[pyrogyn]

I'm no expert, but it's an incredibly complex process. One of the things about cancer cells is that they mutate at an amazingly fast rate because they are constantly multiplying and dividing, and so it can be difficult to target just a single gene that is responsible for transformation from a normal cell to a cancerous cell. Unfortunately as well, we may be able to tell that a particular gene has been mutated in such a way that it leads to overexpression of X, but it's often not just the overexpression of a gene, it's often the mutation of some enzyme that blocks another protein that will serve as a repressor of some other gene. There's immense bodies of research, but there's a ton that we simply just don't know yet.