Word Count: 1209I chose to do my report onbecause it is a subject I want to
learn about and because it can probably fit 5 pages. My
bibliography is on the ending of the report, my teacher helped me
with it because I didnt know how to do it. Cancer is the name for
tumors that are malignant. Malignant tumors do not respond to
body mechanisms that limit growing. Malignant tumors show a not
normal cell structure the same 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 but grow in masses several layers deep they are said to lack
contact inhibition.
Loss of contact inhibition accounts for two other
characteristics of cancer cells invasiveness of surrounding tissues
and metastasis spreading via the lymph system or blood to other
tissues and organs. Cells are typically controlled by growth factors
competence factors that stimulate cells to enter the beginning phase
of cell replication and progression factors that insure 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 that grows without limits competes with normal
tissue for nutrients kills the normal cells by nutritional deprivation.Cancerous tissue also causes secondary effects with 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 as to 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 also has 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 and 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 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 chicken pox 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
woman.
HPV 16 has been shown to be associated with some forms
of Kaposi's sarcoma. Surgical removal of the warts and lesions has
a 70% prevention of recurrence antiviral treatment with interferons
appear mildly successful when surgical removal is not successful.Some cancers may be triggered by changes in the body's
internal environment as hormone imbalances. A first reported in
1970 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 like breast or
stomach cancer and certain benign tumors like certain 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 of Hiroshima
and Nagasaki is evidence of this carcinogenic effect. In light
skinned people who spend much time outdoors, sunlight may be
carcinogenic. Sometimes irritations and diseases may predispose
an individual to cancer, as in the occurrence of cancer of the
esophagus associated with frequently swallowing very hot liquids.Symptoms are often nonspecific like weakness, loss of
appetite, and weight loss.
Sometimes side effects of tumor growth
are more severe than the actual effects of the malignancy like some
tumors secrete materials such as serotonin and histamine that can
cause drastic vascular changes. A tumor of an endocrine gland
such as an adrenal carcinoma may be responsible for producing
enormously increased numbers of hormone secreting cells. Cancers
that destroy tissue may also have serious effects like malignant
destruction of bone tissue may raise the blood level of calcium.Cancers can often be detected by visual observation palpation
X-ray study inspection by various optical probing instruments.
Cancers caught early before metastasis have the best cure rates.Once they are found cancers are treated by surgery, chemotherapy,
and radiation. Surgery is most effective if the cancer is caught
while still localized. Some cancers that spread to the lymph system
have frequently prompted extensive surgical removal of tissue .
Many cancers formerly treated surgically are now being attacked
by other means such as radiation therapy. Use of radioactive
elements specific for particular target organs such as radioactive
iodine specific for the thyroid gland is effective in treating
malignancies of those organs. Lasers are used to treat certain
cancers and certain subatomic particles like pions, are being used
experimentally.Chemotherapeutic agents that are are used to selectively
destroy cancer cells. In general they interfere with nucleic acid and
protein synthesis rapidly proliferating cells like cancer cells are
most susceptible.
Hormones such as and which may be
carcinogenic under some condition are also used in cancer
chemotherapy. Currently available chemotherapeutic agents are not
usually curative but merely ameliorate the severity of the disease
they are often toxic to normal rapidly proliferating cells such as
bone marrow cells. A chemotherapeutic technique known as
isolated perfusion can be used to minimize exposure to many toxic
drugs. In this method a pump and two tubes are attached to two
places in a network of blood vessels so that the drug only circulates
through the part of the system that is malignant.New approaches to cancer therapy still largely in the
experimental stage include immunological methods such as
vaccinating against cancer causing viruses or injecting sensitized
lymphocytes like antibody forming cells.
Recent research is also
directed toward elucidating the cellular events that are manifested
as uncontrolled growth and cancer. The fact that there are many
ways to interfere with the controls on genes may help to explain
why cancer is apparently caused by a diversity of agents and why
agents that interfere with the expression of genetic information like
nitrogen mustard, radiation, and some hormones, are sometimes
carcinogenic and sometimes therapeutic.This report was very hard to do because I had to look up all
these big scientific words up in the dictionay. I hope you think I did
a good job and I hope to get an A+.
The bibliography you wanted
is below.
Bibliography
D. M. Prescott, Cancer: The Misguided Cell (1973); Jay Roth, All
about Cancer (1985); R. Nery, Cancer (1986); Peter Farmer and
John Walker, ed., The Molecular Basis of Cancer (1985
