gene therapy
Meaning of gene therapy: Instead of managing the effects of a faulty gene for a lifetime, the aim is to change the instruction the cell is reading.
Definition of gene therapy
Gene therapy is treatment that works by adding, removing or altering genetic material inside a person's cells. Rather than easing the symptoms a faulty gene produces, it targets the instruction itself, either supplying a working copy, silencing a gene that is misbehaving, editing the sequence in place, or adding a gene that gives cells a new ability the body can use against disease.
How does the genetic material get into cells?
Delivery is the hard part, and a modified virus is the usual solution. Viruses already excel at entering cells and depositing genetic material, so the viral genes that cause illness are stripped out and the therapeutic gene is packaged in their place. Different carriers behave differently. Some deposit the new sequence as a free standing loop that fades as cells divide, while others insert it into the cell's own chromosomes, which lasts far longer but carries a risk of landing somewhere that disturbs a neighboring gene. Non viral routes exist too, including fatty particles that ferry genetic material across the cell membrane. The other choice is where the work happens. Inside the body, the carrier is injected and finds its targets internally. Outside the body, cells are collected from the person, altered in a laboratory, checked, and returned.
What are the main approaches?
| Approach | What it does |
|---|---|
| Gene addition | Supplies a working copy of a gene that is missing or broken |
| Gene silencing | Switches off a gene whose product is causing harm |
| Gene editing | Rewrites a specific sequence within the cell's own DNA |
| Cell engineering | Adds a gene giving a cell a new function, as in immune cells built to recognize cancer |
The last of these accounts for much of the activity in cancer. Immune cells taken from a person can be given a receptor that recognizes a marker on their tumor and returned to attack it, which is why gene therapy overlaps with treatments aimed at the immune system. A separate cancer strategy is oncolytic virus therapy, in which an engineered virus multiplies inside tumor cells and destroys them.
What are its limits?
Approved treatments alter body cells only, so the change stops with the treated person and is not passed on to children. Editing eggs, sperm or embryos would be inherited, and it is barred from clinical use in most countries. The practical limits are as real as the ethical ones. The immune system can react against the viral carrier, and previous exposure to that virus can block a treatment outright. Effects may fade as treated cells are replaced. Conditions caused by one well understood gene in a tissue that can be reached have proved far more tractable than common diseases involving many genes, and these treatments are among the most expensive medicines ever produced.
Used in a sentence
Gene therapy was considered for the child's inherited condition after standard treatment options were reviewed.
Good to know
Gene therapy for an inherited single gene disorder and gene therapy used to enhance the immune system's response to cancer rely on different strategies despite sharing the same general approach of altering genetic material.
Word origin
Where “gene therapy” comes from
Formed from gene, from Greek genos, meaning birth or kind, and therapy, from Greek therapeia, meaning treatment.