Correlation of hypermethylation of TSP1 gene with TGF-beta?1 level and T cell immunity in gastric cardia adenocarcinoma

Abstract

Thrombospondin-1(TSP1) is an inhibitor of angiogenesis and its promoter hypermethylation has been found resulting in gene silencing in some primary human carcinomas. This study was to investigate the promoter methylation of TSP1 and its correlation with TGF-beta1 level and T cell immunity in gastric cardia adenocarcinoma (GCA). Methylation specific polymerase chain reaction (MSP) approach and immunohistochemistry method were used to examine the methylation status of the 5' CpG island and expression of TSP1 protein, respectively. The level of TGF-beta1 was measured by ELISA and T cell immunity of GCA by flow cytometry analysis. TSP1 methylation frequency was significantly higher in tumor specimens than in corresponding normal tissues (35.4% vs. 3.1%, P<0.001) and significantly higher in Stages III and IV tumor tissues than in Stages I and II tumor tissues (P<0.05). TSP1 protein expression was significantly lower in the tumor tissues than in corresponding normal tissues (P<0.05) and statistically correlated with its methylation status (P<0.01). The total level of TGF-beta1 was significantly higher in the GCA patients than in healthy controls(P<0.05) and significantly higher in Stages III and IV GCA patients than in Stages I and II GCA patients (P<0.05). The level of active TGF-beta1 was significantly higher in the GCA patients with hypermethylation of TSP1 than in the GCA patients without methylation of TSP1(P<0.05), but there was no statistical difference(P>0.05). The function of T cell immunity was significantly different between the GCA patients with hypermethylation of TSP1 and those without methylation of TSP1 (P<0.05). Promoter hypermethylation of TSP1 may play an important role in the development of GCA and reflect the biological behaviours of GCA.