Proto-Oncogenes Explained

Here’s a breakdown of the unique features of proto-oncogenes and oncogenes, and how they’re related:

Proto-oncogenes are a group of typical genes in a cell.

They contain the necessary information for your body to make the proteins responsible for:

• stimulating cell division, which makes cell growth possible
• inhibiting cell differentiation, which is when cells change their function
• preventing apoptosis, also known as cell death

These processes are all essential for cells to maintain healthy tissues and organs in your body.

A proto-oncogene can’t cause cancer unless a mutation occurs, turning it into an oncogene. Healthy proto-oncogenes make proteins that help with cell function.

When a mutation occurs in a proto-oncogene, it becomes permanently activated. The gene then starts making too much of the proteins that code for cell growth.

Cell growth occurs uncontrollably. This is called a gain-of-function mutation because the cell takes on a new purpose. It’s one of the defining features of cancerous tumors.

These mutations are considered “dominant” mutations. This means that only one copy of the gene needs to be mutated in order to cause a proto-oncogene to become an oncogene and cause cancer.

There are at least 3 different types of mutations that can cause a proto-oncogene to become an oncogene:

• Point mutation. This mutation alters, inserts, or deletes one or more nucleotides (building blocks of DNA and RNA) in a gene sequence. This activates the proto-oncogene.
• Gene amplification. This mutation leads to extra copies of the gene.
• Chromosomal translocation (rearrangement). This is when the gene is relocated to a new chromosomal site that leads to higher expression.

According to the American Cancer Society, most of the mutations that cause cancer are acquired, not inherited. This means that you aren’t born with the gene error. Instead, the change happens at some point during your life, usually due to environmental factors.

There are many chemicals, substances, and health conditions that are known to increase the risk of cancer or directly cause cancer. Contact with some carcinogens is very rare, while others appear in our daily life.

According to the 15th Report on Carcinogens from the U.S. Department of Health and Human Services (HHS), these include:

• tobacco
• certain steroids (estrogen, progesterone)
• sunbed and sun lamps
• various dyes, including certain food dyes
• particles from diesel exhaust
• metallic nickel
• asbestos
• forms of radiation
• hepatitis B and C
• human papillomavirus (HPV)
• Epstein-Barr virus

Some proto-oncogene mutations result from an infection with a type of virus called a retrovirus. Some people are more susceptible to mutations in their proto-oncogenes.

Everyone has proto-oncogenes in their body. They’re necessary for our survival. For most people, proto-oncogenes will function normally and never mutate. However, proto-oncogene mutations can happen to anyone.

Over 40 different types of proto-oncogenes have been discovered in the human body.

Here’s an introduction to some key examples:

Ras

Research has shown the first proto-oncogene likely to turn into an oncogene is called Ras.

Ras encodes an intracellular signal-transduction protein. In other words, Ras is one of the on-and-off switches in a pathway that leads to cell growth. When Ras mutates, it encodes for a protein that causes an uncontrolled growth-promoting signal.

Ras gene mutations have been found in people with:

• pancreatic cancer
• lung carcinoma and lung tumors
• colon tumors
• thyroid tumors

HER2

The HER2 gene makes protein receptors that are involved in the growth and division of cells in the breast.

Many people with breast cancer have a gene amplification mutation in their HER2 gene. This type of breast cancer is often referred to as HER2-positive breast cancer.

Myc

The Myc gene is associated with a type of cancer called Burkitt’s lymphoma, a severe form of non-Hodgkin’s lymphoma.

This occurs as the result of an atypical characteristic called chromosomal translocation. A chromosome breaks and part of it reattaches to another chromosome, causing trouble.

In the case of Burkitt’s lymphoma, a section of a gene that enhances gene function gets moved near the Myc proto-oncogene.

Cyclin D

Cyclin D’s normal job is to deactivate a protein called the Rb tumor suppressor. When Cyclin D mutates, it can no longer accomplish this, causing uncontrollable cell growth.

Cyclin D mutations are associated with:

• pancreatic cancer
• lung cancer
• breast cancer
• melanoma

You may not be able to completely prevent a mutation from happening in a proto-oncogene, but your lifestyle can affect your risk factors.

The following approaches to prevention can lower your risk of cancer-causing mutations:

• maintaining a healthy weight
• vaccinating against viruses that can lead to cancer, such as hepatitis B and HPV
• eating a well-balanced diet packed with fruits and vegetables
• exercising regularly
• avoiding tobacco products
• limiting alcohol intake
• using sun protection when you go outdoors
• seeing a doctor regularly for health checkups and cancer screenings

If you have a history of cancer in your family, it’s especially important to stay on top of screenings and get promptly evaluated for any symptoms. Your primary care doctor can help you schedule screenings.

Your cells contain many important genes that regulate cell growth and division. The healthy forms of these genes are called proto-oncogenes. The mutated forms are called oncogenes. Oncogenes cause cells to replicate out of control and can lead to cancer.

The study of oncogenes is at the forefront of modern cancer research. While there’s no perfect way to prevent potential proto-oncogene mutation, you can take steps to limit your cancer risks.

It’s best to avoid known cancer-causing substances, seek timely treatment for other health conditions, maintain a nutritious diet, and prioritize exercise. Make sure you stay up to date on cancer screenings, especially if the disease runs in your family.