Effect of CDT6 on factors of angiogenic balance in tumour cell lines

Background: Cornea-derived transcript 6 (CDT6, also known as AngX) is an angiopoietin-related factor resulting in anti-tumour effect in vivo. However, a recent abstract reported that CDT6 can also induce angiogenesis and promotes tumour growth. In our previous work, CDT6 had failed to show pro- or anti-angiogenic effects. It is unknown if CDT6 expression occurs in human cancer. Materials and Methods: An array of human tumour cell lines and tumour tissues was tested for CDT6-gene expression using RT-PCR. To address the controversial role of CDT6 on angiogenesis in different tumour models, the expression levels of four factors of the angiogenic balance (VEGF, endostatin, TIMP-1 and PAI-1) were determined in CDT6-transfected and control cells of the human and murine melanoma cell lines BLM and B16-F10. Endostatin was significantly up-regulated by CDT6 expression in the human model and significantly downregulated in the mouse model. None of 18 cell lines or 23 tumours expressed CDT6. Conclusion: This contradictory effect on endostatin expression in human and mouse models may be an explanation for the conflicting results for the effect of CDT6 expression on angiogenesis.