Gastric PDX-1 expression in pancreatic metaplasia and endocrine cell hyperplasia in atrophic corpus gastritis.

The homeodomain transcription factor PDX-1 plays a key role in endocrine and exocrine differentiation processes of the pancreas. PDX-1 is also essential for differentiation of endocrine cells in the gastric antrum. The role of PDX-1 in the pathogenesis of endocrine cell hyperplasia and pancreatic metaplasia in corpus and fundus gastritis has not been evaluated. By immunohistochemistry and double-immunofluorescence, we investigated the expression of PDX-1 in 10 tissue specimens with normal human gastric mucosa, nonatrophic and atrophic gastritis and in pancreatic metaplasia, respectively. In normal corpus mucosa and in nonatrophic corpus gastritis, PDX-1 was mainly absent. In pancreatic metaplasia, PDX-1 was found in metaplastic cells and in adjacent gastric glands. In contrast to normal gastric corpus mucosa, PDX-1 could be strongly detected in the cytoplasm of the parietal cells surrounding metaplastic areas. Furthermore, PDX-1 expression was found in hyperplastic endocrine cells and in the surrounding gastric glands in chronic atrophic gastritis. Hyperplastic endocrine cells coexpressed the beta-subunit of the gastric H,K-ATPase. We conclude that PDX-1 represents a candidate switch factor for glandular exocrine and endocrine transdifferentiation in chronic gastritis and that an impaired parietal cell differentiation might play a key role in disturbed gastric morphogenic processes.