gastrins and Gastrointestinal-Stromal-Tumors

The cholecystokinin-2 receptor (CCK2R), is expressed in cancers where it contributes to tumor progression. The CCK2R is over-expressed in a sub-set of tumors, allowing its use in tumor targeting with a radiolabel ligand. Since discrepancies between mRNA levels and CCK2R binding sites were noticed, we searched for abnormally spliced variants in tumors from various origins having been previously reported to frequently express cholecystokinin receptors, such as medullary thyroid carcinomas, gastrointestinal stromal tumors, leiomyomas and leiomyosarcomas, and gastroenteropancreatic tumors. A variant of the CCK2R coding for a putative five-transmembrane domains receptor has been cloned. This variant represented as much as 6% of CCK2R levels. Ectopic expression in COS-7 cells revealed that this variant lacks biological activity due to its sequestration in endoplasmic reticulum. When co-expressed with the CCK2R, this variant diminished membrane density of the CCK2R and CCK2R-mediated activity (phospholipase-C and ERK activation). In conclusion, a novel splice variant acting as a dominant negative on membrane density of the CCK2R may be of importance for the pathophysiology of certain tumors and for their in vivo CCK2R-targeting.

Topics: Alternative Splicing; Amino Acid Sequence; Animals; Binding Sites; Carcinoma, Medullary; Chlorocebus aethiops; Cholecystokinin; COS Cells; Extracellular Signal-Regulated MAP Kinases; Gastrins; Gastrointestinal Neoplasms; Gastrointestinal Stromal Tumors; Humans; Insulinoma; Leiomyoma; Leiomyosarcoma; Molecular Sequence Data; Pancreatic Neoplasms; Protein Structure, Tertiary; Receptor, Cholecystokinin B; RNA, Messenger; Signal Transduction; Thyroid Neoplasms; Type C Phospholipases

The cholecystokinin 2 receptor (CCK2R/CCKBR) is expressed in gastrointestinal stromal tumours (GISTs). We sought to investigate the role of CCK2R in GIST pathogenesis. Molecular characterization of CCK2R was performed on a heterogeneous cohort of 50 GISTs. In addition, CCK2R expression was evaluated by immunohistochemistry (IHC), using tissue microarray (TMA) containing 292 GISTs, two cases of hyperplasia of interstitial Cajal's cells (ICC) and six gastric microscopic GISTs. Mono-allelic loss of the CCK2R/11p15 allele was identified in 13.7% of GISTs, having no impact on the level of CCK2R transcript expression. No CCK2R mutations were found. The CCK2Ri4sv, CCK2R splice variant with retention of intron 4 was detected in six of 20 tumours analysed. Wild-type CCK2R transcripts were commonly expressed (57.1% of cases) and this expression was highly correlated with gastric primary site of GISTs (p < 0.001). At the protein level, expression of CCK2R in incidental ICC hyperplasia and early stages of gastric GIST development was documented, and its gastric association was confirmed on GIST-TMA by IHC. To explore the in vivo effect of CCK2R activation on tumour growth, gastrin versus placebo was administered intraperitoneally in nude mice carrying human GIST xenografts. The tumour volume was followed for 10 weeks. The effect of this stimulation on tumour cell proliferation/apoptosis was assessed by IHC and KIT/PKC-θ signalling was evaluated by western blotting (WB). In vivo experiments showed a two-fold increase in the volume of tumours which were exposed to gastrin in comparison with non-exposed controls (p = 0.03), with a significant increase in mitotic activity (p = 0.04) and Ki-67 proliferation index (p = 0.008). By WB, gastrin stimulation resulted in hyper-activation of KIT and PKC-θ kinases, and in evident PI3K-AKT pathway over-activation. Our results indicate a promoting role of CCK2R on GIST tumourigenesis, particularly in tumours of gastric origin.

Topics: Adult; Aged; Aged, 80 and over; Cell Proliferation; Female; Gastrins; Gastrointestinal Neoplasms; Gastrointestinal Stromal Tumors; Gene Expression Regulation, Neoplastic; Humans; Male; Middle Aged; Polymerase Chain Reaction; Protein Kinase C; Proto-Oncogene Proteins c-kit; Receptor, Cholecystokinin B; Signal Transduction; Stomach Neoplasms

Gastrointestinal stromal tumor is the most common mesenchymal tumor in the gastrointestinal tract. It may coexist with other type of cancers, and if so, the tumors usually involve the stomach. The most common associated cancers are gastrointestinal carcinomas. We report a 65-year-old woman with a history of gastric gastrointestinal stromal tumor who had undergone subtotal segmental gastrectomy. New polypoid lesions were detected on a follow-up gastroscopy one year later. The lesions were biopsied and found to be carcinoid tumors. There was serum hypergastrinemia, and type 1 gastric carcinoid tumor was diagnosed. A total gastrectomy was performed. Pathologic examination revealed both carcinoid tumors and a recurrent gastrointestinal stromal tumor.

Topics: Aged; Biopsy; Carcinoid Tumor; Female; Gastrectomy; Gastrins; Gastrointestinal Stromal Tumors; Gastroscopy; Humans; Lymph Node Excision; Lymphatic Metastasis; Neoplasm Recurrence, Local; Neoplasms, Second Primary; Reoperation; Stomach Neoplasms; Up-Regulation