11-19-2012, 10:36 AM
(This post was last modified: 11-19-2012, 12:45 PM by Administrator.)
Altering the genes as a treatment against a disease is known as gene therapy. A variety of diseases has been known to be caused as a result of defective genes in humans such as Parkinson’s disease, cystic fibrosis, haemophilia, cancer etc. Thus a change in the genes can be used as a treatment mechanism for treating the diseases.
Several modes of mechanism are followed in gene therapy:
(i) Replacement: In this therapy, the defective gene is replaced with a properly functioning one. In certain cases the diseases may be caused by loss of certain genes as a result of mutation, or the diseased condition can arise due to the genes being permanently turned off.
(ii) Regulation: Certain regulations or alterations in genes leading to decline of certain important functions or activation of some defective function can be the cause of the disease. Appropriate regulations of gene expression can lead to proper gene expression and treatment of the disease.
(iii) Enhancement of defective cell appearance: Certain disease can be caused as a result of the defective cell being not recognised by the immune system. The gene therapy is targeted so that these cells become distinct and the same is recognised by the immune system and acted upon them.
In gene therapy, a gene cannot be inserted directly into a human cell. It needs specific carriers which are known as ‘vectors’ which carry these genes into the cell. In gene therapy, viruses are mainly used as vectors.
Depending on the target cell, the gene therapy can be divided into two main types:-
Germline gene therapy and Somatic cell gene therapy.
In germline gene therapy, the gene transfer is targeted to germ cells and the modification of genes in the same is acquired. This results in transfer of modified genes into the future generations. This can help in eradicating certain diseases from a family or from a population as a whole. But this process has been so far possible only theoretically. The dangerous implications of the proposed methodology have inhibited it from being acquiring acceptance.
In somatic gene therapy, the gene is introduced into somatic cells of the diseased. The gene is introduced into the somatic cells where the expression of critical genes is important for restoration of specific cellular activity. Since somatic cells are non reproductive this change in the genes are not transferred into the next generations and remain in the same species.
Mode of action:
In gene therapy, mostly a normal gene is replaced in the position of a defective gene. This transfer of corrected gene is done with the help of carriers known as vectors. The most common vector used in these cases is viruses which have been genetically altered so that it does not actually affect the person negatively but rather improves the diseased condition of the person. The vectors are directed to infect target cells that are cells where a defective gene is present and the corrected genetic material is unloaded into the defective cell. The correction of the defects helps in restoration of the defective condition.
Cancer treatment by gene therapy:-
Gene therapy has been applied most successfully in the treatment of cancer. The property of selective targeting and tumour destruction is the most prominent accounting to its use in cancer cure. A main example is defective P53 gene in tumour cell. The P53 gene is a tumour suppressor gene. It is seen that in persons with tumour, the P53 gene has been affected with mutations and is non functional. Introduction of wild type gene by gene therapy into the affected persons restores the functional gene and results in death of tumour cells.
Another major example in gene therapy in cancer cure is regulation of K-RAS. This is an oncogene known for causing cancer. In cancerous condition, the over expression of the corresponding gene is reported. Gene therapy facilitates introducing antisense gene into the cell over expressing this gene. This causes silencing of the corresponding gene by formation of double stranded RNA affecting the protein production and expression.
The process also involves several risk factors the main one being instability of viruses. The viruses which are used as vectors may develop its infectious property and lead to toxicity, immune responses from the body or the accidental integration into some other site will lead to lethal conditions.
Several modes of mechanism are followed in gene therapy:
(i) Replacement: In this therapy, the defective gene is replaced with a properly functioning one. In certain cases the diseases may be caused by loss of certain genes as a result of mutation, or the diseased condition can arise due to the genes being permanently turned off.
(ii) Regulation: Certain regulations or alterations in genes leading to decline of certain important functions or activation of some defective function can be the cause of the disease. Appropriate regulations of gene expression can lead to proper gene expression and treatment of the disease.
(iii) Enhancement of defective cell appearance: Certain disease can be caused as a result of the defective cell being not recognised by the immune system. The gene therapy is targeted so that these cells become distinct and the same is recognised by the immune system and acted upon them.
In gene therapy, a gene cannot be inserted directly into a human cell. It needs specific carriers which are known as ‘vectors’ which carry these genes into the cell. In gene therapy, viruses are mainly used as vectors.
Depending on the target cell, the gene therapy can be divided into two main types:-
Germline gene therapy and Somatic cell gene therapy.
In germline gene therapy, the gene transfer is targeted to germ cells and the modification of genes in the same is acquired. This results in transfer of modified genes into the future generations. This can help in eradicating certain diseases from a family or from a population as a whole. But this process has been so far possible only theoretically. The dangerous implications of the proposed methodology have inhibited it from being acquiring acceptance.
In somatic gene therapy, the gene is introduced into somatic cells of the diseased. The gene is introduced into the somatic cells where the expression of critical genes is important for restoration of specific cellular activity. Since somatic cells are non reproductive this change in the genes are not transferred into the next generations and remain in the same species.
Mode of action:
In gene therapy, mostly a normal gene is replaced in the position of a defective gene. This transfer of corrected gene is done with the help of carriers known as vectors. The most common vector used in these cases is viruses which have been genetically altered so that it does not actually affect the person negatively but rather improves the diseased condition of the person. The vectors are directed to infect target cells that are cells where a defective gene is present and the corrected genetic material is unloaded into the defective cell. The correction of the defects helps in restoration of the defective condition.
Cancer treatment by gene therapy:-
Gene therapy has been applied most successfully in the treatment of cancer. The property of selective targeting and tumour destruction is the most prominent accounting to its use in cancer cure. A main example is defective P53 gene in tumour cell. The P53 gene is a tumour suppressor gene. It is seen that in persons with tumour, the P53 gene has been affected with mutations and is non functional. Introduction of wild type gene by gene therapy into the affected persons restores the functional gene and results in death of tumour cells.
Another major example in gene therapy in cancer cure is regulation of K-RAS. This is an oncogene known for causing cancer. In cancerous condition, the over expression of the corresponding gene is reported. Gene therapy facilitates introducing antisense gene into the cell over expressing this gene. This causes silencing of the corresponding gene by formation of double stranded RNA affecting the protein production and expression.
The process also involves several risk factors the main one being instability of viruses. The viruses which are used as vectors may develop its infectious property and lead to toxicity, immune responses from the body or the accidental integration into some other site will lead to lethal conditions.
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