Chemotherapy is used to treat extensively proliferating cells. Normally, cells in the body are programmed to die. When this gene is damaged, cells continue to divide and turn into malignant tumor cells. Chemotherapy is used to destroy cancer cells by interrupting their function to grow. Some chemotherapy agents are plants and naturally occurring compounds and others are synthetic chemicals. There are several chemotherapy agents used to treat cancer, and each have their advantages. Your doctor may change agents depending on the progression of the disease, so a list of possible chemicals is helpful for the patient in understanding chemotherapy agents.
Antimetabolites
These chemotherapy agents interrupt the natural process of DNA replication. The interruption of DNA processes causes the cell to malfunction and die. Antimetabolites destroy nucleic acids, which disallow replication of DNA and ultimately cause cells to lose their genome. The loss of genomic instructions causes the cell to lose the ability to create vital proteins.
Genotoxic Drugs
These agents also affect DNA. However, they directly attach to the DNA molecules and interfere with enzymes used to repair, replicate and translate genomic instructions. There are several methods of action with these chemotherapy agents. The first is modifying the actual bases of the DNA molecule, causing them to mutate. Secondly, intercalating agents insert into the tiny spaces of DNA molecules. This interferes with translations and replication. Finally, enzyme inhibitors interfere with the processes that replicate DNA and check for mutations, causing the genome to become unstable and die.
Spindle Inhibitors
Spindles are tiny cell structures that help the chromosomes separate during cell divisions. By interfering with these cell structures, cell division is damaged and improper amounts of chromosomes are distributed during the process. Abnormal amounts of chromosomes create an unstable environment for cells and they are destroyed.
Other Types of Agents
There are several other types of chemotherapy agents. Some affect the RNA molecules, which are responsible for protein synthesis. Others affect cell division by interfering with enzymatic reactions in the cell. For each chemotherapy agent, there is a mode of action that is specific for the type of cancer.
Normal Cells
Normal cells are also affected by chemotherapy agents, although not as severely. Normal cells stop dividing under abnormal conditions. Depending on the frequency of division, normal cells die under chemotherapy. Cells such as those in the intestines, liver and bone marrow are affected the most during chemotherapy, and it's the death of these cells that create the side effects.
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