Cancer cells differ from normal cells in the body in many ways. Normal cells become cancerous when a series of mutations cause cells to continue growing and dividing out of control. In this way, cancer cells achieve a kind of immortality.
Also, unlike normal cells that remain in the area where they started, cancer cells have the ability to invade nearby tissues and spread to distant areas of the body.
This article explains how cancer cells develop, some of the ways cancer cells differ from normal cells, and why the body may not recognize cancer cells and destroy them like other “foreign” cells.
There are as many types of cancer cells as there are types of cancer. Of the more than one hundred cancers, most are named after the type of cancer cell in which the disease begins. E.g:
- Carcinomas are cancers that arise in the epithelial cells that line the body cavity.
- Sarcomas occur in Mesenchymal Cells in bones, muscles, blood vessels, and other tissues.
- Leukemia, lymphoma, and myeloma are blood-related cancers that originate in the bone marrow (leukemia and multiple myeloma) or lymphoid tissue (lymphoma). They are “fed” by nutrients in the blood and lymph fluid, so they do not need to form tumors.
Just as cancers can behave differently from each other, not all cancer cells behave the same way.
Causes and Risk Factors of Leukemia
How do they get started?
Cancer cells through a series of genetic and Epigenetic (or environment-induced) changes. Some of these changes may be inherited or, more commonly, caused by carcinogens (carcinogens) in the environment.
In general, solid tumors contain multiple mutations (also called variants, representing changes from the original). Interestingly, the metastatic process, which is responsible for the high mortality in advanced cancers, is thought to be primarily caused by epigenetic changes, as no specific genetic alterations were found in metastases.
It helps explain genetic susceptibility to cancer. Genetic susceptibility doesn’t mean you’ll get cancer, but if some mutations are already present, fewer acquired mutations may be needed for a cell to become cancerous.
The process by which normal cells become cancerous usually goes through stages in which the cells gradually become more abnormal in appearance. These stages may include precancerous hyperplasia (enlargement) and dysplasia (abnormal growth).
Sometimes this process is described as differentiation. Early on, the cells may look a lot like normal cells in the organ or tissue. As the progression continued, the cells became increasingly undifferentiated. This is why sometimes the original source of cancer cannot be determined.
If you have a family history of cancer, you are never “destined” for cancer. Cancer is a disease caused by a combination of factors (also called multifactorial). Lifestyle and environmental factors will also play a role.
what makes them divide and grow
A cancer cell can have thousands of mutations, but only a certain number of these genetic changes in a cancer cell cause the cancer to divide and grow. Mutations that cause cancer cells to grow are called “driver mutations,” while other mutations are considered “passenger mutations.”
Normal genes that help cells grow, called proto-oncogenes, can become “oncogenes” (or genes that can cause cancer) when mutated and encode proteins that drive cancer growth. In contrast, tumor suppressor genes are genes inside cells that tell cells to slow down and stop growing and repair damaged DNA. They tell cells when to die.
Most cancer cells have mutations in oncogenes and tumor suppressor genes that drive their behavior.
Cancer cells and normal cells
There are many important differences between cancer cells and normal cells. Some of these include:
- Growth: Normal cells grow during developmental stages, such as during childhood, or repair damaged tissue. Cancer cells continue to grow (reproduce) even when no more cells are needed. Cancer cells also can’t hear the signals telling them to stop growing or “cell suicide” (apoptosis) when cells get old or damaged.
- The ability to invade nearby tissue: Normal cells respond to signals from other cells that tell them they have reached the border. Cancer cells do not respond to these signals and extend into nearby tissue, often with finger-like protrusions. This is one reason why it is difficult to surgically remove cancerous tumors.
- The ability to spread (transfer) to other parts of the body: Normal cells produce substances called adhesion molecules that make them stick to nearby cells. Some cancer cells lack the stickiness caused by these adhesion molecules and can break free and float to other parts of the body. They may spread to nearby tissues or travel through the blood and lymphatic systems to areas of the body far away from the original cancer cells. For example, lung cancer cells may spread (or metastasize) to the lymph nodes, brain, liver, or bones.
- Immortality: Most normal cells, like humans, have a finite lifespan. When they reach a certain age, they die. Cancer cells, by contrast, have developed a way to fight death. At the ends of our chromosomes are structures called telomeres. Every time a cell divides, its telomeres get shorter. When telomeres become short enough, cells die. Cancer cells have found a way to restore their telomeres so they don’t continue to shorten as cells divide. And just like that, they became immortal.
The ability to invade and metastasize is important for distinguishing cancer cells from normal healthy cells, but there are many other important distinctions:
likely to continue to grow
May invade nearby tissues
May spread to other parts of the body
can live forever
grow when needed
stay within organizational boundaries
sticks to nearby cells
have a defined lifespan
Why doesn’t the body recognize cancer cells as abnormal and destroy them?
A good question is, “Why can’t our bodies recognize and remove cancer cells the way bacteria or viruses do?” The answer is that most cancer cells are indeed detected and removed by our immune system. Cells in our immune cells called natural killer cells are responsible for finding abnormal cells so they can be cleared by other cells in our immune system. Cancer cells remain viable either by evading detection (they disguise themselves in different ways) or by deactivating immune cells that emerge.
The ability of the immune system to recognize and eliminate cancer cells is thought to be responsible for the uncommon but well-documented phenomenon that causes some cancers to go away on their own without treatment, such as spontaneous remission of cancer. This process is also at the crux of cancer. The new field of cancer treatment is called immunotherapy.
The word “cancer” comes from the Greek carcinogen, It means crab. Hippocrates chose this term because he saw similarities between the claw-like extensions (invading nearby tissues) of crabs and cancer.
Cancer cells are constantly changing
Once cancer forms, cells don’t stay the same. Instead, persistent mutations may occur. This is what causes resistance to chemotherapy and targeted therapy drugs. Cancer cells develop a mutation that allows them to bypass the damaging effects of these treatments.
Changes in cancer cells are very important in treatment. For example, estrogen receptor-positive breast cancer may be estrogen receptor-negative when it recurs or spreads. It also helps explain why cancer cells may be different in different parts of a tumor. This is called “heterogeneity” and is important in diagnosis and treatment.
What it means if you have precancerous cells
How are cancer cells different from precancerous cells?
Precancerous cells may look abnormal and resemble cancer cells, but are distinguished from cancer cells by their behavior. Unlike cancer cells, precancerous cells do not have the ability to spread (metastasize) to other parts of the body.
An often confusing condition is carcinoma in situ (CIS). It consists of abnormally changed cells found in cancer cells. But since they haven’t spread to where they were (or, technically, beyond something called the basement membrane), they’re not technically cancer. Because CIS can turn into cancer, it is often considered an early stage cancer.
Consider an analogy
Many doctors liken cancer cells to a car with the accelerator stuck in the down position. Meanwhile, the brakes don’t work (meaning the cells don’t respond to tumor suppressor proteins.)
You can take this analogy one step further. The invasion of cancer cells can be seen as a car breaking through the front door of a gated community. Normal cells respond to signals from neighboring cells that say, “This is my border; stay outside.”
But cancer cells are the offenders. They join other cancer cells and spread to other communities, like crime. But despite its threat, crime has not taken over America, again, there are many “police” (checkpoints) that keep most of the cells of the body in line.
Believe it or not, normal cells actually have a hard time turning into cancer cells. It must be abnormal in the way that it promotes growth, inhibits repair and death, ignores signals from neighbors, and achieves some form of immortality. This is why cancer is not caused by a single mutation, but by a series of mutations.
Considering the billions of cells that divide in our bodies every day, there are bound to be problems at some point. It does, serving more than 1.6 million Americans each year. They were diagnosed with cancer.
There are as many types of cancer cells as there are types of cancer. Of the more than a hundred cancers, most are named after the type of cancer cell in which they started. Cancer cells emerge through a series of genetic and environment-induced changes. The process by which normal cells become cancerous usually goes through stages in which the cells gradually become more abnormal in appearance. But this is just the beginning. Cancer cells differ from normal cells by their ability to spread, invade nearby tissues, and “live” permanently. They can do this by evading detection (they disguise themselves differently) or by deactivating immune cells that come to the rescue. Once cancer forms, cells don’t stay the same. Instead, persistent mutations may occur. This is what causes resistance to chemotherapy and targeted therapy drugs.
For a disease with such dire connotations, cancer can be fascinating — research. Whatever your motivation for studying cancer cells, keep in mind that your healthcare provider can be a great resource. Ask them to recommend books or articles that will give you an idea of what has long been one of the leading and most baffling causes of death in the United States.
Frequently Asked Questions
What is cancer?
Cancer is a disease that occurs when cells become abnormal and out of control. Normal cells grow — and then die — when they receive a signal. Cancer cells ignore these signals and continue to multiply. Cancer cells can also form tumors at the original site and then spread and form new tumors elsewhere.
How does cancer start?
Cancer cells start to form when genes, which are made of DNA, undergo certain changes or mutations that cause cells to behave abnormally. These changes may be due to external factors such as tobacco smoke and UV light. Mutations can be inherited or completely random.