Guo Y S, Beauchamp R D, Jin G F, Townsend C M, Thompson J C
Department of Surgery, University of Texas Medical Branch, Galveston.
Gastroenterology. 1993 Jun;104(6):1595-604. doi: 10.1016/0016-5085(93)90634-o.
This study determined whether the resistance to the mitogenic effect of insulinlike growth factor 1 (IGF-1) in AGS (we found that IGF-1 had almost no effect on the growth of AGS) cells is caused by the absence of IGF-1 receptor on the cells or by the interference of endogenous IGFs and IGF-binding protein (IGFBP).
IGF-1 receptors were examined by radioligand binding assay. The protein in conditioned medium and the molecular weight of IGF-1 receptors on AGS cells were determined by affinity cross-linking with 125I-IGF-1 followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Messenger RNAs for IGF-1, IGF-2, and IGFBP-4 were detected by Northern analysis.
AGS cells possessed a single class of high-affinity binding sites for IGF-1 (dissociation constant [Kd], 0.51), with a binding capacity approximately 4 x 10(4) sites per cell. The size of the alpha subunit of IGF-1 receptors on cell membranes was approximately 130 kilodaltons. des (1-3) IGF-1, a truncated IGF-1 with very low affinity to IGFBPs, stimulated AGS cell growth in dose-dependent fashion. The medium conditioned by AGS cells contained IGFBPs of 27-32 and 37-42 kilodaltons. AGS cells expressed messenger (mRNA) RNAs for IGF-2 and IGFBP-4 but not for IGF-1, whereas another gastric carcinoma cell line (SIIA), whose growth is stimulated by IGF-1, expressed mRNA IGF-2 but did not express mRNA for IGF-1 or IGFBP-4:
The relative absence of growth response of AGS cells to IGF-1 is due to the endogenously produced IGFBPs sequestering IGF-1 and preventing receptor interaction.
本研究旨在确定AGS细胞（我们发现胰岛素样生长因子1（IGF-1）对AGS细胞生长几乎没有影响）对IGF-1促有丝分裂作用的抗性是由细胞上IGF-1受体的缺失还是内源性IGF和IGF结合蛋白（IGFBP）的干扰所致。
通过放射性配体结合试验检测IGF-1受体。用125I-IGF-1进行亲和交联，随后进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳，测定条件培养基中的蛋白质和AGS细胞上IGF-1受体的分子量。通过Northern分析检测IGF-1、IGF-2和IGFBP-4的信使RNA。
AGS细胞具有一类单一的高亲和力IGF-1结合位点（解离常数[Kd]，0.51），每个细胞的结合容量约为4×10(4)个位点。细胞膜上IGF-1受体α亚基的大小约为130千道尔顿。des(1-3)IGF-1是一种对IGFBPs亲和力极低的截短型IGF-1，以剂量依赖性方式刺激AGS细胞生长。AGS细胞条件培养基中含有27-32千道尔顿和37-42千道尔顿的IGFBPs。AGS细胞表达IGF-2和IGFBP-4的信使RNA，但不表达IGF-1的信使RNA，而另一种胃癌细胞系（SIIA）的生长受IGF-1刺激，表达mRNA IGF-2，但不表达IGF-1或IGFBP-4的mRNA。
AGS细胞对IGF-1生长反应相对缺乏是由于内源性产生的IGFBPs螯合IGF-1并阻止受体相互作用。
