AGO2 and neuroblastoma: Accumulating evidence reported that NB malignant progression involved the altered expression of circRNAs, such as circ_0133622 [20], circRNA generated from AGO2 gene (circAGO2) [21] and circRNA TBC1 domain family member 4 (circTBC1D4) [22], which suggested the importance of circRNAs in NB progression.