Apoptosis in the Cell Cycle & Cancer

Instructor: Betsy Chesnutt

Betsy teaches college physics, biology, and engineering and has a Ph.D. in Biomedical Engineering

Learn about natural cell death, called apoptosis, in normal cells and cancer cells, as well as treatments that are being developed to treat cancer by controlling apoptosis.

What is Apoptosis?

Throughout your life, the cells in your body are constantly dividing and reproducing to keep you alive and healthy. However, you may have noticed that you don't keep growing and growing forever. Why not?

As new cells are produced, the older ones undergo a series of biochemical changes that cause them to die and be reabsorbed into your body. This process is called programmed cell death, or apoptosis.

Cell apoptosis is carefully regulated by your body to remove damaged cells or cells that are simply no longer needed, but in some cases, something goes wrong and you can have too much or too little apoptosis. Both of these can be very dangerous! Before we see what happens when apoptosis gets out of control, let's talk a little more about how and why apoptosis occurs in normal, healthy tissue.

Process of Apoptosis

Sometimes your cells are damaged by infections, radiation, nutrient deficiencies, or some other type of trauma. In other cases, cells have simply lived out their lifetimes and must die in order for new cells to take their place. In both of these situations, the affected cell will then start a process known as apoptosis that will ultimately lead to its death.

To start the process of apoptosis, proteins called caspases are activated and trigger a series of events that cause the structure of the cell to break down. This can occur inside or outside the cell. Eventually, the cell membrane disintegrates and the nucleus breaks up. Then all the pieces of the cell are eaten by other cells called phagocytes so that they can be recycled into new cells.

During apoptosis, the cell dies and breaks up. Apoptosis can be triggered by proteins that originate inside or outside of the cell, but the result is the same: the cell breaks down and is eventually recycled by phagocytes.
apoptosis diagram

Apoptosis is a normal part of the life cycle of a cell, and it helps your body work efficiently and stay healthy. Scientists are learning more about how apoptosis occurs and is regulated. With a better understanding, we can develop treatments for conditions that result from impairment in apoptosis.

Apoptosis and Cancer

What would happen if your cells didn't undergo apoptosis but just continued to divide and grow? Although we often think living forever would be great, it is definitely NOT great when it happens to your cells. When damaged cells continually divide and do not undergo normal apoptosis, the result is cancer.

Although many things go wrong to make a cell turn into a cancer cell, one of the most important is deregulation of the process of apoptosis. A cancerous tumor occurs when cell division gets out of control and the mechanisms that regulate apoptosis stop working correctly. The tumor cells divide rapidly, invading and crowding out normal, healthy tissues and organs.

apoptosis and cancer

Cancer Treatments that Target Apoptosis

The majority of current cancer treatments seek to limit the ability of cells to proliferate. These treatments can have devastating side effects for the patient because other cells that divide rapidly like blood cells and hair cells can also be destroyed.

Healthy cells are also damaged by traditional cancer treatments like chemotherapy, causing patients to lose their hair and be unable to produce blood cells.
Cancer patient with his nurse

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