Gene Therapy What is Gene Therapy

Document Sample
Gene Therapy What is Gene Therapy Powered By Docstoc
					What is Gene Therapy?

Human gene therapy is a scientific technique, by which a segment of nucleotide sequence or
gene is inserted into an individual's cell for the purpose of treating diseases. The main principle
behind gene therapy is to restore the normal functioning of cells and tissues by replacing
abnormal or mutated genes. In simple terms, it is a method of correcting defective genes. There
are several ways of implementing gene therapy; inserting a normal gene in the genome to replace
a defective gene and changing the regulation for expression of a specific gene. Another method
of gene therapy is to apply selective reverse mutation so that the defective gene returns to its
original                                                                                     form.

Gene therapy can be broadly classified into two types:

One is the somatic cell gene therapy and the other is the reproductive cell or germline gene
therapy. In somatic cell gene therapy, the somatic cells are targeted for gene replacement,
whereas in the reproductive cell gene therapy, the defective gene lies in the reproductive cells
that are replaced by the correct gene. The alterations made in the genetic makeup of the somatic
cells is corrective only for the patient. This change is not inherited by the treated person's
offspring. However, in case of germline gene therapy, the changes are passed on to the
descendants                 of                the                treated              individual.

                            Gene therapy Pros & Cons
Some cried when the concept of gene therapy first surfaced. For them tinkering with the genetic
constitution of human beings was equivalent to playing God, and this they perceived as being
sacrilegious! On the other side was the scientific community, abuzz with excitement at the
prospect of being able to wipe certain genetic disorders in humans entirely from the human
gene pool. Although the term gene therapy was first introduced during the 1980s, the
controversy about the rationality of this line of treatment still rages on. In the center of the debate
lie the gene therapy pros and cons that derive opinions from religious, ethical and undoubtedly,
political domains.

In order to be able to appreciate people's concerns about gene therapy there is need to first
understand the pros and cons of gene therapy. Gene therapy is thought of by some people as an
terrific discovery that could greatly improve the human population and also give people with
certain disabilities some glimmer of hope. And on the other side of the coin there is some people
that think we have no business playing God. They feel that playing God may possibly cause
devastating effects to the human gene pool and may also led to misuse.

Pros of Gene Therapy:
I think the pros all seem like very good ideas and gene therapy is a successful experiment.The
single most factor that gives gene therapy its edge is its incredible therapeutic potential.Gene
therapy absolutely is the key to solving many mysteries about genetic disorders and potentially
can help to develop cures.

“We   used to think that our fate was in our stars,” but now we know that, in large measure, our
fate is in our genes, quotes James Watson. This fate that Watson is talking about is contained in
our genes, and deals with a new technique, gene therapy. Gene therapy is revolutionizing the
world of medicine. Many physicians are predicting that in twenty years gene therapy may change
the practice of medicine from a treatment-based to a prevention-based practice. Our future is
locked away inside of our genes. Gene therapy is unlocking these doors. Researchers are starting
to move away from developing new drugs, and towards finding an ultimate solution. That
solution is to use gene therapy as a treatment for many genetic diseas es. Researchers hope that
in the coming years, every genetic disease will have gene therapy as its treatment. Gene therapy
could be the last therapy that the human race will ever need.

    The human race has always been under the continuous onslaught of diseases. As we find
     cure for some of the diseases, we are attacked by new and more virulent forms of germs.
     Although such diseases can be cured through medicines, genetic disorders have no cure
     unless the defective gene is replaced by the correct one and this is what gene therapy
     aims at. Moreover, by targeting the reproductive cells, such defects can be got rid of for
     good. People suffering from genetic disorders like Parkinson's disease,Alzheimer's
     disease and Huntington's disease are some of those whose only hope for cure is gene

    There have been numerous revolutionary breakthroughs in gene therapy of disorders
     like     inherent blindness, cancer,    myeloid     disorders,   and     sickle-cell
     disorders. Cancer treatments focus on re-engineering lymphocytes to target and
     attack cancer cells, or using tumor-suppressing genes to reduce number and size of

    There are many other diseases that may be cured by gene therapy of which include
     Rubinstein-taybi syndrome, partial epilepsy, cataracts, prostate cancer , male infertility,
     Alzheimer’s, schizophrenia, usher syndrome, and maternal acute fatty liver of pregnancy.
     All of these disorders had there genes identified in 1995.Because of its accuracy, gene
     therapy has the potential to eliminate cancer cells without damaging normal, healthy
     tissue. Furthermore, cancer gene therapies may provide alternatives when a disease does
     not respond to other older treatments.

    Though the technology of human gene therapy is not so advanced in the present
     scenario, it has already widened the scope of medical science. As all genetic disorders
     and most of the chronic diseases involve malfunctioning of the genes, gene therapy is a
     promising technique for treatment of such severe health conditions. Genetic researches
     based on human gene therapy are ongoing to discover treatment options for chronic
     medical conditions such as heart disease, cancer, cystic fibrosis and AIDS. Nowadays, private
       grants as well as government grants are provided so as to encourage studies on human
       gene therapy.

    Many families have fears that existing conditions will continue to be passed on to future
     generations. Gene therapy offers these people the hope that hereditary disorders will one
     day be eradicated. People with existing conditions also may benefit from current and
     future developments in the research of gene therapy. Gene therapy is the only existing
     option for one day curing and preventing future genetic disorders.

Cons of Gene therapy:

Meanwhile, the cons are a bit more negative though. Some people think that we will get burnt
trying to play God while others think this is a great advancement for man kind.
One reason for unacceptance may be that gene therapy may be used for the enhancement or
modification of human capabilities. If this were feasible, the standards of a normal human being
would be changed. Even if some small countries experimented with gene therapy, could they
develop unstoppable armies? If gene therapy was done to a certain extent could it alter the
human gene pool for good? And also would this form of treatment be a luxury only for the rich
which could very well make the rich, richer and make the poor, poorer.

Scientific Issues:

A negative aspect of gene therapy includes that it is still largely uncharted territory. Most of the
science behind it depends on theories and ideas rather than solid facts.
     Although the most popular choice as a vector, using virus for the purpose is not
       foolproof. There is a specific point within the host genome where the correct gene should
       be introduced. There is no guarantee that the viral enzyme that is responsible for this step
       will be able to introduce the correct gene at the specific point in the host chromosome. In
       case, there is an error in this process, it would result in error in the genetic makeup of the
       cell and can result in serious disorders.

    There are many potential side effects of using viruses as vectors, some of which include
     target-related problems, inflammatory response of the immune system and at times,

    A more recent technique of human gene therapy is to introduce the normal gene directly to
     the target cell without using vectors. Though this method sounds comparatively easy, it is
     not applicable to all types of target cells. Another disadvantage of this method is that it
     requires                large                amount                of               DNA.

    Moreover, the body's immune system may destroy the vector as it may perceive the
     carrier as a foreign body. Then there are problems with introducing therapeutic DNA and
     the rapidly dividing nature of certain cells that are hurdles in gene therapy providing long
     term benefits to patients. Due to this reason a patient may need to undergo multiple gene
     therapy treatments. But with this again comes the problem of the immune system. Once
     the immune system is triggered by a foreign body, it attacks the foreign body more
     aggressively        when        it      invades         the       body       next      time.

Ethical Issues:

Ethical as well as legal issues are concerns when discussing gene therapy.Given the technology
involved, it is obvious that gene therapy treatment will be expensive. It will be just the rich
who would be able to afford its benefits. This gives rise to the refrain that gene therapy will
make the rich, richer and the poor, poorer.We know the potential of reproductive gene therapy.
The scope of this line of treatment triggers the fear of eugenics - a term that denotes creation of a
superior race, the idea that media has tried to embody in the concept of designer babies. The cost
of gene therapy is high at this time and could be a concern for families with that need lifelong
treatment and do not have health care.

Religious Issues:

Manipulating genetic makeup of man is absolutely unacceptable by those with strong religious
beliefs. According to them altering genes is similar to tinkering with nature. It's like questioning
God's will or in other words, 'playing God'. They feel that playing God may possibly cause
devastating effects to the human gene pool and may also led to misuse.
Invasion of privacy:

Invasion of privacy is also a concern for many. Insurance companies could make it mandatory to
have genetic screening before a policy before they issue a policy. This could cause
discrimination to families with genetic diseases. Or potential employers could question a person's
genetic background and pass them up for a promotion or job.

Risk of the procedure:

The most important concern is the risk of the procedure. It is still in the developmental stage.
Finding the precise location of the defected gene is still under research. Any miscalculation
could cause a risk of a new disease such as cancer to form.

Short-term effectiveness:

A major drawback of gene therapy is the short-term effectiveness of the therapeutic gene after
introducing into the target cell. It is the dividing cells present in the body that prevents the
expression of therapeutic genes. After inserting the foreign therapeutic gene into the target cell, it
is necessary to regulate the autoimmune responses of the body. Human gene therapy is less
effective for multigene problems (presence of many defective genes).

Current status of gene therapy research:
The Food and Drug Administration (FDA) has not yet approved any human gene therapy
product for sale. Current gene therapy is experimental and has not proven very successful in
clinical trials. Little progress has been made since the first gene therapy clinical trial began in
1990. In 1999, gene therapy suffered a major setback with the death of 18-year-old Jesse
Gelsinger. Jesse was participating in a gene therapy trial for ornithine transcarboxylase
deficiency (OTCD). He died from multiple organ failures 4 days after starting the treatment. His
death is believed to have been triggered by a severe immune response to the adenovirus carrier.

Another major blow came in January 2003, when the FDA placed a temporary halt on all gene
therapy trials using retroviral vectors in blood stem cells. FDA took this action after it learned
that a second child treated in a French gene therapy trial had developed a leukemia-like
condition. Both this child and another who had developed a similar condition in August 2002 had
been successfully treated by gene therapy for X-linked severe combined immunodeficiency
disease (X-SCID), also known as "bubble baby syndrome."

FDA's Biological Response Modifiers Advisory Committee (BRMAC) met at the end of
February 2003 to discuss possible measures that could allow a number of retroviral gene therapy
trials for treatment of life-threatening diseases to proceed with appropriate safeguards. In April
of 2003 the FDA eased the ban on gene therapy trials using retroviral vectors in blood stem cells.

Future of Gene therapy:
The potential of gene therapy is great but, compared to its promise, the results to date are still
quite limited. However, the benefits of gene therapy are believed to be on the near horizon. Gene
therapy is one of the hottest areas of medical research today. (And gene therapy companies have
been among the hottest in the stock market.)
The remarkable advances in genetics, including the human genome project, have opened new
doors for the exploration of gene therapy. New technologies are needed to speed the progress of
gene therapy.Gene therapy will play an increasingly important and prominent part in medicine in
the decades to come.

Gene therapy is an exciting new approach that is just making the news.Gene therapy will change
the field of medicine from what it is today. As s cientists discover more genes and their
functions, the potential of this treatment is limitless. Our genome is the blueprint of our body.
The key to our future is locked in our genome. As researchers start to understand this blueprint,
our lives will be forever changed. We now know our fate is indeed in our genes.

To take a stand on gene therapy means accepting both the pros and cons. It is clear gene therapy
will have an affect on the future of genetics. I think with careful planning and regulation gene
therapy will become the "medicine" of the near future. The concern of interfering with evolution
is misconceived.

Shared By: