In the present study we show that demethylation with 5-aza-dC resulted in an increase of the TBX15 mRNA expression in TPC-1 thyroid cancer cells; however, no correlation was found between methylation levels in the CpG island of TBX15 analyzed and the TBX15 mRNA expression, in nine thyroid cancer cell lines and HeLa cells. This evidence concerns the gene TBX15 and thyroid gland carcinoma.