6926

TBX3

T-box 3;TBX3;T-box 3

T-box protein 3|T-box transcription factor TBX3|bladder cancer related protein XHL

12q24.21

protein-coding

OBJECTIVE: To explore the role of TBX3 gene in the pathogenesis of breast cancer. METHODS: The total RNA of 51 fresh breast cancer tissues and the corresponding adjacent tissues were extracted and reverse transcribed into cDNA to detect the expression of TBX3 mRNA by real-time PCR. The correlation between TBX3 mRNA expression and the clinicopathologic parameters in relation to breast cancer metastasis was analyzed. RESULT: Compared to that in the adjacent tissues, the expression of TBX3 mRNA was markedly increased in breast cancer tissues. TBX3 mRNA expression was significantly higher in metastatic breast cancer than in non-metastatic tumors. CONCLUSION: Increased expression of TBX3 mRNA suggests the involvement of TBX3 in the pathogenesis and metastasis of breast cancer.

The T-box transcription factor TBX3 provides an important link between embryonic development and cancer. TBX3 mediates limb, mammary gland and heart development and, in humans, mutations resulting in haplo-insufficiency of TBX3 lead to ulnar-mammary syndrome. Importantly, the de-regulation of TBX3 gene expression has been linked to several cancers, where it acts to suppress senescence and promotes proliferation and tumour invasion. Despite the negative impact of de-regulated TBX3 expression as seen by developmental defects and cancer, surprisingly little is known about the regulation of the TBX3 gene. In the present paper, we show that the phorbol ester PMA increases TBX3 protein and mRNA levels in a protein kinase C-dependent manner via the AP-1 (activator protein 1) transcription factors c-Jun and JunB. Furthermore, these AP-1 factors are shown to mediate the activation of the TBX3 gene by binding a non-consensus PMA-response element in the TBX3 promoter in vitro and in vivo. We also demonstrate that TBX3 contributes to the PMA-induced migration previously observed for the MCF-7 breast epithelium cancer cell line. Our present results reveal a previously unidentified pathway that up-regulates TBX3 expression and provides additional evidence that increased levels of TBX3 contribute to metastasis.