Like normal, healthy cells , cancer cells go through a continuous process of change. Each cell divides into two daughter cells. These cells grow, rest and then divide again. The drugs used in chemotherapy are powerful chemicals designed to interrupt this cycle and stop the cells from growing.
Several different types of drugs are used in chemotherapy. Each type kills cells at a different stage of the cell's life cycle. Each does its job in a different way.
Antimetabolites attack the cells during the process of division, when they are more easily killed. The antimetabolites imitate normal cell nutrients. The "antivitamin" methotrexate , for example, resembles the normal B vitamin, folic acid. The cancer cell consumes the drug—"thinking" it's getting a good meal—and starves to death.
Alkylating agents attack all the cells in a tumor whether they are resting or dividing. These drugs bind with the cells' DNA in various ways to prevent reproduction.
Antitumor antibiotics insert themselves into strands of DNA. They either break up the chromosomes or inhibit the DNA-directed synthesis of RNA that the cell needs to grow.
Alkaloids prevent the formation of chromosome spindles necessary for cell duplication.
Hormones such as estrogen and progesterone inhibit the growth of some cancers, although how they do it is not clearly understood.
