PCSK2 and gastric cancer: The expression of the serum exosomal lncRNA PCSK2-2:1 is significantly downregulated in GC patients compared with that in healthy controls and is associated with tumor size, tumor stage, and venous invasion, suggesting that exosomal RNA PCSK2-2:1 may be a new prospective biomarker for GC diagnosis (Cai et al., 2019).