More than 300,000 Americans a year are diagnosed with lung cancer, according to the Centers for Disease Control. Lung cancer poses difficult challenges for oncology, given its ability to invade local and distant tissues, a lack of effective prevention and therapy, uncontrollable cell proliferation and lack of control of cellular differentiation. Lung cancer can be caused by numerous factors including cigarette smoke, toxins and harmful chemicals. Chemotherapy is a type of drug therapy that can stop cancer cells from multiplying.
Topoisomerase Inhibitors
These drugs cause DNA damage to lung cancer cells. They act by interfering with enzymes called topoisomerases, which aid in the separation of DNA strands so they can be duplicated. Examples of topoisomerase inhibitors include camptosar and hycamtin. Topoisomerase inhibitors are commonly combined with other chemotherapy agents to treat lung cancer.
Alkylating Agents
Alkylating agents prevent lung cancer cells from reproducing by causing disruption of DNA function and cellular death. However, these drugs are toxic to healthy cells. Because they deal damage to DNA directly, they can destroy the cells of the bone marrow which can lead to leukemia. In addition, alkylating agents can also damage the ovaries, which can lead to infertility.
Mitotic Inhibitors
Mitotic inhibitors are commonly derived from plant alkaloids and other natural substances. Lung cancer cells are capable of growing and metastasizing (spreading) through nonstop mitotic division. Mitotic inhibitors disrupt microtubule polymerization by preventing lung cancer cells from undergoing mitosis, thereby inhibiting cancerous growth. Mitotic inhibitors act by halting and interfering with mitosis, so that the lung cancer cell will cease to divide. Additionally, mitotic inhibitors can prevent mitosis by suppressing the protein tubulin, which is necessary for mitosis to happen.
Anthracyclines
Anthracyclines are anti-tumor antibiotics used in lung cancer chemotherapy derived from the streptomyces bacteria. The anthracyclines inhibit lung cancer cell division by breaking the structure of DNA, preventing replication and new tumor growth. They do so by inserting themselves into the base pairs in the DNA minor grooves and causing the destruction of the structural backbone of DNA. Anthracyclines are effective in treating lung cancer. Side effects of anthracyclines include heart damage and vomiting.
Antimetabolites
Lung cancer can be treated effectively with a group of drugs called antimetabolites. These drugs act by directly interfering with the production of DNA in cancer cells, preventing growth of tumors and cell division. Examples of antimetabolites include methotrexate, hydroxyurea and 6-mercaptopurine. Side effects of this type of chemotherapy include easy susceptibility to infections and bleeding. Urine and blood tests are used to monitor the abnormalities caused by antimetabolites.
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