Differential expression of gastrin, cholecystokinin-A and cholecystokinin-B receptor mRNA in human pancreatic cancer cell lines

Background: It has been assumed that gastrin stimulates the growth of pancr eatic cancer in an autocrine way through co-expression of gastrin and the c holecystokinin-B receptor (CCK-BR). However, pancreatic cancer cell lines e stablished directly from patients have revealed a great heterogeneity in ce ll proliferation when exposed to CCK, gastrin and their receptor antagonist s. The aim of this study was therefore to examine co-expression of CCK-A an d CCK-B receptor (CCK-AR and CCK-BR), and gastrin mRNA as well as the secre tion of CCK and gastrin peptides in these cell lines. Methods: Fourteen cel l lines were established from primary pancreatic cancers or their metastase s. Total RNA was isolated from the cell lines and reverse-transcribed into single-stranded cDNA. A PCR technique based on Tag polymerase-antibody inte raction and CCK-AR, CCK-BR and gastrin-specific primers, followed by Southe rn blot analysis, were the methods used. The incubation mediums were analys ed for the presence of secreted CCK/proCCK and gastrin/progastrin peptides by specific radioimmunoassays (RIA). Results: By means of nested Reverse-Tr anscribed Polymerase Chain Reaction (nested RT-PCR), combined with Southern blot analysis of the PCR amplified products, CCK-AR and gastrin mRNA co-ex pression was detected in cell Lines LPC-6p and LPC-10m, whereas CCK-BR and gastrin mRNA could be detected in cell lines LPC-8p and LPC-12m. A low leve l of secreted CCK peptides was detected in cell line LPC-6p. which also exp ressed CCK-AR mRNA. In no other cases were CCK or gastrin peptides detected in the cell culture mediums. Conclusion: The lack of CCK-BR and gastrin mR NA co-expression, and not detectable levels of secreted CCK and gastrin in culture media, does not lend support to the hypothesis that concomitant gen e-expression of CCK receptors and gastrin or CCK are essential to maintaini ng pancreatic cancer cell proliferation.