The human neuroblastoma cell lines, SH‐SY5Y and SK‐N‐SH, were purchased from ATCC (Rockville, MD, USA) and grown as previously described 54. Briefly, cells were incubated at 37°C in a humidified 5% CO2/95% air atmosphere and maintained in DMEM/F12 (Sigma‐Aldrich) supplemented with 10% FBS (Sigma‐Aldrich), 2 mM L‐glutamine (Sigma‐Aldrich), penicillin (50 U/ml, Sigma‐Aldrich) and streptomycin (50 mg/ml, Sigma‐Aldrich, Saint Louis, Missouri, USA). The medium was replaced twice a week.