肝转移显著影响结直肠癌预后。西妥昔单抗治疗RAS野生型肠癌肝转移有效，但尚有半数患者原发耐药，且机制不明。申请人通过大样本基因芯片二代测序，发现肠癌MIC-B基因rs1051788位点突变（简称MIC-B突变）与西妥昔原发耐药显著相关。细胞实验显示，MIC-B突变导致可溶性MIC-B显著增加，促进巨噬细胞向TAMs极化；临床标本免疫组化也证实，TAMs极化与MIC-B突变、西妥昔耐药显著相关。目前MIC-B已知的唯一受体是NKG2D，免疫荧光也表明巨噬细胞表面表达NKG2D。申请人据此推想，可溶性MIC-B作用于巨噬细胞NKG2D，促进TAMs极化，导致西妥昔耐药。本项目拟重点研究NKG2D激活后促进TAMs极化的精细机制：通过检测NKG2D/DAP10-内吞体-ERK通路及PI3K-Akt通路，明确调控方式。本项目紧密结合临床，有助于筛选西妥昔单抗治疗适应人群，为多靶点联合治疗提供依据。

Liver metastasis is significantly associated with prognosis of colorectal cancer. Cetuximab is effect for colorectal cancer liver metastasis (CLM) with wild-type RAS. However, there are still half patients with primary cetuximab resistance. And the mechanism is still unknown. By gene microarray and next generation sequencing of a large sample size, we find that MIC-B mutation at rs1051788 in CLM is significantly associated with primary resistance of cetuximab. In cell line, MIC-B mutation significantly increases the expression of soluble MIC-B, and promotes TAMs polarization. Immunohistochemical stains in FFPE tumor sections also prove that TAMs polarization is significantly associated with MIC-B mutation and cetuximab resistance. At present, NKG2D is the only receptor of MIC-B. Immunofluorescences also prove that macrophages also express NKG2D on the membrane. Thus, we suppose that soluble MIC-B stimulate NKG2D on macrophages, and promotes TAMs polarization, then finally induces cetuximab resistance. In this project, we will concentrate on the mechanism in which NKG2D promotes TAMs polarization. We will detect the NKG2D/DAP10-endosome-ERK pathway and PI3K-Akt pathway to make clear the mechanism. This project is tightly associated with clinical questions. The achievement will help screen the applicable population for cetuximab, and prove evidence for multi-targeted treatment.