Cancer cells are cells that no longer have control over their rate of growth or death. All cells of the body grow and die at a rate determined by genetic instructions. Normal cells may become cancer cells if a change occurs in the genes that express proteins that regulate cell growth and death. In most instances, the cell repairs the alteration in its DNA, fails to replicate or dies. More rarely, it divides and produces exact copies of itself, thereby producing multiple cells with the same change in the gene that increases cell growth or decreases death. A mass of abnormally growing cells may lead to cancer. The National Cancer Institute reported that the incidence of cancer in the United States is 461.6 per 100,000 men and women per year and the death rate from cancer as 181.6 per 100,000 men and women per year (see Reference 1).
Mutations
Any change in the DNA that alters the gene product or affects its level of expression is called a mutation. A mutation that occurs in a gene that regulates cell growth or death may develop into cancer. Most commonly, more than one mutation must take place in a cell for it to become a cancer cell. “Cancer Quest” noted that normal cells become cancer cells by a step-wise occurrence of genetic changes (see Reference 2).
Normal Cell Growth
Normal cells have multiple controls over cell growth. The expression of proteins that are encoded by genes determines if a cell will grow or die. During normal cellular growth a cell passes through four different checkpoints in a cell growth cycle. At each checkpoint genetic instructions are issued by the cell and different proteins carry-out the orders. Checkpoints are also the time at which a cell surveys and repairs DNA damage.
Abnormal Cell Growth
If a protein that stimulates cell growth is over-expressed or another that suppresses growth is under-expressed than a normal cell may divide more often producing a mass of cells, also known as a tumor. Having a tumor does not mean a person has cancer. Cells that divide faster often take on more mutations by moving rapidly through the normal cell growth checkpoints. As the mass of abnormal cells grows it may acquire more abnormal features, like faster unrestricted growth, the expression of digestive enzymes and internal blood vessels. Tumors can be benign or malignant or in some stage in between.
Malignant Growth
Malignant cancer cells have three properties: they exhibit uncontrolled growth, they can invade nearby tissues and they can spread to tissues that are far away by being transported in the blood or lymph. The spreading of cancer cells to other tissues is called metastasis. An article in the “European Journal of Cancer” stated that 90 percent of all cancer deaths are the result of metastasis (see Reference 3).
Benign Growth
Tumor cells that display moderately uncontrolled growth but are encapsulated are called benign. Most benign tumors do not cause disease, but if they originate in endocrine glands, they can increase the secretion of hormones. They also could compress organs or blood vessels. Benign tumor cells have the potential to become malignant.
