Video Transcript: The Cell Cycle and Cancer

The Cell Cycle and Cancer

Today's topic is the cell cycle and mitosis. But before we get into the cell cycle and mitosis, we want to make sure and talk about why these words are important, and how they relate to real life.

So if I say the word cancer, this word probably mean something to you, either you know, somebody who's been diagnosed with cancer, or you've heard about it on the news. There's many different types of cancers, but one thing they all have in common is that they are caused by uncontrolled cell growth, that means somebody's own cells grow out of control. Now, that doesn't mean that there aren't other contributing factors. For example, for some cancers, having genetic links, meaning it runs in the family, can make somebody more likely to develop it, or having excessive exposure to UV light. For some cancers, those are risk factors that can increase your risk. But the major cause of cancer is uncontrolled cell growth. That also means it's something that is not contagious. And it's something that anyone can develop. 

You have to realize that all the cells in your body are very, very busy, and they're either in one of two different phases, they are either in a phase called interphase. During interphase, they are just growing, they're replicating their DNA, they're doing their cell functions. Or they are in mitosis. Mitosis is a fancy word, that means that they are dividing, they are making new cells. Well, if you think about the cell cycle, whether they're in interphase, or mitosis, is kind of like a pie graph. They're spending about 90% of their time in interface. Most of the time, cells are not dividing. Most of the time cells are an interface, they're growing, they're doing their daily cell functions, and they're replicating their DNA, most of the time, cells are not dividing.

Now, depending on what kind of cell it might do mitosis more or less often, for example, your hair follicle cells, they do mitosis frequently, which is why your hair can grow up to half an inch every month. But other cells, like for example, your brain cells, your neurons, some of them actually do not perform mitosis, which is why if you have some type of major injury to the spinal cord, or to the brain, sometimes those do not heal very well, because those cells, they do not replicate. So miosis is very important in order to generate new cells, which can help with growth. Also if you damage your cells, if you're walking down the street, and you have some kind of accident, and you skin, your knee, what you're going to need to repair those damaged cells, you're going to need to be able to do mitosis to make those new cells.

The thing is, you don't want your cells to always be doing mitosis, because if they're always doing mitosis, then they're always dividing, and then they're not carrying out their actual function. And that's a problem. That's where checkpoints come in handy. Along the cell cycle, there are checkpoints to check that the cell is growing correctly, and replicating its DNA correctly, and doing everything it's supposed to do correctly before it divides. And what happens if the cell fails its checkpoint, the cell does something called apoptosis, which basically means the cell destroys itself: it self-destructs. This might seem kind of harsh, but actually, it's really important because it ensures that you don't have the cells that are messed up, continue on and divide: you don't want damaged cells to continue on divide, because they might not do what they're supposed to, they might start to grow out of control, they might not be regulated correctly. That's where cancer cells come in. See, cancer cells, as we had said, are your body's own cells that are growing out of control. They're not following the rules of these checkpoints. They're flying past the checkpoints going through the cell cycle, and frequently doing mitosis, which means that they're dividing very, very often. And by doing that, they can grow into these things called tumors, which are really a mass of cancer cells. We're not really sure what causes them to escape these checkpoints. There's a lot of risk factors that can that a person can have that can increase their risk of this happening. But when these cells get past these checkpoints and grow out of control, they become a problem because many times they can travel through the bloodstream, they start growing out of control, the body can't identify them and destroy them with the immune system. This becomes an issue and usually One of the treatments that somebody who has cancer will undergo is chemotherapy. This works by targeting cells that go through the cell cycle quickly and hit mitosis quickly. And that's one reason why somebody often will lose their hair when they're on chemotherapy, because they're on this medication that's targeting fast growing cells and your hair follicle cells are also fast-growing cells. Cancer cells have some other factors that make them difficult to treat. One is that cancers have the ability to secrete their own growth hormone.

This is very bad. Because growth hormone in a sense, think of it is a hormone that says, feed me. And what happens is the blood vessels will divert over to those cancer cells and supply the cancer cells with nutrients. This is not good, because this means the cancer cells will have the nutrients they need to keep growing out of control. It also can take nutrients away from nearby healthy cells. There's some medications that are being researched, that maybe could stop the growth hormone from cancer cells. And in a sense, that would be great because the cancer cells would not be able to get the nutrients to grow out of control. And the more of course, you have to make sure that the medication is targeting just the cancer cells, and that you're not you're not affecting the growth hormone of nearby healthy cells, you wouldn't want that. So it's kind of a tricky situation. Let's recap what we talked about today. We talked about the cell cycle, how cells are more frequently in interphase, than they are mitosis. Interphase is when cells are replicating their DNA, or their growing, carrying out cell processes. In mitosis, the cells are actually dividing. We talked about how during the cell cycle, there's checkpoints that regulate the cell and keep the cell from being able to continue on if it's damaged. Unless we're talking about cancer cells, which are cells that have escaped the checkpoint and are growing out of control. Be sure to check out our clip on mitosis. This process is really fascinating, but it's also really important one in order to understand how your body cells work, that's it for the amoeba sisters, and we remind you to stay curious