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AIM: To study histidine decarboxylase(HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite. METHODS: Control tissues from fundus(n = 3) and corpus(n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and/or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumours(GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2(VMAT-2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid(U-Me Im AA) was determined using highperformance liquid chromatography in 27 of the 64 patients.RESULTS: In the gastric mucosa of the control tissues, co-localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HDC. A third cellpopulation co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumours. The relative incidence of the three aforementioned markers varied in the tumours that were examined using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumours. In four patients, increased U-Me Im AA excretion was detected, but only two of the patients exhibited related endocrine symptoms. CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Coexpression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.
AIM: To study histidine decarboxylase (HDC) expression in normal and neoplastic gastric neuroendocrine cells in relationship to the main histamine metabolite. METHODS: Control tissues from fundus (n = 3) and corpus (n = 3) mucosa of six patients undergoing operations for gastric adenocarcinoma, biopsy and / or gastric surgical specimens from 64 patients with primary gastric neuroendocrine tumors (GNETs), as well as metastases from 22 of these patients, were investigated using conventional immunohistochemistry and double immunofluorescence with commercial antibodies vs vesicular monoamine transporter 2 (VMAT -2), HDC and ghrelin. The urinary excretion of the main histamine metabolite methylimidazoleacetic acid (U-Me Im AA) was determined using high performance liquid chromatography in 27 of the 64 patients .RESULTS: In the gastric mucosa of the control tissues, co -localization studies identified neuroendocrine cells that showed immunoreactivity only to VMAT-2 and others with reactivity only to HD The A third cellpopulation co-expressed both antigens. There was no co-expression of HDC and ghrelin. Similar results were obtained in the foci of neuroendocrine cell hyperplasia associated with chronic atrophic gastritis type A and also in the tumors. The relative incidence of the three types markers varied in the tumors that were selected using conventional immunohistochemistry. All of these GNETs revealed both VMAT-2 and HDC immunoreactivity, and their metastases showed an immunohistochemical pattern and frequency similar to that of their primary tumors. CONCLUSION: Human enterochromaffin-like cells appear to partially co-express VMAT-2 and HDC. Coexpression of VMAT-2 and HDC might be required for increased histamine production in patients with GNETs.