Molecular alterations of the WWOX gene in nasopharyngeal carcinoma

The WW domain-containing oxidoreductase (WWOX) gene is a candidate tumor suppressor gene. However, its exact mechanism is unclear. This study aimed to investigate the role of the WWOX gene in the development of nasopharyngeal carcinoma (NPC). Tissues were collected from 65 NPC patients. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis and immunohistochemistry were performed on NPC tissues to determine the expression of WWOX in NPC. The status of WWOX promoter methylation was analyzed by methylation-specific PCR. Moreover, a PCR-based loss of heterozygosity (LOH) assay was conducted to detect the presence of WWOX deletion in NPC. The expression of WWOX in NPC tissues was significantly downregulated compared with that in non-tumorous tissues (P<0.05). The low expression of WWOX was significantly correlated with clinical TNM stage (P<0.05). In addition, methylation of WWOX was detected in 27 (87%) of 31 WWOX protein negative tissues, suggesting that methylation of the WWOX promoter may regulate its expression. We found that a relatively high percentage of LOH was observed in NPC tissues. A significant inverse correlation between WWOX expression and methylation of its promoter was found in NPC tissue (rs=-0.582, P=0.001). However, LOH was not correlated with WWOX expression and methylation of its promoter. Our results show that WWOX gene alteration is an early genetic alteration and may contribute to tumorigenesis of NPC. WWOX may be an important prognostic marker in NPC.