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Diseases

CANCER

*The first cancer experiments took place in 1910
*Peyton Rous took chicken tumor cells and was able to “infect” healthy chicken cells
*Scientists couldn’t explain the reasoning for this because so many different things seemed to be associated with cancer
*In 1700, an Italian physician wrote about the high rate of breast cancer among nuns and speculated that it was related to their celibacy and childlessness
*This was the first indication that how one lived might affect the development of cancer
*In 1775, a London physician, suggest that the very high rate of scrotal and nasal cancers among chimney sweeps was a result of their exposure to soot
*This was the first indication that exposure to certain chemicals could lead to cancer
*In 1886, a professor at the Medical School in Rio de Janeiro, reported the case of a family with an increased susceptibility to retinoblastoma, a form of cancer that normally occurs in only one out of about 20,000 children
*This was the first indication that cancers have a hereditary basis
*The discovery of x-rays in 1895 led to its association with the skin cancer on the hand of a lab technician by 1902.  Within a decade, many more physicians and scientists, unaware of the dangers of radiation, developed a variety of cancers
*In 1907, an epidemiological study found that the meat-eating Germans, Irish, and Scandinavians living in Chicago had higher rates of cancer than did Italians and Chinese who ate considerably less meat
*First indication that your home environment can cause cancer
*“Tumors destroy man in a unique and appalling way, as flesh of his own flesh which has somehow been rendered proliferative, rampant, predatory, and ungovernable…Yet, despite more than 70 years of experimental study, they remain the least understood…What can be the why for these happenings?”
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*Peyton Rous, in Nobel Prize Acceptance Speech 1966
*Much research has been done to answer Peyton Rous’ question of why cancer happens
*Cancer develops when mutations occur in genes that normally operate to control cell division
*Mutations can be caused by a wide variety of environmental agents, viruses, and inheritance
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*What is cancer?
*Cancer is  a group of more than 100 diseases that develop across time and involve the uncontrolled division of the body’s cells
*Cancer can develop in any of the body’s tissues and each type of cancer is unique but the basic processes that produce cancer are similar in all forms of the disease
*Cancer begins when a cell breaks free from the normal restraints on cell division and begins to follow its own agenda for proliferating
*All of the cells produced from the first mutated cell also divide inappropriately creating a tumor
*A tumor, or mass of cells, formed of these abnormal cells may remain within the tissue in which it originated or it may invade nearby tissues
*An invasive tumor (cells that invade nearby tissues) is said to be malignant
*Cells of malignant tumors can create tumors in other parts of the body by traveling through the blood

Body's Defenses

*In order to prevent cancer, your body has three lines of defense
*1.  DNA repair mechanisms – when DNA is replicated it is checked to make sure it was copied correctly.  If not then the cell does not move on in the cell cycle until the correction is fixed
*2.  Apoptosis – ‘cell suicide’ if something is wrong in the cell, the cell will ‘kill itself’
*3.  Cells have a fixed number of divisions – this assures cells cannot reproduce endlessly
*Let’s review the cell cycle so we can see where the body’s defenses come into play
*Interphase consists of 3 stages:
*G1 – Growth 1
*S – Synethesis (DNA replication)
*G2 – Growth 2
*Mitosis consists of 4 Stages:
*Prophase
*Metaphase
*Anaphase
*Telophase
*Cytokinesis
*The first defense acts directly on the DNA
*As DNA replicates, it is being checked for mutations
*Apoptosis is regulated cell death
*If a major component of the cell is damaged or if the control system is deregulated, the cell will ‘kill itself’
*It sends signals out to surrounding phagocytes that will digest the cell and get rid of it
*Apoptosis can also occur during the cell cycle if the damage is extreme
*The cell cycle has 3 checkpoints:
*G1
*G2
*Mitosis
*Finally, cells have a fixed number of divisions
*As they divide, the telomeres shorten, when they shorten enough the cell can no longer replicate
*Early observations suggested that certain life styles were responsible for cancer because life styles exposed people to certain chemicals
*But then there was also the fact that cancer can be hereditary
*These facts confused scientists because so many chemicals could eventually cause cancer
*The variety of observations also allowed scientists to figure out how cancer comes to be
*For example, when Rous transferred tumor chicken cells into healthy chicken cells, displayed to scientists that cancer can be traced simply and definitely back to a  single cause
*Rous’ work forced scientists to research cancer at the cellular level (DNA and cell cycle)
*Cell biologists studied cells by observing them in the lab and creating inferences from their appearance in the whole organism
*This approach allowed doctors to realize that tumors arise from one’s own tissues, not from cells introduced into the body by infection
*Cell biology has also discovered that tumors are monoclonal, meaning that tumors arise from one type of normal cells
*There are two scenarios that describe this.
*The first scenario:
*Many individual cells become cancerous and the tumor is a result of these original cells
*The second scenario:
*One cell becomes abnormal and the tumor is a result of the decedents of that one cell
*Again, cancer is a disease which a single normal body cell undergoes a genetic transformation into a cancer cell
*This cell proliferates causing a tumor
*It is still difficult to find the exact origin of a tumor because once a tumor forms, the cells display different characteristics
*Tumor cells are constantly changing depending on the environment
*A second trend found by cell biologists is that cancer cells are very different from normal cells
*Cancer cells are unstable and are prone to rearrangements, duplications, and deletions of their chromosomes
*Because of these characteristics, all cancer cells display unusual and different traits
*The nucleus of normal cells is 1/5 the size of the cell, the nucleus in cancer cells occupies most of cell’s volume
*Because of the mutations, tumor cells have different traits from their original cell
*For example: Normal secretory cells produce and release mucus.  Cancer cells may no longer do this
*The key difference between cancer and normal cells is that cancer cells have lost restraints on growth that characterize normal cells
*A large number of tumor cells are engaged in mitosis while normal cells rarely go through mitosis
*Through all this research, scientists were able to create a unified view of cancer in the 1970s
*Cancer begins because carcinogens (cancer causing agents) induce mutations in critical genes and these mutations direct the cell and its offspring to grow abnormally
*The result of this abnormal growth appears years later as a tumor
*We now know the body’s defenses against cancer
*Because of these defenses, cancer does not develop at once from a mutation of one or two genes
*Instead it develops step-by-step, across time, as an accumulation of many molecular changes
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*Tumors generally consist of 10 billion to 100 billion cells
*It can take years before this happens and then spreads to other parts of the body
*Understanding cancer as a multistep process explains many observations
*This explains why cancer occurs more often in older people
*Older people have experienced a complex and extended succession of events,
*Cancer as a multistep event also explains why people who are exposed to carcinogens more often develop cancer
*It also explains inheriting a cancer-susceptibility mutation.  Instead of the mutation being a rare event, it has already occurred
*Finally, it also explains the lag time between the exposure to a cancer-causing agent and the development of cancer
*For example, it explains the 20-25 year lag between the onset of lung cancer of women who smoked during World War II
*Now we have a basic understanding of what cancer is and how it is caused, let’s look at who is effected by it the most
*More than 8 million Americans have a history of cancer
*Cancer is the second leading cause of death in the United States, exceeded only by heart disease
*Cancer among children is relatively rare
*Cancer is the second leading cause of child death
*Leukemias and cancer of the brain and other nervous system organs account for more than one-half of the cancer among children
*The overall survival rate for all cancer sites combined is increasing
*From 1974-1976 there was a 49.3% chance of survival
*From 1983-1990 it increased to 53.9%
*This increase can be credited to science research and the improvement in detecting cancer
*There have been improvements in detecting and diagnosing cancer early
*Americans are more aware of symptoms and are cautious
*Surgery, radiation, and chemotherapy are being used more specifically based on the type of cancer
*There is also ongoing drug research to restore a cancer cell to normalcy

 *We have been discussing the history of cancer and how scientists discovered it

*Now we will discuss society’s role in fighting cancer
*The cost of cancer is large
*The National Cancer Institute estimates annual costs of cancer at about $107 billion
*This includes:
*$37 billion for direct medical costs
*$11 billion for morbidity costs (morbidity – probability of getting sick)
*$59 billion for mortality (death)
*The treatment for breast, lung, and prostate cancers account for more than ½ of the direct medical costs
*One way to decrease the costs of cancer is to prevent it
*Although citizens know the harmful effects of certain lifestyles, people are still not convinced about prevention
*This could be because cancer is random and scientists can not pinpoint who will get cancer and who will not
*Unhealthful habits also may persist because of the long time that elapses between exposure and actual development of cancer
*Because of the lag time scientists have developed four levels on which to prevent cancer
*First level of prevention: Individual
*Individuals need to take responsibility and live healthier lives
*Second level of prevention: Health care Providers
*They provide counseling and screening to individuals
*Third level of prevention: National
*Government impose regulations that help minimize the public’s exposure to carcinogens
*Forth level of prevention: International
*Actions of individual countries can help prevent world-wide spread
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*Is it okay for the government to make these decisions for us?
*Ethics is the study of good and bad, right and wrong
*For our purposes, something that is “right” or“good” fosters the interests of individuals
*Something that is “wrong” or “bad” impairs the interests of individuals
*Although certain ideas and actions may be ethical in America, they may not be ethical in other countries
*For example, developing countries who do not have the resources America does, take different approaches to cancer and different standards for marketing tobacco and other carcinogens
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*That brings us to the question: is it ethical for the Unites States to prevent the widespread use of tobacco in other countries since tobacco contributes to lung cancer?
*Is there any legal and/or ethical way to govern other choices of individuals that contribute to cancer? (Such as poor diet and lack of exercise?)
 
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