Significance of Skp2 expression in human gastric carcinoma and the relationship between Skp2, p27 and PTEN expression

Objective: S-phase kinase-associated protein 2 (Skp2) is a positive regulator of G1-S transition and promotes ubiquitin-mediated proteolysis of the cyclin-dependent kinase inhibitor p27. Its overexpression has been implicated in cell transformation and oncogenesis. In this study, we investigated significance of Skp2 expression in human gastric carcinoma and the relationship between Skp2, p27 and PTEN expression. Methods: Immunohistochemical analysis was performed on 138 surgical resected primary gastric carcinoma specimens, 102 paired metastasis carcinoma tissue specimens in lymph node from the same set of 138 surgical resected primary gastric carcinoma specimens, 30 dysplasia specimens, 30 intestinal metaplasia specimens, and 20 normal gastric mucosa specimens for Skp2 and performed on the same set of 138 surgical resected primary gastric carcinoma specimens for p27 and PTEN. Results: Skp2 labeling frequency % was increased dramatically in intestinal metaplasia, dysplasia, and primary gastric carcinoma compared with normal gastric mucosa (P=0.000, all the same). Skp2 labeling frequency % in metastasis gastric carcinoma in lymph node was significantly higher than primary gastric carcinoma (P=0.037). Skp2 labeling frequency % was positively associated with differentiated degree (rho=0.315, P=0.000), vessel invasion (rho=0.303, P=0.000) and lymph node metastasis (rho=0.254, P=0.000) respectively. An inverse correlation of Skp2 was observed with both its biochemical target p27 expression in gastric carcinoma (rho=-0.451, P=0.000) and with its putative negative regulator, the PTEN tumor suppressor protein (rho=-0.480, P=0.000). p27 expression had positive relationship with PTEN expression in gastric carcinoma (rho=0.642, P=0.000). Conclusion: Skp2 overexpression is correlated with carcinogenesis and progression of gastric carcinoma: elevated Skp2 expression is correlated with decreased p27 and PTEN in gastric carcinoma, and p27 expression is parallel with PTEN expression. These suggest that PTEN may regulate expression of p27 through the Skp2 pathway, and the effects of Skp2, p27 and PTEN together play an important role in carcinogenesis and progression of gastric carcinoma.