Cancer & Cell Cycle

How do cancer cells get past the checkpoints?

This is not an easy question to answer, because there are many ways that cancer cells seem to do it. Whatever the way is, it starts when a single cell finds itself capable of division without worrying about checkpoints. That can happen if a single cell undergoes some sort of mutation (a change in a gene). A mutation can occur through exposure to certain chemicals (like in smoke), exposure to ultraviolet radiation (from too much sun exposure), exposure to too many X-rays, or just from some error in the way the DNA divided in a previous cell division. Here are some of the types of mutations that can lead to cancer:

	mutation in a protein that makes up part of one of the checkpoints. Such a mutation would prevent the checkpoint from working properly, and so the cell could always pass the checkpoints.
	mutation in a protein that helps a cell realize that it has contacted another cell. Remember, membranes recognize and respond, so when they attach to other cells that can be a kind of recognition, and a response would be to not divide. So the proteins in the response would be messed up here.
	mutation in a protein that signals the checkpoint proteins that all is OK to divide. This would make the OK signal exist permanently.

Unfortunately, there are many, many proteins that could be involved for any of these steps. That is why it has been so hard to figure out how to fight cancer. Each person can have cancer for a different reason. Even if we had a genetic intervention (gene therapy, which we will talk about soon), we would have to figure out which one each person needed. This is a big task!

Right now, we are fighting cancer by surgery (physically removing the cells that don't know how to stop dividing), chemotherapy (to hinder cancer cell division and kill dividing cells), and radiation (to try to kill the cancer cells). These treatments are somewhat effective, but not entirely effective. New approaches are constantly under investigation as well.

How do cancer cells get past the checkpoints?

Last changed: January 21, 2007