Identification, characterization, and biological activity of specific receptors for natural (ghrelin) and synthetic growth hormone secretagogues and analogs in human breast carcinomas and cell lines
Identification, characterization, and biological activity of specific receptors for natural (ghrelin) and synthetic growth hormone secretagogues and analogs in human breast carcinomas and cell lines
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DOI：
10.1210/jc.86.4.1738
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发表时间：
2001-04-01
影响因子：
5.8
通讯作者：
Muccioli, G
中科院分区：
文献类型：
--
作者：
Cassoni, P;Papotti, M;Muccioli, G
CH促分泌素（GHS）家族包括合成肽基（海沙瑞林）和非肽基（MK-0677）分子，在垂体和中枢神经系统以及外周组织（包括心脏和一些内分泌器官）中具有特异性受体。胃促生长素（ghrelin）是一种胃源性肽，最近被认为是GHS受体（GHS-Rs）的天然配体。现在已经使用放射性碘标记的肽基GHS（[I-125]-Tyr-Ala-hexarelin）作为配体研究了非肿瘤和肿瘤性人类乳腺组织中特异性GHS-Rs的存在。在几种类型的乳腺癌的膜中检测到GHS的特异性结合位点，而在纤维腺瘤和乳腺实质中发现了可忽略不计的结合。在分化良好（G1）的浸润性乳腺癌中发现最高的结合活性，并在中度（G2）至分化不良（G3）的肿瘤中逐渐降低。与肿瘤膜结合的[I-125]-Tyr-Ala-hexarelin被不同的未标记GHS（如hexarelin、Tyr-Ala-hexarelin、人ghrelin和MK-0677以及去辛酰基-ghrelin和hexarelin衍生物EP-80317）取代，这些GHS在体内缺乏GH释放特性。相比之下，在放射性标记的Tyr-Ala-海沙瑞林和一些在结构和功能上与海沙瑞林无关的肽（CRF和胰岛素样生长因子I）之间或在置换研究中检测GHRH和SRIF时，未观察到竞争。在三种不同的人乳腺癌细胞系（MCF 7、T47 D和MDA-MB 231）中也证明了特异性GHS结合位点的存在，其中，令人惊讶的是，通过RT-PCR没有证明GHS-R1 a的信使RNA。在这些细胞系中，生长素释放肽（以及海沙瑞林、MK-0677、EP-80317，甚至去辛酰基生长素释放肽）在接近其结合亲和力的浓度下引起细胞增殖的显著抑制。总之，这项研究首次证明了乳腺癌中GHS-R1以外的特异性GHS结合位点。这些受体可能介导体外乳腺癌细胞的生长抑制作用。
The family of CH secretagogues (GHS) includes synthetic peptidyl (hexarelin) and nonpeptidyl (MK-0677) molecules possessing specific receptors in the pituitary and central nervous system as well as in peripheral tissues, including the heart and some endocrine organs. A gastric-derived peptide, named ghrelin, has recently been proposed as the natural ligand of the GHS receptors (GHS-Rs). The presence of specific GHS-Rs has now been investigated in nontumoral and neoplastic human breast tissue using a radioiodinated peptidyl GHS ([I-125]-Tyr-Ala-hexarelin) as ligand. Specific binding sites for GHS were detected in membranes from several types of breast carcinomas, whereas a negligible binding was found in fibroadenomas and mammary parenchyma. The highest binding activity was found in well-differentiated (G1) invasive breast carcinomas and was progressively reduced in moderately (G2) to poorly (G3) differentiated tumors. [I-125]-Tyr-Ala-hexarelin bound to tumor membranes was displaced by different unlabeled GHS such as hexarelin, Tyr-Ala-hexarelin, human ghrelin, and MK-0677 as well as bydesoctanoyl-ghrelin and hexarelin derivative EP-80317, which are devoid of GH-releasing properties in vivo. In contrast, no competition was seen between radiolabeled Tyr-Ala-hexarelin and some peptides (CRF and insulinlike growth factor I) structurally and functionally unrelated to hexarelin or when GHRH and SRIF were tested in the displacement studies. The presence of specific GHS binding sites was also demonstrated in three different human breast carcinoma cell lines (MCF7, T47D, and MDA-MB231), in which, surprisingly, no messenger RNA for GHS-R1a was demonstrated by RT-PCR. In these cell lines, ghrelin (as well as hexarelin, MK-0677, EP-80317, and even desoctanoyl ghrelin) caused a significant inhibition of cell proliferation at concentrations close to their binding affinity. In conclusion, this study provides the first demonstration of specific GHS binding sites, other than GHS-R1, in breast cancer. These receptors probably mediate growth inhibitory effects on breast carcinoma cells in vitro.