新辅助同期放化疗是直肠癌综合治疗的重要组成部分。近年来，放化疗导致残余肿瘤生物学行为变化的现象开始受到重视。我们前期研究发现，放化疗后的残余肝癌出现侵袭转移能力增强的现象，其原因与上皮-间质转化等机制有关。目前尚不清楚在直肠癌的放化疗过程中是否也存在类似现象，其关键的调控基因是什么。更为重要的是，目前尚未从人肿瘤组织中找到放化疗导致肿瘤细胞生物学行为恶化的有力证据。本项目拟通过①建立人结直肠癌细胞体外同期放化疗模型，研究放化疗后残余癌细胞侵袭转移相关生物学特性的变化趋势，利用基因芯片筛选与之相关的关键基因。② 在人直肠癌标本中寻找和验证放化疗后残余癌细胞的分子表型变化及关键基因的表达，分析其与患者预后的关系③探索阻断关键基因的表达和（或）功能，改善放化疗后残余直肠癌细胞生物学特性的可能。本项目将为揭示新辅助放化疗后残余直肠癌生物学特性的变化及其机制，提高直肠癌综合治疗疗效提供科学依据。

Neoadjuvant chemoradiotherapy is important among the multidisciplinary management of rectal cancer. Recent years it has been concerned that chemotherapy and radiotherapy can effect the biological behavior of tumor cells. In our previous study it was found that residual hepatocellular carcinoma cells after chemotherapy and radiation gained enhanced metastatic ability with relevance to epithelial mesenchymal transition. It is not clear whether the same phenomenon appears in the chemoradiotherapy of rectal cancer and what is the key gene responsible for it. More importantly, there is still not enough evidence from human rectal cancer tissue to prove the chemo and radiation related deterioration of biological behavior in tumor cells. This study is proposed to: 1) establish the model of in vitro chemoradiotherapy on rectal tumor cells , detect the changes of biological features concerning invasion and metastatic ability of residual colorectal cancer cells and determine the key gene responsible for it. 2) search and prove the changes of molecular phenotypes and the expression of the key gene in residual rectal cancer after chemoradiotherapy, analyze the relationship between the expression of the key gene and the prognosis of the patients. 3)explore the possibility of modulating the biological behavior of residual rectal cancer cells through blocking the expression or function of the key gene. This program will reveal the changes of biological behavior of residual rectal cancer cells after chemoradiotherapy and provide the scientific evidence to improve the outcome of multidisciplinary management of rectal cancer.