Development of various somatostatin analogs for the treatment and diagnosis of tumors utilizing somatostatin receptor genes

生长抑素通过其特异性高亲和力受体发挥作用。我们以前曾报道克隆，功能特性，和组织分布的两种亚型的人和小鼠生长抑素受体（SSTR 1，SSTR 2）。在本研究中，我们克隆了另外三个人生长抑素受体（SSTR 1，SSTR 2，SSTR 3）。人SSTR 1、SSTR 2和SSTR 3分别是418、388和364个氨基酸的蛋白质，RNA印迹研究表明，在人脑中检测到SSTR 3 mRNA，在人胰腺癌细胞系MIA PaCa 2中检测到SSTR 4 mRNA，而在所检查的人组织中未检测到SSTR 5 mRNA。SSTR 3 mRNA在大鼠胰岛中也有高水平表达。人SSTR 3、SSTR 4和SSTR 5表现出与生长抑素-14特异性结合，IC 50值分别为1.7、1.6和0.16 nM。我们还表征了各种生长抑素类似物对SSTR 3、4和5的结合亲和力。类似物的效力等级为：对于hSSTR 3，生长抑素28（SS-28）= CGP 23996>生长抑素-14（SS-14）> SMS 201 -995;对于hSSTR 4，SS-14=SS-28>>RC-160>> SMS 201 -995;对于hSSTR 5，SS-28>SS-14>>RC-160> SMS 201 -995。我们已经确定了生长抑素受体亚型表达的人内分泌肿瘤。在2例胰高血糖素瘤中，除SSTR 5 mRNA外，所有SSTR亚型mRNA均表达。4例胰岛素瘤hSSTR呈异质性表达。在类癌中，检测到SSTR 1和SSTR 4 mRNA。由于已被批准用于治疗内分泌肿瘤的生长抑素类似物SMS 201 -995在治疗存在SSTR 2 mRNA的胰高血糖素瘤患者中有效，而在未检测到SSTR 2 mRNA的类癌患者中无效，因此这些结果表明，SMS 201 -995的疗效可能至少部分取决于SSTR 2在肿瘤中的表达。5种人生长抑素受体亚型的克隆促进不同生长抑素受体的发育

Somatostatin exerts its effect through its specific high affinity receptors. We have previously reported cloning, functional characterization, and tissue distribution of two subtypes of human and mouse somatostatin receptors (SSTR1, SSTR2). In the present study, we have cloned three additional human somatostatin receptors (SSTR1, SSTR2, SSTR3). Human SSTR1, SSTR2, and SSTR3 are proteins of 418, 388, and 364 amino acids, respectively, RNA blotting studies have revealed that SSTR3 mRNA was detected in human brain and SSTR4 mRNA was present in human pancreatic cancer cell line, MIA PaCa2, while SSTR5 mRNA was not detected in the human tissues examined. The SSTR3 mRNA was expressed at high levels in rat pancreatic islets as well. The human SSTR3, SSTR4, and SSTR5 exhibit specfic binding to somatostatin-14 with IC50 values 1.7, 1.6 and 0.16nM, respectively. We also have characterized the binding affinity of various somatostatin analogs to the SSTR3, 4, and 5. The rank of the potency of the analogs are : somatostatin 28 (SS-28) = CGP 23996>somatostatin-14 (SS-14)>SMS201-995 for hSSTR3 ; SS-14=SS-28>>RC-160>>SMS201-995 for hSSTR4 and SS-28>SS-14>>RC-160>SMS201-995 for hSSTR5. We have determined somatostatin receptor subtypes expressed human endocrine tumors. In two cases of glucagonomas, all the SSTR subtype mRNAs except for SSTR5 mRNA were expressed. In 4 cases of insulinoma, there was a heterogeneous expression hSSTRs. In a carcinoid, SSTR1 and SSTR4 mRNA were detected. Since somatostatin analog, SMS201-995 which has been approved for the treatment of endocrine tumors, was effective in the treatment of a patient with glucagonoma in which SSTR2 mRNA was present, whereas it had no effect in a patient with carcinoid in which SSTR2 mRNA was not detected, these results suggest that the efficacy of SMS201-995 may depend, at least in part, on the expression of SSTR2 in tumors. Cloning of five human somatostatin receptor subtypes facilitates the development of various somatosta