Stepan V M, Sawada M, Todisco A, Dickinson C J
Department of Pediatrics, University of Michigan, Medical Center, Ann Arbor 48109-0658, USA.
Mol Med. 1999 Mar;5(3):147-59.
Since human colon cancers often contain significant quantities of progastrin-processing intermediates, we sought to explore the possibility that the biosynthetic precursor of fully processed amidated gastrin, glycine-extended gastrin, may exert trophic effects on human colonic cancer cells.
Binding of radiolabeled glycine-extended and amidated gastrins was assessed on five human cancer cell lines: LoVo, HT 29, HCT 116, Colo 320DM, and T 84. Trophic actions of the peptides were assessed by increases in [3H]thymidine incorporation and cell number. Gastrin expression was determined by northern blot and radioimmunoassay.
Amidated gastrin did not bind to or stimulate the growth of any of the five cell lines. In contrast, saturable binding of radiolabeled glycine-extended gastrin was seen on LoVo and HT 29 cells that was not inhibited by amidated gastrin (10(-6) M) nor by a gastrin/CCKB receptor antagonist (PD 134308). Glycine-extended gastrin induced a dose-dependent increase in [3H]thymidine uptake in LoVo (143 +/- 8% versus control at 10(-10) M) and HT 29 (151 +/- 11% versus control at 10(-10) M) cells that was not inhibited by PD 134308 or by a mitogen-activated protein (MAP) or ERK kinase (MEK) inhibitor (PD 98509). Glycine-extended gastrin did stimulate jun-kinase activity in LoVo and HT 29 cells. The two cell lines expressed the gastrin gene at low levels and secreted small amounts of amidated gastrin and glycine-extended gastrin into the media.
Glycine-extended gastrin receptors are present on human colon cancer cells that mediate glycine-extended gastrin's trophic effects via a MEK-independent mechanism. This suggests that glycine-extended gastrin and its novel receptors may play a role in colon cancer cell growth.
由于人类结肠癌通常含有大量胃泌素加工中间体，我们试图探讨完全加工的酰胺化胃泌素的生物合成前体——甘氨酸延伸胃泌素，是否可能对人类结肠癌细胞产生营养作用。
在五种人类癌细胞系（LoVo、HT 29、HCT 116、Colo 320DM和T 84）上评估放射性标记的甘氨酸延伸胃泌素和酰胺化胃泌素的结合情况。通过[3H]胸腺嘧啶掺入量和细胞数量的增加来评估这些肽的营养作用。通过Northern印迹和放射免疫测定法测定胃泌素的表达。
酰胺化胃泌素不与这五种细胞系中的任何一种结合，也不刺激其生长。相反，在LoVo和HT 29细胞上观察到放射性标记的甘氨酸延伸胃泌素的可饱和结合，这种结合不受酰胺化胃泌素（10^(-6) M）或胃泌素/CCKB受体拮抗剂（PD 134308）的抑制。甘氨酸延伸胃泌素在LoVo（10^(-10) M时为143±8%，相对于对照组）和HT 29（10^(-10) M时为151±11%，相对于对照组）细胞中诱导[3H]胸腺嘧啶摄取呈剂量依赖性增加，这不受PD 134308或丝裂原活化蛋白（MAP）或细胞外信号调节激酶（ERK）激酶（MEK）抑制剂（PD 98509）的抑制。甘氨酸延伸胃泌素确实刺激了LoVo和HT 29细胞中的JNK激酶活性。这两种细胞系低水平表达胃泌素基因，并向培养基中分泌少量的酰胺化胃泌素和甘氨酸延伸胃泌素。
人类结肠癌细胞上存在甘氨酸延伸胃泌素受体，其通过一种不依赖MEK的机制介导甘氨酸延伸胃泌素的营养作用。这表明甘氨酸延伸胃泌素及其新型受体可能在结肠癌细胞生长中起作用。
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