HER2
HER2, or Human Epidermal Growth Factor Receptor 2, is a protein that plays a critical role in cell growth and division. Its presence and activity are particularly significant in the context of certain cancers, where its overexpression can influence disease progression and treatment strategies.
Key Takeaways
- HER2 is a protein on cell surfaces that normally helps regulate cell growth.
- When cells have too many HER2 proteins, it can lead to uncontrolled growth, a condition known as HER2-positive cancer.
- HER2-positive cancers are often more aggressive but can be effectively treated with targeted therapies.
- Accurate HER2 testing is essential for diagnosing HER2-positive cancers and guiding treatment decisions.
What is HER2 (Human Epidermal Growth Factor Receptor 2)?
HER2 (Human Epidermal Growth Factor Receptor 2) is a gene that produces a protein found on the surface of all human cells. This protein is a receptor that plays a vital role in normal cell growth, division, and repair. It is part of a family of four epidermal growth factor receptors (EGFRs or ErbB proteins) that help transmit signals from outside the cell to inside, instructing the cell to grow and divide.
The primary HER2 protein function involves receiving growth signals. When growth factors bind to the HER2 receptor, it triggers a cascade of events within the cell that promotes cell proliferation and survival. In healthy cells, this process is tightly regulated, ensuring balanced growth and development. However, in some cancers, the HER2 gene can become amplified, leading to an overabundance of HER2 proteins on the cell surface. This excess of receptors can cause cells to receive too many growth signals, leading to uncontrolled cell division and tumor formation.
HER2-Positive Cancer Explained
HER2-positive cancer refers to cancers where the cancer cells have an abnormally high number of HER2 proteins on their surface. This overexpression of HER2 acts like an “on” switch, constantly signaling the cells to grow and divide rapidly. Consequently, HER2-positive cancers tend to be more aggressive and can grow and spread more quickly than HER2-negative cancers. Historically, this made them more challenging to treat.
However, the identification of HER2 as a driver of cancer growth has revolutionized treatment for these specific types of malignancies. Cancers commonly associated with HER2 positivity include:
- Breast cancer (approximately 15-20% of cases)
- Gastric (stomach) and gastroesophageal junction cancer (approximately 10-30% of cases)
- Other less common cancers, such as salivary gland cancer and some types of lung cancer
The good news is that HER2-positive cancers respond well to targeted therapies designed specifically to block the HER2 protein or its signaling pathways. These treatments can significantly improve outcomes for patients by inhibiting the growth signals that fuel the cancer.
HER2 Testing Information
HER2 testing information is crucial for patients diagnosed with certain cancers, particularly breast and gastric cancers, as it determines whether targeted HER2 therapies will be effective. Testing is typically performed on a tissue sample obtained during a biopsy or surgery. The results help oncologists tailor the most appropriate treatment plan for each individual.
There are two primary methods used for HER2 testing:
| Test Method | Description | Result Interpretation |
|---|---|---|
| Immunohistochemistry (IHC) | Measures the amount of HER2 protein on the surface of cancer cells using antibodies. Staining intensity is scored from 0 to 3+. | 0 or 1+: HER2-negative 2+: Equivocal (further testing needed) 3+: HER2-positive |
| Fluorescence In Situ Hybridization (FISH) | Measures the number of HER2 gene copies within the cancer cells. Used when IHC results are equivocal or sometimes as a primary test. | Normal gene copies: HER2-negative Increased gene copies (amplification): HER2-positive |
A positive HER2 test result indicates that the cancer cells have an overexpression or amplification of the HER2 gene, making the patient a candidate for HER2-targeted therapies. These therapies, such as trastuzumab, pertuzumab, or lapatinib, work by specifically blocking the HER2 protein, thereby inhibiting cancer cell growth and survival. The accuracy of HER2 testing is paramount for guiding treatment decisions and improving patient prognosis.
