PCSK9 and familial hypercholesterolemia: Transfection studies with McA-RH7777 cells that stably expressed the D374Y mutant form of PCSK9 (identified in human familial hypercholesterolemia) showed that the pathogenic variant expression resulted in increased secretion of apoB-100 lipoproteins (by 2-4-fold) but expression of the wildtype PCSK9 did not increase apoB-100 secretion [137].