Sethi T, Herget T, Wu S V, Walsh J H, Rozengurt E
Imperial Cancer Research Fund, London, England.
Cancer Res. 1993 Nov 1;53(21):5208-13.
Gastrin, cholecystokinin (CCK), and CCK-related peptides comprise a hormonal family characterized by an identical carboxy-terminal amino acid sequence, a domain critical for receptor binding. The addition of gastrin to small cell lung cancer (SCLC) cells causes a rapid and transient increase in the intracellular concentration of calcium ([Ca2+]i). Furthermore, gastrin acts as a direct growth factor through CCKB/gastrin receptors. We report here that the expression of the mRNA coding for CCKB/gastrin receptors correlates with the responsiveness of SCLC cells to gastrin in terms of Ca2+ mobilization and stimulation of clonal growth in semisolid medium. The GLC19 SCLC cell line had no detectable expression of CCKB/gastrin receptor mRNA. Accordingly, gastrin (1-100 nM) did not cause any measurable increase in [Ca2+]i. In contrast, the addition of cholecystokinin residues 26-33 (CCK-8) caused a rapid and transient increase in [Ca2+]i in this cell line. CCK-8 mobilized Ca2+ in a dose-dependent manner in the nanomolar range (half-maximal stimulatory concentration = 12 nM). Furthermore, the selective CCKA antagonist CAM-1481 inhibited the increase in [Ca2+]i induced by CCK-8 (half-maximal inhibitory concentration = 3 nM) in GLC19 but not in H510 cells. The selective CCKB/gastrin antagonist blocked the increase in [Ca2+]i induced by CCK-8 (half-maximal inhibitory concentration = 80 pM) in H510 but not in GLC19 cells. Thus, the effects of CCK-8 are mediated through CCKA receptors in GLC19 cells and via CCKB/gastrin receptors in H510 cells. CCK-8 markedly stimulated colony formation in GLC19 cells in a dose-dependent manner in the nanomolar range, whereas over the same concentration range, gastrin had no effect on clonal growth. CAM-1481 inhibited the CCK-stimulated colony formation in GLC19 but not in H510 cells. Our results show, for the first time, that CCKA receptors can mediate Ca2+ mobilization and growth in SCLC cells and that SCLC cells express two distinct functional CCK receptor subtypes.
胃泌素、胆囊收缩素（CCK）及CCK相关肽构成了一个激素家族，其特征是具有相同的羧基末端氨基酸序列，这是一个对受体结合至关重要的结构域。向小细胞肺癌（SCLC）细胞中添加胃泌素会导致细胞内钙浓度（[Ca2+]i）迅速且短暂地升高。此外，胃泌素通过CCKB/胃泌素受体发挥直接生长因子的作用。我们在此报告，编码CCKB/胃泌素受体的mRNA表达与SCLC细胞在钙动员和半固体培养基中克隆生长刺激方面对胃泌素的反应性相关。GLC19 SCLC细胞系未检测到CCKB/胃泌素受体mRNA的表达。因此，胃泌素（1 - 100 nM）未引起[Ca2+]i的任何可测量的升高。相反，添加胆囊收缩素26 - 33残基（CCK - 8）会使该细胞系中的[Ca2+]i迅速且短暂地升高。CCK - 8在纳摩尔范围内以剂量依赖方式动员Ca2+（半数最大刺激浓度 = 12 nM）。此外，选择性CCKA拮抗剂CAM - 1481抑制了CCK - 8诱导的GLC19细胞中[Ca2+]i的升高（半数最大抑制浓度 = 3 nM），但对H510细胞无此作用。选择性CCKB/胃泌素拮抗剂阻断了CCK - 8诱导的H510细胞中[Ca2+]i的升高（半数最大抑制浓度 = 80 pM），但对GLC19细胞无此作用。因此，CCK - 8的作用在GLC19细胞中通过CCKA受体介导，在H510细胞中通过CCKB/胃泌素受体介导。CCK - 8在纳摩尔范围内以剂量依赖方式显著刺激GLC19细胞中的集落形成，而在相同浓度范围内，胃泌素对克隆生长无影响。CAM - 1481抑制了GLC19细胞中CCK刺激的集落形成，但对H510细胞无此作用。我们的结果首次表明，CCKA受体可介导SCLC细胞中的钙动员和生长，且SCLC细胞表达两种不同功能的CCK受体亚型。
