Cancer is a multifactorial disease, meaning that a variety of factors contribute to tumor growth.
We can’t point out a single reason, but it is also true that some types of cancer run down in families. Thus, a genetic cause is very likely in these cases.
But how does that work? Are we programmed to get cancer since the day we are born?
In this article, you will see that genetic problems are widespread in cancer. It is not only reserved to a hereditary cancer syndrome.
Still, we will also address different types of inherited genetic mutations and tell you how they work.
How genes work
First off, it is important to define what is a gene and how it works.
The DNA contains genetic material that makes up the blueprint of how the body looks and how it works. However, it has several parts and smaller sections. Genes are tiny sections of the DNA in charge of causing an effect or function.
Each gene codes for a protein, and this protein has a specific function in the body. Certain genes may code for proteins that change the color of your eyes. Others have very complex roles once they have formed.
For example, regulating how your immune system works and how it reacts to certain stimuli. Other proteins may even help cells detect abnormalities and trigger cell death. These genes and proteins are particularly important to detect and prevent cancer.
Throughout our lives, our DNA experiences mild genetic change. This genetic change is probably the trigger of aging and decaying of body tissues. Thus, changing the structure of genes is usually not a good idea. Cancer is the most obvious example.
What are gene mutations?
Gene mutations are changes to the DNA that modify how it is meant to work. After gene structures change, their proteins change as well.
When proteins encoded by a broken gene are modified, they are no longer useful. The function is affected or completely lost.
There are different types gene mutations. To make it simple, we can narrow them down into two main groups:
- Germline mutation: It is a mutation to your germ cells. A woman’s egg or a man’s sperm cell is affected by a mutation and changes the DNA. This is the cause of inherited gene mutations such as Down’s syndrome. Certain types of cancer arise in young patients because they are born with defective genes.
- Somatic mutation: This type of mutation is acquired later in our lifetime. Thus, it is not found in every cell of the body. You can find somatic mutations in specific tissues, such as cancer. These cells no longer function properly and start dividing without control. However, cells outside the tumor may work correctly and have intact DNA.
Genetic counseling will help you determine if there are any defective genes in your DNA. After genetic testing, you will know if there’s a chance that you can pass down a genetic disease to your children.
You will also confirm if your family has an inherited disease such as Lynch syndrome. This syndrome features hereditary cancer, as we will address in the following section.
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How gene mutations cause cancer
All cancer cells have a gene mutation. These gene mutations make up the pathogenic variants of cancer.
Certain DNA changes would make the cell immortal, while others accelerate cell growth and promote metastasis. You can say that a gene mutation dictates the aggressiveness of the cancer.
In fact, cancer would never show up if there were no mutations. To evaluate how various mutations cause cancer, let us go through a few of the most important cancer genes. They include:
Mutations of the BRCA gene
This gene has two subtypes, BRCA1 and BRCA2. They produce vital proteins that repair damage to the DNA. Having an intact BRCA gene protects against several other mutations. That’s why they are known as tumor suppressor genes or oncogenes.
If you have a BRCA1 mutation or a BRCA2 mutation, you lose this protection. You will have a higher propensity to certain types of cancer. This is a hereditary mutation that increases breast cancer risk in women. It may also increase the risk of ovarian cancer if you get a defective variant of either BRCA1 or BRCA2.
Breast cancer develops at a younger age, and it tends to be more aggressive. A BRCA mutation can be passed down from either your mother or father, and it is a germline mutation. It means that you still have an intact copy of the BRCA gene coming from the other parent.
However, this intact copy can undergo a somatic mutation, too. When that happens, the risk of breast cancer and ovarian cancer increases dramatically.
Breast cancer develops in 13% of women. But women with this mutation will have a risk of 55-72% if they get a BRCA1 mutation and a 45-69% risk of breast cancer if they have a BRCA2 mutation.
This gene is similar to BCRA in terms of function. It is also an oncogene or tumor suppressor gene. It also repairs DNA when there’s damage to its structure. Thus, gene mutations develop quickly in people with a defective ATM gene.
In this case, if you inherit an ATM mutation, the ovarian cancer, and breast cancer risk increases. However, the risk of lymphoma, leukemia, brain cancer, and ovarian cancer increases, too.
Additionally, if you get two abnormal copies of this gene, you will display a rare disease known as ataxia-telangiectasia. It features immune problems and neurological symptoms. Thus, doctors can find a pattern and diagnose the disease.
This is probably the most popular tumor suppressor gene. It is also one of the most common germline mutations. It is associated with something called Li-Fraumeni syndrome and increases the risk of a variety of cancers.
The most common is ovarian cancer. But you can also get hereditary colon cancer (colorectal cancer), esophageal cancer, lung cancer, pancreatic cancer, among others.
Thus, P53 mutations are particularly dangerous, and these patients should receive careful follow-up.
But even if you don’t have a germline mutation such as the ones above, you can still develop breast cancer, ovarian cancer, pancreatic cancer, prostate cancer, and others.
The cause is usually a somatic mutation happening in a healthy cell. This cell divides, and now two cells have the same mutation, then four, and so on until a tumor is developed.
As the tumor keeps growing, new mutations are added one after another, making up the characteristics of cancer. That’s why cancer does not behave the same in every patient, and every cancer patient should be treated individually.
Genes are useful to trigger a variety of body functions. For example, we have tumor suppressor genes that prevent DNA damage.
A defective tumor suppressor gene leads to DNA damage and further mutations. This is how inherited mutations can increase your risk of different types of cancer.
An example is the BRCA2 gene mutation, which increases the risk of hereditary breast cancer and ovarian cancer.
It does not mean that you will undoubtedly have cancer, but the risk increases exponentially. That’s why every patient should be treated individually.
One way to do so is targeted therapy. This targets a specific cancer gene mutation that modulates how cancer grows and survives in the body.