The media is going overboard coving the measles virus being used to cure, or at least treat, cancer. Well, they should but they don't explain things very well. I thought this could be a useful place for me to speak up and present a very informal education that covers the biology needed to understand what these scientists are doing to these viruses and why.
Genetics and Cancer
We've all heard of DNA, but it's not often explained what it does. Very simply, one of it's necessary functions is to tell cells how to put molecules together that are necessary for the cell and organism to survive. RNA is used to take a copy of the "instructions" to whatever part of the cell is responsible for production of that molecule. Tumors and cancers usually have an increased replication rate, so those cells divide like bunnies procreate. This takes the space and resources healthy cells need, so healthy cells get starved or bred out. When the cancer stops enough healthy cells from functioning complications occur. When a cancer metastasizes, cancer cells have made it to the bloodstream, and can now start dividing wherever blood goes, namely anywhere.
Viruses, Vaccines, and Cells
Viruses are like little hit-men, not an invading army. Each "hit-man" is called a virion. On a molecular level, cells and other microscopic organisms are like jigsaw puzzle pieces. If the pieces don't match up, they don't merge. Each virus is very specific about what cell it will attach to. For example HIV merges with T-Cells, which are kind of the bodies warning system that something foreign has come to visit, so the virus in essence takes out the "alarm."
Once these hit-men find their target cell, they "poison them," with DNA or RNA, and become inert. This now makes the cell a slave, the production centers start making more virions. Eventually the cell will die or burst and release all the new hit-men to poison other cells. Viruses are simple, they "live," inject a cell, "die."
Vaccines, try to take the inert virions which are really just shells that do nothing anymore. By injecting the dead virions in someone, they won't get the virus. That doesn't mean you won't get sick. Getting sick is the body's response to foreign particles, and when you get inoculated, there are definitely foreign particles. You just don't have the virus spreading its poison and replicating.
Antigens and Antibodies
Remember how microscopic organisms act like jigsaw puzzles, this is where antigens come in. An antigen is a specific identifier on a microscopic unit. This is why you can't give B blood to anyone who isn't B or AB. Different antigens. It's like B blood cells wear a top hat, and A blood cells wear a cowboy hat. In a person with type B blood, anything not wearing a top hat is foreign and needs to be removed. The hats represent the antigen of the cell or particle. Same thing with viruses, they each wear a different hat.
Antibodies are like bouncers, they check hats to make sure it's the appropriate type. If it's not, there's a fight going down. The trick is, if a new hat comes in, it takes time to train a new bouncer to identify it. That's the point of vaccines, to train the bouncers before the wild virus can show up, so it can be taken out quicker.What sucks about cancer cells, is they are from you, so antibodies can't distinguish them.
Modified Viruses and Treatment
Remember the inert virions? The plan with modifying viruses, is to have them deliver what WE want to just cancer cells. So now we have hit-men going specifically, or mostly, after the cancer cells with minimum damage to the healthy ones. This could be modified DNA, chemotherapy, literally anything we can fit inside the virion. Like a Trojan Horse, everything says it's a virus until it injects it's payload. Right now the purpose is to kill cancer cells. As this advances we could possibly "fix" cancer cells and make them healthy again.
The difficulty here is every cancer is different as far as jigsaw and antigens. This isn't saying lung cancer being different from liver cancer. Cancer is a random change to a cell, literally it's a mutated cell. So cancer of the same organ from two different people can have nothing in common, and each requiring a different virus.
Now, those bouncers still won't like this version of the virus. So it's effectiveness will vary depending on the virus, and if the person has been inoculated or infected previously. That would be why an excess amount of virions would be required. Our bodies are actually trying to protect the cancer cells from the virus. The more times it's administered, the better our body gets at stopping it, this is why some vaccines have multiple shots spaced out.
The problem with cancer is it came from the person diagnosed. If it mutated to look foreign to the body, it would be killed by the immune system, and it couldn't grow. Current treatments are excission, targeted radiation, or chemotherapy. The only truly targeted method is cutting it out, but if one cell isn't removed, the cancer comes back. Yes ONE cell is all it takes, that's how it started, one cell mutated. Cutting out the cancer also runs the risk of letting a cell escape to another part of the body.
This is why radiation and chemotherapy are used so widely. To kill every cell. It's targeted as much as possible, but both kill and damage healthy cells in the process. We have no cure for cancer, and those who never relapse, really got the luck of the draw. One cell survives and cancer comes back, that's why the term remission. We can't see if that one cell is still there to honestly say cured. We cannot operate on a microscopic level, so we need to "train" or make something to do it for us. Virotherapy is just one method being developed to try and take this fight where we cannot go ourselves.