Targeted cancer therapy, also called ‘molecularly targeted therapy,’ uses drugs or other substances to identify and attack cancer cells with little or no harm to normal cells. Targeted therapies stop the growth, division and progression of cancer cells by interfering with specific molecules inside of these cells.
Definition of treatment
To become cancer cells that develop into a tumor, normal cells must undergo a process called carcinogenesis. Molecules are part of this process, and the cells in which they reside receive signals to keep this process going. Targeted cancer therapies interrupt the signaling process by zeroing in on certain parts of the cellular changes and signals that are needed for a cancer to develop and grow.
Targeted cancer therapies allow doctors to ‘customize’ cancer treatments, especially when a target molecule is present in some, but not all, tumors of a particular type. Treatments may one day be individualized based on the unique molecular targets found in a person’s tumor. Most targeted therapies use small-molecule drugs which diffuse into your cells and work internally, or monoclonal antibodies which cannot penetrate your cell’s plasma membrane and function externally.
Types of treatment
The drugs involved in targeted therapies are often grouped by their function or the part of the cell they target.
- Enzyme inhibitors: Enzymes, or proteins, are responsible for how a cell functions and act as signals for cancer cells to grow. Targeted therapies block these signals, thus preventing cancer cells from growing and spreading. These drugs are sometimes called small-molecule drugs, signal-transduction inhibitors or enzyme-inhibitors.
- Apoptosis-inducing drugs: Apoptosis-inducing drugs change proteins within the cancer cells that control cell survival and death and cause the cells to die.
- Angiogenesis inhibitors: Cancer cells need healthy blood vessels to grow and survive. Angiogenesis is the process by which new blood vessels are formed. Angiogenesis inhibitors are targeted therapies that inhibit the blood supply to cancer cells so they cannot grow. Other targeted therapies work by blocking vascular endothelial growth factor (VEGF), a group of protein growth factors produced by some tumors. VEGF proteins attach to VEGF receptors in blood vessel cells, and cause new blood vessels to form around the tumors. Angiogenesis inhibitors stop this process, thus cutting off the blood supply to tumors.
UC San Diego Health System expertise
Targeted therapies can be used to treat different kinds of cancers, including lung, pancreatic, head and neck, liver, colorectal, breast and kidney cancers.
UC San Diego Health System has been integrally involved in the development of Herceptin, a targeted therapy that is demonstrating dramatic effectiveness in curing localized HER2-overexpressing breast cancer, as well as targeted therapies for lethal ventricular arrhythmias, abnormal heart rhythms and sudden cardiac death. Researchers are also focusing on the biology of metastatic disease and developing targeted therapies designed to halt the spread of neuroblastoma.
What was the first molecular target?
The first molecular target for targeted cancer therapy was the cellular receptor for estrogen, a female hormone, which is required by various types of breast cancer for growth. When estrogen binds to the estrogen receptor (ER) inside cells, it activates the expression of certain genes responsible for cell growth and spread. By interfering with this process, cancer cells are not able to proliferate.
How is targeted therapy used?
Unlike most standard chemo drugs, targeted cancer therapies do not damage bone marrow or blood cells. Targeted therapies can be used alone or with other drugs. As part of combination therapy, they can be used with other types of cancer treatments to help boost the effects of the main treatment. Currently, targeted therapies are most often combined with chemotherapy.