Gene expression and methylation status of 14‐3‐3σ in human renal carcinoma tissues

Loss of 14-3-3σ expression mainly by methylation-mediated silencing has been reported in several human cancers, but the methylation status of 14-3-3σ in human renal carcinoma is rarely studied so far. In this report, 14-3-3σ expression was first examined by RT-PCR and immunohistochemistry, and further we investigated the methylation status by methylation-specific PCR and the correlation between 14-3-3σ expression and its methylation. We found 14-3-3σ expression was lost in 27 of 31 renal tissues including 16 renal carcinoma tissues, eight para-cancerous kidney tissues and seven normal kidney tissues. Among 16 renal carcinoma tissues, 14 cases had complete hypermethylation of 14-3-3σ. Eight para-cancerous kidney tissues were almost completely methylated except one case had both methylation and unmethylation. Among seven normal kidney tissues, five cases had partial methylation, and the other two cases were completely methylated. In addition, 14-3-3σ mRNA had weak expression in OS-RC-2 cells, but it increased with gradual demethylation after treatment by a demethylation agent, 5-aza-2′-deoxycytidine. In general, 14-3-3σ mRNA was mostly unexpressed, and its DNA frequently hypermethylated within 14-3-3σ coding region was closely associated with the gene silencing in cancerous and para-cancerous kidney tissues. 14-3-3σ was also frequently methylated and almost silencing in normal kidney tissues. However, the methylation frequency was gradually reinforced with the extent of malignancy from normal to para-cancerous and cancerous kidney tissues. © 2008 IUBMB IUBMB Life, 60(8): 534–540, 2008