Frequent downregulation of 14-3-3 sigma protein and hypermethylation of 14-3-3 sigma gene in salivary gland adenoid cystic carcinoma.
14-3-3 sigma:, a target gene of the p53 tumour suppressor protein, has been shown to regulate the cell cycle at the G2/M checkpoint. Recent studies have demonstrated that 14-3-3 sigma is downregulated by hypermethylation of the CpG island in several types of cancer. In this study, we investigated the expression and methylation status of 14-3-3 sigma in human salivary gland adenoid cystic carcinoma (ACC) and mucoepidermoid carcinoma (MEC). Immunohistochemical analysis revealed that the positive expression rate of 14-3-3 sigma in ACC (one out of 14) was markedly lower than that in MEC (ten out of 10). Since most of the ACCs carried the wild-type p53 protein, downregulation of 14-3-3 sigma in ACC may not be due to the dysfunction of p53 pathway. Microdissection-methylation-specific PCR revealed that frequent hypermethylation of the 14-3-3 sigma gene was observed in ACC when compared to that in MEC. In cultured-ACC cells, we confirmed the downregulation of 14-3-3 sigma via hemimethylation of the gene by sequencing analysis after sodium bisulphite treatment. Furthermore, re-expression of 14-3-3 sigma in the ACC cells was induced by the treatment with DNA demethylating agent, 5-aza-2'-deoxycytidine. Irradiation apparently induced the enhanced expression of 14-3-3 sigma and G2/M arrest in normal salivary gland cells; however, in the ACC cells, neither induction of 14-3-3 sigma nor G2/M arrest was induced by irradiation. These results suggest that downregulation of 14-3-3 sigma might play critical roles in the neoplastic development and radiosensitivity of ACC.
Uchida
D
D
Second Department of Oral and Maxillofacial Surgery, Tokushima University School of Dentistry, 3-18-15 Kuramoto, Tokushima 770-8504, Japan. daisuke@dent.tokushima-u.ac.jp
Begum
N-M
NM
Almofti
A
A
Kawamata
H
H
Yoshida
H
H
Sato
M
M
D048948:14-3-3 Proteins; D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000235:genetics*; D003528:Carcinoma, Adenoid Cystic / Q000235:genetics* / Q000473:pathology; D019175:DNA Methylation; D017931:DNA Primers; D005092:Exonucleases / Q000235:genetics*; D005095:Exoribonucleases; D016158:Genes, p53; D006801:Humans; D007150:Immunohistochemistry; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D012468:Salivary Gland Neoplasms / Q000235:genetics* / Q000473:pathology
D048948:14-3-3 Proteins; D014408:Biomarkers, Tumor; D017931:DNA Primers; D009363:Neoplasm Proteins; D005092:Exonucleases; D005095:Exoribonucleases; C413442:SFN protein, human