Abstract 5291: A novel gain of function of deltaNp63 in tumor angiogenesis

Proceedings: AACR 103rd Annual Meeting 2012‐‐ Mar 31‐Apr 4, 2012; Chicago, IL Background: The p53 families of transcription factors (p53, p63, and p73) are known to be involved in cell stress response, development and tumor suppression. It has been shown that multiple splicing sites and alternative promoter regions lead to each of these proteins having multiple isoforms. The TA isoforms, which contain the transactivation domain, have been shown to induce apoptosis and inhibit cell-cycle progression, suppressing tumorigenesis, while the deltaN isoforms enhance proliferation and inhibit apoptosis, promoting tumorigenesis. Previous studies have shown that the deltaN isoforms are overexpressed in various types of tumors and somehow modulate the expression of proangiogenic and antiangiogenic factors in a different way thus determining the overall angiogenic activity of tumors. Methods: Since expression of deltaNp63 isoform in primary tumors has been shown to correlate with poor prognosis, we attempted to analyze their relationships with tumor angiogenesis. One quick assessment of angiogenesis is the measurement of the ability of endothelial cells to form three-dimensional structures (tube formation) that mimics angiogenesis in vitro. In the presence of angiogenic mediators, endothelial cells form tubes on collagen or fibrin clot coated dishes. To test whether overexpression of oncogenic deltaNp63 in HEK-293T can stimulate tube formation in endothelial cells (like HUVEC), we performed the endothelial tuber formation assay. In addition, we tested in human primary human cells whether there is any a strong correlation between overexpression of oncogenic deltaNp63 isoform and VEGF secretion. Moreover, we performed gene affymetrix as well protein micro array analysis in primary cells compared to cells overexpressed deltaNp63 isoform. In addition, we used siRNA technics to verify any potential role of deltaNp63 isoform in tumor angiogenesis Results: We found that overexpression of oncogenic isoform of p53 family member deltaNp63 in HEK-293T cells resulted in stimulation of tubular structures in HUVEC cells, which can be observed and counted under the microscope. As 293T cells lack functional p53, these results strongly suggest a gain of function for deltaNp63 isoform. In addition, in contrast to pcDNA-electroporated NHFB, used as a control for detection of endogenous VEGF, deltaNp63 overexpressed NHFB show 4 to 5-fold increased VEGF production. Interestingly, our gene expression array showed that ADAMTS8 were induced around 20-Fold in the presence of oncogenic ΔNp63. Conclusions: We found that deltaNp63beta increased VEGF and ADAMTS8 production by p53 independent manner. Our further studies showed that elevated deltaNp63 induced stabilization of HIF-1alpha protein resulting in VEGF secretion in p53 deficient cells. Furthermore, we showed, in the presence of deltaNp63beta isoform, the stabilization of HIF-1alpha and induced ADAMTS8 secretion was dependent on increased STAT3 phosphorylation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5291. doi:1538-7445.AM2012-5291