Re: Genetically engineered micro-organisms to fight disease?

bae_at_cs.toronto.no-uce.edu.yyz
Date: 07/06/04

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    Date: 6 Jul 2004 18:10:05 GMT

    In article <q62je0ptpdunud4tvt6hkv4iiiins6hen4@4ax.com>,
    klsk <laksdjk@jasjh.com> wrote:
    >bae@cs.toronto.no-uce.edu.yyz wrote:
    >
    >[snip]
    >>>I was thinking along the lines of creating a micro-organism (virus,
    >>>bacteria,
    >>>phage whatever) that homes in on cancer cells or whatever and destroys it.
    >>>I assume changing ones own gene is more difficult and carries more risk.
    >>
    >>If only it were so easy to distinguish a patient's cancer cells from
    >>his normal cells! This is the goal of chemotherapy and other methods,
    >>especially the extensive efforts to develop immunotherapies for
    >>cancer. Immunotherapy, in which the patient's immune system is induced
    >>to attack the cancer, is very promising, but it's been promising for a
    >>long time, and never seems to get out of clinical trials. The immune
    >>system is capable of being exquisitely tuned to identify molecular
    >>markers, far more than any microorganism could be. There's substantial
    >>evidence that the immune system normally recognizes cancer cells and
    >>extirpates them, and it's only when this mechanism fails that the cancer
    >>can develop. Spontaneous remissions are rare but real, and one theory
    >>is that the immune system suddenly recognizes the abnormal cells and
    >>attacks them. Immunotherapies try to induce this mechanism.
    >[snip]
    >
    >>From what I gather from diabetes (a family member has it, hence my interest)
    >the
    >immune system for some reason begins to think beta cells are foreign and
    >attacks them.

    This is Type I diabetes, also called juvenile diabetes or
    insulin-dependent diabetes. More common, and becoming epidemic, is
    Type II diabetes, in which the body's cells no longer respond
    adequately to insulin produced by the pancreas. It usually occurs in
    middle aged obese people and can often be controlled by weight loss,
    careful diet and/or drugs that reduce blood sugar.

    >While reason for it is not known it is assumed that a viral infection somehow
    >changes some "protein lining" (I'm not sure what it was called) in the
    >betacells
    >making them look foreign. Other reasons are assumed also. Current research is
    >looking for ways to change this.

    The last time I looked the popular theory was that some people have a
    variant form of one of the surface proteins on their beta cells which
    is similar enough antigenically to some viral or bacterial antigen that
    when the person is exposed to the virus or bacterium, the antibodies
    produced to fight the pathogen cross-react and also attack the beta
    cells. So Type I diabetes is an autoimmune disease, in which the
    immune system mistakenly attacks normal tissue as if it were a
    pathogen. Some other autoimmune diseases are lupus and rheumatoid
    arthritis and IIRC, myasthenia gravis and multiple sclerosis.

    >What if other cells have a similar structure and in same ways vulnerable.
    >Could a
    >virus be designed to induce cancer cell attack in the same way beta cells are
    >attacked? It is also believed that when new betacell grow they are attacked
    >and
    >destroyed. Some diabetics have minuscule insulin production. So the immune
    >system
    >has developed an immunity against it own body (unfortunately). Could there be
    >a way to create a similar immunity to cancer cells.

    Ideally, yes. This is the goal of immunotherapy for cancer -- to
    identify some distinctive antigen on the patient's cancer cells'
    surface that is not found in normal cells, and induce the immune system
    to regard that antigen as foreign and produce antibodies to attack the
    cancer cells. I.e., to "immunize" the person against the cancer.

    Unfortunately, in practice, since the cancer cells have the same genome
    as the patient' normal cells, the surface antigens, which are proteins,
    are pretty much the same. There have been some promising clinical
    trials of these techniques, but AFAIK, none have panned out in general
    use. Research continues along these lines, because if it can be gotten
    to work, it would be very good treatment method.

    Your idea of using a virus to 'flag' cancer cells with a foreign antigen
    so the immune system can identify and destroy them is an interesting one,
    but the virus would have to flag only cancer cells and not normal ones,
    i.e. distinguish the two, which is not easy. Also, one characteristic
    of cancer cells is that the 'quality control' mechanisms for reproduction
    and self-repair in normal cells are disrupted, so they mutate rapidly,
    become diverse, and any cells that happen to be resistant to a particular
    treatment will survive, multiply and take over in the same way that
    strains of bacteria become resistant to antibiotics.

    >Just trying to bring up ideas. Like I posted previously treatment research
    >that
    >fails for one ailment may suprisingly benefit another.

    That's certainly true. Since people often have more than one thing wrong
    with them, drugs developed to treat one condition may have surprising
    effects on others. The first class of drugs to be effective in treating
    schizophrenia was developed as antihistamines to treat allergies. The
    antibacterial sulfa drugs were started out as textile dyes. A class of drugs
    developed to kill parasitic worms in livestock is now being used in cancer
    chemotherapy.

    Again, your ideas are good. Some are already being worked on, and some
    will be promising if the technology to implement them is developed.

    Btw, I'm not as au courant with this field as I was some years ago, and
    things are rapidly changing. So if anything I've posted is incorrect or
    out of date, I'd appreciate corrections.

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