The ERBB2 gene, often called HER2, gives cells a surface protein that helps control growth, repair, and survival. If it does not work normally, cells can receive too many growth signals, which may contribute to some cancers, especially certain breast and stomach cancers. Some people first learn about this gene when a tumor is described as HER2-positive. Doctors also check it because HER2 status can help guide diagnosis and treatment choices.
What is a gene?
Genes are stretches of DNA that carry instructions your cells use to make molecules or direct activities in the body. Some genes hold the instructions for producing proteins, which are the working parts of cells. Others mainly regulate when certain processes take place, where they occur, and how active they are. Taken together, genes affect how the body develops and works, and they can also shape how you respond to food, stress, or medications. More information on this topic is available in the LearnHub.
Overview
ERBB2Gene function
What if the gene works
The ERBB2 gene makes HER2, a cell surface protein that helps cells receive growth signals. It supports controlled cell growth, survival, and repair, especially in tissues like the breast and stomach.
Risk
What if the gene does not work
Variants in the ERBB2 gene can range from milder to more severe. Increased activity is linked to some breast and stomach cancers, while rare inherited variants can affect development and the heart, with effects ranging from mild to more marked.
Treatment
What does that mean for your treatment
No ERBB2-specific treatment is established for inherited loss-of-function variants. In cancer care, treatment relevance is tied instead to ERBB2 overactivity, such as amplification or certain activating variants, which can guide use of HER2-targeted medicines including trastuzumab, pertuzumab, and related drugs.
Conditions associated with ERBB2
Gene function
What if the gene works
In healthy cells, the ERBB2 gene helps pass growth and maintenance signals from the cell surface to the inside of the cell. Its protein, often called HER2, sits in the cell membrane and works with other cell surface receptors. Understanding how the ERBB2 gene works in normal cell growth and signaling helps put its importance in context.
The ERBB2 gene makes a receptor, a protein that sits on the cell surface and helps pick up growth related signals. This helps cells notice cues from nearby cells and respond in a controlled way.
Its protein often works with related receptors on the cell surface rather than acting alone. This pairing strengthens the message and passes it inward to the cell’s control systems.
These messages help guide everyday cell growth, survival, and division so tissues can renew themselves in an orderly way. This is part of the normal role of the ERBB2 gene in cell growth and signaling.
What is a variant?
A genetic variant is a small difference in the DNA sequence of a gene. Variants are common and form part of normal human diversity, including differences in appearance, metabolism, or the way the body responds to environmental influences. Many have no noticeable effect and simply reflect natural genetic variation. In some cases, though, a variant can change how a gene functions more substantially and may contribute to or cause a genetic condition.
Genetic variants
What if the gene does not work
Variants in the ERBB2 gene can change how much HER2 protein a cell makes or keep the protein’s signaling switch stuck on, which helps explain how ERBB2 variants affect cell growth control. Some changes cause a mild rise in signaling, while stronger activating variants or extra ERBB2 copies can produce more persistent signals. Less often, disruptive variants reduce protein stability or enzyme activity, and these different functional effects can influence how strongly a related cancer pathway is driven.
How variants are linked to conditions
Changes in the ERBB2 gene are best known for their link to breast cancer and are also found in some stomach and esophageal cancers. Research on inherited ERBB2 gene variants and breast cancer risk has found links in some families, although these variants are uncommon. Many ERBB2 findings in cancer are acquired in the tumor rather than inherited, so they help classify the cancer more than they predict risk for relatives.
A variant is not necessarily a diagnosis
Gene variants are a usual feature of human biology and are widely found across the population. Most do not directly affect health and instead represent normal human diversity. For many genes, having a variant associated with a condition points to a possible link rather than confirming a diagnosis, particularly when several genes and environmental influences play a role. Still, in certain situations, one well-studied variant in a particular gene is enough to establish the diagnosis.
Are there things that can increase or change my risk?
For inherited changes in the ERBB2 gene, risk is shaped mainly by the specific variant, family history, sex, and age, and other genes may also play a part. Usual breast cancer risk factors, such as alcohol use, higher body weight after menopause, and limited physical activity, can still influence overall risk.
Inheritance of ERBB2 variants
There is not yet a single, broadly confirmed Mendelian pattern that fully explains how ERBB2 gene variants are inherited across all ERBB2-related conditions. In practice, how ERBB2 gene variants are inherited depends on the specific condition and the exact variant involved. The ERBB2 gene is located on chromosome 17, which is an autosome, so you inherit one copy from each parent.
What does my ERBB2 result mean for my family?
There is not yet a broadly confirmed inherited condition pattern tied to ERBB2 in the way seen for some other genes. If you have a specific ERBB2 result and want to know what it could mean for parents, siblings, or children, a doctor or genetic counselor can explain whether it is likely to be an inherited finding or a change limited to the tumor.
Genetic information
Genetic testing
How you find out about variants
ERBB2 genetic testing looks for variants in blood, saliva, or a tumor sample, depending on why testing is being done. If you want to know how to test for ERBB2 variants, the lab reads the DNA in the ERBB2 gene to check for sequence changes or extra copies. Results can show inherited changes or tumor-only changes.
When should I consider getting a genetic test?
ERBB2 testing is most often considered after a diagnosis of breast cancer, stomach cancer, or some lung cancers, because changes in this gene in the cancer can help guide treatment. Testing for an inherited ERBB2 change is not routine and is usually weighed alongside your personal and family cancer history.
A genetic result is only one part of your health story
Genetic results can be informative, but the amount they reveal varies with the condition and the kind of variant found. How your body functions over time is also shaped by many factors, including lifestyle, environment, age, and medical history. For some conditions, particularly those influenced by many genes, genetic information offers context rather than certainty and is most useful when considered with the rest of a person’s care. In other situations, a genetic result can give a clear answer. In areas like medication response, it can also help make sense of individual experiences.
Pharmacogenetics
How variants shape your response to medicine
Genetic variation can affect how people respond to medicines. Small differences in DNA may change how the body breaks down a drug, moves it through the body, or responds to its effects. This helps explain why the same treatment works well for one person but less well for another, or why some people are more sensitive to side effects. This kind of variation is common and is one reason medication response can differ from person to person.
What is Pharmacogenetics?
Pharmacogenetics studies how differences in genes can shape a person’s response to medications. It examines relationships between genes and drugs to help explain why the same treatment can work differently from one person to another. With many medicines, genes influence either how strongly a drug works or how the body processes it. This information can support more informed and more individualized treatment decisions. You can read more about this topic in the LearnHub.
Drugs influenced by the ERBB2 gene
When should I seek medical advice?
There is not yet a broadly confirmed role for this gene in inherited medication response, so general questions about medicines or side effects are best discussed with your doctor. ERBB2 is different in cancer care, where changes in the tumor itself can help guide the use of certain targeted treatments, so people being treated for cancer may want to discuss this with their oncology team.
History
The ERBB2 gene entered cancer medicine in the 1980s, when researchers linked extra copies of this gene to a more aggressive form of breast cancer. Initially understood only through visible traits, later recognized as tied to a specific gene, this finding helped explain why some breast cancers behaved differently from others. Soon after, the gene was also widely known by the name HER2, which became familiar to many patients during pathology testing. Building on this early work, scientists developed trastuzumab, one of the first cancer treatments designed for a tumor with a specific genetic change. That step reshaped breast cancer care and helped make targeted treatment part of everyday oncology. Today, the ERBB2 gene remains one of the best known examples of how gene discoveries can change diagnosis and treatment.