Abstract 5213: RUNX2 modulates the angiogenic potential of human neuroblastoma cells

Abstract

Abstract Neuroblastoma is the most common extracranial pediatric solid tumor with an undifferentiated status and characterized by heterogeneous clinical courses ranging from spontaneous regression to a very aggressive malignant progression. The RUNX gene family comprises RUNX1, RUNX2, and RUNX3 transcription factors and plays pivotal roles in development, differentiation and tumorigenesis. Hypoxia is known to be a significant physiological stress in the tumor microenvironment and is associated with tumor malignant phenotype. In this study, we examined the effects of hypoxia on the Runx2 expression in human neuroblastoma cells and the role of RUNX2 on angiogenic potential of neuroblastoma cells. Runx2 has two isoforms, Runx2-I and Runx2-II. Isoform I is controlled by the P2 proximal promoter whereas isoform II is transcribed from the P1 distal promoter. Increased expression of mRNAs of isoform I and II as well as intact isoform of RUNX2 was observed in NB1691 cells exposed to hypoxia. Furthermore, hypoxia enhanced the activity of a luciferase reporter containing Runx2 P1 promoter in NB1691 cells. Hypoxic exposure caused an increase in protein levels of RUNX2 as well as survivin, a RUNX2 downstream target gene in NB1691 cells. Hypoxia also stabilized RUNX2 protein levels in NB1691 cells without altering the stability of RUNX2 mRNA. Hypoxia enhanced angiogenic potential of NB1691 cells. Knockdown of Runx2 significantly decreased VEGF mRNA and protein in NB1691 cells exposed to hypoxia. A decrease in angiogenesis was observed in chorioallantoic membrane assay performed using conditioned medium collected from RUNX2 siRNA treated hypoxic NB1691 cells compared with control. Further, transcript levels were measured by PCR array of human angiogenesis pathway and the analysis showed down regulation of EDN1, FIGF, TEK and VEGF A mRNAs in hypoxic NB1691 cells treated with RUNX2 siRNA. In conclusion, our study suggests that hypoxia upregulates RUNX2 expression in NB1691 cells and knockdown of RUNX2 decreases the angiogenic potential of hypoxic NB1691 cells. Citation Format: Manu Gnanamony, Indra Mohanam, Sanjeeva Mohanam. RUNX2 modulates the angiogenic potential of human neuroblastoma cells. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5213. doi:10.1158/1538-7445.AM2015-5213