PCSK9 and colorectal carcinoma: Importantly, based on a set of 13 genes analyzed in 20 CRC/NT sample pairs, the same regulation occurred at both the mRNA and protein levels in at least 17 samples (roughly 90% concordance with mRNA levels), except for the PCSK9 protein, which showed no consistent protein expression pattern, or the GPI protein that remained essentially unchanged (Additional file 5: Figure S3C).