ADAM9 mRNA expression in malignant tissue samples compared to non-malignant paired samples in depending on different normalization approaches. Gene expression in the matched malignant tissue samples was calculated as multiple of the expression in the non-malignant sample that was set 1.0. The columns represent the median and interquartile ranges of the multiple gene expression. The four blank columns result from ADAM9 mRNA expression related to the two non-regulated reference genes (PPIA, TBP) and to the normalization factors (mr, of the two genes; NF, calculated using geNorm; see text). The three striped and two black columns illustrate the normalization of ADAM9 expression using either up-regulated (GAPDH, ACTB, and TUBB) or down-regulated (ALAS1 and HPRT1) genes.