Why don't we get cancer all the time?

Discussion in 'Biology & Genetics' started by S.A.M., Dec 22, 2007.

  1. S.A.M. uniquely dreadful Valued Senior Member

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    In human cells, both normal metabolic activities and environmental factors such as UV light can cause DNA damage, resulting in as many as 1 million individual molecular lesions per cell per day

    A cell that has accumulated a large amount of DNA damage, or one that no longer effectively repairs damage incurred to its DNA, can enter one of three possible states:

    1. an irreversible state of dormancy, known as senescence
    2. cell suicide, also known as apoptosis or programmed cell death
    3. unregulated cell division, which can lead to the formation of a tumor that is cancerous


    So why don't we get cancer all the time?

    John W. Pepper of The University of Arizona in Tucson and his colleagues used a kind of computer model called an agent-based model to compare different modes of cellular reproduction.

    The results indicate that if cells reproduce by simply making carbon-copies of themselves, the cells' descendants are more likely to accumulate mutations.

    In contrast, if cellular reproduction was much more complicated, the cells' descendants had fewer mutations.

    Multicellular organisms use a seemingly inefficient process to replace lost cells.

    An organ such as the skin calls upon skin-specific stem cells to produce intermediate cells that in turn produce skin cells.

    Although great at their job, the new skin cells are evolutionary dead ends. The cells cannot reproduce.

    Losing the ability to reproduce was part of the evolutionary path single-celled organisms had to take to become multicellular...
     
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  3. cosmictraveler Be kind to yourself always. Valued Senior Member

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    We have a IMMUNE system that gets rid of the unwanted cells. It is when

    the IMMUNE system breaks down is when cancer takes over.
     
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  5. USS Exeter unamerican american Registered Senior Member

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    ^you are correct
     
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  7. Shangorilla Registered Member

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    Wait, wait…I have an immune system? Lol.
     
  8. Idle Mind What the hell, man? Valued Senior Member

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    Umm, did anyone that's posted above me actually read SAM's topic? Her thread title was rhetorical, I'm sure. The last line of her post is the one she is likely trying to generate discussion with.
     
  9. [a-5] Sex machine, coin operated. Registered Senior Member

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    Winnar!
     
  10. Donnal Registered Member

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    my white cells are showing thru my skin
    and when the doctors thought i had cancer in moles they cut one big one out
    and it was not cancerous the doctor said to me thats impossible
    for a cancerous mole to be not at all cancerous
    well i defied the laws of cancer then
    i still got one mole and these white cells are popping round it
    and i know they are attacking my moles fighting cancer off
    my body has more white cels than normal is why im very neamic
    i showed people my mole and the white cells only cause they asked what are those
    i cant get rid of them doctors tried they eventually said after tests my white cells show thru my skin
    kinda hate it really untill they finished there fight they remain showing
    kinda weird i reckon
     
  11. Hercules Rockefeller Beatings will continue until morale improves. Moderator

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    Point 3 isn’t necessarily true. Just because a given cell accumulates lots of DNA damage and/or mutations does not mean it will develop unregulated division and become cancerous. A cell (or clonal descendents thereof) needs to gain a variety of different traits in order to become cancerous. This requires very specific mutations in very specific genes. The gene mutations required for metaplastic growth vary from tissue to tissue, although there are some common mutations found in nearly all cancers.

    It could be said that the more irreversible mutations a cell accumulates, the more chance that it will suffer the precise mutations in the precise genes that will result in cancer. But at the same time, the more irreversible mutations a cell accumulates, the greater the chance it will enter apoptosis.

    It takes a long time for a cell to accumulate the very specific mutations necessary for it to become cancerous which is why cancer is, predominantly, a disease of the middle-aged to elderly.


    AFAIK our immune system does not play a significant (if any) role in homeostasis of tissue cell number. Cancerous cells are usually able to evade the immune response. Development of cancer does not require the “break down” of the immune system. People with early stage cancer can have perfectly healthy and functional immune system.


    No, he/she isn’t.
     
  12. cosmictraveler Be kind to yourself always. Valued Senior Member

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    That is correct however after awhile the immune system gets "overloaded"

    and cannot keep up with trying to take care of all that is happening to the

    cells and becomes weaker and weaker until it finally gives out.
     
  13. kmguru Staff Member

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    December 21, 2007
    Scientists Weigh Stem Cells’ Role as Cancer Cause

    By GINA KOLATA
    Within the next few months, researchers at three medical centers expect to start the first test in patients of one of the most promising — and contentious — ideas about the cause and treatment of cancer.

    The idea is to take aim at what some scientists say are cancerous stem cells — aberrant cells that maintain and propagate malignant tumors.

    Although many scientists have assumed that cancer cells are immortal — that they divide and grow indefinitely — most can only divide a certain number of times before dying. The stem-cell hypothesis says that cancers themselves may not die because they are fed by cancerous stem cells, a small and particularly dangerous kind of cell that can renew by dividing even as it spews out more cells that form the bulk of a tumor. Worse, stem cells may be impervious to most standard cancer therapies.

    Not everyone accepts the hypothesis of cancerous stem cells. Skeptics say proponents are so in love with the idea that they dismiss or ignore evidence against it. Dr. Scott E. Kern, for instance, a leading pancreatic cancer researcher at Johns Hopkins University, said the hypothesis was more akin to religion than to science.

    At stake in the debate is the direction of cancer research. If proponents of the stem-cell hypothesis are correct, it will usher in an era of hope for curing once-incurable cancers.

    Read more...
     
  14. Exhumed Self ******. Registered Senior Member

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    Does molecular lesion = dna mutation in this context?

    I think she knows. She said it was one of the possibilities, not necessarily going to be the result.

    Is it that cancer is usually able to evade immune response or that by the time we actually find a cancer it means it has grown beyond the control of our immune response? The immune system can eliminate tumors, though I don't know the extent of its role either. Cosmictraveler was partially right.

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    By the way, what happened to the journal club?! Does this qualify?
     
  15. alanejackson Search + Share ~ Magnetrition Registered Senior Member

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    nuclear envelopes deteriorate

    <"So why don't we get cancer all the time?"

    After a study of "The Theory of Magnetrition", one becomes aware of the reasoning indicating that the cells of all warm-blooded animals are like a bird's egg, and must be reoriented periodically in a magnetic field like the Earth's. It becomes understood, that the function and structure of cells deteriorate due to the lack of sufficient turning in the Earth's magnetic field, in warm-blooded animals, after a certain age. One realizes, that cancer occurs mainly in older people because their nuclear envelopes deteriorate, along with their bones and other tissues, resulting in insufficient protection of the DNA while replicating. Yet it has been recorded that most people are willing to jump on bandwagons which blame things other than the true culprit, which is them not facilitating the required reorienting of their cells in a magnetic field, as they did when they were younger.
     
  16. Exhumed Self ******. Registered Senior Member

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    Mutagenesis is a well studied area. It is quite simple to test for a lot of mutagens in bacteria cultures. Mutations are cause cancer if they happen on proto-oncogenes. Usually those are genes we know that are involved in the regulation of growth. This has been verified by testing, and the explanation makes perfect sense. That is not what I'd call a bandwagon.

    I'd like to see some evidence for your magnetic-cancer theory. You could cheaply and quickly prove your magnetic theory by seeing if causes mutations with an Ames test. All you need to do is make a cell culture of mutant bacteria that are histidine auxotrophs in a histidine lacking culture and see if it causes any back mutations when you expose it to whatever magnetic changes you think are cancer causing. If you are right you will see a very noticeable increase in bacteria compared to before.
     
  17. alanejackson Search + Share ~ Magnetrition Registered Senior Member

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    side effects of osteoporosis

    The Theory of Magnetrition points out that menopause and cancer are side effects of osteoporosis, which occurs due to a lack of magnetically driven stirring in the cells of all warm-blooded animals. And also predicts menopause occurring as osteoporosis effects female astronauts who have left the Earth's magnetic field behind while venturing into space. As warm-blooded animals age, magnetosynthesis decreases. A point at which decreased magnetosynthesis is sufficient to prevent child development within the womb, is the onset of menopause.
     
  18. Exhumed Self ******. Registered Senior Member

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    All you have is a weak case of correlation. Where is the scientific testing behind your hypothesis?
     
  19. S.A.M. uniquely dreadful Valued Senior Member

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    *cough cough*

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  20. Hercules Rockefeller Beatings will continue until morale improves. Moderator

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    Cancer?

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  21. invert_nexus Ze do caixao Valued Senior Member

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    Quite an interesting phenomenon, that. Has this transition ever been witnessed?

    Reminds me of social insects.

    Some social mammals as well, for that matter.
     
  22. S.A.M. uniquely dreadful Valued Senior Member

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    I was hoping someone would think of the pRb or Retinoblastoma protein or some such.

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    Tumor suppression vs cell division?
     
  23. S.A.M. uniquely dreadful Valued Senior Member

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    Cellular differentiation into a specialised cell type, in general, suppresses cell division. Hence when neurons and heart muscle cells die, (stroke, spinal injuries etc), recovery is slow and difficult.

    Interestingly, although hepatic (liver) cells do not divide, if part of a liver is transpalnted the rest will grow back.

    Malfunctioning of signaling proteins (like pRb) which regulate cell division can result in tumors.
     
    Last edited: Dec 25, 2007

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