Coexpression of gastrin and gastrin receptors (CCK-B and ΔCCK-B) in gastrointestinal tumour cell lines

Abstract

Background - The peptide hormone gastrin is a recognised growth factor for gastrointestinal (GI) tumour cells. Carboxyamidated gastrins bind to the cell surface gastrin/cholecystokinin B (CCK-B) receptor which can be expressed as either a normal or a truncated isoform (ΔCCK-B). Aims - To compare gastrin gene expression with ΔCCK-B and total CCK-B (both isoforms) gene expression in both GI and non-GI tract derived human tumour cell lines. Methods - Total RNA was extracted and gene expression was assayed by the reverse transcription-polymerase chain reaction followed by Southern blotting and hybridisation with specific oligo probes. Results - Gastrin was expressed by 5/5 gastric and 7/8 colorectal cell lines. Coexpression of gastrin CCK-B isoform was found in 80% of gastric and 75% of colorectal cell lines. Non-GI cell lines, with the exception of a lymphoblastic leukaemia cell line, showed no coexpression. The truncated receptor, ΔCCK-B, was shown in 3/5 gastric and 5/8 colorectal cell lines and was always coexpressed with gastrin. Conclusion - The truncated gastrin receptor, ΔCCK-B, is coexpressed with gastrin in 8/13 GI tumour cell lines. Gastrin and CCK-B receptor isoforms may be involved in maintaining autocrine/paracrine growth pathways in GI cancer cells.