Cancer develops when normal cells from any tissue of the body become mutated, allowing for uncontrolled cell growth and the development of tumors. One cancer treatment uses chemotherapy drugs that halt cell growth and trigger cell death, thus shrinking tumors. Many chemotherapeutic agents target healthy cells as well as tumor cells, leading to a range of side effects. To address this problem, targeted cancer therapeutics have been developed that selectively kill cancer cells and minimize side effects.
Trastuzumab
One therapeutic that has been designed to specifically target cancer cells is trastuzumab, trade name Herceptin, a drug used to treat certain forms of breast cancer. Trastuzumab is designed to selectively target cells that contain high levels of a protein called HER-2 and help the immune system kill and destroy those cells. HER-2 is a protein found on the surface of breast cells, which promotes cell growth under normal conditions. In some cases of breast cancer, the HER-2 protein is found at very high levels, so the cell is always receiving signals to divide, leading to uncontrolled proliferation and the development of a breast tumor.
Trastuzumab works by identifying cells that have high levels of HER-2 and leaving neighboring cells alone. Once trastuzumab binds to the surface of the cancer cell, it recruits white blood cells, which then come and kill the cancer cell. Trastuzumab is very effective in treating HER-2-positive forms of breast cancer.
Imatinib
Imatinib, trade name Gleevec, is a targeted cancer drug that works by inhibiting a class of proteins called tyrosine kinases. The language the cell uses to carry out signals to proliferate and become cancerous is called signal transduction, and tyrosine kinases are essential to many signal transduction pathways. In cancer, tyrosine kinases are overactive, leading to increased cell division and growth. The inactivation of tyrosine kinases by imatinib stops these signal transduction events, and therefore stops cell proliferation.
According to the National Cancer Institute, imatinib is an effective targeted cancer therapeutic used to treat gastrointestinal stromal tumors as well as certain forms of leukemia. Over time, cancer cells may become resistant to imatinib, so a combination of cancer therapies may be required.
Gefitinib
Gefitinib, trade name Iressa, is another type of targeted cancer therapy. It is commonly used in patients with non-small-cell lung cancer, according to the National Cancer Institute. Like imatinib, gefitinib is a type of tyrosine kinase inhibitor. It specifically targets a protein called EGFR, which is found on the surface of cancer cells. Under normal conditions, activation of the EGFR protein stimulates cell proliferation and survival. In cancer, EGFR is constantly active, so the cell can continually divide and evade death, two key steps in cancer development.
