Clinical implications of CES2 RNA expression in neuroblastoma

Background/Purpose: Human carboxylesterase 2 (CES2) is the key enzyme for metabolic activation of irinotecan (CPT-11). The aim was to evaluate the clinical implications of CES2 RNA expression in neuroblastoma cells. Methods: CES2 RNA expression was determined by real-time reverse transcription-polymerase chain reaction in five neuroblastoma cell lines and 42 clinical samples of untreated neuroblastoma. Sensitivity to CPT-11 was assessed by WST-8 colorimetric assays. Induction of apoptosis was evaluated by flow cytometry after CPT-11 exposure. Protein expression of CES2 was evaluated by Western blotting analysis. CES2 RNA expression in clinical samples was investigated for its associations with the clinicopathological characteristics. Results: CES2 RNA expression was observed in neuroblastoma cells, and its expression in neuroblastoma cell lines was positively correlated with sensitivity to CPT-11 and apoptosis after CPT-11 exposure in vitro. CES2 RNA expression was correlated with the protein levels of CES2 in vitro. CES2 RNA expression was significantly higher in patients with a characteristic related to advanced disease. Conclusions: Our results suggest the potential of clinical application of CPT-11 in neuroblastoma treatment for patients with advanced disease.