How do oncogenes cause cancer? What are proto oncogenes?
Get link
Facebook
X
Pinterest
Email
Other Apps
What are oncogenes?
Oncogenes, which are genes that can cause cancer, have
become a hot topic in cancer research. The word comes
from the Greek term onco, meaning tumor. Most cancer
researchers believe that somehow, usually over a period of
years, cancer causing agents (carcinogens) repeatedly
brought into the body, finally damage a critical piece of a
cell's genetic code. The damage causes the cell to send out
abnormal messages related to some aspect of cell growth.
As new cells spring from old, the misled cell leads an onslaught
of others that result in runaway growth. The altered
ones oncogenes take charge. More than twenty cancer
genes have been identified in experiments in animals or in
normal cells grown in the laboratory.
How do oncogenes work?
The oncogenes start dominating the way the cells behave.
They disrupt the usual schedule and direct the cell to continue
to grow. Most researchers believe that at least two
cancer genes must be created, by random error, before the
process starts. Although the role of each cancer gene is not
yet understood, scientists believe that the cancerous cell
growth is set off through a series of steps within the cell.
Some cancer genes apparently instruct the cell to overproduce
a growth factor protein or mistakenly produce an
abnormal growth factor. Others may tell the cell to ignore
signals to stop growing, perhaps by leaving growth factor receptor switches on at various points along the cell's surface.
Where have oncogenes been found?
Scientists have found versions of oncogenes in several kinds
of human cancer, including those of the breast, lung, bladder,
and bowel. In addition, DNA sequences nearly identical
to oncogenes have been discovered in normal tissue
cells throughout the animal kingdom, including those of
man. Researchers think that such "proto-oncogenes" have
existed throughout evolution and play a useful role in normal
cell division. What the researchers are investigating is
how these seemingly harmless genes become altered and
turned into cancer genes. They have found that by replacing
the genetic "on-off" switch of one gene, called c-myc, they
are able to control when and in what tissues it causes tumors
in mice. This is a critical breakthrough in learning precisely
how this gene and perhaps other cancer genes function.
The gene c-myc plays a role in the human cancer known
as Burkitt's lymphoma. Other researchers working with another
strain of oncogene, the ras family of oncogenes, have
found a single changed amino acid in the protein product
as the site for an altered gene product which they feel is
somehow critical in the development of cancer.
Oncogenes and proto oncogenes
Can viruses cause cancer?
Researchers believe there is some relationship between
viruses and cancers of the liver and cervix, Burkitt's lymphoma,
nasopharyngeal cancer, and adult T-cell leukemia.
However, although it is believed that these cancers may be
stimulated by viruses, there is no evidence that they spread
like typical viruses. Some other factor appears to be necessary
to cause the disease to spread.
What is malignant melanoma? Malignant melanoma is a less common form of skin cancer . When diagnosed early, it is easily cured. But if it is not found soon enough, it can be very difficult to treat. It is dangerous because, unlike the other skin cancers, it mestastasizes early and spreads quickly. It is one of the more uncontrollable cancers. The cell involved is the melanocyte, the cell which produces melanin, the dark protective pigment of the skin . What is the difference between an ordinary mole and melanoma? An ordinary mole is evenly colored, and either brown, tan or black. It may be flat or raised. It is round or oval and its edges are sharply defined. An ordinary mole is usually less than 6 millimeters in diameter about the size of a pencil eraser. Ordinary moles may be present at birth. Sometimes several appear at the same time, usually on areas of the skin which have been exposed to the sun. Once the mole develops, it usually stays the same size, shape and color for ma
What kinds of cancers are found in the mouth? The cancers of the mouth (oral cavity) include the lip, tongue, floor of the mouth, cheeks (buccal mucosa), and gums (gingivae). Who is at high risk to get cancer of the mouth? This cancer is predominantly found in men between the ages of 60 and 70. People who are heavy smokers (more than a pack a day), drink alcohol heavily, are over 45, and have a family history of this kind of cancer are at a higher risk to develop cancers of the oral cavity, the mouth, and the throat. Is cancer of the mouth easy to detect? Yes, it is usually discovered early, since it can be seen easily. White patches ( leukoplakia ), velvety red spots (erythroplasia), or dark patches are symptoms which should be seen by a doctor, who will do a biopsy of them. Many cancers of the mouth are first discovered by dentists. What are the symptoms of oral cancer? The warning signs of oral cancer are as follows: • A lump in the cheek that can be felt with the
Yes. After prostatectomy , the ability to ejaculate through the penis is lost. What happens is that ejaculation occurs but it is directed backward into the bladder , rather than forward through the urethra. The semen remains in the bladder until urination, and is carried out via that route. The man who ejaculates in this manner has the very same sensations during sex that he had before except that there is no discharge through the penis. Can a total prostatectomy be done without impairing the ability to have an erection? Dr. Patrick C. Walsh, a surgeon at Johns Hopkins University Hospital in Baltimore, Maryland, has developed a way of removing the prostate which preserves potency by bypassing the intricate nerve branches of the pelvic plexus. This technique is now being adopted by many surgeons for patients with early stage prostate cancer. Until the advent of this type of surgery, 90 percent of those having prostatectomies lost their sexual ability, and 2 to 5 percent became in
Fractures of the Ankle How do ankle fractures occur? Ankle fractures are caused by a forceful and excessive twisting of the ankle , either in or out. The twist comes from stumbling, catching the foot in a crevice, or falling, in which the weight of the body is unevenly distributed. Many skiers suffer fractured ankles, and some of the best treatments have been evolved by surgeons practicing near ski slopes. The stress and strain factors in the ankle are so uniform that the pattern of the injury, dislocation and deformity is specific. Many varieties of ankle fractures are grouped together under the name of Pott's fracture. What shall I do, Doctor? I'm at a gas station phone and my wife just fell down and twisted her ankle. If it is painful and she can't walk, it may be a fracture. Don't manipulate it, don't pull it. Just wrap a towel or pillow around it and take her to a hospital for an X ray. It is best if she does not walk. You can carry her in a chair.
What is a bone marrow transplant? Bone marrow transplantation is an approach used over the past 10 years for the treatment of acute leukemia and lymphoma. It is a complex procedure and should be undertaken only by physicians with the experience and resources needed to get the best results. When is a bone marrow transplant used? It may be used in some cases of several types of diseases aplastic anemia (when patients do not have enough red cells to carry oxygen, enough white cells to fight bacteria, or enough platelets to help clotting), in some types of acute and chronic leukemia, for some lymphomas, for severe combined immunodeficiency syndrome, and for certain inherited blood disorders such as thalassemia. A bone marrow transplant replaces a patient's abnormal or diseased marrow with healthy marrow from a donor. Can any leukemia patient undergo a bone marrow transplantation? No. When patients and doctors consider the possibility of treatment with a bone marrow transpl
Would the doctor prescribe estrogen if my ovaries were removed because of cancer? No. If there is any sign of a cancerous condition, estrogen would probably not be prescribed. What is the estrogen controversy? Estrogen is a female hormone produced by the ovaries. Scientists have also developed chemical estrogen. Both regulate the development of female sexual characteristics. For a number of years, estrogens have been prescribed for women during and after menopause to make up for the decline in this hormone normally produced by the ovaries. Estrogen has been found helpful in relieving symptoms associated with menopause, such as hot flashes, in overcoming drying of vaginal tissues and in retarding osteoporosis (thinning of bones). However, the use of estrogen during and after menopause has been linked to an increase in endometrial cancer (cancer of the lining of the uterus), and it may be linked to other cancers as well. At this time,scientists do not agree about whether t
Head Injuries The brain is man's most vital possession. Recent details about organ transplants have centered on the definition of death. These discussions have emphasized that, even though the heart may continue to beat, the individual is considered dead if there is no brain activity. Nature provides a thick scalp and skull to protect the brain and further encloses it in envelopes called the meninges. Some injuries to the head may be trivial, others may be fatal. The surgeon who is called upon to evaluate the patient with a head injury tackles the problem from within out. Damage to the brain and its envelope is most important; injury to the skull is of concern in only some instances. Bleeding from the scalp is the most apparent manifestation of injury but is the least important. Survival and the late effects of a head injury depend on the extent of the injury to the brain and not to its coverings. The best possible supportive medical crre is provided to those who will reco
Chest Injuries The chest consists of the bony thorax and the organs that lie within it. The thorax comprises twelve ribs on each side of the chest, each of which attaches to the bony spine in the back and to the chest bone ( sternum ) in front. Each chest cavity has a smooth delicate lining ( pleura ) within which the lung rhythmically expands and deflates. The diaphragm is the dome shaped muscle that seals off the lower end of the chest from the abdomen. Its upand down motion provides the bellows action for the expansion of the lungs that fills them with air. The function of the lungs is to provide ventilation. Air is moved in to provide oxygen, and carbon dioxide is moved out as a waste product. The heart is in its own envelope in the center of the chest, behind the breastbone. The heart functions solely as a pump. It circulates the blood into the lung for oxygenation and delivers oxygenated blood to the entire body. The chest also harbors the large blood vessels and the br
Hodgkin's Disease and Non-Hodgkin's Lymphoma What are lymphomas? Lymphomas are cancers that affect the white blood cells of the immune system. They are characterized by the abnormal growth of lymphocytes, the infection fighting cells in the lymph nodes, spleen, and thymus. The tonsils, stomach, small intestine, and skin may also be affected. Lymphomas are usually classified as Hodgkin's disease, the most common form, or non-Hodgkin's lymphoma. There are also other rare forms of the disease, such as mycosis fungoides, a primary skin lymphoma. Burkitt's lymphoma , rare in most of the world, is the most common childhood cancer in central Africa and is one of the fastest growing human cancers. What is the role of the lymph system in the body? The lymph system is made up of nodes and thin walled tubelike veins along which the nodes lie. Its job is to help fight diseases and infection, and it serves as part of the body's drainage system. Lymph nodes are
Hand Injuries Most of us earn our living with our hands. The goal of the treatment of hand injuries is maximum preservation of function. In terms of possible permanent disability, there is no minor surgery in this area. The magnitude of the problem is apparent in the frequency with which it appears in the statistics of the Workmen's Compensation Board and insurance companies. The best treatment is prevention. One must be constantly alert to the possibility of punctures, door slams, burns, pressure injuries, and the perverse potential of certain mechanical tools. Failing this, early treatment to prevent infection is best. There are relatively clearly defined methods of managing various types of injury. The patient can describe the site of the injury by indicating its relation to the various creases in the palm or to the knuckles and nails on the back of the hand. Physicians can treat all hand and finger injuries under some form of nerve blocking anesthesia, so the patient feels
Comments
Post a Comment