(a) Schematic of approximate siRNA target sites within the LIN28B mRNA. (b) qPCR analysis of LIN28B mRNA levels in BE(2)C cell 48 hours after transfection with the indicated LIN28B targeting siRNAs. (mean of two independent experiments shown) (c) Immunoblot analysis of LIN28B in cells from a. For gel source data, see Supplemental Figures. (d) qPCR analysis of indicated let-7 levels in cells from a. (mean of two independent experiments shown) (e) Immunoblot analysis of MYCN and LIN28B in serially transfected MYCN-amplified cells for 6 or 9 days. Identical transfections were performed of days 0, 3, and 6. For gel source data, see Supplemental Figures. (f) Day 9 qPCR analysis of the let-7 family in the cells from a. (n = 3 independent experiments, mean plus s.e.m. shown) (g) Cell growth analysis of day 0 to day 6 cells from a (BrdU incorporation, n = 3 independent experiments, mean plus s.e.m. shown). (h) Lentiviral CRISPR-Cas9/LIN28B gRNA strategy targeting LIN28B at four distinct exon/intron junctions used in b–g.