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

Abstract

Simple Summary: Neuroblastoma is a common pediatric cancer that spreads systemically, making therapy difficult. Tumors are frequently resistant to radiation therapy, a last line of defense in patients with aggressive disease. In this study, we found that there are distinct gene expression patterns dependent on neuroblastoma subtype; however, both neuroblastoma types examined showed only subtle gene expression differences early following radiation exposure. This indicates that while neuroblastoma tumors are diverse in phenotype and gene expression, they have similarly stable gene expression and resistance during early response to stressors such as radiation. Abstract: 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. In this study, clonogenic assays were used to establish radiation responses for SK-N-AS and SK-N-DZ cell lines; 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. Statistically significant differences were detected for expression of several thousands of genes when the two cell lines were compared with each other. In comparison, radiation led only to minor gene expression differences of less than two-fold at the 1h post-irradiation timepoint in both cell lines. Overexpression of miR-34a and miR-1228 in either cell line did not change this outcome. Therefore, neuroblastoma cell lines SK-N-AS and SK-N-DZ are phenotypically diverse and gene expression differences between them are extensive. At the same time, the regulation of gene expression in both of these cell lines is in a stable equilibrium at early timepoints after exposure to ionizing radiation.