USP3 and neuroblastoma: Interestingly, the USP3 protein level was also low in RA-induced differentiation of neuroblastoma cell lines when compared to the RA-untreated cells (Fig. 6D, lane 3 and Supplementary Fig. 8B, lane 4), suggesting that downregulation of USP3 may promote REST ubiquitination during neuroblastoma differentiation.