Quantification of gene amplification by a SYBR-Green I assay. A) Gene amplification detected in cell lines. Cell lines with known levels of gene amplification (open bars) were tested for GLI  or MYC-C  gene amplification using real-time PCR and/or QM-Multiplex PCR. Results obtained using the SYBR-Green I real-time assay (black bars, triplicates) correlated well with the levels of amplification for both genes described previously in these cell-lines. However, QM-Multiplex PCR gave lower levels of amplification in two out of five samples compared to reported results. B) Detection of gene amplification in DNA extracted from neuroblastoma tumor samples. Tumor samples with known levels of MYC-N gene amplification, established using standard FISH techniques (open bars, estimated 1, 10, 50 or 100 amplification fold were tested for MYC-N gene amplification using our real-time PCR assay (black bars, triplicate). Results obtained correlated well with reported levels and confirmed either the presence of an MYC-N gene amplification in 6 out of 9 tumors or its absence in 3 tumors.