Homologous recombination repair and cholesterol-mediated drug efflux induce dose-dependent chemoresistance in nutrient-deprived neuroblastoma cells

Neuroblastoma is a solid pediatric tumor with heterogeneous clinical behaviors. Chemotherapy is widely used to treat neuroblastoma. However, dose-dependent responses and chemoresistance mechanisms of neuroblastoma cells to anticancer drugs remain challenges in various conditions. Here, we investigated the dose-dependent effects of topotecan on human neuroblastoma cells (SK-N-SH, SH-SY5Y, and SK-N-BE) under various nutrient supply conditions. Serum-starved human neuroblastoma cells showed reduced toxicity, and their survival rate increased upon treatment with a high concentration (1 μM) of topotecan. Quantitative profiling of global and phosphoproteome identified 12,959 proteins and 48,812 phosphosites, respectively, from SK-N-SH cells. Network analysis revealed that topotecan up-regulated DNA repair and cholesterol-mediated topotecan efflux, resulting in topotecan resistance. Results of DNA damage assay, cell cycle, and quantitative analyses of membrane cholesterol supported the validity of these resistance factors and their applicability to all neuroblastoma cells investigated in this study. Our results provide a model for high dose-dependent chemoresistance in neuroblastoma cells that could enable a patient-dependent chemotherapy screening strategy.