Word Count: 1209I chose to do my report onbecause it is a subject I want tolearn about and because it can probably fit 5 pages. Mybibliography is on the ending of the report, my teacher helped mewith it because I didnt know how to do it. Cancer is the name fortumors that are malignant. Malignant tumors do not respond tobody mechanisms that limit growing. Malignant tumors show a notnormal cell structure the same functional specialized cells. Alsocancer cells growing in laboratory tissue culture do not stopgrowing when they touch each other on a glass or other solidsurface but grow in masses several layers deep they are said to lackcontact inhibition. Loss of contact inhibition accounts for two othercharacteristics of cancer cells invasiveness of surrounding tissuesand metastasis spreading via the lymph system or blood to othertissues and organs. Cells are typically controlled by growth factorscompetence factors that stimulate cells to enter the beginning phaseof cell replication and progression factors that insure completion ofthe replication cycle.
The unrestricted growth rates of cells are dueto the activation and lack of inhibition of oncogenes. They arecancer causing genes.Cancer tissue that grows without limits competes with normaltissue for nutrients kills the normal cells by nutritional deprivation.Cancerous tissue also causes secondary effects with the symptomsof a malignant growth caused by the pressure of the growing tumoragainst surrounding tissue or the metastasis of cancer cells andtheir invasion of other organs. Cancers are graded as to degree ofmalignancy on a scale of one through four the distinction betweeneven benign and malignant neoplasms is obscure. All organs andtissues are susceptible to cancer.A lot of human cancers may be caused or at least triggered byvarious chemical agents. Alkylating agents are thought to have acarcinogenic effect because they chemically alter the cell’s nucleicacids.
Nitrites common additives in processed meat react withamines in the stomach to form nitrosoamines which someauthorities believe may be carcinogenic to humans. Othercommonly occurring carcinogens are azo dyes, polycyclichydrocarbons, and urethane. Certain carcinogens presentoccupational hazards. Asbestos particles once inhaled stay in thelung and act as an irritant. In the asbestos and constructionindustries workers have a high probability of developing a fatalcancer of the chest lining or abdominal lining 25 to 30 years afterthe initial inhalation of . Asbestos also has been linked to lung andcolon cancers in exposed individuals.
Oral cancer common in Indiais commonly attributed to the chewing of betel nuts. Although theapparently increasing incidence of some types of highly malignantcancers certain lung cancers and may be a result of improvementsin disease detection and diagnosis cigarette smoking and anincrease of atmospheric pollutants are also thought to play a part.Increasing evidence implicates viruses in induction of cancer.In the early 20th century Peyton Rous an American virologistshowed that certain fowl sarcomas could be transmitted byinjection of an agent invisible under the microscope and latershown to be an RNA containing virus. Since then other oncogenicor tumor causing viruses have been identified in experimentalanimals. Viruses of the herpes group some of which cause coldsores and chicken pox have been shown to cause cancer inexperimental animals.
Recent evidence indicates that othermembers of the herpes group such as the virus causing infectiousmononucleosis may cause human cancer. Human papillomavirushas also been shown to cause or initiate cancers. Some types ofHPV cause genital warts known as condylomata acuminata whichappear to cause invasive cancer of the cervix, vulva, vagina, orpenis.
There is evidence of synergistic effects of smoking andsome forms of HPV and cancer particularly cervical cancer inwoman. HPV 16 has been shown to be associated with some formsof Kaposi’s sarcoma. Surgical removal of the warts and lesions hasa 70% prevention of recurrence antiviral treatment with interferonsappear mildly successful when surgical removal is not successful.Some cancers may be triggered by changes in the body’sinternal environment as hormone imbalances. A first reported in1970 some daughters of mothers who had been givendiethylstilbestrol during pregnancy to prevent miscarriagedeveloped vaginal adenocarcinomas as young women.
There aregenetic tendencies for certain types of cancer like breast orstomach cancer and certain benign tumors like certain tumors ofthe eye, cartilage, and skin, some of which may later becomemalignant. Physical agents such as X-rays and radioactive elementsare also carcinogenic the high incidence of leukemia and othercancers in Japanese survivors of the atomic bombing of