Ito Hirotaka, Funahashi Shin-ichi, Yamauchi Naoko, Shibahara Junji, Midorikawa Yutaka, Kawai Shigeto, Kinoshita Yasuko, Watanabe Akira, Hippo Yoshitaka, Ohtomo Toshihiko, Iwanari Hiroko, Nakajima Atsushi, Makuuchi Masatoshi, Fukayama Masashi, Hirata Yuichi, Hamakubo Takao, Kodama Tatsuhiko, Tsuchiya Masayuki, Aburatani Hiroyuki
Genome Science Division, Research Center for Advanced Science and Technology, the University of Tokyo, Japan.
Clin Cancer Res. 2006 Jun 1;12(11 Pt 1):3257-64. doi: 10.1158/1078-0432.CCR-05-2787.
Hepatocellular carcinoma is the most common primary malignancy of the liver and accounts for as many as one million deaths annually worldwide. The present study was done to identify new transmembrane molecules for antibody therapy in hepatocellular carcinoma.
Gene expression profiles of pooled total RNA from three tissues each of moderately differentiated and poorly differentiated hepatocellular carcinoma were compared with those of normal liver, noncancerous liver tissue in hepatocellular carcinoma patients, 30 normal tissue samples, and five fetal tissue samples. Target genes up-regulated specifically in hepatocellular carcinoma were validated by immunohistochemical analysis and complement-dependent cytotoxicity assay using monoclonal antibodies generated against target molecules.
The human homologue of the Drosophila Roundabout gene, axon guidance receptor homologue 1, ROBO1/DUTT1, a member of the immunoglobulin superfamily, was highly expressed in hepatocellular carcinoma, whereas it showed only a limited distribution in normal tissues. On immunohistochemical analysis using a newly generated anti-ROBO1 monoclonal antibody, positive signals were observed in 83 of 98 cases of hepatocellular carcinoma (84.7%). The mAb B2318C induced complement-dependent cytotoxicity in ROBO1-expressing cell lines and in the liver cancer cell line PLC/PRF/5. Strikingly, the ectodomain of ROBO1 was detected not only in the culture medium of liver cancer cell lines (PLC/PRF/5, HepG2, etc.) but also in sera from hepatocellular carcinoma patients (6 of 11).
This is the first report that ROBO1 is overexpressed in hepatocellular carcinoma and shed into serum in humans. These observations suggest that ROBO1 is a potential new serologic marker for hepatocellular carcinoma and may represent a new therapeutic target.
肝细胞癌是肝脏最常见的原发性恶性肿瘤，全球每年有多达100万人死于该病。本研究旨在鉴定用于肝细胞癌抗体治疗的新跨膜分子。
将来自中分化和低分化肝细胞癌各三个组织的总RNA池的基因表达谱，与正常肝脏、肝细胞癌患者的非癌肝组织、30个正常组织样本及5个胎儿组织样本的基因表达谱进行比较。通过免疫组织化学分析以及使用针对靶分子产生的单克隆抗体进行补体依赖性细胞毒性试验，验证在肝细胞癌中特异性上调的靶基因。
果蝇Roundabout基因的人类同源物，轴突导向受体同源物1，ROBO1/DUTT1，免疫球蛋白超家族的一员，在肝细胞癌中高表达，而在正常组织中仅呈有限分布。使用新产生的抗ROBO1单克隆抗体进行免疫组织化学分析时，在98例肝细胞癌中的83例（84.7%）观察到阳性信号。单克隆抗体B2318C在表达ROBO1的细胞系和肝癌细胞系PLC/PRF/5中诱导补体依赖性细胞毒性。令人惊讶的是，不仅在肝癌细胞系（PLC/PRF/5、HepG2等）的培养基中，而且在肝细胞癌患者的血清中（11例中的6例）均检测到ROBO1的胞外域。
这是关于ROBO1在人类肝细胞癌中过表达并释放到血清中的首次报道。这些观察结果表明，ROBO1是肝细胞癌潜在的新血清学标志物，可能代表一个新的治疗靶点。
