It also provides examples of oncogenes and the cancers they can cause.
What Are Oncogenes?
Proto-oncogenes are normal cellular genes that help cells grow, divide, and stay alive.Every person has them.
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In most people, proto-oncogenes never mutate into oncogenes.
Unlike proto-oncogenes, an oncogene will not turn off when it should.
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?
Carcinogens
Environmental carcinogens both occur naturally and are generated by humans.
Known carcinogens include:
Tobacco smoke is strongly associated with the development of various cancers.
It contains over 7,000 chemicals that are breathed in both by the smoker and anyone exposed tosecondhand smoke.
At least 69 of those chemicals, including arsenic, benzene, cadmium, and formaldehyde, are carcinogens.
Exposure to a carcinogen can either trigger a proto-oncogene to mutate, or amplify a pre-existing mutation.
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.
How Do Oncogenes Cause Cancer?
Oncogenes cause cancer through what’s known as gain-of-function (GOF).
Oncogenes can promote the following GOF activities:
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.
DNA repair genes are tasked with fixing mistakes in DNA.
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.
Two of the most well-known DNA repair genes implicated in cancer are BRCA1 and BRCA2.
Some of these oncogenes play a greater role in the growth and survival of cancer cells than others.
When cancers rely on these particular oncogenes, it is known as oncogene addiction.
These drugs are known as targeted therapies.
Some mutations are associated with certain cancers.
For example, most ovarian cancers are linked to a mutation in the TP53 tumor suppressor gene.
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