Cellular prion protein and cancers

Abstract

Prion was first identified as the infectious agent of prion disease, since then the biological functions of PrP have been extensively studied. One of the functions of this glycosylphosphatidylinositol (GPI)-anchored protein is to act as an apoptotic regulator. Studies have shown that prion protein (PrP) is upregulated in some cancers including gastric, breast, and colorectal cancers. In these cancers, PrP has been postulated to regulate apoptosis through various pathways. However, the most recent data showed that in human pancreatic cancer and melanoma, PrP might play a different role. In these cancers, the upregulated PrP exist as a Pro-PrP instead of a mature, glycosylated, and GPI-anchored PrP. The Pro-PrP does not have the GPI anchor as it retains its GPI anchor peptide signal sequence (GPI-PSS). The GPI-anchor peptide signal sequence is normally removed in the endoplasmic reticulum prior to the addition of the GPI anchor. The GPI-PSS of PrP has a motif, which binds filament A (FLNA), a cytolinker protein. Binding of pro-PrP to FLNA disrupts the normal function of FLNA, which then facilitates the adhesion, migration, and invasion of the tumor cells. Most importantly, the upregulation of PrP is a marker of poorer prognosis in pancreatic cancer.