Okay, so I've not taken Biology or Chemistry yet, so this is probably impossible in real life (or else it would have been tried already). Please don't kill me or flame me for my ignorance, I'm just trying to get feedback on my idea.
My idea is basically this: We could take samples of at least 2000 people’s cancer tissues, and sequence the DNA from that. Then we could sequence the DNA of the same peoples’ healthy tissues and compare the two sequences in each case. Then we could compare the differences among all of the comparisons and see what the common variable is. One we find what causes cancer, we can create an artificial protein to destroy it. Then the protein is administered in a saline solution into the site of the cancer, which should kill it.
Like I said, it's probably either impossible or impractical.... Or it would have been tried already. I'm just trying to share my ideas though. Please don't hate on me for my comparative ignorance to the rest of you.