Fig. 4
Validation of the gene expression variability of the novel reference genes by RT-qPCR. RT-qPCR analyses for two commonly used reference genes (GAPDH and β-actin, light blue-colored box), and 11 newly identified reference genes (PCBP1, HNRNPC, HNRNPL, EMC4, SNX17, MRPL43, IST1, FAM32A, PFDN1, RNF10, and RER1) that were highly ranked among the 38 analyzed genes according to their expression levels (indicated by their calculated CV values). ΔCT indicates average difference of CT value between cancerous and normal tissue samples (i.e., CT [cancer] - CT [normal]). Newly identified reference genes whose ΔCT value was found to be lower than that of both β-actin and GAPDH in all samples are highlighted (red-colored box). *Samples from seven types of cancerous tissues, including breast (n = 9), colon (n = 6), liver (n = 4), lung (n = 4), thyroid (n = 4), kidney (n = 1), and cervical (n = 1) were combined. Note that kidney and cervical tissues have not been separately represented in the box plot