Park J H, Corkins M R, Vanderhoof J A, Caruso N M, Hrbek M J, Schaffer B S, Slentz D H, McCusker R H, MacDonald R G
Department of Pediatrics, Creighton University, Omaha, Nebraska, USA.
J Cell Physiol. 1996 Feb;166(2):396-406. doi: 10.1002/(SICI)1097-4652(199602)166:2<396::AID-JCP18>3.0.CO;2-9.
The components of the insulin-like growth factor (IGF) axis and their roles in regulating proliferation and differentiation of the human colon adenocarcinoma cell line, Caco-2, have been investigated. Caco-2 cells proliferated in serum-free medium at 75% the rate observed in medium containing 10% fetal bovine serum. IGF-I (10 nM) increased Caco-2 cell growth in serum-free medium, but not to the rate seen with serum. Multiple IGF-II mRNA species were produced by Caco-2 cells, but IGF-I mRNA was undetectable. Secretion of radioimmunoassayable IGF-II corresponded with steady-state levels of IGF-II mRNA, neither of which was observed to change markedly over the course of 16 days of Caco-2 cell differentiation. Levels of sucrase-isomaltase mRNA, a marker for enterocytic differentiation, increased 12-fold between days 5 and 16 of culture. Northern blotting of total RNA and ligand blot and immunoblot analyses of serum-free conditioned medium revealed that Caco-2 cells produce several IGF binding proteins (IGFBPs), including IGFBP-2, -3, and -4, as well as a 31,000 M(r) species that was not identified. The pattern of IGFBP secretion changed dramatically during Caco-2 cell differentiation: IGFBP-3 and IGFBP-2 increased 8.5-fold and 5-fold, respectively, whereas IGFBP-4 and the 31,000 M(r) species decreased 43% and 90%. Caco-2 cell clones stably transfected with a human IGFBP-4 cDNA construct exhibited a 60% increase in steady-state level of IGFBP-4 mRNA, and secreted twice as much IGFBP-4 protein as controls. Moreover, IGFBP-4-overexpressing cells proliferated at only 25% the rate of control cells in serum-free medium, in conjunction with a 70% increase in expression of sucrase-isomaltase. In summary, these studies indicate that a complex IGF axis is involved in autocrine regulation of Caco-2 cell proliferation and differentiation.
胰岛素样生长因子（IGF）轴的组成成分及其在调控人结肠腺癌细胞系Caco-2增殖和分化中的作用已得到研究。Caco-2细胞在无血清培养基中的增殖速率为含10%胎牛血清培养基中所观察到速率的75%。IGF-I（10 nM）可增加Caco-2细胞在无血清培养基中的生长，但未达到血清存在时的速率。Caco-2细胞产生多种IGF-II mRNA种类，但未检测到IGF-I mRNA。放射免疫分析法可检测到的IGF-II分泌量与IGF-II mRNA的稳态水平相对应，在Caco-2细胞分化的16天过程中，二者均未观察到明显变化。蔗糖酶-异麦芽糖酶mRNA水平作为肠细胞分化的标志物，在培养的第5天至第16天之间增加了12倍。总RNA的Northern印迹分析以及无血清条件培养基的配体印迹和免疫印迹分析表明，Caco-2细胞产生几种IGF结合蛋白（IGFBPs），包括IGFBP-2、-3和-4，以及一种未鉴定的31,000 M(r)种类。在Caco-2细胞分化过程中，IGFBP的分泌模式发生了显著变化：IGFBP-3和IGFBP-2分别增加了8.5倍和5倍，而IGFBP-4和31,000 M(r)种类分别减少了43%和90%。稳定转染人IGFBP-4 cDNA构建体的Caco-
