gastrins and Leiomyosarcoma

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

Gastrin and cholecystokinin (CCK) are two major regulatory peptides synthesized by human gut and brain tissues as well as by selected tumors, in particular gastrin-producing neuroendocrine tumors. In the present study we have evaluated gastrin and CCK gene expression in a group of primary human tumors, including neuronal, renal, and myogenic stem cell tumors, using in situ hybridization techniques. In addition, CCK-A and CCK-B receptors were evaluated in the same group of tumors with receptor autoradiography. Most tumors had gastrin messenger ribonucleic acid (mRNA): 10 of 11 medulloblastomas, 5 of 5 central primitive neuroectodermal tumors, 11 of 11 Ewing sarcomas, 8 of 10 neuroblastomas, 4 of 4 Wilms' tumors, 5 of 5 rhabdomyosarcomas, and 10 of 10 leiomyosarcomas. CCK mRNA was restricted predominantly to Ewing sarcomas (9 of 11) and leiomyosarcomas (5 of 10). CCK-A and CCK-B receptors were not frequently found in these tumors, except for leiomyosarcomas. These data suggest that gastrin and CCK may play a previously unrecognized role in this group of human stem cell tumors. If the increased gastrin mRNA indeed translates into increased gastrin production, measurement of gastrinemia may have a diagnostic significance in the early detection of these tumors. As these two hormones have been reported to act as potent growth factors, they may be of pathophysiological relevance for patients with such stem cell tumors.

Topics: Blotting, Northern; Brain Neoplasms; Cholecystokinin; Gastrins; Humans; In Situ Hybridization; Kidney Neoplasms; Leiomyosarcoma; Medulloblastoma; Neuroblastoma; Neuroectodermal Tumors, Primitive; Receptor, Cholecystokinin A; Receptor, Cholecystokinin B; Receptors, Cholecystokinin; Rhabdomyosarcoma; RNA, Messenger

Little is known about the regulation of sarcoma proliferation by hormones and/or growth factors. We therefore characterised the in vitro proliferative influence on eight sarcoma cell lines of the platelet-derived growth factor, the insulin-like growth factor 1, triiodothyronine, the epidermal growth factor, the luteinising-hormone-releasing hormone, progesterone, gastrin and 17 beta-oestradiol. The influence of the different factors on the proliferation of sarcoma cell lines was measured by the colorimetric 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test. Two culture media were studied: (1) a nutritionally poor medium containing 2% of fetal calf serum and (2) a nutritionally rich one containing 5% or 10% FCS both with and without the addition of non-essential amino acids. The results were analysed either by conventional statistical analyses or by a classification method based on a decision-tree approach developed in Machine Learning. This latter method was also compared to other classifiers (such as logistic regression and k nearest neighbours) with respect to its accuracy of classification. Monovariate statistical analysis showed that each of the eight cell lines exhibited sensitivity to at least one factor, and each factor significantly modified the proliferation of five or six of the eight cell lines under study. Of these eight lines one of fibrosarcoma origin was the most "factor-sensitive". Decision-tree-related data analysis enabled the specific pattern of factor sensitivity to be characterised for the three histological types of cell line under study. The effects of hormone and growth factors are significantly influenced by the type of culture medium used. The method used appeared to be an accurate classifier for the kind of data analysed. Sarcoma proliferation can be modulated, at least in vitro, by various hormones and growth factors, and the proliferation of each histopathological type exhibited a distinct sensitivity to different hormone and/or growth-factors.

Topics: Cell Division; Colorimetry; Culture Media; Epidermal Growth Factor; Estradiol; Fibrosarcoma; Gastrins; Gonadotropin-Releasing Hormone; Growth Substances; Hormones; Humans; Insulin-Like Growth Factor I; Leiomyosarcoma; Platelet-Derived Growth Factor; Progesterone; Reproducibility of Results; Rhabdomyosarcoma; Sensitivity and Specificity; Tetrazolium Salts; Thiazoles; Triiodothyronine; Tumor Cells, Cultured