It’s Tuesday folks! That means the New York Times’, “Science Times” came out today. Here’s one article you should know about:
Cancer’s Random Assault
Denise Grady wrote a great article on cancer, discussing a recent paper in Science (the Grey Goose of scientific journals) that suggests the onset of cancer is due more to “genetic mutations” than to “environmental factors”. However, she kind of glosses over the main point that this scientific paper is trying to make. I’m here to explain to you what that paper really meant.
Curiously, cancer occurs in some tissues WAY more often than in others. You’ve heard of skin cancer right? What about penile cancer? Probably not, its very rare. These authors say there’s a reason for that: “genetic mutations”. Their hypothesis for the study was quite simple; the more a cell divides, the more likely it is to accrue a mutation that leads to cancer. To be honest, this makes loads of sense, and here’s why:
Let’s say I’m your boss and I’m feeling especially mean today. I hand you a printed-out essay and tell you to type it up in a Word document. Reluctantly, you grab the paper and start going to town, copying the letters on the papers into letters on the screen. You’re a pretty good typist, moving quickly and without making too many errors. But alas, you will eventually make a typo. This same sort of thing occurs when a cell is trying to copy DNA. Except cells are way better at copying letters than you are at typing (only one mistake gets by for about every 10,000,000,000 letters copied).
The real point is, if I never told you to copy that paper, would you have made that mistake? Of course not, you can’t make a typo if you aren’t typing. Similarly, the body can only introduce mistakes into your DNA when it copies them (not entirely true, but we’ll come back to that). So the authors are simply saying that in tissues where the cells have to replicate themselves more often, you’re going to have higher cancer rates. And using complicated statistical analyses, they show that this is in fact true. Moreover, they show that the correlation between rate of division and cancer incidence is much much stronger than it is between cancer incidence and any given environmental factor (e.g. smoking).
Right, so about that lie. Well, DNA mutations can take place for reasons other than “spelling errors”. For example, UV exposure actually alters the chemical structure of DNA. Meanwhile, cigarette smoke contains compounds that cause your cellular machinery to make more mistakes when replicating. So at the end of the day, cancer is very much (2/3 according to the paper) due to what the authors call “bad luck” or “genetic mutations”. But you can also help your cells not make mistakes (that could lead to cancer-causing mutations) by eating healthy, exercising, wearing sunscreen, and not smoking (among many other things).
And that is what they were trying to convey in this paper.