benzotript and Colonic-Neoplasms

Polyamines are essential factors of cell growth and differentiation. Modulation of the cellular polyamine content by 2-difluoromethylornithine (DFMO) inhibiting ornithine decarboxylase (ODC), or by hormones inducing ODC, influences cell growth. Gastrin acts trophically on some colonic carcinomas and their growth is inhibited by gastrin receptor blockers. The mechanism of the trophic action of gastrin on colonic carcinomas is not known. In this study the effect of gastrin, gastrin receptor blockers, epidermal growth factor (EGF) and DFMO on growth and ODC activity of four human colon carcinoma cell lines (SW 403, SW 1116, LS 174 T and Lovo) was investigated. Growth and ODC activity of all cell lines were inhibited by DFMO. Growth of the SW 403 cell line was increased by gastrin and inhibited by the gastrin receptor blocker benzotrypte. The other cell lines did not respond to gastrin and the gastrin receptor blocker. In SW 403 cells ODC activity was increased by gastrin, and was also elevated after treatment with the gastrin receptor blocker. These in vitro results were confirmed by studies on tumours that developed from SW 403 cells in nude mice. Combination of benzotrypte and DFMO did not enhance the antiproliferative effect. EGF increased growth of SW 403 cells, but no induction of ODC activity was measured. LS 174 T cells were not stimulated by EGF. Medium replacement was the strongest stimulus of ODC activity in SW 403 cells already inducing ODC after 3 h. During cell culture ODC activity was high after seeding and decreased continuously with increasing cell density. These data suggest that gastrin induces ODC in gastrin-sensitive colonic carcinoma cells. DFMO appears to be a valuable antiproliferative agent in colonic carcinoma cells.

Topics: Animals; Anti-Ulcer Agents; Benzamides; Cell Division; Colonic Neoplasms; Eflornithine; Epidermal Growth Factor; Gastrins; Humans; Mice; Mice, Nude; Neoplasm Transplantation; Ornithine Decarboxylase; Ornithine Decarboxylase Inhibitors; Pentagastrin; Receptors, Cholecystokinin; Tumor Cells, Cultured

We have previously demonstrated trophic effects of gastrin on mouse colon cancer (MC-26) cells, in vivo, and demonstrated the presence of gastrin receptors (GR) on these cells. The cellular and intracellular mechanism by which gastrin expresses trophic effects on colon cancer cells is, however, as yet unknown. For us to start investigating the possible mechanisms involved, it was important that we first develop an in vitro model, in which gastrin expresses its trophic effects directly on the MC-26 cells. The growth-promoting effects of gastrin on the MC-26 cells were examined in various in vitro culture models, in terms of [3H]thymidine incorporation and cell number. A significant trophic effect of gastrin could be demonstrated on quiescent cells in culture, in the absence of serum. The optimal cell-culture conditions for observing trophic effects of gastrin were defined and included a 24-h period of rapid growth of MC-26 cells in serum-supplemented normal growth medium, followed by a 24-h period of culture in serum-free medium containing an optimal dose (1.0 mM) of thymidine, to achieve growth-arrest of the cells. Addition of gastrin (0.5 to 25 nM) to the quiescent, growth-arrested cells resulted in significant dose-dependent increases in both the incorporation of [3H]thymidine uptake by the cells, and a significant increase in cell number. The concentration of GR on the growth-arrested quiescent MC-26 cells in culture was significantly increased compared to the GR concentration on the control, asynchronized cells. The increased presence of GR on the growth-arrested, synchronized MC-26 cells may have allowed us to observe a significant trophic effect of gastrin on the MC-26 cells, in vitro itself. To determine if gastrin was functioning as an autocrine growth factor for MC-26 cells, we examined the effect of gastrin antibodies on the growth of MC-26 cells; no significant effect of the antigastrin IgG on the growth of MC-26 cells was observed.

Topics: Animals; Antibodies; Benzamides; Cell Cycle; Cell Division; Colonic Neoplasms; Gastrins; Growth Substances; Mice; Proglumide; Receptors, Cholecystokinin; Thymidine; Tritium; Tumor Cells, Cultured

The gastrointestinal hormone gastrin has been shown to stimulate the growth of normal colonic mucosa. To examine for a possible role of gastrin in the proliferation of cultured colon tumor cells, we have studied the effects of two gastrin receptor antagonists, proglumide and benzotript, and of antibodies to gastrin. We find that proglumide (50% effective concentration, 2 to 5 mM) and benzotript (50% effective concentration, 0.4 to 0.8 mM) inhibit the monolayer growth of six human colon cancer cell lines. Addition of exogenous gastrin abrogated the growth-inhibitory effect of proglumide. The anchorage-independent growth of colon carcinoma cells was also inhibited by the two gastrin antagonists. Also, a dose-dependent increase in carcinoembryonic antigen secretion was observed upon treatment with proglumide and benzotript in three cell lines examined. Half-maximal inhibition of labeled gastrin binding was observed at concentrations of 0.4 mM benzotript and 8.6 mM proglumide. In addition, antigastrin antiserum added to HCT 116 cells adapted to growth in serum-free medium resulted in a concentration-dependent inhibition of cellular proliferation. These data suggest that gastrin may function as an autocrine growth factor in colon carcinoma.

Topics: Antibodies; Benzamides; Carcinoembryonic Antigen; Cell Division; Cell Line; Colonic Neoplasms; Gastrins; Humans; Proglumide; Receptors, Cholecystokinin