FBXO32, a new TGF-β/Smad signaling pathway target gene, is epigenetically inactivated in gastric cardia adenocarcinoma.

FBXO32 has recently been identified as a TGF-β/Smad signaling pathway target gene, involved in regulating cell survival and may be transcriptionally silenced by epigenetic mechanisms in some kind of carcinomas. The present study was to investigate the role and promoter methylation status of FBXO32 in gastric cardia adenocarcinoma (GCA), and determine the prognostic significance of FBXO32 in GCA. Bisulfite Conversion-Specific and Methylation-Specific PCR, real-time RT-PCR and immunohistochemical staining methods were used to detect the methylation status and expression of FBXO32 in GCA samples. The frequency of FBXO32 methylation in GCA tumor tissues (44.6%) was significantly higher than that in corresponding normal tissues (3.6%) and was associated with TNM stage, pathological differentiation, distant metastasis or recurrence and upper gastrointestinal cancers (UGIC) family history. Decreased mRNA and protein expression of FBXO32 was observed in GCA tumor tissues and was associated with FBXO32 promoter methylation status. A positive correlation between FBXO32 and p-Smad2/3, Smad4 protein expression was also found in clinical specimens. GCA patients in stage III and IV, with positive UGIC family history, and hypermethylation and down-expression of FBXO32 were most likely to develop metastatic disease and also showed the worse survival. In all, aberrant hypermethylation of FBXO32 may be one of the mechanisms that lead to loss or down expression of the gene in GCA, FBXO32 may be a functional tumor suppressor and reactivation of FBXO32 gene may has therapeutic potential and may be used as a prognostic marker for GCA patients.