Re: how does brain cancer affect cell mitosis

Chris-

     In a nutshell, brain cancer (or any other cancer) is caused by an unregulated level of mitosis in the cancerous cells. I'll explain a few of the nuts and bolts of cancer, and then briefly talk about brain cancers in general.

     Normally, most cells in your body divide at a particular rate. Some cells may divide faster than others, depending on where they are (i.e. liver versus skin versus brain). But before a cell divides, it has to replicate its DNA (make 2 copies, one for each future cell) and grow big enough to split into two easily enough. The process which regulates how the cell knows when it is large enough and its DNA is fully replicated is called the cell cycle (some details can be found here). The cell cycle dictates the order of how things are to be made and replicated, and but also if the cell should continue dividing or not. The reasons a cell might stop dividing is a) because there's not enough food or energy around, or b) because it got a signal not to divide (like at the outer surface of an organ - we don't want our stomach to grow and grow and grow!). I won't go into the nitty gritty details here (you can find them in any biology text, and even online). The main point is that, normall, cell division is very closely regulated. Your body wants to keep all different cell types in line.

     Occasionally, a cell loses the ability to respond to signals that say "stop dividing!" When that happens, we say that cell is cancerous. And as it keeps dividing, the resulting cells are cancerous, and they keep dividing. If this happens enough and these cells are able to evade the immune system, a tumor will develop.

     When we consider brain tumors specifically, we need to consider the different cell types in the brain. There are neurons, supporting cells called glia and a few other types. Neurons, for the most part, do not divide, and thus do not generally form tumors. Many of the tumors (as you can see here) are formed from glial cells which divide out of control. So two big points emerge about brain tumors: a) some cells - glia - in your brain do divide, and b) those are the cells that form brain tumors.

     I hope that answers your question. You can find more information about brain cancers in the links below.

-Alex G
cgoddard@fas.harvard.edu

links:

http://www.nlm. nih.gov/medlineplus/braincancer.html

http://www.cancer.gov/cancerinfo/