Hoosein Moinuddin M, Dashwood Michael R, Dawas Khaled, Ali Haythem M M D A, Grant Katherine, Savage Felicity, Taylor Irving, Loizidou Marilena
Department of Surgery, Royal Free and University College Medical School, London, UK.
Eur J Gastroenterol Hepatol. 2007 Sep;19(9):775-82. doi: 10.1097/MEG.0b013e3282c563de.
The vasoactive peptide endothelin-1 (ET-1) acts via two endothelin receptor subtypes, ETA (ETAR) and ETB (ETBR). ET-1 and ETAR are overexpressed in colorectal cancer tissues. In vitro, ET-1 acting via ETAR, is a mitogen for colorectal cancer cells. To identify other potential stimulatory loops, we investigated the distribution and cell-specific localization of both ETAR and ETBR in tissue sections from patients with colorectal cancer.
Frozen sections from specimens of colorectal cancer (n=9) and normal colon (n=9) were cut and subjected to either (i) autoradiography or (ii) a combination of cell type-specific immunohistochemistry, using antibodies against fibroblasts (AS02), endothelial cells (CD31) or nerve fibres (NF200) and in-vitro receptor microautoradiography, using ETAR-specific and ETBR-specific radioligands.
ETARs were upregulated in all cell types, apart from nerve, in cancer compared with normal colon (1:1.59 normal to cancer). Specifically, ETAR binding was highest in cancer-associated blood vessels and fibroblasts and to a lesser extent in epithelial cancer cells. In contrast, ETBRs were the predominant receptors in normal colon (1:0.59 normal to cancer) and were markedly down-regulated in cancer-associated blood vessels, fibroblasts and to a lesser extent in epithelial cells. Nerve colocalization was demonstrated, but remained unchanged for all tissues.
The shift in ET receptor binding observed in epithelial cancer cells and cancer-associated fibroblasts and endothelial cells may favour ET-1 signals contributing to colorectal cancer growth and neovascularization via ETAR. This may provide the basis for therapeutic use of specific ETAR antagonists as adjuvant treatment of colorectal cancer.
血管活性肽内皮素 -1（ET-1）通过两种内皮素受体亚型，即ETA（ETAR）和ETB（ETBR）发挥作用。ET-1和ETAR在结直肠癌组织中过度表达。在体外，通过ETAR起作用的ET-1是结肠癌细胞的促有丝分裂原。为了确定其他潜在的刺激环路，我们研究了ETAR和ETBR在结直肠癌患者组织切片中的分布和细胞特异性定位。
切取结直肠癌标本（n = 9）和正常结肠标本（n = 9）的冰冻切片，进行以下操作：（i）放射自显影，或（ii）使用针对成纤维细胞（AS02）、内皮细胞（CD31）或神经纤维（NF200）的抗体进行细胞类型特异性免疫组化与体外受体放射自显影相结合，体外受体放射自显影使用ETAR特异性和ETBR特异性放射性配体。
与正常结肠相比（正常与癌之比为1:1.59），除神经外，ETAR在癌组织的所有细胞类型中均上调。具体而言，ETAR结合在癌相关血管和成纤维细胞中最高，在上皮癌细胞中程度较轻。相比之下，ETBR是正常结肠中的主要受体（正常与癌之比为1:0.59），在癌相关血管、成纤维细胞中明显下调，在上皮细胞中下调程度较轻。证实了神经共定位，但所有组织中均保持不变。
在上皮癌细胞、癌相关成纤维细胞和内皮细胞中观察到的ET受体结合变化可能有利于ET-1信号通过ETAR促进结直肠癌生长和新生血管形成。这可能为使用特异性ETAR拮抗剂作为结直肠癌辅助治疗提供依据。
