Possible Involvement of BRAFV600E in Altered Gene Expression in Papillary Thyroid Cancer

Abstract

Somatic mutations in BRAF, especially BRAFV600E, are frequently identified in papillary thyroid cancer (PTC) tumors. It has been established that expression levels of numbers of genes are characteristically altered in PTC, however, the link between BRAF mutation and gene expression patterns are still elusive. In the present study, we analyzed relative expression levels of the wild type BRAF and BRAFV600E mRNA by using quantitative PCR (qPCR) and cDNAPCR- RFLP in 19 PTC specimens and adjacent normal thyroid tissues. BRAFV600E mRNA was detected in 17 out of 19 PTC specimens, and the expression levels were valuable among the specimens, suggesting alternative expression of BRAFV600E in each cell and/or alternative population of BRAFV600E-positive clones in the tumor. We then analyzed expression levels of 20 genes by qPCR, and analyzed for possible correlation with expression levels of BRAFV600E mRNA. Expression levels of fibronectin, vimentin and CITED1 (Cbp/p300 interacting protein with glutamic acid and aspartic acid rich carboxyl terminal domain) were positively correlated with those of BRAFV600E, suggesting pathophysiological links between activated BRAF and overexpression of these genes. Among these genes expression of vimentin was decreased by inhibiting BRAF expression in NPA cells that express BRAFV600E by means of siRNA, suggesting activated BRAF positively regulate expression of vimentin. Collectively, our analyses illustrated the possibilities that variable expression of BRAFV600E may modify characters of PTC through its effects on gene expression.