Cancer out-of-control growth because of damage to DNA

By Jacob Payne,2014-02-09 23:33
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Cancer out-of-control growth because of damage to DNA

Cancer out-of-control growth because of damage to DNA

What is cancer?

    cancer is a group of more than 100 diseases that develop over time and involve the uncontrolled division of the body’s cells.

     cancer can develop in virtually any of the body’s tissues

     each type of cancer has its unique features

     the basic processes that produce cancer are quite similar in all forms of the disease.

How does it start?

     Cancer begins when a cell breaks free from the normal restraints on cell division and begins to follow its own agenda for



     A tumor, or mass of cells

     may remain within the tissue in which it originated (a condition called in situ cancer),

     or it may begin to invade nearby tissues (a condition called invasive cancer).

     An invasive tumor is said to be malignant

     cells shed into the blood or lymph from a malignant tumor are likely to establish new tumors (metastases) throughout

    the body.

Benign tumors are often enclosed in a capsule of connective tissue.

    a. The cells are organized in orderly array.

    b. The cells grow slowly and are well differentiated.

    c. Because they do not affect surrounding tissue they usually are not considered a threat to health.

     Tumors threaten an individual’s life when their growth disrupts the tissues and organs needed for survival.

Some Major types of Cancer

    Cancers are named according to the type of tissue they affect.

     1. Sarcomas are cancers of connective tissues.

     2. Carcinomas arise from epithelium, including skin and epithelial linings of internal organs.

     3. Cancers of glands are adenocarcinomas.

     4. Lymphomas are cancers of lymph tissue.

     5. Cancer of bone marrow is leukemia.

    Dysplasia is an abnormal change in the sizes, shapes, and organization of cells in a tissue.

     It is often a precursor to cancer.

     Microscopically, the edges of the tumor look ragged and the cells clumped.

     These cells have many characteristics that alter their behavior from that of normal cells.

Characteristics of cancer cells

    Structural Abnormalities

     A cancer cell has a large nucleus, less cytoplasm, and is poorly differentiated.

     The cytoskeleton shrinks and becomes disorganized.

     Proteins of the plasma membrane become altered.

Uncontrolled Growth

     In a cancerous tumor, more cells are dividing than dying so growth continues unaffected by the usual contact inhibition

    provided by crowding.

     Cancer cells lack strong cell-to-cell junctions and so tend to move about (metastasis) and become malignant.

     Some cancer cells produce HCG which can be detected in blood and signal cancer somewhere in the body; cancer cells also

    produce angiogenin, which encourages new blood vessel development.

The Genetic Triggers for Cancer

    The transformation of a normal cell into a cancerous one is called carcinogenesis.

     1. Proto-oncogenes are normal genes that regulate cell growth and development.

     2. Oncogenes are modified from proto-oncogenes; they code for altered proteins that remove the controls on cell division--that

    is, cancer.

     Cancer cannot be caused by oncogenes alone but requires the absence or mutation of tumor suppressor genes.

    For example, retinoblastoma is normally suppressed by at least one gene, but if this gene is altered, the suppression

    is removed and cancer develops.

Oncogene activation

     During cell division, an oncogene may mutate in a way that triggers expression.

     Translocation may move an oncogene away from a regulatory nucleotide sequence that normally prevents its expression.

     New genetic material may be introduced into a cell (as by a virus) and disrupt controls.

Other Routes to Carcinogenesis

    Inherited Susceptibility to Cancer

     a. If a mutation occurs in a germ cell that removes controls over a proto-oncogene, the defect can be passed on to offspring.

     b. Most instances of inherited cancer susceptibility are more complicated due to the probable involvement of several genes. Viruses

     a. Viruses can become inserted into host cell DNA, possibly altering the functioning of proto-oncogenes.

     b. Viruses can carry oncogenes and insert them into host cell DNA.

    Chemical Carcinogens

     Some of the chemicals that cause cancer are by-products of an industrialized society, such as asbestos, coal tar, vinyl

    chloride, and benzene.

     Others are natural carcinogens such as aflatoxin produced by a fungus that grows on peanuts.

     Some chemicals may be "precarcinogens" that cause changes only after they have been altered by metabolic activity of the


     Radiation can damage DNA.

     Sources include UV from sunlight, X rays, cosmic rays, radon gas, and nuclear reactors.

Breakdowns in Immunity

    1. A healthy immune system regularly detects and destroys cancer cells by using cytotoxic T cells. 2. The protective function of the immune system can be compromised by drugs or even anxiety and severe depression. 3. Sometimes, the cancer itself can suppress the immune system.

Diagnosing Cancer

    A. Treatment is most effective in the early stages of cancer.

    B. Heeding the warning signs and undergoing routine screening is important to the early detection of cancer.

     1. Blood tests can detect tumor markers, such as the presence of the hormone HCG or PSA (prostate cancer).

     2. Radioactively labeled monoclonal antibodies are useful in pinpointing the location and size of certain tumors.

     3. Medical imaging techniques such as MRI, X rays, ultrasound, and CT are also used.

     4. The definitive detection tool is biopsy, the taking of a small piece of tissue for microscopic observation.

     5. A snippet of radioactive labeled DNA, called a DNA probe, can be used to locate gene mutations; however, it is expensive

    and usually not covered by insurance.

Treating and Preventing Cancer

    Chemotherapy can be used to disrupt DNA replication during the S phase of mitosis; unfortunately, these chemicals are toxic to healthy

    cells as well.

     1. Surgery is effective if the tumor is accessible and has not spread.

     2. Adjuvant therapy combines chemotherapy and surgery.

     3. Monoclonal antibodies are used to deliver lethal doses of radiation or anticancer drugs to tumor cells specifically. Immunotherapy is the use of substances such as interferon and interleukins to activate cytotoxic T cells to attack the cancer.

Biogen Idec

     World’s third largest biotech company

     goal is to enhance its therapeutic areas of oncology, neurology, dermatology and rheumatology.

     expertise in protein expression in mammalian cells and process sciences capability for cell culture

     In November 1997, RITUXAN became the first monoclonal antibody to be approved by the U.S. Food and Drug Administration

    for a cancer indication, and today it is the #1 seller of cancer therapeutics in the United States.

     Primary Target: B-cell non-Hodgkin’s lymphoma (NHL), which is a cancer of the lymphatic system

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