Loss of WW domain-containing oxidoreductase expression in the progression and development of gastric carcinoma: clinical and histopathologic correlations

The purpose of this study is to investigate the role of the WW domain-containing oxidoreductase (WWOX) tumor suppressor that maps to the common fragile site FRA16D (16q23.3-24.1) during the development of gastric carcinoma (GC), we examined the altered expression of WWOX in GC cell lines and tissue samples as well as the effects of restoration of the WWOX gene into WWOX-deficient GC cells. All GC cell lines (HSC-45, HSC-57, HSC-59, MKN-7, and MKN-74) showed reduced WWOX expression at the mRNA and protein levels and hypermethylation at the WWOX regulatory site was detected in HSC-45 and HSC-59 cells. Interestingly, treatment with the deacetylating agent trichostatin A and the demethylating agent 5-aza-2'-deoxycytidine restored endogenous WWOX expression levels in HSC-59 cells. Restoration of the WWOX gene with Ad-WWOX into HSC-59 cells effectively suppressed cell growth and increased the population of cells in subG(1) DNA content. In GC tissue samples, the loss of WWOX expression was detected in 24 (33%) of 73 GC cases in accordance with the hypermethylation at the WWOX regulatory site. Surprisingly, negative immunoreactivity against WWOX showed a significant relationship with several clinicopathologic findings, including histology (P = 0.0001), depth of invasion (P = 0.0004), lymph node metastasis (P = 0.0003), vessel infiltration (lymphatic vessels, P = 0.0167 and venous vessels, P = 0.0005), and clinicopathologic stage (P = 0.001). These findings suggest that repression of WWOX expression may play an important role in stomach carcinogenesis. WWOX thus appears to be a good biomarker for molecular diagnosis of the grade of malignancy of GCs.