Overcome the Challenges of Cancer Care. M. D. Rosenberg
checks and balances in a cell as well. For example, tumor suppressors stop the cell’s signal to keep growing. Just like the name implies, they suppress or stop tumors from forming. The most well-known tumor suppressor, p53, is known as the “guardian of the genome.”
Kicking Out the Business Partners:
The Cancer Takes Charge
The business owner in our example doesn’t realize anything is wrong! It’s annoying having the partners mess with their work. Therefore, the owner gets rid of the partners and runs the company alone.
Now that the partners are gone, there’s no one to stop the owner. The owner is clear to keep handing instructions down the chain of command.
In cell terms, the cancer cell gets rid of the tumor suppressors. This may be done through mutations. Once the cancer finds ways around the tumor suppressors, it’s free to do what it wants. This allows the cancer cell to focus on growing and dividing.
This is the basic process of cancer growth.
Cancer Orders In: Gorging on Sugar
For cancer cells to keep on growing, they need nutrients: sugar and oxygen (just like the rest of us). To help bring in extra supplies, cancer cells demand that the body form new blood vessels directed to the cancer. These vessels bring in sugar and oxygen.
The cancer cell uses sugar in an inefficient way. Because the cancer cell constantly needs energy, it must bring in and use lots of sugar—an endless process. In biology, this idea is called the Warburg effect (see glossary).
When looking for cancer cells, we use the Warburg effect to our advantage. A PET scan involves tracking a labeled sugar that is taken up by cancer cells. The labeled sugar shows up on our scans, helping us see where cancer may be located throughout the body.
I discuss PET scans in chapter 3, on diagnosis. Chapter 12 discusses whether cancer patients should avoid sugar in their diet.
Not Knowing When to Stop
Normal cells in your body have self-control. For example, if a normal cell senses damage to its DNA, the cell hits the stop button—it stops growing. This is called cell cycle arrest.
A cancer cell is like someone with a drinking problem that keeps getting worse. Each opportunity for the cell to divide is like another drink. These cells don’t know when to stop. Even if they’re sick or broke, they always ask for one more round. As cancer cells grow, they don’t care about damage or other tissues; all they care about is the chance to keep dividing. And just as continuing to drink can further hurt someone’s thinking, mutations can lead to more mutations and instability in the cell. More mutations may give cancer cells more advantages to grow over time.
The Unwelcome Houseguest: Cancer Moves In
If cancer stayed in one place, it would be way less scary. Unfortunately, cancer finds ways to move from one part of the body to the next. This movement is known as metastasis.
When trying to understand metastasis, think of cancer as an unwelcome houseguest. It invades your personal space, taking up precious resources like food without bringing anything positive in return.
The unwelcome guest crashes on the couch, eats all your food, and then asks for more! As cancer spreads to almost any part of the body (say, a bone or organ), it keeps on growing and dividing. There is no signal telling it to stop. Because of this, the cancer may interrupt the normal function of an organ or that part of the body. This is what makes cancer lethal.
Not all cancers are likely to spread. For example, many types of skin cancers rarely metastasize. Tumors that don’t spread may meet the definition of cancer (unchecked cell growth) but are much less likely to cause death.
Cancer Cells Don’t Age
As we grow older, we get wrinkles and show signs of time’s toll on our bodies. But cancer cells don’t play by the same rules; they do not age. Cancer cells can invade our organs and use our resources indefinitely.
If we grow cancer cells in a lab dish with appropriate nutrients, they’ll grow forever. On the other hand, if we do the same thing with normal cells (even with enough nutrients), they’ll eventually stop growing.
How do cancer cells do this?
When cells divide to make new cells, they lose a little bit of DNA each time. This is normal: to ensure you don’t lose anything important, DNA includes some scrap material. Protective ends of your DNA—called telomeres—help prevent damage to the necessary parts of the DNA. In normal cells, these protective ends get shorter with age (after each cell division). Just as tree rings give away the age of a tree, the shortening of telomeres gives away the age of a cell. Eventually, a normal cell can’t divide anymore as its telomeres get too short to protect DNA, and the cell dies.
Every cell produces a protein known as telomerase that repairs the DNA’s protective ends. In a cancer cell’s mutated DNA, more telomerase is produced than usual. This allows cancer cells to indefinitely protect their DNA ends and avoid the aging process.
Immune-System Evasion: Hiding in Plain Sight
Part of the immune system’s job is to look for any new cancers or precancerous cells and destroy them. This is happening all the time in our bodies.
In the human body, the immune system acts like the police. In fact, the immune system is always on patrol looking for cancer. But cancer cells have ways to keep the immune system from recognizing them. By avoiding the immune system, the cancer can keep on growing.
Cancer cells avoid the immune system by throwing up smoke screens. These cells can also get part of the immune system to help the cancer grow!
How does it do this? The cancer tricks another type of immune cell into destroying the immune cell that was going to destroy the cancer. This is kind of like when internal affairs arrests a good cop, preventing the cop from arresting the criminal (cancer).
Biology: The Big Picture
To summarize, cancer cells are just reflections of our normal cells. Information in cancer cells is moved from the nucleus (DNA) to other parts of the cell. Abnormal cell “thinking” leads to strange instructions being sent throughout the cell. A cancer cell’s only concern is getting enough oxygen and sugar to go on to its next cell division. Cancer cells may move into other areas of the body and take over—or metastasize—to get the necessary nutrients. Cancer can evade the immune system and overcome the aging process.
Now that you understand how cancer cells behave, we can use that information to help identify cancer. We’ll dive into the diagnosis of cancer in the next chapter.
Chapter 3
How Cancer Is Diagnosed
Cancer is sneaky, which can make diagnosing cancer a real challenge. Many of the symptoms of cancers are nonspecific, which means the symptoms could point to a lot of different diseases. Often, it’s hard to know whether cancer is the cause of any particular symptom. This can lead to significant delays in the diagnosis of cancer. These delays often make patients feel frustrated and angry.
Cancer cells are so closely related to normal cells that it can be hard to find the differences. To understand each patient’s cancer, doctors use information from biopsies, scans, and clinical exams. We use that information to stage a patient’s tumor. This allows us to make appropriate treatment decisions.
Screening for Cancer
Finding cancer can be difficult. Cancer can spread to other parts of the body, leading to vague symptoms. We want to catch cancer early, before it has