The age of the retrovirus is quickly approaching as more and more is understood about the process of cellular replication. A virus is simply a means of describing a class of organelles which are neither living nor inanimate, they are a parasitic capsule which usually encapsulates a strand of code, and the means with which to 'inject' it into a host cell. The virus is usually nothing more than a protein capsule with a receptor site that can attach it to specific cells. This follows the lock and key theory of protein receptor sites on cell membranes whereby the viral receptor is a sort of key that will open a transport across the membrane and allow the viral RNA to enter the cell. Of course this is a very simplistic description of how the virus operates but bear with me. Once the alien code is inserted into the cell it will begin to infiltrate the cell's functionality whereby its code will tell the cell to make copies of the virus. The hijacked cell will begin churning out as many of the viral copies as it can though they are usually still trapped inside the cell, eventually causing the cell to die as it bursts open releasing the copies.
Now to engineer a virus we need to overcome several conditions, the appropriate receptor site is needed to access the correct cells and only those cells as we will also need a method for killing them. This is one means of attempting to kill cancer cells without harming the rest of the body, but it relies on there being some distinct transport in the cell membrane which is rather unlikely as cancer cells come from your body, thus this approach is more suited to bacterial infections and such. The other way is to determine what is happening inside the cell itself. We would need to mutate a set of enzymes like helicase and ligase and a few more in order to open the dna, recognize a specific mutated sequence and remove it and reseal the dna. Now as anyone might start to notice this is getting to be ungodly difficult in even the theoretical realm. The complexity alone of the enzymes is still somewhat of a mystery as to how they fold and function. But with programs like [email protected] we are learning how to build and manipulate the functions of many proteins and enzymes. The idea for the recognition system is overly simplistic compared to what is really needed but lets imagine that we have our enzymes already recognizing specific sequences of dna, which we already do, start and stop codons are semi simple and the other amino acids are relatively easy to model, now we have to extend the recognition enzyme further than a single codon, we will probably need on the order of 20 to 30 amino acids in the chain for proper recognition instead of just the one. then we can tailor the sequence to be recognized and removed based on the mutation that caused the cancer.
This is all well and good and seems around the corner but the possibility of causing mutations elsewhere is far too great. Any random sequence of dna is likely to appear in several places just by the laws of large numbers. Most dna is structured into sequences of STR's and MTR's, which lessens the randomness of the data but not enough to be sure. Further there is the problem of how to remove or destroy the mutated enzymes once you are done as well as how to remove the rogue strand of dna which it removed. Most mutations come from pieces of dna swapping places with other strands and if this cancer mutation is present then what is going to stop it from happening again? We are far from a real solution but there is promise and the current progress may take us there, but the research will go into many more applications than cancer.
The most notable application of the retrovirus is literally the fountain of youth. As dna ages, some of the amino acids eventually break down into other codons of the same amino acid. Acting sort of like a clock if you will, with each division of the cell a sequence of amino acids may break down one at a time giving the cell a sort of death clock. It would also serve to specialize the cell's along their way but if it could be reset by some amount we may soon see the first generation to never die.