Clarke P, Mann J, Simpson J F, Rickard-Dickson K, Primus F J
Division of Immunology, Beckman Research Institute of the City of Hope, Duarte, California 91010, USA.
Cancer Res. 1998 Apr 1;58(7):1469-77.
Mice transgenic for the human carcinoembryonic antigen (CEA) gene were prepared for use as a preclinical model for immunotherapy. A 32.6-kb fragment containing the complete human CEA gene and flanking sequences was isolated from a genomic cosmid clone and used to produce transgenic C57BL/6 mice. A homozygous line was established that was designated C57BL/6J-TgN(CEAGe)18FJP. Southern blot analysis showed that this line contained intact copies of the cosmid clone, with approximately 19 integrated copies at one chromosomal location. A mouse-human chimeric anti-CEA monoclonal antibody was used to examine CEA expression by immunohistochemical staining of frozen tissue sections. In the cecum and colon, approximately 20% of the luminal epithelial cells had strong cytoplasmic staining, whereas occasional glands showed intense staining. CEA was also expressed in gastric foveolar cells, whereas small intestine villi had only a few (<1%) positive cells. CEA was not found by immunohistochemistry in other tissues of the digestive tract, nor was it found in a wide range of other tissues or organs. Concordance in results was obtained between immunohistochemistry and analysis of tissue extracts by enzyme immunoassay. The lone exception was the testis, which was positive only by enzyme immunoassay. Expression of human CEA was not observed in tissues derived from nontransgenic mice. The fecal content of CEA in transgenic mice was approximately 100-fold less than that observed for humans. Circulating CEA was not detected. A CEA-transfected syngeneic murine colon carcinoma cell line, MC-38, was prepared that had stable expression of CEA in vitro and in vivo. The molecular size of CEA produced by CEA-transfected MC-38 cells and by the colon of transgenic mice was similar to that obtained with CEA purified from human colon tumors. Anti-CEA antibody appeared in nontransgenic but not transgenic mice bearing transfected MC-38 tumors. These findings demonstrate that CEA distribution and its properties in tissues of mice transgenic for the human CEA gene are similar to that observed in human tissues. As in humans, immune responsiveness to CEA, as reflected by antibody formation, was not detectable in transgenic mice bearing CEA-positive tumors. Thus, CEA transgenic mice may serve as a useful model for studying the efficacy and safety of various immunotherapy strategies directed at this tumor self-antigen.
制备了转人癌胚抗原（CEA）基因的小鼠，用作免疫治疗的临床前模型。从基因组黏粒克隆中分离出一个包含完整人CEA基因及其侧翼序列的32.6 kb片段，并用于培育转基因C57BL/6小鼠。建立了一个纯合子品系，命名为C57BL/6J-TgN(CEAGe)18FJP。Southern印迹分析表明，该品系包含黏粒克隆的完整拷贝，在一个染色体位置上约有19个整合拷贝。使用一种小鼠-人嵌合抗CEA单克隆抗体，通过对冷冻组织切片进行免疫组织化学染色来检测CEA的表达。在盲肠和结肠中，约20%的腔上皮细胞有强烈的细胞质染色，而偶尔有腺体显示强烈染色。CEA也在胃小凹细胞中表达，而小肠绒毛中只有少数（<1%）阳性细胞。通过免疫组织化学在消化道的其他组织中未发现CEA，在其他广泛的组织或器官中也未发现。免疫组织化学与酶免疫分析组织提取物的结果一致。唯一的例外是睾丸，仅通过酶免疫分析呈阳性。在非转基因小鼠来源的组织中未观察到人类CEA的表达。转基因小鼠粪便中的CEA含量比人类观察到的低约100倍。未检测到循环CEA。制备了一种CEA转染的同基因鼠结肠癌细胞系MC-38，其在体外和体内均稳定表达CEA。CEA转染的MC-38细胞和转基因小鼠结肠产生的CEA分子大小与从人结肠肿瘤中纯化的CEA相似。抗CEA抗体出现在携带转染MC-38肿瘤的非转基因小鼠中，而在转基因小鼠中未出现。这些发现表明，人CEA基因转基因小鼠组织中CEA的分布及其特性与在人体组织中观察到的相似。与人类一样，在携带CEA阳性肿瘤的转基因小鼠中，未检测到抗体形成所反映的对CEA的免疫反应性。因此，CEA转基因小鼠可作为研究针对这种肿瘤自身抗原的各种免疫治疗策略的有效性和安全性的有用模型。
