Somatostatin and its analog lanreotide inhibit the proliferation of dispersed human non-functioning pituitary adenoma cells in vitro

• DOI: 10.1530/eje.0.1410396
• Publication Date: 2005-01-24T21:34:41Z
• Authors: T Florio; S Thellung; S Arena; A Corsaro; R Spaziante; G Gussoni; G Acuto; M Giusti; G Giordano; G Schettini
• Keywords: Adenoma; Male; 0303 health sciences; Middle Aged; Peptides, Cyclic; Membrane Potentials; 03 medical and health sciences; Tumor Cells, Cultured; Humans; Female; Pituitary Neoplasms; Calcium Channels; Drug Screening Assays, Antitumor; Somatostatin; Cell Division

OBJECTIVE: Somatostatin is a powerful inhibitor of hormone secretion and cell proliferation. Treatment with somatostatin analogs in humans causes a reduction in size and secretory activity of some endocrine tumors, including somatotropic pituitary adenomas. Less studied are the effects of somatostatin agonists on non-functioning pituitary adenomas (NFPAs). In this study we characterized the effects of somatostatin and its analog lanreotide on the proliferation of NFPAs in vitro and the intracellular mechanisms involved. DESIGN: Twenty-three NFPA post-surgical specimens were analyzed for somatostatin receptor (SSTR) expression and 12 of them were cultured in vitro to study somatostatin's effects on cell proliferation, assessed by means of [(3)H]thymidine uptake, and the intracellular signaling. RESULTS: One or more SSTR subtypes were expressed in 90% of the adenomas tested. Somatostatin and lanreotide treatment inhibited phorbol myristate acetate (PMA)-induced cell proliferation. Vanadate pretreatment reversed somatostatin and lanreotide inhibition of PMA-induced DNA synthesis suggesting an involvement of tyrosine phosphatase in this effect. In the only adenoma tested, somatostatin directly induced a tyrosine phosphatase activity. Somatostatin and lanreotide caused also a significant inhibition of voltage-sensitive calcium channel activity induced by 40mmol/l K(+) depolarization in microfluorimetric analysis. CONCLUSIONS: These data show that somatostatin and lanreotide inhibit human NFPA cell proliferation in vitro, and suggest that activation of tyrosine phosphatases and inhibition of the activity of voltage-dependent calcium channels may represent intracellular signals mediating this effect.