Table of ContentsView AllTable of ContentsWhat Are They?ActivationRole in CancerWhat Are TSGs?What Are Repair Genes?Treatment
Table of ContentsView All
View All
Table of Contents
What Are They?
Activation
Role in Cancer
What Are TSGs?
What Are Repair Genes?
Treatment
A combination of mutations involving the following genes are frequently involved in cancer development:
This article takes a closer look at the role of oncogenes in cancer, along with how they differ from tumor suppressor genes and DNA repair genes. It also provides examples of oncogenes and the cancers they can cause.
Simon Jarratt / Corbis / VCG / Getty Images
What Are Oncogenes?
Proto-oncogenes are normal cellular genes that help cells grow, divide, and stay alive.Every person has them.
In most people, proto-oncogenes never mutate into oncogenes. If a mutation does occur, the gene can start to “turn on” in an uncontrolled manner, at which point it is called an oncogene.
Unlike proto-oncogenes, an oncogene will not turn off when it should. As a result, cells can grow out of control, potentially leading to the growth of a cancerous tumor.
Cancer Cells vs. Normal Cells: How Are They Different?
Examples of Oncogenes
Oncogenes most frequently linked to cancer include:
Several gene mutations typically precede the development of cancer. Certain pairs of gene mutations are linked to a greater risk of certain cancers, too. For example, co-occurring BRAF and NRAS mutations have a particularly strong link to melanoma.
What Causes Oncogenes to Activate?
Oncogenes may be activated due to inherited causes, or they can activate upon short or prolonged exposure tocarcinogens(cancer-causing agents) in the environment.
Carcinogens
Exposure to a carcinogen can either trigger a proto-oncogene to mutate, or amplify a pre-existing mutation. KRAS mutations in lung cancer, for example, are more common in people who have smoked than never smokers.
7 Foods That May Cause Cancer (Or Increase Your Risk)
Genetic Causes
Most mutations that activate oncogenes are not inherited, but rather acquired throughout a person’s lifetime.
Nonetheless, DNA damage may occur as an accident during the normal growth of cells. So, even if we lived in a world free from carcinogens, cancer would occur.
Gene-related causes of oncogene activation include the following:
It’s important to note that oncogenes do notalwayscause cancer, nor does exposure to a carcinogen mean you will certainly develop cancer.
An Overview of Lynch Syndrome
How Do Oncogenes Cause Cancer?
Oncogenes cause cancer through what’s known as gain-of-function (GOF). In other words, the oncogene gains new functions or expresses itself in new ways as a result of the mutation.
Oncogenes can promote the following GOF activities:
How Does Cancer Become Resistant to Chemotherapy?
What Are Tumor Suppressor Genes?
Whereas oncogenes cause cancer through gain-of-function activities,tumor suppressor genescause cancer through loss of function.
Tumor suppressor genes help repair damaged DNA or eliminate damaged cells. These proteins can reduce the risk of cancer even when an oncogene is present.
Mutations in tumor suppressor genes cause them to lose this function. The likelihood of cancer developing thus increases, as abnormal cells cannot be repaired, and continue to survive instead of undergoing apoptosis (programmed cell death).
Tumor suppressor genes most frequently linked to cancer include:
There are several differences between oncogenes and tumor suppressor genes:
Most often autosomal dominant, meaning that only one copy of the gene needs to be mutated to elevate cancer risk
Can be visualized as the accelerator, when viewing a cell as a car
Most often (but not always) autosomal recessive, a mutation in both copies must occur before it increases the risk of developing cancer
Can be visualized as the brake pedal, when viewing the cell as a car
What Are DNA Repair Genes?
If oncogenes are the accelerator, and tumor suppressor genes are the brake pedal, then DNA repair genes can be thought of as the repair mechanic.
DNA repair genes are tasked with fixing mistakes in DNA. If they cannot fix the DNA, then the DNA repair genes trigger the cell to die so that harmful mutations cannot occur.
A mutation in a DNA repair gene causes loss of function. As a result, mistakes within cells may accumulate and lead to the development of cancer.
Just like oncogenes and tumor suppressor genes, mutations in DNA repair genes can be inherited at birth or acquired throughout a person’s life.
Two of the most well-known DNA repair genes implicated in cancer are BRCA1 and BRCA2. About 3% of breast cancers and 10% of ovarian cancers result from inherited mutations in BRCA1 and BRCA2.These gene mutations also increase the risk of pancreatic cancer andhigh-grade prostate cancer.
BRCA Mutations and Breast Cancer
Oncogenes and Cancer Treatment
Research on oncogenes has played a significant role in some of the newer treatment options for cancer, as well as understanding why some particular treatments may not work as well for some people.
Cancers and Oncogene Addiction
Cancer cells tend to have many mutations that can affect a number of processes in the growth of the cell. Some of these oncogenes play a greater role in the growth and survival of cancer cells than others.
For example, several oncogenes are associated with breast cancer, but only a few seem to be essential for cancer to progress. When cancers rely on these particular oncogenes, it is known as oncogene addiction.
Examples of targeted therapies include:
Other targeted therapiesinclude:
Targeted Therapies for Breast Cancer
Oncogenes and Immunotherapy
Other oncogenes that appear to negatively affect the immune system include EGFR, beta-catenin, MYC, PTEN, and BCR-ABL.
Summary
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