The role of HER2 in breast cancer

HER2-positive breast cancer is a highly malignant form of breast cancer, which tends to grow stronger than other types of breast cancer.
What is HER2?

HER2 is the epithelial growth factor receptor 2, a gene that may play a role in the development of breast cancer. Patients with breast cancer should perform a test of HER2 status to determine if the HER2 gene is a carcinogen.

The genes contain codes to create the different proteins that cells need to stay healthy and function normally. Some of the genes and proteins they make can affect how breast cancer works and respond to specific treatments. Cancer cells extracted from the patient's tissue will be checked to see which genes are normal and which are abnormal.

Patients with breast cancer should have a test for HER2 status. (Illustration)

The HER2 gene produces the HER2 protein (sometimes called the HER2 protein / neu). The HER2 protein is receptors on breast cells. Normally, the HER2 receptor helps control how breast cells work, grow, divide and repair themselves. But in about 25% of breast cancer patients, the HER2 gene does not work correctly and makes too many copies of itself (called HER2 gene amplification).

All HER2 genes produce this excess, causing the breast cells to produce too many HER2 receptors (overexpression of HER2 protein). This causes breast cells to grow and divide uncontrollably.

Breast cancer with HER2 gene amplification or overexpression of HER2 protein is called HER2 positive. HER2-positive breast cancer tends to grow faster, is more likely to develop metastatic breast cancer earlier and recurs earlier than HER2-negative breast cancer.

Types of HER2 status tests

There are four tests for HER2.

IHC test (ImmunoHistoChemology) to detect whether breast cancer patients have too much HER2 protein in cancer cells or not. The results of the IHC test may be: 0 (negative), 1+ (also negative), 2+ (uncertain) or 3+ (positive - overexpression of HER2 protein).

The FISH (Fluorescence In Situ Hybridization) test checks for breast cancer patients who have too many copies of the HER2 gene in cancer cells. FISH test results may be positive (amplify HER2 gene) or negative (not amplify HER2 gene).

The SPoT-Light HER2 CISH (Subtraction Probe Technology Chromogenic In Situ Hybridization) test detects too many copies of the HER2 gene in breast cancer cells. SPoT-Light test result may be positive (amplify HER2 gene) or negative (not amplify HER2 gene).

The HER2 Dual ISH test (Inform Dual In Situ Hybridization) to see if breast cancer patients have too many copies of the HER2 gene in cancer cells. Inform HER2 Dual ISH test results may be positive (amplify HER2 gene) or negative (not amplify HER2 gene).

Research has shown that some HER2-positive breast cancers can become HER2-negative over time. In contrast, HER2 negative breast cancer can become HER2 positive over time. If the breast cancer recurs in the future as the disease progresses, doctors should consider a biopsy and check for HER2 status.

Treatment for HER2-positive breast cancer

Currently, there are several treatments specifically for HER2-positive breast cancer, such as:

Herceptin (chemical name is trastuzumab), has an anti-HER2 positive breast cancer effect by preventing cancer cells from receiving chemical signals for these cells to grow further.

Kadcyla (chemical name is T-DM1 or ado-trastuzumab emtansine) is a combination of Herceptin and emtansine chemotherapy drug. Kadcyla was designed to deliver emtansine to target cancer cells by attaching emtansine to Herceptin. Herceptin then brings emtansine to HER2-positive cancer cells.

Nerlynx (chemical name is neratinib), fights HER2-positive breast cancer by blocking the ability of cancer cells to receive growth signals.

Perjeta (chemically named pertuzumab), like Herceptin, fights HER2-positive breast cancer by preventing cancer cells from receiving growth signals.

Tykerb (chemical name lapatinib) fights HER2-positive breast cancer by blocking certain proteins that cause uncontrolled cell growth.