Verification of selected microarray results by rtRT-PCR. The 16 reproducible differentially-expressed genes in 3 clones induced by IGFBP-rP1 in RKO cells and the differentially-expressed cytoskeleton associated genes keratin 7, keratin 8, profilin2 analysed by chip were selected for rtRT-PCR validation. RtRT-PCR was performed on RNA extracted from IGFBP-rP1-RKO transfectants and the control cells. Delta-delta Ct method was used to calculate relative fold changes normalized against the GAPDH gene. The relative fold change for IGFBP-rP1 from rtRT-PCR is 2.1 × 106. Results represent the mean (± SD) of six experiments.