In his book Genome, author Matt Ridley tries to dispel a common misconception about genes, namely that the presence of certain genes 'cause' diseases, when in fact it is the malfunction, mutation or absence of those genes that cause disease1. For instance, we all have the gene that 'causes' Huntington's Disease, but the disease only occurs in people who have inherited a mutated version of this gene. Inherited mutations are called "germline mutations."
Gene therapy is therefore an aspect of targeted therapy. The general idea is to deliver a corrected version of a certain gene into the genome. In order to do this, you need a carrier molecule known as a vector2. The most effective vector known to science is a virus, which is capable of delivering genetic material into the DNA.
What gene therapy is effective for and why
As gene therapy applies to cancer treatment, there are currently no functional therapies, but there are several fields of investigation3. Researchers are examining ways to enlist gene therapy to boost the immune system's response to cancer cells. They are also exploring methods of altering the genome of cancer cells to make them more responsive to current treatment modalities like chemotherapy, or to inhibit their ability to form blood vessels within a tumor.
Perhaps the most accessible area of investigation involves sequencing the genome of a tumor and then comparing that genome to the genomes of known tumors in order to make more molecularly precise treatment decisions4.
Risks and obstacles: Overview
The potential for incredible cancer treatment breakthroughs via gene therapy is matched only by the enormous risks and obstacles that the therapy represents. For instance, using a manipulated virus as a vector risks infection of healthy cells. Other hurdles include inserting a corrected gene into the precise spot along the genome, as well as making sure that the corrected gene, once inserted, doesn't become overexpressed to the point that it does more harm than good.
References
- Ridley, Matt. Genome: The Autobiography of a Species in 23 Chapters. 2000. New York: HarperCollins.
- Human Genome Project: How does gene therapy work?
- National Cancer Institute: Gene therapy in the treatment of cancer
- The Cancer Genome Atlas: Mission and Goal
