Over-expression of gastrin-releasing peptide in human esophageal squamous cell carcinomas

Gastrin-releasing peptide (GRP) is known as an autocrine growth factor for a number of gastrointestinal cancers. There is, however, little information on the expression of GRP in the squamous epithelia and squamous cell carcinoma, particularly in the esophagus. With a differential display approach, up-regulated GRP was observed in human esophageal squamous cell carcinoma (ESCC) samples obtained from a high-risk area for esophageal cancer, Linzhou in northern China. Up-regulation of phosphoglycerate mutase and P311 HUM (3.1) and down-regulation of keratin 13, cystatin B, endoglin and annexin I were observed. Using a reverse transcription-polymerase chain reaction (RT-PCR) method, significant over-expression of GRP was observed in 10 out of 12 ESCC samples (83.3%) and all four ESCC cell lines. With in situ hybridization, GRP mRNA expression was detected in nine out of 21 (42.8%) samples with basal cell hyperplasia (BCH), five out of seven (71.4%) samples with dysplasia (DYS) and 17 out of 24 (70.9%) ESCC samples. In contrast, GRP was expressed only in three out of 16 (18.7%) normal epithelium. Digital image analysis revealed that the mean value of GRP expression index, determined by intensity and area ratio of staining, was 0.19 in normal epithelium, 1.23 in BCH, 2.94 in DYS and 2.38 in ESCC, showing a progressive increase. Studies on ESCC cell lines showed GRP increased cell growth in a dose-dependent pattern in GRP receptor-positive ESCC cells, but not in GRP receptor-negative ESCC cells. GRP (1 mM) also increased cyclooxygenase-2 protein expression by 3.4-fold. This is the first demonstration that GRP is over-expressed in ESCC, and its over-expression may play a role in ESCC development and growth.