Prions are those weird protein molecules that somehow destroy normal cells. they appear to be unstoppable-could their unusual properties be used to fight cancerous tumors? Suppose you could genetically alter a human prion to attack cancer cells-and ignore normal cells-could the prions be injected into a tumor and destroy it? or would such an approach be too dangerous? Are prions recognized as invaders by the immune system?
Prions, from what I remember, are proteins that are folded differently and have the incredible ability of altering other proteins to have the same folding. As to whether or not it could fight cancer… I doubt it. You’d have to have it target cancer cells specifically, and if you can do that, why bother with the prions? Cancer has many different causes, so even if you could manage to come up with a prion that targets malfunctioning proteins in cancer, it would only be useful for cancer that stems from that specific protein malfunction.
I don’t think prions have genes, so there can be no genetic altering of them.
Sure a prion (a thermodynamically favorable misfolded protein that catalyzes other proteins to misfold in the same thermodynamically favored) fashion could be used to fight cancer in the same way that 12 gauge shotguns, garbage disposals, autoclaves, and freefalls out of airplanes at 35,000 feet onto concrete can fight cancer.
Practically? I doubt it.
Very few prions have actually been identified. All of them are for proteins expressed in central nervous tissue.
To make an effective prion treatment against cancer you would need to identify a protein specific to cancer cells and then determine that there was some thermodynamically favorable orientation in existence that could fold other proteins in the same manner. All in all, about a snowballs chance in hell, and frankly you’d be better off using more conventional means to attack a protein that you know to be specific to a type of cancer. But it’s really the first part that’s the tricky part, and the real challenge in the second part is either targeting or modulating this attack on a given protein so that it doesn’t kill healthy cells.
Good luck.
Starting from the basics, the Central Dogma of Molecular Biology:
DNA encodes genes, which are transcribed to mRNA, which is translated to protein. A protein is a sequence of amino acids, each of which is specified by a sequence of three bases in the mRNA (3 bases = 1 codon). This sequence of amino acids then folds onto itself, forming a three-dimensional structure that actually carries out the function. This functional, three-dimensional structure is what I will refer to as a “protein”. (An unfolded string of amino acids is merely a “polypeptide”.)
Now then. The folding of a protein is kinetically, rather than thermodynamically controlled. Like all processes, it tends to the lowest reachable energy level. However, since the temperature and pressure in an organism are relatively constant, the determining factor in this process is the rate at which various parts of the protein fold. Keep this in mind - it’ll be important later.
Normally, there are additional mechanisms in the body (“chaperone proteins”) which ensure that the folding takes place correctly. It makes certain folds energetically favorable, and others energetically unfavorable. Once folded, the configuration is usually very stable, and unlikely to shift. (It occupies an “energy valley”). Prions break this property.
A prion is a protein that was misfolded in a very pernicious fashion. The normal functional configuration “slipped” into a new, pathogenic configuration. What’s important about this is that the pathogenic configuration is more thermodynamically stable than the normal configuration! This means that it occupies a lower energy state, and will actively resist any attempt to fold it back to the “normal” configuration. Secondly, and more perniciously, the pathogenic configuration actively catalyzes the conversion of “normal” proteins into prions. So one prion will turn a regular protein into another prion, making two prions. Two prions convert two regular proteins, making four prions. 8, 16, 32, 64…and on it goes.
So, to summarize: Normal gene makes normal mRNA, makes normal polypeptide, that folds a normal protein. Except sometimes, it misfolds and does this. The only gene that I know in mammals whose product can misfold like this is PrP, whose normal form (PrPc) can convert to the prion form (PrPsc).
Now, remember what I said about thermodynamic control? Prions, since they occupy a thermodynamically lower energy state than the natural form of the protein, can resist denaturing. You can cook prions in an autoclave (high heat and pressure) and not destroy their pathogenicity. This property, you see, is entirely a function of their structure, and their structure is very stable.
Protein folding, the heart of this problem, is currently being intensively studied. We can’t just simulate it at the atomic level - the process takes too long to be feasibly simulatable, and current approximations are insufficient. (An aside: I’ve done molecular dynamics simulations. The usual time-step they use is 1-2 picoseconds. A protein folds on a timescale of microseconds. For a decently-sized system, a nanosecond of activity takes a day or two to compute on a 50-CPU cluster. A microsecond would take a thousand times as long to compute. We’re looking at a century of CPU-time to fold one protein.) Once we understand how proteins fold, and how you can convince a protein that a certain shape is a more kinetically-favorable one, we can start trying to understand how PrPsc, when associated with PrPc, makes a molecule of PrPc convert to another PrPsc molecule.
Now, to your question: Prions are quite difficult to target using the immune system. Remember, they have the same sequence as the normal protein, just a different conformation. There have been monoclonal antibodies synthesized for prions, and some vaccination experiments are being done in mice, but by definition this is very touch-and-go - you have to be very careful to target ONLY the prion, and not the natural epitope, because otherwise, you’ll just induce the disease by autoimmune response.
That said, cancer isn’t really something you can target with this. Prions are very indiscriminate. Current cancer therapies either target cancer spatially (for example, radiotherapy) or kinetically (introducing metabolic poisons that affect cancer because cancer metabolism is faster than surrounding tissue). Prions would only work if the cancer - and only the cancer - expressed a certain protein, we could somehow figure out how to induce a prion-state in that protein, and we could introduce it back into the body. Cancers may express proteins that cells of their lineage don’t naturally express, but it’s a sure bet that the proteins are expressed by some cells, somewhere in the body. Attacking those proteins may cause more harm than good, and prions, once injected, are a lot of trouble to get rid of. Secondly, we’d need to be able to induce prion-state in arbitrary proteins - a very difficult proposition, since we don’t really understand protein folding too well.
So, in short…no. Prions may be unstoppable, but that’s a bad thing in this case. Honestly, you’re better off using antimatter.
And threemae wins with a demonstration of how elegant is better than exhaustive. 
Anyone else think the title said 'Could PRON be used to fight cancer?"
Possibly in the fight against prostate cancer 
Si
We make medical research fun!
No, your explanation was exceptional. Especially for someone a little unclear on how a certain folding pattern could be more thermodynamically stable than another.