T-box genes regulate development processes, some of these genes having also a role in cell proliferation and survival. TBX15 is a T-box transcription factor that, recently, has been proposed as a marker in prostate cancer, but its function in carcinogenesis is unknown. Here the role of TBX15 in carcinogenesis was investigated using thyroid cancer cell lines. First, using western blot analysis, we show that the expression of TBX15 was altered in thyroid cancer cells lines with respect to normal thyroid cells. Transfection of thyroid cancer cells with TBX15, in the presence or absence of camptothecin as a cytotoxic agent, proved non effect of TBX15 in cell viability; but, it increased cell proliferation after 48 h of transfection (P < 0.01). Consistently, apoptosis was reduced in TBX15 transfected cells (P < 0.01) which also showed a decrease of the proapoptotic Bax regulator and an increase of the antiapoptotic Bcl2 and Bcl-XL regulators. Additionally, siRNA shutdown of constitutive TBX15 increased apoptosis. TBX15 transfection did not alter colony formation and cell migration. Taken together, these results indicate for the first time an antiapoptotic role of TBX15 in cancer cells, suggesting a contribution of TBX15 in carcinogenesis and the potential therapeutic target of TBX15.

TBX15 is a T-box transcription factor essential for development, also proposed as a marker in prostate cancer; and, recently, its antiapoptotic function indicates a role in carcinogenesis. Regulation of TBX15 is uncovered. In this study, we investigated the regulation of TBX15 expression in human cancer cells, by analyzing the regulatory function of a 5’-distal conserved region of TBX15. Bisulfite sequencing showed high methylation of the CpG island contained in this region that was not correlated with TBX15 mRNA levels, in the cancer cell lines analyzed; however, after 5-aza-dC treatment of TPC-1 cells an increase of TBX15 expression was observed. We also found a significant response of TBX15 to TNF-α activation of the NF-κB pathway using five cancer cell lines, and similar results were obtained when NF-κB was activated with PMA/ionomycin. Next, by luciferase reporter assays, we identified the TBX15 regulatory region containing two functional NF-κB binding sites with response to NF-κBp65, mapping on the -3302 and -3059 positions of the TBX15 gene. Moreover, a direct interaction of NF-κBp65 with one of the two NF-κB binding sites was indicated by ChIP assays. In summary, we provide novel data showing that NF-κB signaling up-regulates TBX15 expression in cancer cells. Furthermore, the link between TBX15 and NF-κB found in this study may be important to understand cancer and development processes.

The transcription factor Yin Yang 1 (YY1) has an important regulatory role in tumorigenesis, but its implication in thyroid cancer has not been yet investigated. In the present study, we have analyzed the expression of YY1 in differentiated thyroid cancer and assessed the association of YY1 expression with clinical features. Expression of YY1 was evaluated in human thyroid cancer cell lines, a series of matched normal/tumor thyroid tissues and in a thyroid cancer tissue microarray, using real-time PCR, Western blot, and/or immunohistochemistry. YY1 was overexpressed in thyroid cancer cells, at transcription and protein levels. A significant increase of YY1 mRNA was also observed in tumor thyroid tissues. Moreover, immunohistochemical analysis of the thyroid cancer tissue microarray revealed that both papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) present increased YY1 protein levels (48 and 19%, respectively). After stratification by the level of YY1 protein, positive YY1 expression identifies 88% of patients with PTC. The association of YY1 expression with clinicopathological features in PTC and FTC showed that YY1 expression was related with age at diagnosis. Our data indicates for the first time overexpression of YY1 in differentiated thyroid cancer, with YY1 being more frequently overexpressed in the PTC subtype.