Rab23促进鳞状细胞癌侵袭的分子机制研究

Cutaneous squamous cell carcinoma is the second most common cancer overall among white patients. Although most cutaneous squamous cell carcinoma is curable, 4% result in nodal metastasis and 1.5% in death. Squamous cell carcinoma on head and neck is associated with severe disease- and treatment-related morbidity and has a 5-year survival rate of approximately 50%, mainly due to the strong invasive capacity. Recent studies have advanced our understanding of the molecular mechanisms of the disease. It has been reported that small GTPases play a pivotal role in tumorigenesis and metastasis of squamous cell carcinoma. As a member of the Rab family of small GTPase, Rab23 was found overexpression at both the RNA and protein level and strongly association with diffuse-type gastric cancer. .Under support by NSFC grant (No 30872264), we firstly observed no expression of Rab23 protein in normal skin, weak expression in actinic keratosis, an incipient form of squamous cell carcinoma, and high expression in squamous cell carcinoma, which is negatively related to histological differentiation, indicating that Rab23 expression is altered during squamous cell carcinoma development. Secondly, we found cell invasion by Transwell assay significantly reduced by siRNA silencing of RAB23 in Hsq-89 cells, whereas significantly enhanced by overexpression of RAB23 in Sa-3 cells. Thirdly, we detected the correlation of Rac1, a very important factor in tumorigenesis and metastasis, with Rab23 expression, suggesting that Rab23 could somehow regulate Rac1. .However, the molecular mechanism by which Rab23 enhance cell invasion of squamous cell carcinoma still remains unclear. The aim of this study is to comprehensively clarify the mechanism underlying Rab23 promoting cell invasion of squamous cell carcinoma, from the view of clinical specimens, cell and animal experiments respectively. Firstly, we are to detect the correlation of expression of Rab23 and Rac1 in clinical specimens of squamous cell carcinoma. Secondly, we are to confirm Rac1 as a central molecule in the regulation of squamous cell carcinoma cell invasion enhanced by Rab23, with stable cell lines of different Rab23 activity. Thirdly, we are to explore how Rab23 regulate Rac1 expression and activity through integrin. Lastly, we are to find Rac1's downstream effectors, which play an important role in mediating cell invasion of squamous cell carcinoma promoted by Rab23. .The anticipated results will lay a solid foundation for comprehensively clarifying the mechanism underlying promotion of Rab23 on the cell invasion of squamous cell carcinoma, and will be helpful for further understanding of function of Rab23 and mechanism of cell invasion regulated by Rac1, will provide new strategy and new target for the treatment of squamous cell carcinoma.

头颈部鳞癌五年生存率仅50%，主要原因是其侵袭性强。Rab23是小GTP酶Rab超家族成员，与肿瘤侵袭密切相关。我们前期研究发现，Rab23在正常皮肤中不表达，癌前病变（光线性角化病）中低表达，而鳞癌高表达，且与鳞癌分化负相关；细胞培养证实Rab23显著促进鳞癌细胞侵袭，并调控侵袭关键分子Rac1的表达。但Rab23促进鳞癌细胞侵袭的机制尚不清楚。本项目拟以皮肤鳞状细胞癌为研究对象，从临床标本、细胞水平和动物实验三方面，分别观察Rab23与Rac1在鳞癌中表达的相关性，明确Rac1在Rab23促进鳞癌侵袭中的关键作用， 探讨Rab23调控Rac1的作用机制，确认Rac1受Rab23调控后促进鳞癌侵袭的效应分子，为全面阐明Rab23促进鳞癌侵袭作用的分子机制奠定基础。预期结果将有助于深入认识Rab23的功能及作用，完善Rac1调控肿瘤侵袭机制的认识，并为鳞癌侵袭的防治提供新的策略和治疗靶点。

皮肤鳞状细胞癌是皮肤的第二常见肿瘤，发生率仅次于基底细胞癌，具有侵袭性，可早期转移。虽然目前的治疗对大部分鳞癌有效，但头颈部鳞癌5年生存率仅约50%，侵袭性是影响头颈部鳞癌预后的关键因素。我们前期在国家自然科学基金项目（No 30872264）资助下，发现Rab23可以促进鳞癌侵袭，但其分子机制尚不清楚。.本项目按计划分年度展开工作，以皮肤鳞状细胞癌为研究对象，从临床标本细胞水平和动物实验三方面，为全面阐明Rab23促进鳞癌侵袭作用的分子机制进行了研究，深入认识了Rab23促进鳞癌侵袭的作用及机制，为鳞癌侵袭的防治提供新的策略和靶点，已按计划达到预期目标。.1、检测了Rab23对鳞癌侵袭的影响，通过检测光线性角化病、鲍温病及皮肤鳞状细胞癌组织的表达，通过检测不同鳞癌细胞系中Rab23的表达对鳞癌细胞侵袭的影响，明确了Rab23能够明显促进鳞癌及鳞癌细胞的侵袭；.2、明确了Rac1在介导Rab23促进鳞癌侵袭中的关键作用，研究发现不同方法抑制Rac1活性后均可显著下调Rab23的促鳞癌细胞侵袭及迁移能力，表明Rac1是Rab23促进鳞癌侵袭的关键分子；.3、观察了Rab23调控Rac1的作用方式，阐明了二者之间的相互作用机制，激光共聚焦检测到Rab23与Rac1存在共定位，但二者之间无直接相互作用，Rab23对Rac1的调控是通过整合素β1和Tiam1完成的；.4、探讨了Rab23调控UVB照射引起角质形成细胞自噬的机制，发现UVB照射可诱导角质形成细胞产生自噬，过表达Rab23可影响自噬通路中的重要信号调控分子Erk和mTOR，提示这两个分子可能是Rab23调控UVB诱导角质形成细胞自噬的关键分子。