Cancer treatment aims to kill cancer cells while leaving normal healthy cells intact. The difficulty, however, is strictly limiting the effects of chemotherapy to the cancerous cells. Chemotherapy is delivered throughout the body and affects some healthy cells, which accounts for the side effects. Advances in cancer research are leading to targeted therapies that focus on factors specific to cancer cells.
Targeted Therapies
Targeted cancer therapies seek specific proteins or enzymes found inside or on the surface of cancer cells that are necessary for cell growth. Defining characteristics of cancer cells include uncontrolled growth, the ability to metastasize (spread) to other organs, resistance to natural cell death (apoptosis) and the ability to form new blood vessels to fuel growth. Targeted therapies focus on the chemical signals necessary for cancer cells to carry out these functions. Because the drugs are specific to cancer cells, they are more effective than general chemotherapy and are less harmful to healthy cells. Targeted therapies are classified according to their action. They are either small-molecule drugs, which enter the cell and act from the inside, or monoclonal antibodies, which are larger and attach to receptors on the cell surface. Although these therapies may lead to individualized treatment with fewer side effects, cancers may become resistant. Targeted therapies are most effective when used in combination with traditional chemotherapy, radiation or other targeted therapies.
Signal Transduction Inhibitors
Signal transduction inhibitors block the enzymes and growth factor receptors necessary for cell growth. By disrupting the growth cascade, tumor growth slows or stops.
Apoptosis Inducers
Another class of targeted therapies stimulates cell death, or apoptosis, in cancer cells. These compounds degrade the proteins regulating cell growth and division, causing the cancer cells to die. Normal cells may also be affected, but to a lesser degree than cancer cells.
Anti-Angiogensis Agents
Tumors form new blood vessels, enabling them to metastasize. Anti-angiogenesis agents inhibit these new blood vessels from developing by binding to receptors for vascular endothelial growth factor (VEGF), blocking tumor growth.
Immune System Boosters
Monoclonal antibodies are also being used to boost the body's immune system and trigger it to fight cancer cells. The agents target a protein on the surface of cancerous cells that initiates the immune response. Other monoclonal antibodies carry toxic agents directly to the inside of cancer cells, where they disrupt the process of cell division.
Vaccines and Gene Therapy
Vaccines are available to prevent the viruses that may lead to certain types of cancers. Chronic hepatitis B virus may cause liver cancer, and strains of human papillomavirus (HPV) have been associated with an increased risk of cervical cancer. Therapeutic vaccines to treat cancer are in development. Gene therapies are being explored to replace damaged genes, which may have mutations that develop into cancer, to increase the vulnerability of cancer cells to treatment and to improve the immune response.
Tags: cancer cells, blood vessels, cell growth, healthy cells, cancerous cells, cell death
