Establishment of an appropriate metastasis model and a novel treatment for advanced human colorectal cancer using RAG2/common-γ double knockout mice

本研究的目的是建立一种免疫治疗人结肠癌的动物模型。结果表明，RAG 2/common-γ knockout（DKO）小鼠体内的人大肠癌组织大部分存活，部分浸润到肌层和腹侧淋巴管通道，与普通免疫低下小鼠、裸鼠和scid小鼠不同。这些小鼠在脾内注射人结肠癌细胞系HT-29后显示出比其他小鼠更多的肝转移灶。人结肠癌在DKO小鼠中的适应性、侵袭性和肝转移在几个小鼠器官中更普遍。植入DKO小鼠皮下组织中的人结直肠癌组织在抑制方法中显示出对抗癌药物的相似敏感性。DKO小鼠中的人结直肠癌表型保持与植入前相同。测定标准化疗剂对结直肠癌细胞系中MHC I类和CEA表达的影响。当以IC_50值给药时，所有检测的抗癌药物均诱导人结肠癌细胞系COLO 201中MHC I类的表达。然而，CEA mRNA的表达仅在暴露于5-FU时被诱导。关于在小鼠中的体内研究，结肠26的肿瘤大小仅响应于用CDDP处理而减小，CDDP也介导了MHC I类表达的最高诱导。这些结果表明，癌症特异性免疫疗法与全身化疗联合使用时可能具有协同作用。

The aim of this study is to establish an animal medel for immunothrerapeutic treatment of human colon cancer. Our results demonstrate that most of human colorectal cancer tissues remain alive in RAG2/common-γ knockout (DKO) mice, moreover, some of them invade into the muscular layer and lymphovascular channel in the flank, unlike with the ordinary immuno-compromised mice, nude mice and scid mice. These mice showed more foci of liver metastases than other mice after intrasplenic injection of the human colon cancer cell line, HT-29. Adaptation, invasion and liver metastasis of human colon cancer into several mice organs were more prevalent in DKO mice. Human colorectal cancer tissue implanted in the subcutaneous tissue of DKO mice showed the similar sensitivity to anti-cancer drugs in the HDRA method. Phenotypes of human colorectal cancer in DKO mice were kept as same as those before implantation. The effect of standard chemotherapeutics on MHC class I and CEA expression in colorectal cancer cell lines was determined. All anti-cancer drugs examined, when given at IC_50 values, induced expression of MHC class I in the human colon cancer cell line, COLO201. However, expression of CEA mRNA was only induced upon exposure to 5-FU. Regarding the in vivo studies in mice, the tumor size of colon26 was reduced only in response to treatment with CDDP, which also mediated the highest induction of MHC class I expression. These results indicate that cancer-specific immunotherapy may be synergistically effective when used in combination with systemic chemotherapy.