Effect of reference gene choice on relative expression of oncogenic target miRNAs in colorectal tumour (n = 35) and normal (n = 39) tissues. Boxplots depict median lines, interquartile-range boxes and outliers (*). Error bar represent range of values. Relative expression of oncogenic miRNAs: (a) miR-21 and (b) miR-31 between colorectal tumour and normal tissues normalised to different reference genes with p values indicated. The use of the two most stable reference genes: miR-16 and miR-345 detected significant dysregulation both target miRNAs between colorectal tumour and normal tissues. Dysregulation of miR-31 was observed regardless of the choice of reference indicating that it's highly differentially expressed in colorectal cancer.