局部复发是鼻咽癌放疗失败的主要原因。研究表明肿瘤细胞在分次照射后会诱发放疗抵抗，而目前分子机制尚不明确。我们的前期研究显示放疗可以激活鼻咽癌IL-6/STAT3通路，促使pSTAT3表达增加，E-cadherin表达下降，EGFR表达增加。在此基础上，我们提出假设：分次照射后诱导鼻咽癌IL-6/STAT3通路激活，下调E-cadherin表达，继而转录调控EGFR的表达增加，从而诱发放疗抵抗。本项目拟利用接受不同照射剂量的鼻咽癌细胞株、放疗后局部复发组织以及裸鼠移植瘤模型作为研究对象，用免疫组化、免疫荧光共聚焦、RT-PCR、RNA干扰、Western、CHIP以及EMSA等技术，分别从细胞、组织、体内水平验证IL-6/STAT3/E-cadherin/EGFR信号通路是诱导鼻咽癌细胞分次照射后放疗抵抗的主要分子机制之一的理论假设，并探索E-cadherin调控EGFR表达的可能分子机制。

Local recurrence is the main reason for the failure of radiotherapy in nasopharyngeal carcinoma (NPC). Studies have shown that fractionated irradiation could induce radiation resistance in cancer cells，however, the molecular mechanism is unclear at present. Our previous studies have indicated that radiation therapy induced IL-6/STAT3 signal pathway activation in NPC cells, promoted pSTAT3 expression, downregulated the downstream gene E-cadherin expression and increased EGFR expression.On this basis, we propose hypotheses:fractionated irradiation induce IL-6/STAT3 pathway activation in NPC, downregulate its downstream gene E-cadherin expression, then transcriptionally upregulate EGFR expression which finally induces radiation resistance. A panel of nasopharyngeal carcinoma cell lines treated with different doses of radiation、local recurrent tissue and nude mouse xenograft model were experiment objects in this project. Immunohistochemistry, Confocal immunofluorescence,RT-PCR,RNA interference,Western,CHIP and EMSA techniques will be used to verify the hypotheses at cellular、tissue and in vivo level that IL-6/STAT3/E-cadherin/EGFR signaling pathway is the major molecular mechanism for radiation resistant induced by fractionated radiation in nasopharyngeal carcinoma cells, and explore the possible molecular mechanism of IL-6/STAT3/E-cadherin signaling pathway in transcriptional regulation of EGFR expression.