ACTB and colorectal cancer: To evaluate the potential impact of chromosomal aberrations on the 4Plex compared to the previously suggested single locus controls ACTB [22] and C-LESS [23], the normalized concentrations of the target genes were compared in groups of colorectal cancer cell lines harboring no aberrations, gain, loss, or both gain and loss in the control loci (Additional file 1: Table S3).