Ligand binding assay
Encyclopedia
In medicine
and pharmacology
, a ligand binding assay (LBA) is a technique to identify the presence of a molecule
and quantify it. There are numerous types of ligand binding assays, both radioactive and non-radioactive. As such, ligand binding assays are superset of radiobinding assay
s, which are the conceptual inverse of radioimmunoassay
s (RIA). Some newer types are called "mix-and-measure" assays because they do not require separation of bound from free ligand.
Historically, LBA techniques were used extensively to quantify hormone or hormone receptor concentrations in plasma or in tissue. The ligand
-binding assay
methodology quantified the concentration of the hormone in the test material by comparing the effects of the test sample to the results of varying amounts of known protein (the ligand
).
A prominent use was the test for classification of estrogen receptor status (ER) and progesterone receptor
(PR) in breast tumors
. The LBA was performed by homogenization of fresh or frozen tumor tissue, incubation of centrifuged cytosol
with increasing quantities of radioactive estradiol-17β
, followed by separation of unbound estradiol with dextran-coated charcoal (DCC) to quantify the concentration of high-affinity estrogen-binding sites (ER) using standard amounts of known protein.
It was replaced by immunohistochemistry
(IHC), which may be superior to LBA for assessing estrogen receptor
(ER) status in primary breast cancer because it is easier, safer, and less expensive, and has an equivalent or better ability to predict response to adjuvant endocrine therapy.
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....
and pharmacology
Pharmacology
Pharmacology is the branch of medicine and biology concerned with the study of drug action. More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function...
, a ligand binding assay (LBA) is a technique to identify the presence of a molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
and quantify it. There are numerous types of ligand binding assays, both radioactive and non-radioactive. As such, ligand binding assays are superset of radiobinding assay
Radiobinding assay
A radiobinding assay is a method of detecting and quantifying antibodies targeted towards a specific antigen. As such, it can be seen as the inverse of radioimmunoassay, which quantifies an antigen by use of corresponding antibodies.-Technique:...
s, which are the conceptual inverse of radioimmunoassay
Radioimmunoassay
Radioimmunoassay is a very sensitive in vitro assay technique used to measure concentrations of antigens by use of antibodies...
s (RIA). Some newer types are called "mix-and-measure" assays because they do not require separation of bound from free ligand.
Historically, LBA techniques were used extensively to quantify hormone or hormone receptor concentrations in plasma or in tissue. The ligand
Ligand (biochemistry)
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. In a narrower sense, it is a signal triggering molecule, binding to a site on a target protein.The binding occurs by intermolecular forces, such as ionic bonds, hydrogen...
-binding assay
Assay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
methodology quantified the concentration of the hormone in the test material by comparing the effects of the test sample to the results of varying amounts of known protein (the ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
).
A prominent use was the test for classification of estrogen receptor status (ER) and progesterone receptor
Progesterone receptor
The progesterone receptor also known as NR3C3 , is an intracellular steroid receptor that specifically binds progesterone...
(PR) in breast tumors
Breast cancer
Breast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
. The LBA was performed by homogenization of fresh or frozen tumor tissue, incubation of centrifuged cytosol
Cytosol
The cytosol or intracellular fluid is the liquid found inside cells, that is separated into compartments by membranes. For example, the mitochondrial matrix separates the mitochondrion into compartments....
with increasing quantities of radioactive estradiol-17β
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...
, followed by separation of unbound estradiol with dextran-coated charcoal (DCC) to quantify the concentration of high-affinity estrogen-binding sites (ER) using standard amounts of known protein.
It was replaced by immunohistochemistry
Immunohistochemistry
Immunohistochemistry or IHC refers to the process of detecting antigens in cells of a tissue section by exploiting the principle of antibodies binding specifically to antigens in biological tissues. IHC takes its name from the roots "immuno," in reference to antibodies used in the procedure, and...
(IHC), which may be superior to LBA for assessing estrogen receptor
Estrogen receptor
Estrogen receptor refers to a group of receptors that are activated by the hormone 17β-estradiol . Two types of estrogen receptor exist: ER, which is a member of the nuclear hormone family of intracellular receptors, and the estrogen G protein-coupled receptor GPR30 , which is a G protein-coupled...
(ER) status in primary breast cancer because it is easier, safer, and less expensive, and has an equivalent or better ability to predict response to adjuvant endocrine therapy.