Data from ΔNp63 Promotes Pediatric Neuroblastoma and Osteosarcoma by Regulating Tumor Angiogenesis

Abstract

<div>Abstract<p>The tumor suppressor gene <i>p53</i> and its family members <i>p63</i>/<i>p73</i> are critical determinants of tumorigenesis. ΔNp63 is a splice variant of p63, which lacks the N-terminal transactivation domain. It is thought to antagonize p53-, p63-, and p73-dependent translation, thus blocking their tumor suppressor activity. In our studies of the pediatric solid tumors neuroblastoma and osteosarcoma, we find overexpression of ΔNp63; however, there is no correlation of ΔNp63 expression with p53 mutation status. Our data suggest that ΔNp63 itself endows cells with a gain-of-function that leads to malignant transformation, a function independent of any p53 antagonism. Here, we demonstrate that ΔNp63 overexpression, independent of p53, increases secretion of interleukin (IL)-6 and IL-8, leading to elevated phosphorylation of STAT3 (Tyr-705). We show that elevated phosphorylation of STAT3 leads to stabilization of hypoxia-inducible factor 1α (HIF-1α) protein, resulting in VEGF secretion. We also show human clinical data, which suggest a mechanistic role for ΔNp63 in osteosarcoma metastasis. In summary, our studies reveal the mechanism by which ΔNp63, as a master transcription factor, modulates tumor angiogenesis. <i>Cancer Res; 74(1); 320–9. ©2013 AACR</i>.</p></div>