSCN1的抑制性结合，从而促进FSCN1表达。总体上，本项目通过多个方面阐明了XIAP促进乳腺癌发生和发展的分子机制。