New and On-going Targeted Therapies for Breast Cancer.

With breast cancer awareness month going on, I thought it would be appropriate to blog about the newest and on-going targeted therapies (mainly monoclonal antibody therapy) happening, as breast cancer is the most commonly diagnosed malignancy among women.

One of the biggest developments in breast cancer therapy to date is the use of the drug trastuzumab (Herceptin), which directly attacks the protein HER2 (human epidermal growth factor receptor). HER2 is the protein that aggressively promotes tumor growth in malignant breast cancer. Herceptin is a human monoclonal antibody which binds extracellularly to the HER2 protein to promote cell death (apoptosis). This will subsequently inhibit the proliferation of HER2 dependent tumors. This is extremely helpful, as more than 20 percent of breast cancer tumors overproduce this certain protein.

This is not the only type of therapy being done today to target this certain type of protein. Other monoclonal antibody-based therapies include another drug called pertuzumab. This certain type of antibody will bind to different sites of the cancer cells preventing proliferation of the tumor. This drug has been shown to be quite effective when used with trastuzumab to fight against the cancer cell lines that are resistant to trastuzumab. It has shown much success with the over-production of the HER2 protein.

Another type of targeted therapy, not using an antibody, is the use of a tyrosine kinase inhibitor. For the HER2 protein to activate tumor cell proliferation it has to be acted upon by a certain enzyme; this case being tyrosine kinase. This certain type of enzyme will act as a growth stimulating factor subsequently activating proliferation of the tumor cells. So by inhibiting the tyrosine kinase enzyme, you can stop the tumor from proliferating. A drug called Lapatinib is currently being clinically tested. It has shown much success in inhibiting the tyrosine kinase enzyme and causing growth arrest as well as cell suicide. Again, certain cell lines of breast cancer can become resistant to the drug trastuzumab, and combining the drug with Lapatinib will increase the effectiveness of trastuzumab.

The last type of therapy that I wanted to talk about is actually one of the newest therapies being worked on. It has been shown that high levels of IGF-1 (insulin-like growth factor) can increase the risk for breast cancer. The IGF-1 receptor is responsible for numerous cellular processes including proliferation and protection from apoptosis. Basically it keeps tumor cells alive and metastasizing. Current research is showing that using an antibody that could potentially block the IGF-1 receptor could help the effectiveness of trastuzumab, and stop tumor growth.

The importance of advancing these therapies becomes evident as more breast cancer cell lines are developing resistance to the drug trastuzumab, which has been around for a couple of decades. As more and more research is being done, and more targeted therapies are being developed, the survival rates for breast cancer patients are rising; yet this is just the beginning for breast cancer therapy.