Hoeflich A, Yang Y, Rascher W, Blum W F, Huber S, Koepf G, Kolb H J, Kiess W
Children's Hospital, Justus Liebig University, Giessen, Germany.
Eur J Endocrinol. 1996 Jul;135(1):49-59. doi: 10.1530/eje.0.1350049.
Insulin-like growth factor II (IGF-II) has been implicated in the differentiation of skeletal muscle cells. In this study the putative role of IGF-II in epithelial cell differentiation was investigated. The expression of IGF-II, IGF-I receptor and IGF-II/mannose-6-phosphate receptor (IGF-II/M6P receptor) mRNA during spontaneous differentiation of the colon carcinoma cell line Caco-2 was measured. In addition, differentiation of Caco-2 cells during the cell culture period (days 1-21 in culture) was studied in parallel using morphological (light and scanning electron microscopy) and biochemical markers of growth (DNA, RNA and protein content, and beta-actin mRNA and glyceraldehyde phosphate dehydrogenase mRNA expression) and differentiation (alkaline phosphatase activity, carcinoembryonic antigen content). A putative correlation between the markers of growth and differentiation and IGF gene expression was studied using linear regression analysis. Expression of IGF-II mRNA and IGF-II/M6P receptor mRNA correlated significantly with the progress of differentiation, while the IGF-I receptor was stably expressed throughout the culture period and exhibited a crucial role for the survival of Caco-2 cells, as shown by blocking experiments employing the monoclonal anti-IGF-I receptor antibody alpha-IR3. We hypothesize that: IGF-II mRNA and IGF-II/M6P receptor mRNA are expressed in a coordinate fashion during the differentiation of Caco-2 cells; coordinate expression of IGF-II and of IGF-II/M6P receptor mRNA might point to a role for IGF-II as a growth stimulant and for the IGF-II/M6P receptor for a regulator of IGF-II bioavailability in differentiating cells; alternatively, high IGF-II/M6P receptor mRNA and protein expression in differentiated cells but low IGF-II binding to the IGF-II/M6P receptor point to an important intracellular role of this receptor type in differentiated colon epithelial cells; the IGF-I receptor mRNA is stably expressed during the differentiation process of Caco-2 cells; the IGF-I receptor protein seems to be a prerequisite for the survival of Caco-2 cells.
胰岛素样生长因子II（IGF-II）与骨骼肌细胞的分化有关。在本研究中，对IGF-II在上皮细胞分化中的假定作用进行了研究。测定了结肠癌细胞系Caco-2自发分化过程中IGF-II、IGF-I受体和IGF-II/甘露糖-6-磷酸受体（IGF-II/M6P受体）mRNA的表达。此外，在细胞培养期间（培养第1 - 21天），使用形态学（光学和扫描电子显微镜）以及生长（DNA、RNA和蛋白质含量，β-肌动蛋白mRNA和甘油醛-3-磷酸脱氢酶mRNA表达）和分化（碱性磷酸酶活性、癌胚抗原含量）的生化标志物，并行研究Caco-2细胞的分化。使用线性回归分析研究了生长和分化标志物与IGF基因表达之间的假定相关性。IGF-II mRNA和IGF-II/M6P受体mRNA的表达与分化进程显著相关，而IGF-I受体在整个培养期间稳定表达，并且如使用单克隆抗IGF-I受体抗体α-IR3的阻断实验所示，对Caco-2细胞的存活起着关键作用。我们假设：在Caco-2细胞分化过程中，IGF-II mRNA和IGF-II/M6P受体mRNA以协同方式表达；IGF-II和IGF-II/M6P受体mRNA的协同表达可能表明IGF-II作为生长刺激剂的作用以及IGF-II/M6P受体在分化细胞中对IGF-II生物利用度的调节作用；或者，分化细胞中高IGF-II/M6P受体mRNA和蛋白质表达但低IGF-II与IGF-II/M6P受体的结合表明这种受体类型在分化的结肠上皮细胞中具有重要的细胞内作用；IGF-I受体mRNA在Caco-2细胞分化过程中稳定表达；IGF-I受体蛋白似乎是Caco-2细胞存活的先决条件。
