Human Caco-2 cells transfected with c-Ha-Ras as a model for endocrine differentiation in the large intestine.

Endocrine cells occur in approximately 30% of all colorectal adenocarcinomas, and this feature appears to correlate with a relatively poor prognosis. To study the factors regulating endocrine differentiation in colorectal cancer, which may bear resemblance to the regulation of endocrine differentiation in normal intestinal mucosa, models in which differentiation can be manipulated are essential. However, endocrine features in colorectal cancer cell lines are scarce and are almost exclusively observed in xenografts, presumably as a result of differentiation induction by stromal components. We attempted to demonstrate endocrine differentiation in the colonic adenocarcinoma cell line Caco-2, which is frequently used as a model for enterocytic differentiation. In vitro endocrine tumor cells were not encountered. In vivo studies were cumbersome, because of the low take rate of Caco-2 cells. We did manage to establish nude mouse xenografts of Caco-2 cells by inoculating cells in collagen gel and by suppressing natural killer cell activity. In an attempt to induce a better take rate and to investigate the effect of Ras oncoprotein overexpression on endocrine differentiation, Caco-2 cells were transfected with a point-mutated c-Ha-Ras gene. The cell line Caco-2 EJ6, generated from these experiments, could be xenografted in nude mice with a high take rate, yielding a moderately well differentiated adenocarcinoma, morphologically identical to the tumors derived from untransfected Caco-2 cells. The xenografts displayed goblet cell, enterocytic, Paneth cell and endocrine differentiation. In vitro endocrine differentiation was observed neither under standard conditions nor with extracellular matrix components as differentiation inducers. We conclude that the Caco-2 cell line and its c-Ha-Ras transfected subline Caco-2 EJ6 in vivo display endocrine differentiation. Ras overexpression does not enhance endocrine differentiation. Due to its favorable growth properties in vivo, Caco-2 EJ6 is a suitable model for studies on endocrine differentiation in colorectal cancer.

Extracellular matrix components induce endocrine differentiation in vitro in NCI-H716 cells.

Endocrine cells occur in +/- 30% of colorectal adenocarcinomas. The significance of this phenomenon in terms of tumor behavior is still controversial. Endocrine differentiation in colorectal cancer cell lines is almost confined to tumor xenografts in vivo, suggesting that endocrine differentiation might be regulated by epithelial-stromal interactions. This hypothesis was studied in the cecal adenocarcinoma-derived cell line NCI-H716 by comparing the expression of chromogranin A protein and messenger RNA in vivo and in vitro and by attempts to induce differentiation in vitro. We found that chromogranin A expression, which was strongest in vivo, could be significantly enhanced in vitro by culturing tumor cells in the presence of native extracellular matrix, on fibroblast feeder layers, and in a defined medium with basic fibroblast growth factor. The results suggest that the extracellular matrix induces endocrine differentiation through factors (e.g., basic fibroblast-growth factor) that may be produced by stromal cells and after secretion bind to the extracellular matrix.

NCI-H716 cells as a model for endocrine differentiation in colorectal cancer.

In colonic neoplasms, endocrine differentiation is encountered not only in carcinoid tumors but also in adenocarcinomas, where endocrine cells may represent a distinct line of differentiation in the tumor. The significance of endocrine differentiation in colorectal cancer is not well established, partly because of the paucity of tumor cell lines which can serve as a model for studying endocrine differentiation. In this report we describe the properties of NCI-H716 cells, a cell line derived from a poorly differentiated adenocarcinoma of the caecum, under various in vitro conditions and as xenografts in athymic mice. Phenotypical properties were immunohistochemically assessed using a panel of differentiation related antibodies, and also by Northern blot analysis and by electron microscopy. Receptors for biogenic amines and peptide hormones were analyzed by ligand binding assay. These studies show that: 1. NCI-H716 cells can be undifferentiated, or show endocrine, mucin-producing or "amphicrine" properties. 2. Endocrine differentiation of NCI-H716 cells preferentially occurs in xenografts in athymic mice, which suggests that mesenchymal elements induce endocrine differentiation. 3. NCI-H716 cells express large amounts of high affinity receptors for gastrin, serotonin and somatostatin and these substances can regulate growth. Thus, NCI-H716 cells form a suitable model for the study of endocrine differentiation in intestinal epithelium and of auto- or paracrine growth regulation in intestinal neoplasia.