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Cancer is the second leading cause of death in the United States. Half of all men and one-third of all women in the U. S. will develop cancer during their lifetimes.
Although it is common knowledge that cancer is generally inherited, this paper will further explore the causes and what happens on a cellular level when cancer develops in the human body. Basics of signal transduction Cell communication, or signal transduction, is simply the means by which cells in the body respond to signals coming from outside those cells. The purpose of this chemical communication is to coordinate functions inside the cell, between cells or between organs in the body, allowing us the means to respond to our external environment. Normally, cell division is a very carefully regulated process that ensures the body has neither too few nor too many of a given cell type. Some cell types in the body wear out quickly and need to be continuously replaced as they die, such as most blood cells and cells lining the digestive tract. The production of these cells must be precisely regulated based on their rate of cell death so that the body has the exact number of cells it needs. (Kruh, 2000) The relationship with cancer Abnormal - or more specifically - uncontrolled, rapid cell growth is a central feature of cancer.
Virtually every cancer is caused by mutations of DNA, the genetic material that controls how cells behave. Genes that regulate cell division are most susceptible to mutations, which may lead to abnormal cell growth. Cancer is a disease of the genes - it arises from defects in certain genes, the genes that normally regulate cell growth and cell death. Some genes, known as oncogenes, promote normal cell growth. Other genes, known as tumor suppressor genes, have the opposite effect, to retard cell growth. The normal division of our cells is a delicate balance of positive and negative growth signals from these genes.
This balance may be upset by either the abnormal over activation of oncogenes or the abnormal inactivation of tumor suppressor genes. These genetic events may be caused by environmental toxins, random internal changes, and also may be inherited from a family who has a history of cancer where a defective growth-regulatory gene is passed down through generations. Cell division can get out of control when damage to specific genes in the cells DNA results in abnormally functioning growth regulatory proteins. For instance, melanoma is a cancer that arises in the melanocytes, the cells that produce melanin.
The primary cause of melanoma is damage to the DNA of melanocytes by UV radiation from the sun. When we are overexposed to the sun and receive too much UV radiation, the DNA may be damaged, thus resulting in abnormal cell growth and eventually, cancer. When a cell becomes cancerous, over time a tumor forms from these abnormal cells. Because the tumor is made up of defective cells, it cannot function as it should. The body suffers in two ways: from both the loss of the normal function of that tissue and from the damage to other tissues. Tumors can invade and destroy nearby tissue.
Some tumors secrete hormones or enzymes that disrupt the bodys normal functions. As tumors grow, they develop networks of blood vessels and begin robbing the body of essential nutrients. Eventually, cells may break away from the tumor and spread to other parts of the body, when they establish tumor colonies. This spread of cancer is called metastasis.
New research by scientists at Emory University in Atlanta, Georgia sheds light on a new class of enzymes that may be active in cancer. The enzymes convert oxygen to a destruction form called reactive oxygen and appear to play a role in abnormal cell growth. Reactive oxygen has been associated with damage to cells as well as damage to DNA. Mox 1, a member of the new class of enzymes, was found to be a growth promoter for cells by producing the reactive oxygen.
The oxygen in turn causes the cells to divide quicker than normal. When the Mox 1 gene was inserted into mice cells, the cells began to divide more quickly taking on characteristics of abnormal cells. When these cells were inserted into mice, tumors resulted. (Coleman, 2001) Types of cancer Cancers are grouped into the following categories: Carcinomas Melanomas Lymphomas Sarcomas Carcinomas, such as lung cancer, breast cancer, colon cancer, and prostate cancer, are by far the most common group and account for over 90 percent of all cancer cases. Carcinomas arise from the cells that comprise the inner linings of organs and the glands of the body.
Melanomas, making up about four percent of all cancers, stem from the pigment-forming cells in the skin. Lymphomas are less common and account for about five percent of all cancer cases. This group arises from cells of the blood, bone marrow, and immune system. Sarcomas are the least common group and account for only one percent of all malignancies. These tumors arise from the skeletal and connective tissues such as cartilage, bone and muscle. Drugs that fight cancer The use of drugs to treat cancer is called chemotherapy.
The general aim of chemotherapy is to decrease the growth rate of cancer cells. Chemotherapy drugs that are effective in treating cancer interfere with the activity of cancer cells, either by directly sabotaging a specific phase of cell development or by sending confusing messages to the cells, thus causing them to act the wrong way and ultimately destroy themselves. They are usually administered orally or intravenously. In general, chemotherapy drugs can be divided into three main categories based on their goals: 1.
Directly damage the DNA in the cancer cell nucleus These drugs chemically damage DNA by disrupting replication and either totally halt replication or cause the manufacture of nonsense DNA that does not code anything useful. Examples of drugs in this class include cisplatin (Platinum), daunorubicin (Cerubidine), doxorubicin (Adriamycin) and etoposide (VePesid). This is an example of an aklylating agent, which affects cancer cells in all phases of their life cycle and confuses the DNA by directly reacting with it. 2. Stop the synthesis of new DNA strands to stop the cell from replicating which allows the tumor to grow These agents stop the production of new DNA strands by blocking the formation of nucleotides or deoxyribonucleotides, which are the building blocks of DNA and RNA.
Examples of drugs are methotrexate (Abitrexate), mercaptopurine (Purinethol), fluorouracil (Adrucil), and hydroxyurea (Hydra). These are examples of anti metabolites, which interfere with the cells ability for normal metabolism. These are phase-specific drugs - they work in one phase of the cells life cycle. 3. Stop cancer cell mitosis by breaking down or disrupting the mitotic spindles Mitotic spindles are like molecular railroads that are like the north and south poles in the cell when a cell starts to divide itself into two new cells.
They help to split the newly copied DNA that goes into the new cells during cell division. These agents disrupt or stop the formation of these spindles and interrupt cell division as a result. Examples of drugs include Vinblastine (Velban), Vincristine (On covin), and Pacitaxel (Taxol). (Langerak, 2001) Side effects of chemotherapy Chemotherapy drugs doses and schedules are developed so that the drugs enter the body, kill the rapidly dividing cancer cells, and are expelled before they can damage most healthy cells. The majority of drugs currently on the market are not specific, which leads to the many common side effects associated with cancer chemotherapy. Since the goal of chemotherapy is to decrease the growth of cancer cells, the side effects are seen in bodily systems that naturally have a rapid turnover of cells, such as white blood cells, hair follicle cells, and cells lining the gastrointestinal tract. These normal cells also end up damaged by the chemotherapy.
Common side effects include: Dry, flaky skin and mouth sores (when skin and mouth cells are damaged) Loss of hair (when hair cells are damaged) Nausea and vomiting and appetite changes (when stomach and intestine cells are damaged) Blood clotting problems (when bone marrow cells are damaged, interrupting normal platelet production) Compromised immune system making it more difficult to fight infections (when white blood cells are destroyed by the chemotherapy) Possible sterility (when the reproductive organs are damaged) Anemia (when damaged bone marrow cells cannot produce enough red blood cells, causing fatigue) Decreased sexual desire (when hormones are affected by the drugs) The severity and presence of side effects differ from person to person. Individuals also have different reactions with each treatment. (Mckinnell, 1998) Conclusion Through chemotherapy and the use of other drugs that directly affect the body on a cellular level, many cancer patients are able to carry on happy and fulfilling lives. The focus now is not so much curing the symptoms of cancer, as it was before, but dealing with the source and root of the origin of cancer, which demands that we learn more about what happens inside our bodies and how our cells function. Although our knowledge of signal transduction is still limited, it is nevertheless widely accepted that the more we discover and know about how cells communicate with each other and grow, the closer we come to finding the ultimate cure for the deadly cancer.
References Coleman, William B. , Tsongalis, Gregory J. 2001, The Molecular Basis of Human Cancer, Humana Press. Kruh, Gary D. , Tew, Kenneth D. 2000, Basic Science of Cancer. Current Medicine. Langerak, Alan D. , Dreisbach, Luke P. 2001, Chemotherapy Regimens and Cancer Care. Landes Bioscience. Mckinnell, Robert Gilmore, Parchment, Ralph E. , Pierce, G.
Barry. 1998, The Biological Basis of Cancer. Cambridge University Press.
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Research essay sample on Abnormal Cell Growth Leading To Cancer
