Characterization of the functional and growth properties of long-term cell cultures established from a human somatostatinoma

Somatostatin system: molecular mechanisms regulating anterior pituitary hormones

The somatostatin (SRIF) system, which includes the SRIF ligand and receptors, regulates anterior pituitary gland function, mainly inhibiting hormone secretion and to some extent pituitary tumor cell growth. SRIF-14 via its cognate G-protein-coupled receptors (subtypes 1-5) activates multiple cellular signaling pathways including adenylate cyclase/cAMP, MAPK, ion channel-dependent pathways, and others. In addition, recent data have suggested SRIF-independent constitutive SRIF receptor activity responsible for GH and ACTH inhibition in vitro. This review summarizes current knowledge on ligand-dependent and independent SRIF receptor molecular and functional effects on hormone-secreting cells in the anterior pituitary gland.

Somatostatinoma: clinico-pathological features of three cases and literature reviewed

Somatostatinoma is a rare endocrine tumor that comprises around 1% of all gastroenteropancreatic endocrine neoplasms. This paper gives an updated review on somatostatinoma and describes three sporadic cases of somatostatinoma located in the pancreas, duodenum, and jejunum. Approximately 200 case histories of somatostatinoma have been published, with the duodenum being the most frequent site, followed by the pancreas. Somatostatinomas may be sporadic or associated with neurofibromatosis type 1, Multiple Endocrine Neoplasia type 1, and Von Hippel-Lindau syndromes. Functional somatostatinomas release excessive amounts of somatostatin suppressing gallbladder motility and inhibiting the secretory activity of various endocrine and exocrine cell types. A triad of mild diabetes mellitus, cholelithiasis, and diarrhea/steatorrhoea characterizes the somatostatinoma or 'inhibitory' syndrome. Non-functional somatostatinomas tend either to be asymptomatic or to present with obstructive symptoms. These tumors are often malignant and by the time they are detected, nearly two-thirds have already metastasized to the regional lymph nodes or the liver. A comparison between our three cases and those in the literature provides useful insights into the clinical management of these patients. Interestingly, the jejunal somatostatinoma described here is the second case ever reported.

Characterization of the functional and growth properties of cell lines established from ileal and rectal carcinoid tumors

Carcinoids of the intestine are the most common gastrointestinal carcinoid tumors. Therapeutic options to treat patients with these tumors are limited. There are very few ileal carcinoid cell lines available for in vitro studies to analyze new drugs that could be effective in treating patients with metastatic tumors. A replication defective recombinant adenovirus with an SV40 early T-antigen insert was used to infect two intestinal carcinoid tumors to create carcinoid cell lines. The cell lines were studied by cell culture, reverse transcription polymerase chain reaction, Western blotting, and immunohistochemistry. Both cell lines expressed SV40 large T antigen and receptors for TGFbeta1, TGFbeta2, EGFR, and somatostatin receptors. Treatment with TGFbeta1 led to growth inhibition and increased apoptosis in the cultured cells. Octreotide inhibited cell growth of both cell lines while stimulating apoptosis. Treatment of the HC45 cells with gefitinib also inhibited cell growth in a concentration-dependent manner. TGFbeta treatment stimulated chromogranin A expression while expression of two other granins, chromogranin B and 7B2, did not change significantly. RNA profiling of cells treated with TGFbeta1 showed increased expression of vitamin D3 receptor. This finding was validated by real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. These results indicate that these carcinoid cell lines can be used to study the proliferative and apoptotic mechanisms involved in intestinal carcinoid tumor growth regulation.