I chose to do my report on cancer because it is a subject I want to learn about and because it can probably fit 5 pages. My bibliography is at the end of the report. My teacher helped me with it because I didn’t know how to do it. Cancer is the name for tumors that are malignant. Malignant tumors do not respond to body mechanisms that limit growth. Malignant tumors show abnormal cell structure compared to functional specialized cells.
Also, cancer cells growing in laboratory tissue culture do not stop growing when they touch each other on a glass or other solid surface. Instead, they grow in masses several layers deep. This lack of contact inhibition accounts for two other characteristics of cancer cells: invasiveness of surrounding tissues and metastasis, which is the spreading of cancer via the lymph system or blood to other tissues and organs. Cells are typically controlled by growth factors and competence factors that stimulate cells to enter the beginning phase of cell replication, as well as progression factors that ensure completion of the replication cycle. The unrestricted growth rates of cells are due to the activation and lack of inhibition of oncogenes.
They are cancer-causing genes. Cancer tissue grows without limits and competes with normal tissue for nutrients, killing normal cells by nutritional deprivation. Cancerous tissue also causes secondary effects, such as the symptoms of a malignant growth caused by the pressure of the growing tumor against surrounding tissue or the metastasis of cancer cells and their invasion of other organs. Cancers are graded according to the degree of malignancy on a scale of one through four. The distinction between even benign and malignant neoplasms is obscure. All organs and tissues are susceptible to cancer.
A lot of human cancers may be caused or at least triggered by various chemical agents. Alkylating agents are thought to have a carcinogenic effect because they chemically alter the cell’s nucleic acids. Nitrites, common additives in processed meat, react with amines in the stomach to form nitrosoamines, which some authorities believe may be carcinogenic to humans. Other commonly occurring carcinogens are azo dyes, polycyclic hydrocarbons, and urethane. Certain carcinogens present occupational hazards. Asbestos particles, once inhaled, stay in the lung and act as an irritant.
In the asbestos and construction industries, workers have a high probability of developing a fatal cancer of the chest lining or abdominal lining 25 to 30 years after the initial inhalation of asbestos. Asbestos has also been linked to lung and colon cancers in exposed individuals. Oral cancer, common in India, is commonly attributed to the chewing of betel nuts. Although the apparently increasing incidence of some types of highly malignant cancers, certain lung cancers, may be a result of improvements in disease detection and diagnosis, cigarette smoking and an increase of atmospheric pollutants are also thought to play a part. Increasing evidence implicates viruses in the induction of cancer.
In the early 20th century, Peyton Rous, an American virologist, showed that certain fowl sarcomas could be transmitted by injection of an agent invisible under the microscope and later shown to be an RNA-containing virus. Since then, other oncogenic or tumor-causing viruses have been identified in experimental animals. Viruses of the herpes group, some of which cause cold sores and chickenpox, have been shown to cause cancer in experimental animals. Recent evidence indicates that other members of the herpes group, such as the virus causing infectious mononucleosis, may cause human cancer.
Human papillomavirus has also been shown to cause or initiate cancers. Some types of HPV cause genital warts known as condylomata acuminata which appear to cause invasive cancer of the cervix, vulva, vagina, or penis. There is evidence of synergistic effects of smoking and some forms of HPV and cancer, particularly cervical cancer in women. HPV 16 has been shown to be associated with some forms of Kaposi’s sarcoma.
Surgical removal of warts and lesions has a 70% prevention rate for recurrence. Antiviral treatment with interferons may be mildly successful when surgical removal is not successful. Some cancers may be triggered by changes in the body’s internal environment, such as hormone imbalances. In 1970, it was first reported that some daughters of mothers who had been given diethylstilbestrol during pregnancy to prevent miscarriage developed vaginal adenocarcinomas as young women. There are genetic tendencies for certain types of cancer, such as breast or stomach cancer, and certain benign tumors, such as tumors of the eye, cartilage, and skin, some of which may later become malignant.
Physical agents, such as X-rays and radioactive elements, are also carcinogenic. The high incidence of leukemia and other cancers in Japanese survivors of the atomic bombing is evidence of this.
