Cancer Gene Therapy
Genes are the biological units that determine heredity - the transfer of traits or characteristics from parent to offspring. Genes determine obvious traits, such as eye and hair color. They also determine more complex human attributes, such as body shape, physical strength, and health. These complex characteristics are shaped by the absence or presence of particular genes as well as by the interaction of multiple genes with each other and with environmental influences.
Humans have between 30,000 and 40,000 genes. Genes are stored in the chromosomes inside cells and are made of a particular type of biological molecule called deoxyribonucleic acid (DNA). Each DNA molecule in turn is a polymer made up of many thousands of subunits called nucleotides. DNA is usually many thousands of nucleotides long. Although there are only four types of nucleotides, the variable sequence of nucleotides within the DNA strand makes up a code that carries the instructions that allow cells to produce specific proteins, such as enzymes.
To make proteins, a cell must first copy the information stored in genes into another type of nucleotide polymer molecule called ribonucleic acid (RNA). The cell’s protein synthesizing machinery then decodes the information in the RNA to manufacture specific proteins. Only certain genes are active or expressing themselves as proteins at any given time in a cell. As cells mature, many genes become permanently inactive. The pattern of the resulting proteins expression determines the cells development - what kind of cell it will become and its function.
Flaws in gene activity can occur. One possibility is that an errors can occur in the nucleotide sequence within a DNA molecule (called gene mutation) and this is passed down to offspring. The error may result in incorrectly decoded RNA and the production of an abnormal protein. Malfunctions in gene expression that may lead to abnormal cell function and disease can also be more complex such as the expression of too much or too little protein, or the production of particular proteins at the wrong time. For example, a cell that has matured and is normally in a resting state within a tissue in the human body may be induced through abnormal gene expression to divide and proliferate in a uncontrolled manner to produce cancer.
Gene therapy is an experimental technique that uses genetic material (DNA or RNA) to prevent or treat disease. Researchers are testing several approaches to gene therapy, including:
- The replacement of a mutated gene that causes disease with a healthy copy of the gene.
- “Knocking out,” or inactivating a mutated gene whose function is causing a problem.
- Introducing new gene(s) into the body to help fight a disease.
Gene therapy is a promising treatment option for a number of diseases including inherited disorders, certain types of viral infections such as HIV/AIDS, and cancer. However, gene therapy is currently available only in a research setting (a "clinical trail"). The U.S. Food and Drug Administration (FDA) has not yet approved any gene therapy products for sale in the United States but hundreds of research studies are under way.
How Does Gene Therapy Work?