Cancer

Cancer

Introduction:

Cancer is a disease that has killed and continues to kill many people around the world. Even though it includes many illnesses, approximately 150 illnesses, they have one characteristic in common: the uncontrolled growth of cells.

In the American society, cancer is the disease that most feared by the majority of people within the U.S. In the United States, more than one fifth of the deaths in the early ’90s was caused by cancer. In addition, in some the rate of growth of cells is fast; in others, slow; but in all cancers the cells never stop dividing. Cancers are clones. No matter how many trillions of cells are present in the cancer, they are all descended from a single ancestral cell. First of all, cancers begin as a primary tumor. At some point, however, cells break away from the primary tumor and establish metastases in other locations of the body. Metastases is what usually kills the patient. Cancer is a gene disorder of somatic tissue in which genes that are damaged fail to properly control cell proliferation.

Causes of Cancer:

There are different types of causes for different types of cancers. The main reasons one can get cancer are smoking, dietary factors, exercise, genetics, radiation, occupation, and even prescription drugs. Out of all the main causes of cancer obesity and smoking are the leading causes. About one third of all cases of cancer in the United States are directly attributable to cigarette smoking. As an example, for individuals who smoke two or more packs a day, the risk of contracting lung cancer is at least 40 times greater than it is for nonsmokers, whose risk level approaches at zero. Therefore, the greatest thing to do to make a longer life is not to smoke. Furthermore, most cancer results from the mutation of growth- regulating genes(Raven and Johnson 413). Thus, the easiest way to get rid of cancer is to avoid exposure to mutagens.

Cancer cells contain several mutated genes. There are three types of genes that are associated with the control of the cell cycle. First one is the Oncogenes. They are the genes that when introduced into a normal cell cause it to become a cancer cell. Their mutated or over-expressed products stimulate mitosis even though normal growth signals are absent. And these genes act as dominants in which only one of the pair need be mutated to predispose the cell to cancer. The second type of genes are Tumor suppressor genes. These genes normally inhibit mitosis. For instance, the gene p53 normally senses DNA damage and either halts the cell cycle until it can be repaired or, if the damage is too massive; triggers apoptosis. And these genes are recessive in which either both copies must be mutated for their function to be lost or the healthy copy of the gene has been lost. Finally, the third type of genes are Metastasis genes. They enable cells of the tumor to separate from the primary tumor and migrate to other parts of the body.

What probably happens is a single cell in a tissue suffers a mutation in a gene involved in the cell cycle. This results in giving that cell a slight growth advantage over other dividing cells in the tissue. After that cell develops into a clone, some of its descendants suffer another mutation in another cell-cycle gene. This further deregulates the cell cycle of that cell and its descendants. As the rate of mitosis in that clone increases, the chances of further DNA damage increases. Eventually, so many mutations have occurred that the growth of that clone becomes completely unregulated and uncontrolled. The result comes as a full cancer. The another reason that causes cancer is chemicals. Chemicals that produce mutations in DNA are often potent carcinogenes which causes cancer. Also, many viruses have been studied that reliably cause cancer when laboratory animals are infected with them. For example, there are two Papilloma viruses that infect the reproductive organs; and the hepatitis B and hepatitis C viruses that infect the liver and are closely associated with liver cancer.

In conclusion, cancers are caused by anything that is mutagenic, which is anything that damages DNA. Also, cancers are caused by anything that stimulates the rate of mitosis.

Types of Cancer:

Over twenty different types of cancer have been found to exist in the world today. The most fatal cancer in the world is lung cancer, which has grown drastically since the spread of cigarette smoking in growing countries. Also, after lung cancer, stomach cancer is the second leading form of cancer in men. Another on the increase, for women, is breast cancer, particularly in China and Japan. The fourth known cancer is colon and rectum cancer, which occurs mostly in older people. Moreover, in the United