The fatal attraction between pro-prion and filamin A: prion as a marker in human cancers.

Department of Pathology, School of Medicine, Case Western Reserve University, 2103 Cornell Road, Cleveland, OH 44106, USA.
Biomarkers in Medicine (Impact Factor: 3.22). 06/2010; 4(3):453-64. DOI:10.2217/bmm.10.14
Source: PubMed

ABSTRACT Pancreatic cancer is the fourth leading cancer causing deaths in the USA, with more than 30,000 deaths per year. The overall median survival for all pancreatic cancer is 6 months and the 5-year survival rate is less than 10%. This dismal outcome reflects the inefficacy of the chemotherapeutic agents, as well as the lack of an early diagnostic marker. A protein known as prion (PrP) is expressed in human pancreatic cancer cell lines. However, in these cell lines, the PrP is incompletely processed and exists as pro-PrP. The pro-PrP binds to a molecule inside the cell, filamin A (FLNa), which is an integrator of cell signaling and mechanics. The binding of pro-PrP to FLNa disrupts the normal functions of FLNa, altering the cell's cytoskeleton and signal transduction machineries. As a result, the tumor cells grow more aggressively. Approximately 40% of patients with pancreatic cancer express PrP in their cancer. These patients have significantly shorter survival compared with patients whose pancreatic cancers lack PrP. Therefore, expression of pro-PrP and its binding to FLNa provide a growth advantage to pancreatic cancers. In this article, we discuss the following points: the biology of PrP, the consequences of binding of pro-PrP to FLNa in pancreatic cancer, the detection of pro-PrP in other cancers, the potential of using pro-PrP as a diagnostic marker, and prevention of the binding between pro-PrP and FLNa as a target for therapeutic intervention in cancers.

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    ABSTRACT: Inherited mutations are known to cause familial cancers. However, the cause of sporadic cancers, which likely represent the majority of cancers, is yet to be elucidated. Sporadic cancers contain somatic mutations (including oncogenic mutations); however, the origin of these mutations is unclear. An intriguing possibility is that a stable alteration occurs in somatic cells prior to oncogenic mutations and promotes the subsequent accumulation of oncogenic mutations. This review explores the possible role of prions and protein-only inheritance in cancer. Genetic studies using lower eukaryotes, primarily yeast, have identified a large number of proteins as prions that confer dominant phenotypes with cytoplasmic (non-Mendelian) inheritance. Many of these have mammalian functional homologs. The human prion protein (PrP) is known to cause neurodegenerative diseases and has now been found to be upregulated in multiple cancers. PrP expression in cancer cells contributes to cancer progression and resistance to various cancer therapies. Epigenetic changes in the gene expression and hyperactivation of MAP kinase signaling, processes that in lower eukaryotes are affected by prions, play important roles in oncogenesis in humans. Prion phenomena in yeast appear to be influenced by stresses, and there is considerable evidence of the association of some amyloids with biologically positive functions. This suggests that if protein-only somatic inheritance exists in mammalian cells, it might contribute to cancer phenotypes. Here, we highlight evidence in the literature for an involvement of prion or prion-like mechanisms in cancer and how they may in the future be viewed as diagnostic markers and potential therapeutic targets.
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