Real-time PCR-based verification of HAL-PDT effect. Nine selected genes – HIST1H1C, HIST1H2AM, HIST1H3C, HIST2H2AB, MT1B, MT1G, mitochondrial encoded genes (mito), mito-CYB, mito-ND2 and mito-ND5- were assessed for expression (relative mRNA level) at 1 h, 2 h and 4 h after HAL-PDT by real time PCR using the housekeeping RPLPO and TBP genes as reference genes. The fold change in gene expression (ΔΔCt) in photochemically treated samples compared to non-treated controls was calculated and presented as the mean ± St. Dev (A). The fold-changes obtained by the microarray analysis for the selected genes are presented for comparison. Fold-change of three repeated experiments presented as the mean ± St. Dev (B). Correlation factors for arrays and RT-PCR verified genes were 0.77; 0.99 and 0.85 for 1 h, 2 h and 4 h respectively.