Expression of mRNAs of Urocortin in the STKM-1 Gastric Cancer Cell Line

Background: Urocortin is analogous to corticotrophin-releasing factors (CRFs) and a member of the CRF family. We previously demonstrated that urocortin mRNAs were expressed in both human and rat glioma cell lines, and that some of these lines transcribed the receptors. We hypothesize that urocortin might also be expressed in a gastric cancer cell line. The aim of the present study was to clarify the expression of mRNAs of urocortin1 (UCN1), -2 and -3 and of CRF and CRF receptors 1 and 2 in a gastric cancer cell line. Materials and Methods: STKM-1 a poorly-differentiated adenocarcinoma cell line was used. Transcripts in the cells were analyzed using cDNA. The fluctuation of mRNA with cellular stress, such as the one caused by a chemotherapeutic agent, serum supplementation and forskolin was examined. Results: Transcripts of UCN1, -2 and CRFR2 were expressed. No changes in transcription of UCN1 and UCN2 were observed with cellular stress. However, expression of CRFR2 mRNA transcripts significantly increased after an initial 24-h exposure to forskolin. Conclusion: Expression of the mRNAs of UCN1, 2 and CRFR2 was confirmed in the human gastric cancer cell line, STKM-1. Although the quantity of CRFR2 transcripts varied with forskolin, the overall transcription pattern was not influenced by cellular stimuli. Corticotropin releasing factor (CRF) promotes the secretion of adrenocorticotropic hormone (ACTH) in the pituitary gland and plays an important role in the stress response. Urocortin is analogous to CRF and a member of the CRF family (1, 2). Three types of urocortins, UCN1, UCN2 and UCN3, have been identified and these bind to CRF receptors. CRF receptors constitute a family of G protein-coupled receptors, and two major classes, CRF receptor type-1 (CRFR1) and type-2 (CRFR2), have been identified (3-5). CRFR1 binds with a higher affinity to CRF than urocortin (6). UCN1 has equal affinity for CRFR1 and CRFR2, while UCN2 and UCN3 specifically bind to CRFR2 (7). In the central nervous system, urocortin mRNA expression is widespread (8). In particular, UCN1 is highly expressed in the Edinger-Westphal nucleus (2) and UCN3 is widely distributed in the hypothalamus and pituitary gland (9). UCN2 has been detected in the endometrium, myocardium, adrenal gland and peripheral blood cells. Urocortin responds via CRFR2 to stresses, such as anxiolysis, anorexia, vasodilation and myocardial contraction (10). In the gastrointestinal system, urocortin was found to be expressed in normal and inflammatory human gastric mucosa (11, 12). In carcinomas, urocortin was detected in adrenal cortical tumor, renal cell carcinoma, endometrial carcinoma, and prostatic carcinoma (13). In a previous study, we demonstrated that urocortin mRNAs were expressed in glioma cell lines, and some of these lines transcribed the receptors (14). While normal and inflammatory human gastric mucosa and some malignant tumors express urocortin, whether or not mRNAs for urocortin and the receptors are expressed in a gastric cancer cell line is not known. We hypothesized that urocortin and the receptors might be expressed in a gastric cancer cell line. Accordingly, we examined the expression of urocortin mRNA in a gastric cancer cell line and studied the fluctuation of mRNA under cellular stresses, such as a chemotherapeutic agents, serum supplementation and forskolin. Materials and Methods Cells. STKM-1 is a human gastric cancer cell line established from malignant cells in the pleural effusion from a 41-year-old female patient. Histologically, the primary gastric cancer was revealed to be a poorly-differentiated adenocarcinoma. The cells cultured in vitro secrete carbohydrate antigen 19-9 (CA19-9) into the medium as a 5289 Correspondence to: Yoshinobu Manome, Department of Molecular Cell Biology, Jikei University School of Medicine, 3-25-8 Nishishimbashi, Minato-ku, Tokyo, 105-8461, Japan. E-mail: manome@jikei.ac.jp