Hypomethylation of the 14-3-3σ promoter leads to increased expression in non-small cell lung cancer

The 14-3-3 proteins are a set of seven highly conserved proteins that have recently been implicated in having a role in human tumorigenesis. However, the mechanism by which 14-3-3 proteins may act in this capacity is not well understood. In this study, we examined the expression of one of the 14-3-3 family members, 14-3-3σ, since it was shown previously to be aberrantly altered in human tumors. Using quantitative rtPCR and immunohistochemistry, we found that the expression levels of 14-3-3σ were elevated in the majority of human non-small cell lung cancers (NSCLC) we examined. Surprisingly, we found that the 14-3-3σ gene was hypomethylated in lung tumors relative to normal lung tissue suggesting that decreased DNA methylation resulted in increased expression of 14-3-3σ in NSCLC. We also determined the gene copy number for 14-3-3σ in tumor samples and found no significant correlation with elevated mRNA expression. And also no mutations were found in 14-3-3σ gene. Overall, our data suggest that misregulated expression of 14-3-3σ gene may be due to altered methylation status.