Health Care 1/22/2021

How does cancer grow?

Hallmarks of Cancer

This course will help you understand the hallmarks of cancer, how cancer overcomes the body’s defenses to grow, and how it can be treated.

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Shaundra has just received scary news. She has developed cancer.

Shaundra goes to a doctor who treats cancer. The oncologist explains that cancer happens when cells, tiny units that make the body work, grow out of control.

Shaundra’s oncologist orders a series of tests to determine the best treatment plan for her. But while she waits, she has a lot of questions.

How did her body allow these cancer cells to grow? Her body has fought off bacteria and viruses before. Why didn’t it fight off the cancer cells?

Cancer cells aren’t invaders, like bacteria or a virus. The cancer in Shaundra’s body grew from her own cells.

Shaundra feels that her cells are turning against her. But most of her cells are actually cancer-fighting champions.

Shaundra’s oncologist explains: Her body has worked very hard to keep cancer cells in check. Only one very sneaky unruly cell likely started the path toward cancer.

We all have many defenses that unruly cells must overcome on their way to becoming cancer.

A cell has controls for everything, from growing to dividing. But these controls can be broken by gene mutations. Genes are pieces of DNA that have specific functions in the body.

Researchers have learned of many common gene mutations in cancer. They’ve developed some drugs that only affect cancer cells with certain mutations.

Tumor suppressors are an example of genes that are commonly mutated in cancer. These genes normally tell cells to stop growing.

But with tumor suppressors out of the way, cancer cells can grow and divide when they shouldn’t, without the body’s permission.

A normal cell can only divide around 60 times. Cancer cells can divide as many times as they want, basically becoming “immortal”.

So how can we stop cancer cells that are growing and dividing out of control? It’s more difficult than it would seem, because cancer cells are sneaky.

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Shaundra’s oncologist might decide to have her undergo radiation therapy or chemotherapy. These treatments can destroy dividing cells - including cancer cells.

But cancer cells don’t just sneak by genes that control cell growth and division. They learn to sneak by other defenses as well.

A cell with too many gene mutations should trigger the body’s natural clean-up crew, the immune system. Immune cells fight off and destroy invaders and rogue cells.

But Shaundra’s immune system has a difficult time finding the cancer cells. Why? First, the cancer cells started as her own cells, making them difficult to tell apart from healthy cells.

But cancer cells are also able to mask themselves, hiding from Shaundra’s immune system.

Cancer cells with mutated tumor suppressors and other genes find ways to avoid the body’s immune system, giving them more time to divide and grow.

Cancer researchers today are looking for ways to kickstart the immune system so that it becomes more active and can mount an attack against cancer. This is known as immunotherapy.

Early detection and treatment of cancer is critical because as cancer grows, hidden from the immune system, it can become more difficult to treat.

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As cancers get larger, they start to affect the area around them.

Cancers recruit blood vessels and promote inflammation all in an effort to help get the oxygen they need to keep growing.

One of the scariest things about cancer is its ability to spread to other parts of the body.

If left unchecked, other cancerous tumors could start growing far away from where the cancer first started.

Thanks to Shaundra’s regular checkups, doctors found her cancer early. Her oncologist explains: Her body has worked very hard to keep the cancer cells in check. Now it needs extra help.

Shaundra’s care team has a plan to fight back. They run tests to see exactly how cancer cells are avoiding her body’s natural defenses.

Because the cancer in Shaundra’s body was trying to grow fast, it was disorganized and sloppy.

Cancer cells’ gene mutations may help them grow, divide, survive and spread. But they can also be points of weakness that doctors can treat.

Knowing the specific weaknesses of the cancer cells in Shaundra’s body will help her and her care team decide on the best treatment plan.

Shaundra is a champion. Her body fights alongside the care team’s treatment against the cancer. Together, they work until the cancer is gone.

Every cancer is unique. But the things that cancers have in common can help care teams choose treatments that work best.


In 2011, cancer researchers Douglas Hanahan and Robert Weinberg wrote a paper called the Hallmarks of Cancer: The Next Generation, which summarizes the abilities that cancers get as they advance. These hallmarks are used by cancer researchers as a groundwork for understanding how cancers work and how to better treat them.
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