4'-O-?-d-Glucopyranosyl-4-hydroxy-3,3',5-trimethoxychalcone derived from Brassica rapa L. induces cell cycle arrest and apoptosis in neuroblastoma cells.

Introduction: Neuroblastoma is one of the most commonly encountered malignant solid tumors in the pediatric age group. We examined the antitumor effects of chalcone glycosides derived from Brassica rapa L against neuroblastoma cell lines. Materials and Methods: We used the WST-8 assay to evaluate the cytotoxicity of the glycosides against human neuroblastoma cell lines and normal cell lines. We also performed analysis of cell cycle arrest by flow cytometry, and examined the expression levels of cell cycle-and apoptosis-related proteins by western blot analysis. Results: One of the derivative compounds (compound 6,4'-O-β-d-glucopyranosyl-4-hydroxy-3,3',5- trimethoxychalcone) was found to exert cell cytotoxicity against neuroblastoma cells. Examination of the effects on the cell cycle revealed cell cycle arrest in the G0/G1 phase. Furthermore, exposure of the cells to compound 6 was associated with decreased protein expression levels of cyclin D, phospho-retinoblastoma protein (Rb) and E2 factor (E2F), as evaluatedby western blot analysis. In addition, a Hoechst 33342 staining experiment revealed apoptosis, characterized by cell shrinkage, nuclear chromatin condensation and fragmentation. Annexin V-propidium iodide (PI) double staining also showed an increase in the number of early apoptotic cells. Compound 6 induced activation of executioner caspases (caspase-3 and caspase-7) and Poly (ADP-ribose) polymerase (PARP) cleavage. Conclusion: Compound 6 exerted inhibition of cell growth of neuroblastoma cells by inducing G0/G1 arrest and caspase-dependent apoptosis. This compound may offer promise for development as a useful drug for the treatment of advanced neuroblastoma.