GALC gene is downregulated by promoter hypermethylation in Epstein-Barr virus-associated nasopharyngeal carcinoma.

The aim of the study was to investigate the tumor-suppressor effect of GALC in Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) and determine whether GALC was downregulated by promoter hypermethy-lation in the NPC cell line, CNE-2Z. Forty-one archival NPC biopsy specimens were compared with 15 chronic nasopharyngitis specimens. EBV-encoded RNA (EBER) was verified by in situ hybridization and GALC protein expression was analyzed by immunohistochemistry. Promoter methylation in CNE-2Z cells was analyzed by bisulfite sequencing polymerase chain reaction. The functional role of GALC in NPC was investigated by restoring GALC expression in CNE-2Z cells via treatment with the DNA-deme-thylating agent 5-Aza-2'-deoxycytidine (5-Aza‑dC). EBER was expressed in 92.68% NPC specimens but no chronic nasopharyngitis specimens (P<0.01). GALC protein was present in 60% of chronic nasopharyngitis specimens and 24.39% NPC specimens (P<0.05). GALC protein expression was present significantly more frequently in tumors without lymph node metastasis than in those with metastasis (P<0.05). Logistic regression showed that GALC protein expression protected against lymph node metastasis (P<0.05). GALC protein expression was not correlated with age, gender and TNM stage (P>0.05). Treatment of GALC-negative CNE-2Z cells with 5-Aza-dC reduced GALC promoter methylation and restored GALC expression in a dose-dependent manner (P<0.05). The re-expression of GALC in CNE-2Z cells reduced cell proliferation and migration compared to the controls (P<0.05). GALC was downregulated by promoter hypermethylation and contributed to the pathogenesis of EBV-associated NPC. The findings showed the putative tumor-suppressor effect of GALC in NPC.