Gastrin processing in primary culture of gastrinoma cells

There is a general agreement on the cell specificity of gastrin processing. In order to investigate this processing in Zollinger-Ellison (ZE) patients, we have studied in two primary gastrinoma cultures (one from a pancreatic tumor, the other from a liver metastasis) the proportion of progastrin fragments using immunochemical and immunohistological methods. In tumor extracts as well as in sera, the predominant gastrin form differed between the two patients (i.e. being G17 and G34, respectively). In the two gastrinoma cultures, RIA determinations and electron microscopic observations indicated that the proportion of progastrin increased with time while that of G17 and G34 decreased. On the other hand, as the culture time extended, an increasing proportion of nonimmunostained secretory granules was observed suggesting the presence of other gastrin precursors (e.g. Gly-extended progastrin). From these findings, we suggest that gastrinoma culture cells could be a valuable tool in the biochemical approach to gastrin processing in ZE tumors.