GP73 is down-regulated in gastric cancer and associated with tumor differentiation

BACKGROUND Golgi protein 73 (GP73) is a type II Golgi transmembrane protein. It is over-expressed in several cancers, including hepatocellular carcinomas, bile duct carcinomas, lung cancer and prostate cancer. However, there are few reports of GP73 in gastric cancer. This study is aimed at investigating the expression of GP73 and its relationship with clinical pathological characters in gastric cancer. METHODS GP73 mRNA level was determined by quantitative real-time RT-PCR in 41 pairs of matched gastric tumorous tissues and adjacent non-tumorous mucosal tissues. Western blotting was also performed to detect the GP73 protein level. GP73 protein expression was analyzed by immunohistochemistry in 52 clinically characterized gastric cancer patients and 10 non-tumorous gastric mucosal tissue controls. RESULTS The mRNA and protein level of GP73 were significantly down-regulated in gastric tumorous tissues compared with the non-tumorous mucosal tissues. In non-tumorous mucosa, strong diffuse cytoplasmic staining can be seen in cells located at the surface of the glandular and foveolar compartment; while in tumorous tissues, the staining was much weaker or even absent, and mainly in a semi-granular dot-like staining pattern. The expression level of GP73 protein was associated with patients' gender and tumor differentiation. CONCLUSIONS GP73 was normally expressed in non-tumorous gastric mucosa and down-regulated in gastric cancer. Its expression in gastric cancer was correlated with tumor differentiation.