Breast cancer is a disease in which malignant cells grow in the breast tissue. There are a number of different forms of breast cancer. These include are ductal carcinoma in-situ, infiltrating ductal carcinoma, medullary carcinoma, infiltrating lobular carcinoma and tubular carcinoma. Other forms of breast cancer include mucinous carcinoma and inflammatory breast cancer. According to the Breast Cancer Foundation, breast cancer is a heterogeneous disease and differs by individual. (See Reference 1). Although a diagnosis of breast cancer is frightening, there are a number of treatments available to treat the disease.
Aromatase Inhibitors
Aromatase inhibitors stop the production of estrogen by blocking the enzyme, aromatase. Aromatase inhibitors are only suitable for post-menopausal women and according to breastcancer.org is the best hormonal therapy to start treatment with. In addition, aromatase inhibitors have fewer side effects than tamoxifen. However, patients taking aromatase inhibiitors may experience joint pain. There are three aromatase inhibitors on the market for the treatment of breast cancer. These are anastrazole, exemestane and letrozole. Each of these drugs is an oral treatment that is taken once daily. (See Reference 2).
PARP Inhibitors
A class of drugs known as PARP inhibitors are under investigation as potential therapeutic agents for the treatment of hereditary breast characterized by two mutations known as BRCA1 or BRCA2. PARP inhibitors disrupt chemotherapy resistance in cancer cells. According to 2010 article published in "Oncology Nurse Edition", there were eight PARP inhibitors in clinical trials as of April 2010. These include olaparib, BSI-201, AGO-14699, ABT-888 and MK4827. (See Reference 3). However, in a 2008 article published in "Current Opinion in Pharmacology," lead author C.J. Lord, says, "There are still unanswered questions surrounding PARP inhibitors, namely the levels of specificity and potency that are required to elicit BRCA selectivity." (See Reference 4).
Tyrosine Kinase Inhibitors
Increased resistance to anti-estrogen therapies such as the drug tamoxifen are thought to result from increased expression and signalling through ErbB receptors. Tyrosine kinase inhibitors work by inhibiting ErbB receptors. (See Reference 5). The ErbB receptor family comprises four receptors known as HER1, HER2, HER3 and HER4. According to a 2007 article published in "Clinical and Translational Oncology," studies have shown that members of the ErbB tyrosine kinase receptor family play an important role in the development and progression of breast cancer. An example of a tyrosine kinase inhibitor that targets the HER2 receptor is trastuzumab, also known by the trade name of Herceptin, which according to lead author, J.A. Mestres, has provided "the first definitive evidence for the clinical efficacy of targeting an ErbB receptor in patients with breast cancer". (See Reference 6).
References
- National Breast Cancer Foundation: What is Breast Cancer?
- Breastcancer.org: Aromatase Inhibitors
- Oncology Nurse Edition: PARP*Inhibitors in BRCA-Associated Cancers
- Current Opinion in Pharmacology: Targeted therapy for cancer using PARP inhibitors
- Endocrine-Related Cancer: Overview of tyrosine kinase inhibitors in clinical breast cancer
