Abstract A01: Evaluation of hypoxia adaptation in neuroblastoma identifies reproducible transcriptional and phenotypic responses

Abstract

Although metabolic adaptation is a cornerstone of the hypoxia response, very little is known about hypoxia-induced metabolic changes in neuroblastoma or how the metabolome influences phenotype. Identifying genes that regulate neuroblastoma metabolism and also influence clinical behavior may provide clues for novel therapeutic targets. Mixed linear models were used to identify differentially expressed genes between neuroblastoma cells grown in hypoxia or normoxia in two independent experiments (GEO accessions GSE17714 and GSE55391). Linear models were also used in to identify differentially expressed genes from tumors of two independent cohorts of neuroblastoma patients (GEO accession GSE16254 and EMBL accession E-MTAB-179) who survived compared to those that did not. We utilized a false discovery rate of 0.01 and fold change in the top or bottom 10% of all genes as a significance cutoff. qPCR was used to validate expression differences in multiple neuroblastoma cell lines. 157 genes, significantly exceeding chance (p < 1x10-6) on permutation testing, were present in both neuroblastoma cell line data sets, all but five of which showed consistent directionality of expression change from normoxia to hypoxia, including 44 involved in metabolism. These genes were enriched for hypoxia and metabolic pathways: HIF-1α transcription factor network (p = 1.3x10-11), glycolysis (p = 1.9x10-8) and fructose metabolism (p = 1.0x10-3). 826 genes, significantly exceeding chance (p < 1x10-6) were differentially expressed in both patient cohorts of 478 and 88 patients. These genes were enriched for cell cycle pathways (p = 4.5x10-7). Of these genes, nine of them were also differentially expressed in hypoxia compared to normoxia with consistent directionality, again more than expected by chance (p < 1x10-6). High expression in eight of the nine genes was also significantly associated with poor outcome in a Kaplan-Meier analysis of both of the patient cohorts evaluated. Three of these genes are part of the glycolytic pathway and three more are directly involved in cellular metabolism. In the SK-N-BE2 cell line, all eight of our identified genes are up-regulated in hypoxia (p < 0.05). Analysis of the LAN-5, La1-55n, SK-N-DZ cell lines and show similar results. MTT assays of proliferation show the expected decreased proliferation for all of these cell lines in 48 hours of hypoxia compared to normoxia (p < 0.05). Analysis of cell cycle by flow cytometry in SK-N-BE2 cells shows an increase of cells in G0/G1 in normoxia compared to hypoxia (58.3% vs. 71.5% p = 0.04) and decrease of cells in S phase (24.5% vs. 13.6%, p = 0.001). We have identified eight genes with increased expression in hypoxia and are associated with poor survival in patients. Efforts to use shRNA to alter cellular phenotype are ongoing. Citation Format: Mark A. Aplebaum, Aashish Jha, Alexandre Chlenski, Christopher Mariani, Clara Kao, Mildred Nelson, Kyle Hernandez, Helen Salwen, Marija Dobratic, Kevin White, Barbara Stranger, Susan L. Cohn. Evaluation of hypoxia adaptation in neuroblastoma identifies reproducible transcriptional and phenotypic responses. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr A01.