Anticancer drugs attempt to slow down or stop the ongoing cell division that occurs in cancerous tissues. Treatment protocols include radiation, heat exposure, freezing, surgery, and/or drug therapy. The purpose of most anticancer drugs is to target the overproduction of malignant cells. Different types of cancers arise from different types of tissue. Since every tissue is made up of cells specialized for a certain function, it is not surprising that different forms of cancers will have different responses to the same drug. For example, a drug that targets the overproduction of liver cells (which are adapted to filtering and monitoring the blood supply) might have little effect on nerve cells that specialize in carrying messages.