Gastrin and cholecystokinin-B receptor (CCK-B) were co-expressed in human gastric carcinoma tissues, suggesting that a functional autocrine loop, the gastrin and CCK-B receptor loop, may be presented in gastric cancer cells and play an important role in the pathogenesis and progression of gastric carcinomas. The present study was aimed at studying the effects of blocking the gastrin and CCK-B receptor loop on cell proliferation and apoptosis in gastric cancer cell line SGC-7901 cells (SGC-7901 cells). First, the expression of gastrin and CCK-B receptor mRNAs and gastrin protein in SGC-7901 cells were measured by RT-PCR and immunocytochemistry, respectively. Radioimmunoassay (RIA) was used to detect the concentrations of gastrin in culture medium. The gastrin–CCK-B receptor axis was blocked by using a specific neutralizing antibody against human gastrin and siRNA specifically targeting human CCK-B receptors, respectively. Flow cytometry was used to measure the cell cycle and apoptotic cells, and western blotting was used to measure the expression of CCK-B receptor, caspase-3, and matrix metalloproteinase-2 (MMP-2) in cells. The results showed that SGC-7901 cells not only coexpressed gastrin and CCK-B receptor mRNAs, but also endogenously secreted gastrin protein into the culture medium, thus forming gastrin–CCK-B receptor autocrine loop. Biologically, disrupting gastrin–CCK-B receptor autocrine loop by neutralizing the endogenous gastrin or by knocking down CCK-B receptor expression significantly inhibited the cell proliferation and decreased the percentage of cells residing in the S-phase of the cell cycle, and meanwhile promoted cell apoptosis and increased caspase-3 expression as well as decreased MMP-2 expression. An autocrine loop between endogenously secreted gastrin and CCK-B receptors may play a key role in the regulation of cell proliferation and apoptosis in SGC-7901 cells.

To explore whether cholecystokinin-B/gastrin receptor (CCKBRwt) gene and its alternative splicing variant preserving intron 4 (CCKBRi4sv) are expressed in human gastric carcinoma cell line and tissue, we detect mRNA expression of CCKBRwt and CCKBRi4sv in 30 gastric carcinoma and their corresponding normal tissues, 10 gastritis, and 2 autopsied normal stomach specimens as well as in a gastric carcinoma cell line SGC-7901 cells by RT-PCR and sequencing. The results revealed that human normal, inflammatory, and malignant gastric tissues simultaneously expressed the classical and alternative splicing cholecystokinin-B/gastrin receptor genes. The alternative splicing variant contains the intron 4 of cholecystokinin-B/gastrin receptor gene.

AIM: To compare the expression patterns of cholecystokinin-B (CCK-B)/gastrin receptor genes in matched human gastric carcinoma and adjacent non-neoplastic mucosa of patients with gastric cancer, inflammatory gastric mucosa from patients with gastritis, normal stomachs from 2 autopsied patients and a gastric carcinoma cell line (SGC-7901), and to explore their relationship with progression to malignancy of human gastric carcinomas.METHODS: RT-PCR and sequencing were employed to detect the mRNA expression levels of CCK-B receptor and gastrin gene in specimens from 30 patients with gastric carcinoma and healthy bordering non-cancerous mucosa, 10 gastritis patients and normal stomachs from 2 autopsied patients as well as SGC-7901. The results were semi-quantified by normalizing it to the mRNA level of beta-actin gene using Lab Image software. The sequences were analyzed by BLAST program.RESULTS: CCK-B receptor transcripts were detected in all of human gastric tissues in this study, including normal, inflammatory and malignant tissues and SGC-7901. However, the expression levels of CCK-B receptor in normal gastric tissues were higher than those in other groups (P<0.05), and its expressions did not correlate with the differentiation and metastasis of gastric cancer (P>0.05). On the other hand, gastrin mRNA was detected in SGC-7901 and in specimens obtained from gastric cancer patients (22/30) but not in other gastric tissues, and its expression was highly correlated with the metastases of gastric cancer (P<0.05).CONCLUSION: Human gastric carcinomas and gastric cancer cell line SGC-7901 cells coexpress CCK-B receptor and gastrin mRNA. Gastrin/CCK-B receptor autocrine or paracrine pathway may possibly play an important role in the progression of gastric cancer.

This study was conducted to explore whether cholecystokinin-B/gastrin receptor (CCKBRwt) gene and its alternative splicing variant (CCKBRi4sv) are expressed in human gastric carcinomas cell line and tissues, and to find out their relationship with the development and progression of human gastric carcinoma. The mRNA expression levels of CCKBRwt and CCKBRi4sv were detected in 30 human gastric carcinomas and normal tissues adjacent to cancer, 10 gastritis specimens, 2 autopsied normal stomach specimens as well as in a gastric carcinoma cell line SGC-7901 cells. The results revealed that the transcripts of CCKBRwt and CCKBRi4sv were observed in all of the human gastric specimens tested, but only CCKBRwt was expressed in gastric cancer cell line SGC-7901 cells. The expression levels of the two receptors were not correlated with the differentiation and metastases of gastric cancers. From the results, we infer that human gastric tissues simultaneously express CCKBRwt and CCKBRi4sv, and CCKBRi4sv may have unknown physiological functions in gastric epithelial cells.