A. Endogenous expression of USP14 in a panel of NB cell lines including IMR-32, NGP, NB-19, CHLA-255, SH-SY5Y, SK-N-AS, LAN-6, and SK-N-BE2. B, C. Immunoblotting assay showing USP14 knockdown in IMR-32 (B), NGP (B), SK-N-BE2 (B), SH-SY5Y (C), SK-N-AS (C), and LAN-6 (C) cells by two independent lentivirus shRNAs, sh-1 and sh-2. Cell growth curve assay shows a proliferation defect in six USP14 knockdown NB cells. The cell counting kit-8 (CCK-8) was used to determine cell viability. Error bars represent SDs of six samples. ***P<0.001. D, E. Six USP14-knockdown cells were harvested for the protein immunoblotting assay. PARP and Caspase-3 cleavages were detected by immunoblotting with the antibodies. β-actin was used as a loading control for whole cell extracts in all samples.