Cdc42定位在乳腺癌细胞转移中的作用和机制研究

Directional migration of the malignant cells is responsible for tumor metastasis. Pseudopodia are protrusive structures that associated with directional migration of these cells, and Cdc42 is the main RhoGTPase involved in pseudopodia formation. Although restricted localization of Cdc42 seems to be important for its distinct functions, mechanisms that control Cdc42 localization are still poorly understood. The priorities of our work are to elucidate: (1) Whether the accumulation of Cdc42 at tip of protrusion is responsible for pseudopodia formation and directional movement of breast cancer cell. (2) Whether Rab35 is a vital regulator of Cdc42 recruitment to the site of plasma membrane protrusion and required specifically for pseudopodia formation. (3) Furthermore, the project is to validate the hypothesis that Rab35 may induce MICAL1 activity, and then regulate actin filament reorganization, which further direct Cdc42 transportation and finally cause pseudopodia formation of breast cancer cell. It may be a novel mechanism that Rab35 and MICAL1 participate in Cdc42 localization and regulate consequently directed breast cancer cell migration, which could be a new therapeutic target against metastasis of breast cancer.

恶性肿瘤细胞的定向运动能力对恶性肿瘤细胞转移有着重要的影响。Cdc42是调控伪足形成中最为关键的蛋白之一，Cdc42在细胞前端的定位对其调控细胞定向运动具有极其重要的作用，然而调控其定位的确切分子机制目前尚未明确。本工作将致力于阐明：（1）Cdc42是否靶向定位于细胞前端，进而调控乳腺癌细胞伪足的形成？（2）Rab35是否为调控Cdc42定位和伪足形成的关键分子？（3）Rab35是否通过激活MICAL1，重构微丝运输通路，进而使Cdc42在细胞前端定位，并最终影响伪足形成和乳腺癌细胞定向运动？本研究目标的完成将阐明乳腺癌细胞中Cdc42定位的调控机制，确定其定位与Rab35、MICAL1之间的关系，为从阻断伪足形成角度进行乳腺癌浸润和转移的防治提供新的切入点。

肿瘤细胞转移仍然是导致恶性肿瘤患者死亡的主要原因。对恶性肿瘤细胞转移及其调控的确切分子机制进行更深入的研究是现代肿瘤基础科学研究所关注的重点。MICAL蛋白因含FAD结构域而具有氧化还原酶活性，故而能引起细胞骨架的重构，而细胞骨架重构在细胞的运动、转移等过程中具有重要作用。众所周知，在细胞定向迁移的过程中，信号分子对于细胞极性的建立是必需的，尤其是小G蛋白（Cdc42、Rac1、RhoA）在调节细胞极性的建立过程中发挥着重要的作用。因此，以细胞内小G蛋白作为切入点，分析MICAL的调控功能，可能会在更深层次阐明恶性肿瘤细胞转移的确切分子机制。.重要结果和关键数据:.1、确定MICAL2调控MRTF-A核转移，进而对Cdc42的活性进行调控，促进胃癌细胞的定向迁移(Front Mol Biosci 2021)；.2、确定MICAL-L2通过Cdc42依赖的方式抑制溶酶体中EGFR的降解，从而激活EGFR下游信号通路，增强胃癌细胞的迁移(J Cell Mol Med 2019)；.3、MICAL2通过调控Cdc42和ROS，进而激活YAP入核，促进了胃癌细胞的增殖(Oxid Med Cell Longev, 2021)..4、MICAL1通过活性氧敏感的PI3K/Akt/ERK信号转导通路来保持细胞周期蛋白D的表达，促进乳腺癌细胞增殖(J Cell Mol Med, 2018)；.5、NEDD9调控MICAL1，通过Rac1促进了缺氧时胃癌细胞的迁移(Front Pharmacol 2019).6、确定MICAL-L2通过使c-myc去泛素化，增加了c-myc的稳定性，从而维持了肺癌细胞的增殖（Front Cell Dev Biol 2020）；.7、Rab35通过抑制EGFR的循环，减少EGFR的细胞膜定位，最终增加EGFR的降解((Frontiers in pharmacology, 2017）；.8、确定低氧时SOX2通过上调NEDD9的转录和表达，进而激活Rac1/HIF-1α途径，加速了乳腺癌细胞的迁移（Cell Mol Biol Lett 2019）；. 本研究致力于研究恶性肿瘤细胞迁移时，由小G蛋白和MICAL信号通路调控的细胞内信号，在恶性肿瘤细胞极化-运动中的作用起着关键性作用。