Figure 4

Determination of the optimal number of reference genes for paired tumoral and non-tumoral tissues, tumor tissues and cell lines separately. Pair-wise variations (V_n/n+1) between every combination of sequential normalization factors were calculated to determine the minimum number of reference genes required for accurate normalization in different sample panels (Paired tissues A: paired tumoral and non-tumoral tissues left after the exclusion of RNA samples with relatively high amount of inhibitors; Paired tissues B: all paired tissues). The cutoff value below which the inclusion of an additional reference gene does not result in a significant improvement of normalization, was set at 0.15 (arrowhead = minimum number of reference genes for normalization).