Gene Expression and Early Radiation Response of Two Distinct Neuroblastoma Cell Lines

Abstract

Introduction: Neuroblastoma is one of the most common childhood cancers with one of the lowest survival rates, accounting for 15% of childhood cancer mortality. Approximately half of children treated for high-risk neuroblastoma will relapse following remission, while another 15% of patients do not respond to initial treatment. External beam radiation is infrequently used for treatment of pediatric cancer such as neuroblastoma, typically reserved for palliative care in patients with aggressive metastatic disease who fail to respond to alternative treatments. Understanding effects of radiation on neuroblastoma cells could improve efficacy of this final means of therapy to decrease tumor burden and stabilize the disease.

Methods: In this study, we found that two microRNAs with opposite functions were expressed in two neuroblastoma cell lines with marked differences in radiosensitivity. Clonogenic assays were used to evaluate the radiation responses for these 2 cell lines, designated SK-N-AS and SK-N-DZ; cells were then irradiated at doses that cause 90% cell killing based on clonogenic assay and their RNA isolated and subjected to microarray analysis. In addition, cells were transfected with pre-miRNA constructs that led to overexpression of microRNAs miR-34a and miR-1228 to determine possible microRNA regulation of radiation response.

Results: Statistically significant differences were detected for expression of several thousand genes when the 2 cell lines were compared with each other. In comparison, radiation exposure resulted in only minor gene expression differences of less than 2-fold at the 1 h postirradiation timepoint in both cell lines. Overexpression of miR-34a and miR-1228 in either cell line did not alter this outcome.

Discussion: While these two neuroblastoma cell lines are phenotypically diverse and gene expression differences between them are extensive, we observed that the regulation of gene expression in both cell lines is in a stable equilibrium at early timepoints after exposure to ionizing radiation.

Keywords: External beam radiation; Neuroblastoma; Radiotherapy; microRNAs.