I am sure that most people that are curious about cancer, or know of a loved one that has gone through the entire cancer ordeal, and more specifically Breast Cancer, have heard of the term HER2neu or if their breast cancer was referred to as HER2 + (positive) or - (negative). In cancer care, there happens to be a lot of acronyms and terms thrown out there, or perhaps your physician uses them often, so I want to describe a bit more in detail what HER2 is and what it means to you the patient or loved one of a breast cancer patient to be HER+.
 So let me start by explaining a bit more about what HER2 is and what it means to you the patient. HER2 stands for Human Epidermal growth factor Receptor 2. Each normal breast cell in the body contains copies of the HER2 gene. These genes are located in the DNA of the cell. The HER2 gene then helps to create, or grow, a HER2 protein, and it is this protein that we are the most concerned about. The HER2 protein is really a receptor site on the surface of the cell.
On most normal breast cells there are HER2 receptors found on their surfaces. These receptors help to send signals from the outside of the cell to the inside of the cell.  The signals that they send are the direction to tell the cell when to grow and when to divide.
This is a picture of what it looks like:
                   
In breast cancer patients that are said to be HER2+, this means that there is an overabundance of HER2 genes located inside of the cancer cell. When this happens, there will then be a large number of receptors on the surface of those breast cancer cells. This then in turn allows the cancer cells to grow and divide more rapidly and out of control. This rapid growth and division of the breast cancer cell is thought to be the reason why most HER2+ Breast Cancers are more aggressive and tend to have poorer outcomes for patients.
Some studies have shown that up to 25% of Breast Cancer Patients will be HER2+. This number is very significant because the way in which physicians treat patients with HER2+ breast cancer is different then those patients that are not positive for the HER2 gene. If you have been tested and the results came back that you are positive for the HER2 expression, then you will be placed on a drug that is called Herceptin.
Herceptin is also referred to as a monoclonal antibody. Monoclonal Anitbody means that the drug Herceptin is formed in the laboratory and that it is derived from a single cell. Anitbodies are naturally found in our bodies. Antibodies are a part of our bodies internal defense system. They typically can help in attacking and fighting off bacteria, viruses, and even cancerous cells in our body.
              
AS you can see in the diagram above, that Herceptin works both inside and outside of the cancer cell. If you think of the HER2 receptor as a landing pad, Herceptin attaches itself to these landing pads. In attaching itself to the receptor or landing pads, it  prevents other growth factors from landing on the surface of the receptor. This in turn prevents signals from being sent from these receptors or landing pads to the inside of the cell. By not allowing any signals to travel from the outside of the cell to the inside of the cell, it prevents the growth and division of the cancer cell.
If you block all of the HER2 Receptors or landing pads, then you block the cancer cells ability to grow and divide into more cancer cells. This will eventually also lead to cancer cells becoming idle, and then if they can not grow, they will eventually die.  In some other preclinical studies, this binding with Herceptin has also led to better effects of chemotherapy as well.
Research has shown that women with HER2+ breast cancer have a more aggressive disease, greater likelihood of recurrence, poorer prognosis, and decreased survival compared to women that are HER2 - (negative). This is why it is so important for patients to be tested for the HER2 gene. If you are found to be positive, it is then important to be placed on Herceptin.
In 1998 Herceptin was FDA Approved for use in patients with metastatic breast cancer. In November 2006, the FDA approved the use of Herceptin  as a part of a treatment regimen along with doxorubicin, cyclophosphamide, and paclitaxel for the adjuvant treatment of patients with HER2 positive node positive breast cancer. Adjuvant therapy is given to women with localized breast cancer that have been tested positive for HER2, and have undergone initial treatment. This goal behind the use of the additional therapy is to decrease and reduce the chances for recurrence and/or the occurrence of metastatic disease.
As always, if you or a loved one have any other questions, comments, or concerns; if you would like more information in regards to another cancer related topic, please contact me at: CANCERGEEK@GMAIL.COM or CANCERGEEK@CANCERGEEK.COM
~CancerGeek