不同LET射线对结直肠癌移植瘤细胞侵袭转移及休眠细胞干细胞属性的影响及机制研究

Colorectal cancer(CRC) is one of the most common and leading causes of tumor-related death in China. Its recurrence/ metastasis after radiotherapy has emerged as the greatest barriers to cancer cure. Resently, tumor domancy has been recognized as the main reason for this prevalent clinical behavior. Our preliminary data showed that heavy ion or X-ray radiation both induced a converse change in the invasion potential of HCT116 and DLD-1 cells, and X-rays radiation could reduce the numbers of tumor dormant cells of the CRC xenografts. In this project, using HCT116 and DLD-1 cells and their xenografts, we will investigate the change of the biological behaviors such as cell invasion and tumor metastasis after the CRC cells and xenografts were exposed to high- or low- LET radiation, and compare the differeces in the biological effects and the underlying mechanisms between the two kinds of radiation. Meanwhile, we will also study the effect on the dormant cells and their stem cell characteristics induced by high- or low- LET radiation, discuss how these changes will affect the fate of the tumor, and illustrate the molecular mechanisms and the key factors involved for the modulation of tumor dormant cell and its stem cell characteristics by radiation.Our study may help to provide deeper insights in the molecular basis of the tumor growth, develop and therapy resistance of CRC after radiation, and provide the new theorerical foundation and treatment target to improve the outcome of the radiotherapy of CRC.

结直肠癌(CRC)是目前我国最常见且病死率较高的恶性肿瘤之一，其放疗后易转移复发是目前治疗中亟待解决的重要问题。肿瘤休眠是导致这一临床常见现象产生的主要原因。我们的预实验结果显示，受重离子或X-射线照射后的HCT116和DLD-1侵袭潜能改变趋势相反，且X-射线能够引起CRC细胞裸鼠移植瘤内肿瘤休眠细胞数减少。本项目将以HCT116和DLD-1细胞及其裸鼠移植瘤为研究对象，在体内体外不同层面研究重离子和普通光子照射后，细胞侵袭与转移等生物学行为的改变及其分子机制，并比较两种射线引起的生物学效应及其机制差异；同时，研究不同射线对肿瘤休眠细胞及其干细胞属性的作用，讨论其会对放疗后的肿瘤命运产生何种影响，并将重点探寻辐射调控肿瘤休眠细胞及其干细胞属性的具体分子机制及其中的关键因子。该项目的完成将进一步加深人们对放疗影响肿瘤生长、进展和治疗抵抗机理的认识，为提高肿瘤治疗效果提供新的理论依据和治疗。

放疗是包括结直肠癌（CRC）在内的各种实体瘤实现局部控制的有效非手术手段，但常规放疗后的转移和复发仍然是导致预后不良的主要障碍。本项目发现辐射后细胞运动的变化与辐射类型（光子辐射或重离子）无关，而与细胞的固有特性有关。辐射后两种CRC细胞侵袭迁移呈现相反趋势是由于辐射对两种细胞ANAX2/AKT/GSK3β 信号通路反向调节，这一现象和机制在其他癌种细胞系中也得到验证。此外，我们发现ANAX2可以直接与 GSK3β 结合并作为其在辐射时激活的负调节因子。另一方面，我们成功在体外建立了休眠细胞诱导体系，通过TMT质谱技术绘制正常增殖细胞和休眠细胞的差异蛋白谱，并结合大数据筛选出一系列休眠关键基因。验证发现DDX21在休眠细胞中显著低表达，在增殖肿瘤细胞中敲低该基因可抑制细胞增殖并发生G0/G1期阻滞，进一步研究发现这是由于AKT通路受抑，同时激活p38MAPK通路促进细胞进入休眠状态所致。除此之外，本项目还拓展了休眠对肺癌辐射抵抗的作用方面的研究，发现下调ARL14可致肺癌细胞休眠并产生辐射抵抗，抑制ARL14的表达可能通过CIDEC/ERK/p38信号通路抑制肺腺癌细胞增殖、迁移和侵袭。因此，ARL14/CIDEC可能成为一个有效的肿瘤诊断标志物和治疗靶点。通过该项目研究，我们进一步加深了放疗影响肿瘤生长、进展和治疗抵抗机理的认识，对寻求合理的治疗方式，提高放疗效果具有重要意义。