Oncogenes

What are oncogenes?

Oncogenes are a group of genetic mutations that may cause cancer. They’re a mutated form of genes that manage cell growth. When these genes change into oncogenes, they cause cells to grow and divide uncontrollably.

Oncogenes are powerful. Cancer typically happens when several genes mutate. But research shows a single oncogene may trigger cell growth that leads to cancer. Moreover, research shows certain kinds of cancer rely on oncogenes to survive. Understanding this relationship helps medical researchers develop treatments targeting oncogenes and effectively treating the cancers that oncogenes cause and support.

How do oncogenes work?

To understand how oncogenes work, it may help to know more about proto-oncogenes. Proto-oncogenes are normal genes that may mutate or change and become oncogenes.

Your body contains trillions of cells. Each cell contains different kinds of genes that manage different activities. Proto-oncogenes drive the cell cycle, which is the process cells go through before they can divide. Proto-oncogenes also control how fast cells grow, when cells divide and when cells die (apoptosis).

When a proto-oncogene mutates and becomes an oncogene, the gene never stops sending signals telling cells to grow and divide. Cells respond by multiplying faster than usual, eventually creating tumors.

How do proto-oncogenes mutate?

Proto-oncogenes mutate in three different ways:

• Point mutation. You have trillions of cells in your body that constantly divide to make new cells. When cells divide to create new cells, they copy their DNA genome so the new cells have their own distinct DNA. Sometimes, a change, addition or deletion happens in a single molecule in cells’ DNA genome. Those changes cause proto-oncogenes to mutate.
• Gene amplification. This may happen while proto-oncogenes are replicating or making copies, and they make too many copies.
• Chromosomal rearrangement. Sometimes, genes move to different chromosomes in a process called translocation, which creates a new abnormal gene.

What triggers proto-oncogene mutation?

Medical researchers aren’t sure why proto-oncogenes become oncogenes, but they suspect exposure to the following may play a role:

• X-rays.
• Sunlight.
• Toxins at work, in the air or in chemicals (for example, in tobacco smoke).
• Infectious agents (for example, certain viruses).

Are there different kinds of oncogenes?

Yes, there are. Medical researchers have linked about 100 different oncogenes to various kinds of cancer. For example, about 25% of all cancers involve various forms of Ras genes. Ras genes make proteins that manage how cells receive signals, grow and die.

Other oncogenes link to specific kinds of cancer, including:

• HER2 gene in breast cancer.
• BCR/ABL1 gene in chronic myeloid leukemia and some types of B-cell acute lymphocytic leukemia.
• CMYC gene in Burkitt lymphoma.
• NMYC gene in small cell lung cancer and neuroblastoma.
• EGFR and EML4AK genes in adenocarcinoma of the lung.
• KRAS gene in pancreatic cancer and lung cancer.

Do oncogenes always cause cancer?

No, they don’t. Research shows cancer happens when several genes within gene groups mutate. Oncogenes are one group or class of mutated genes that may cause cancer. Tumor suppressor genes that mutate are another class of genes that may cause cancer. Research shows oncogenes and tumor suppressor genes often work together to cause cancer.

Why are oncogenes important to cancer treatment?

Typically, cancer happens after many kinds of genes mutate. For example, research suggests most cancerous tumors show signs of 30 to 60 different genetic mutations. But in some cases, cancer happens after just a few proto-oncogenes become oncogenes. It’s easier to target one genetic mutation than many mutations, making cancer treatment more effective.

For instance, medical researchers know chronic myelogenous leukemia (CML) happens when a single type of proto-oncogene mutates and becomes BCR-ABL oncogenes. The BCR-ABL oncogene makes abnormal enzymes that let abnormal white blood cells divide and multiply uncontrollably.

Tyrosine kinase inhibitor (TKI) drugs are used in targeted therapy that blocks abnormal BCR-ABL enzymes so the abnormal white blood cells die, putting CML into remission. (Remission means you don’t have cancer symptoms, and tests don’t find signs of cancer.) Before this treatment, only about 20% of people with CML were alive five years after diagnosis.

Can I inherit oncogenes?

No, you can’t. Proto-oncogenes mutate or change into oncogenes after you’re born.

Can I keep proto-oncogenes from becoming oncogenes?

Experts don’t know all the reasons why proto-oncogenes mutate, which means there’s no sure way you can prevent the mutation that turns proto-oncogenes into oncogenes.

A note from Cleveland Clinic

Cancer research is the persistent and patient study of a multifaceted condition. Experts continually study cancer for new ways to treat it. Research into oncogenes — a group of genetic mutations that may cause cancer — changed how healthcare providers treat certain cancers. In some cases, knowing how oncogenes work has led to life-saving medical treatments.

If you have cancer, you may feel overwhelmed trying to understand what’s happening, and why. Some people with cancer benefit by learning about their condition, including research that’s already changed cancer treatment or may lead to changes. If that’s true for you, consider asking your healthcare provider to explain the specific genetic changes behind your condition.