Abstract 4194: Gliomaspheres mimic the hypoxia-Notch signaling axis of glioblastoma tumors

Abstract

Abstract Background and objectives: Notch signaling plays an oncogenic role during gliomagenesis. Synergism of hypoxia with Notch pathway is known to aggravate different cancers. We studied the association between Notch signaling and hypoxia in human glioblastoma (GBM) samples which are characterized by intratumoral hypoxia. We also carried out in-vitro analysis in U87MG cell line enriched in stem cells under low oxygen conditions. The study aimed at identifying a modular gene subset that might be a characteristic of the Notch pathway response in hypoxic GBM tumors and GBM gliomaspheres; which might assist in individualized therapeutics. Methods: Expression of Notch receptors, Dll/Jag ligands, Hes/Hey targets and hypoxia markers was analyzed in 35 GBMs by q-PCR and immunohistochemistry. Spearman's test, clustering and statistical analyses were applied to assess the correlation between hypoxia and Notch pathway upregulation. Expression analysis was also done in U87MG cells grown in stem cell culture conditions under hypoxia using q-PCR and western blot. Results: Using various statistical analyses, we found HIF-1α to be correlated with the expression of maximum number of Notch pathway genes, followed by PGK1, OPN and VEGF. Well-segregated tumor clusters accounting for differential Notch genes' expression were produced using gene clustering and principal components analysis by ordering the GBMs in decreasing levels of HIF-1α/PGK1. By logistic regression, a five hypoxia marker combination (HIF-1α/PGK1/VEGF/CA9/OPN) was determined as the best predictor for Notch signaling augmentation in GBM. A similar Notch-axis (Notch1/Dll1/Hes1/Hes6/Hey1/Hey2) was activated in U87MG gliomaspheres under hypoxia. Interpretation and conclusions: The hypoxia markers most associated with Notch signaling upregulation in resected GBM were identified. Similar components of the Notch pathway were also found to be activated in hypoxia-exposed gliomaspheres, supporting them as an in-vitro model for studying the perturbations of hypoxia-Notch signaling axis. Citation Format: Khushboo Irshad, Saroj Kant Mohapatra, Harshit Garg, Seema Mishra, Chitra Sarkar, Deepak Gupta, Parthaprasad Chattopadhyay, Subrata Sinha, Kunzang Chosdol. Gliomaspheres mimic the hypoxia-Notch signaling axis of glioblastoma tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4194. doi:10.1158/1538-7445.AM2014-4194