Preservation of differential expression after pre-amplification. Differential expression (expressed as difference in Cq or delta-Cq (dCq)) of 10 genes in three MYCN single copy (MNS) neuroblastoma cell lines (1: GI-ME-N; 2: SK-N-AS; 3: SK-N-SH) and three MYCN amplified (MNA) neuroblastoma cell lines (1: IMR-32; 2: N206; 3: NGP) before (light grey bars) and after sample pre-amplification (dark grey bars). The x-axis represents the differentially expressed genes. 1:MYCN; 2:INHBA; 3:RGS4; 4:DKK3; 5:NTRK2; 6:TGFBI; 7:PMP22; 8;PLAT; 9:CMYC; 10:MTHFD2. The dCq between MNS and MNA samples remains almost unchanged after pre-amplification indicating a preservation of differential expression.