Expression of G protein-coupled estrogen receptor in gastric cancer tissues

Objectives: Estrogen possesses important functions in gastric carcinogenesis. However, the expression of G protein-coupled estrogen receptor (GPR30) in gastric cancer (GC) has never been investigated. This study aimed to compare the expression of GPR30 and estrogen nuclear receptors in GC tissues, matched tumor-adjacent tissues and normal gastric mucosa. Methods: Gastric mucosal biopsies were obtained by endoscopy from patients with GC and functional dyspepsia. Expression of GPR30, estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta) was measured by immunohistochemistry (IHC) and real-time polymerase chain reaction. Results: GPR30 was detected in GC and noncancerous tissues. IHC showed a significantly higher GPR30 expression in GC tissues (29 of 38, 76.3%) compared with matched adjacent tissues (11 of 38, 28.9%) and normal gastric tissues (5 of 21, 23.8%). Overexpression of GPR30 was observed in intestinal type GC rather than in diffuse type (88.5% versus 54.5%, P = 0.047). The mRNA level of GPR30 was also higher in GC tissue than in adjacent (P = 0.001) and normal tissues (P = 0.047). No significant differences in the expression of ER alpha and ER beta were found among the three groups. Conclusions: This study is the first to examine the expression of GPR30 in normal gastric mucosa and cancer tissue and demonstrate that GPR30 expression was increased in patients with intestinal type GC. Our findings may provide information on the significance of gender difference in GC patients.