Multi cellular organisms, like humans are made up of billions of cells. These cells need to divide and copy themselves for a variety of reasons. The most common form of cell division is called mitosis. This is used for growth and repair. During the mitosis process a cell makes an exact copy of itself and splits into two new cells. The cell cycle has built in checkpoints that allow problems to be corrected before the cycle advances. Certain proteins, the products of “checkpoint” genes, can monitor weather a cell’s DNA has been copied completely or weather it has been damaged. Such proteins interact to delay or stop the cell cycle while simultaneously enhancing transcription of genes involved in chromosome repair. If this process goes uncorrected it can cause the cell to self- destruct. When checkpoint gene mutates so that its protein product no longer works correctly its production fails. Leaving the cell to either make too much or too little of its product. When too many of the checkpoints fail the cell will eventually lose control over the cell cycle. The problem with this is the checkpoint malfunctions are passed along to the cells descendants. This process is called a neoplasm. It’s an accumulation of cells that lost control over how they grow and divide. Mitosis is closely controlled by the genes inside every cell. Sometimes this control can go wrong. If that happens in just a single cell, it can replicate itself to make new cells that are also out of control. These are cancer cells. They continue to replicate rapidly without the control systems that normal cells have. Cancer cells will form lumps, or even tumors, that damage the surrounding tissues. Sometimes, cancer cells break off from the original tumor and spread in the blood to other parts of the body. When a tumor spreads to another part of the body it is said to have metastasized. Medicines that are used to treat cancer are sometimes aimed at killing cells that are rapidly dividing by mitosis. They inhibit the synthesis or function of DNA - this type of treatment is called chemotherapy. More modern medicines target specific cancers in different ways. Many inhibit the growth signals for that type of cell. Consider growth factors which are molecules that stimulate cells to divide and differentiate. When an epidermal growth factor stimulates a cell to enter mitosis by binding to receptor on the cell’s plasma membrane. This process will change the shape of the receptor so that it becomes enzymatic and phosphorylates itself. Each year cancer causes 15 to 20 percent of all human deaths in developed countries alone. Some life style choices that you can make to reduce your risk are avoiding exposure of unprotected skin to sunlight, smoking and drinking. Some neoplasms can be detected with periodic screening procedures such as Pap tests or dermatology exams. If neoplasms are detected early enough they can often be removed before metastasis occurs.
