Manal,
From what I've read recently, this is exactly what scientists are working on regarding gene therapy. They are trying to figure out how to avoid turning on certain cancer causing genes called oncogenes.
Here is part of the article......
Gene Transfer
While stem cell transplantation has a high success rate among young, HLA-matched patients, researchers hope to find a more universally available cure. Gene transfer may be the solution. "The goal is to introduce a gene to restore normal function in red blood cells, removing the transfusion requirement," said Michel Sadelain, a researcher at Memorial Sloan-Kettering Cancer Center.
"The goal is to introduce a gene to restore normal function in red blood cells."
The process involves removing some of the patient's stem cells, inserting a gene that codes for the healthy globins, and then re-injecting the cells into the body. To introduce the new gene, Sadelain and his team have created a vector based on a lentivirus that is capable of introducing β-hemoglobin genes into the cells. They demonstrated the concept could work in thalassemic mice in 2003. "These mice remained alive only due to transplanted gene," said Sadelain. In the laboratory, they've shown that the gene vector works at least as well in human cells as it does in mouse cells, yielding a level of expression of about 55%.
A clinical trial of gene therapy to cure thalassemia is planned to begin in the next year in France, reported Arthur Bank, a physician and geneticist at Columbia University in New York and Philippe Leboulch at Harvard Medical School and Brigham & Women's Hospital in Boston. The first phase will enroll five patients with β thalassemia and look primarily at safety.
Gene therapy: not without risks
Gene transfer is not without risks, however. Inserting new genes into a person's DNA can inadvertently activate certain cancer-causing genes called oncogenes. To reduce the risk of this happening, researchers have devised a way to confine the gene's expression to maturing red blood cells. In other words, all of the blood-forming cells will carry the gene but only a subset, the red blood cells, will carry the switch to turn it on. The lentivirus vector also contains bulky insulating molecules made of a protein called chromatin that physically block molecules called transcription factors from binding to the wrong site on the patient's DNA and turning on the wrong genes.
A three-dimensional structure brings DNA's regulatory region close to globin genes.
Inserting new pieces of DNA into precisely the right location is made even more difficult by the fact that the globin genes can fold into a three-dimensional structure of DNA and its surrounding chromatin. The three-dimensional structure brings the regulatory region of the DNA close to globin genes. The shape of this three-dimensional complex controls which genes are expressed, and it presents a challenge for researchers who are developing gene vectors. "If you don't control the insertion of new genes precisely, the regulatory elements on the imported section of DNA may start controlling the existing genes in the locus," said Frank Grosveld of the Erasmus Medical Center in Rotterdam, The Netherlands.
Another option for introducing healthy copies of the β-globin gene into thalassemia patients is via somatic cell nuclear transfer, sometimes called therapeutic cloning, said Tim Townes of the University of Alabama. Cells produced this way would be identical to the patient and would presumably not elicit an immune response when implanted into the patient. Townes described a scheme for using this approach.