105 plain-language definitions of the scientific terms and acronyms used across the site, drawn from NIH dictionaries (NCI Cancer Terms, NCI Genetics Terms, NIGMS), The Cell: A Molecular Approach (NCBI Bookshelf), and in-house definitions for specialist terms. Pathway names and Framework role names are defined on their own pages.
- ADME
- An acronym describing pharmacokinetic processes that pharmacologists study regarding drugs in the body: absorption, distribution, metabolism (break down), and excretion.
- agonist
- A molecule that binds to a receptor in a cell to trigger a response, such as muscle contraction or hormone release.
- AKBA (3-O-acetyl-11-keto-β-boswellic acid)
- A boswellic acid constituent of Boswellia extracts that may be measured or standardised as one of the extract's principal bioactive compounds.
- AKT
- A protein-serine/threonine kinase that is activated by PIP3 and plays a key role in signaling cell survival.
- allele
- One of two or more versions of a genetic sequence at a particular region on a chromosome. An individual inherits two alleles for each gene, one from each parent.
- AMPK (AMP-activated protein kinase)
- An energy-sensing enzyme that responds to low cellular energy by promoting energy production and limiting energy-consuming processes such as lipid and protein synthesis.
- angiogenesis
- Blood vessel formation. Tumor angiogenesis is the growth of new blood vessels that tumors need to grow. This process is caused by the release of chemicals by the tumor and by host cells near the tumor.
- angiogenesis inhibitor
- A drug or substance that keeps new blood vessels from forming. In cancer treatment, angiogenesis inhibitors may prevent the growth of new blood vessels that tumors need to grow. Also called antiangiogenesis agent.
- antagonist
- A molecule that binds to a receptor in a cell to prevent a response, such as a muscle contraction or hormone release.
- antioxidant
- A substance that protects cells from the damage caused by free radicals (unstable molecules made by the process of oxidation during normal metabolism). Free radicals may play a part in cancer, heart disease, stroke, and other diseases of aging. Antioxidants include beta-carotene, lycopene, vitamins A, C, and E, and other natural and manufactured substances.
- apoptosis
- A type of cell death in which a series of molecular steps in a cell lead to its death. This is one method the body uses to get rid of unneeded or abnormal cells. The process of apoptosis may be blocked in cancer cells. Also called programmed cell death.
- ATP
- The major source of energy for biochemical reactions in all organisms. ATP is formed when animals digest food or plants undergo photosynthesis.
- AUC (area under the concentration–time curve)
- A pharmacokinetic measure of total exposure to a compound, calculated from its concentration in blood or plasma over time.
- autophagy
- A process by which a cell breaks down and destroys old, damaged, or abnormal proteins and other substances in its cytoplasm (the fluid inside a cell). The breakdown products are then recycled for important cell functions, especially during periods of stress or starvation. Autophagy also helps destroy bacteria and viruses that cause infection and may prevent normal cells from becoming cancer cells. Once cancer has formed, autophagy may protect the cancer cells by providing extra nutrients to them or by keeping anticancer drugs or other substances from destroying them. Autophagy may also affect the body's immune response against viruses, bacteria, and cancer cells.
- bioavailability
- How quickly and to what extent the active part of a drug is absorbed by the body and is available at the site where it's needed.
- biomarker
- A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease. A biomarker may be used to see how well the body responds to a treatment for a disease or condition. Also called molecular marker and signature molecule.
- cachexia
- A condition marked by a loss of more than 10% of body weight, including loss of muscle mass and fat, in a person who is not trying to lose weight.
- carcinogen
- Any substance that causes cancer.
- CD44
- A cell-surface protein that binds components of the extracellular matrix and contributes to cell adhesion, migration, signalling and, in some cancers, stem-like behaviour.
- cell line
- Cancer cells that keep dividing and growing over time, under certain conditions in a laboratory.
- cGMP (current Good Manufacturing Practice)
- The current regulatory requirements and quality systems used to control how products are manufactured, tested, packaged and stored so that they consistently meet established specifications.
- chemoprevention
- The use of certain drugs or other substances to help lower a person's risk of developing cancer or keep it from coming back. For example, tamoxifen and raloxifene are drugs that may be used to prevent certain types of breast cancer in women who are at high risk of developing the disease.
- chromatin
- The part of the nucleus that consists of DNA and proteins and forms chromosomes.
- CLL (chronic lymphocytic leukemia)
- An indolent (slow-growing) cancer in which too many immature lymphocytes (white blood cells) are found mostly in the blood and bone marrow. Sometimes, in later stages of the disease, cancer cells are found in the lymph nodes and the disease is called small lymphocytic lymphoma. Also called CLL.
- cofactor
- A helper molecule (either inorganic, such as a metal ion, or organic, such as a vitamin) an enzyme needs to work.
- COX-2
- An enzyme that speeds up the formation of substances that cause inflammation and pain. It may also cause tumor cells to grow. Some tumors have high levels of COX-2 and blocking its activity may reduce tumor growth. Also called cyclooxygenase-2 and prostaglandin-endoperoxide synthase 2.
- CRP (C-reactive protein)
- A protein that is made by the liver when there is inflammation or tissue damage in the body.
- cytochrome P450 / CYP enzymes
- A large family of enzymes, found mainly in the liver and intestine, that metabolise many drugs and other compounds and can contribute to drug–drug or supplement–drug interactions.
- cytokine
- A type of protein that is made by certain immune and non-immune cells and has an effect on the immune system. Some cytokines stimulate the immune system and others slow it down. They can also be made in the laboratory and used to help the body fight cancer, infections, and other diseases. Examples of cytokines are interleukins, interferons, and colony-stimulating factors (filgrastim, sargramostim).
- DNA
- The molecule inside cells that contains the genetic information needed for a person and most other organisms to develop and grow and is passed from one generation to the next. DNA is made up of two strands that twist into the shape of a spiral ladder called a double helix. Each strand has a backbone that is made up of sugar and phosphate molecules that attach to one of four bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The bases pair up with one another (A with T, and G with C) to form chemical bonds, which act like rungs on a ladder. This holds the two strands of DNA together. Also called deoxyribonucleic acid.
- DNA methylation
- An epigenetic modification in which methyl groups are added to DNA, often altering whether nearby genes are expressed without changing the DNA sequence.
- ECM (extracellular matrix)
- A large network of proteins and other molecules that surround, support, and give structure to cells and tissues in the body. The ECM helps cells attach to, and communicate with, nearby cells.
- EGFR
- A protein found on certain types of cells that binds to a substance called epidermal growth factor. The EGFR protein is involved in cell signaling pathways that control cell division and survival.
- EMT (epithelial–mesenchymal transition)
- A biological process in which epithelial cells lose some of their normal adhesion and polarity and acquire more mobile, invasive mesenchymal-like characteristics.
- endoplasmic reticulum
- A network of sac-like structures and tubes in the cytoplasm (gel-like fluid) of a cell. Proteins and other molecules move through the endoplasmic reticulum. The outer surface of the endoplasmic reticulum can be smooth or rough. The rough endoplasmic reticulum has many ribosomes on its outer surface and makes proteins the cell needs. The smooth endoplasmic reticulum makes other substances that the cell needs, such as lipids (fats) and carbohydrates (sugars). The endoplasmic reticulum is a cell organelle.
- enzyme
- A biological catalyst that is almost always a protein and speeds up the rate of a specific chemical reaction in the cell by reducing the amount of energy needed for the reaction to proceed.
- epigenetics
- The study of heritable changes that do not affect the DNA sequence but influence gene expression.
- ERK (extracellular signal-regulated kinase)
- A protein kinase in the MAPK pathway that transmits signals controlling cell proliferation, survival, differentiation and other cellular responses.
- FASN (fatty acid synthase)
- An enzyme that produces fatty acids from acetyl-CoA and malonyl-CoA and is frequently upregulated in metabolically active cancer cells.
- ferroptosis
- A regulated form of cell death caused by iron-dependent accumulation of damaging lipid peroxides in cell membranes.
- GBM (glioblastoma)
- A fast-growing type of central nervous system tumor that forms from glial (supportive) tissue of the brain and spinal cord and has cells that look very different from normal cells. Glioblastoma usually occurs in adults and affects the brain more often than the spinal cord. Also called GBM, glioblastoma multiforme, and grade IV astrocytoma.
- gene knockdown
- An experimental reduction in the expression or activity of a gene without necessarily removing or permanently disabling it.
- genotype
- A term that refers to the two alleles present at a specific locus in the genome. Genotype also refers to the entire genetic makeup of an individual.
- glutathione
- A substance found in plant and animal tissues that has many functions in a cell. These include activating certain enzymes and destroying toxic compounds and chemicals that contain oxygen.
- glycolysis
- The anaerobic breakdown of glucose.
- GMP (Good Manufacturing Practice)
- A system of manufacturing and quality-control principles intended to ensure that products are consistently produced and controlled to appropriate quality standards.
- GPX4 (glutathione peroxidase 4)
- An antioxidant enzyme that uses glutathione to neutralise lipid peroxides and is a major cellular defence against ferroptosis.
- HCl (hydrochloride)
- A salt form produced by combining a compound with hydrochloric acid, often to improve stability, solubility or suitability for manufacturing.
- HER2
- A protein involved in normal cell growth. HER2 may be made in larger than normal amounts by some types of cancer cells, including breast, ovarian, bladder, pancreatic, stomach, and esophageal cancers. This may cause cancer cells to grow more quickly and spread to other parts of the body. Checking the amount of HER2 on some types of cancer cells may help plan treatment. Also called c-erbB-2, HER2/neu, human EGF receptor 2, and human epidermal growth factor receptor 2.
- HIF-1α (hypoxia-inducible factor)
- One of a group of proteins that play an important role in how cells respond to changing levels of oxygen. When oxygen levels in cells are low, hypoxia-inducible factors activate certain genes involved in cell growth and survival. This allows the cells to function and survive even in low oxygen conditions. Hypoxia-inducible factors may be made in larger than normal amounts by some types of cancer cells. This may cause cancer cells to grow and spread to other parts of the body. Also called HIF.
- histone
- A type of protein found in chromosomes; DNA wraps around histones.
- IC50 (half-maximal inhibitory concentration)
- The concentration of a substance required to reduce a measured biological activity by 50% under the stated experimental conditions.
- IL-6 (interleukin-6)
- One of a group of related proteins made by leukocytes (white blood cells) and other cells in the body. IL-6 is made mainly by some T lymphocytes. It causes B lymphocytes to make more antibodies and also causes fever by affecting areas of the brain that control body temperature. IL-6 made in the laboratory is used as a biological response modifier to boost the immune system in cancer therapy. IL-6 is a type of cytokine. Also called interleukin-6.
- immunotherapy
- A type of therapy that uses substances to stimulate or suppress the immune system to help the body fight cancer, infection, and other diseases. Some types of immunotherapy only target certain cells of the immune system. Others affect the immune system in a general way. Types of immunotherapy include cytokines, vaccines, bacillus Calmette-Guerin (BCG), and some monoclonal antibodies.
- in vitro
- In the laboratory (outside the body). The opposite of in vivo (in the body).
- in vivo
- In the body. The opposite of in vitro (outside the body or in the laboratory).
- inflammation
- A normal part of the body's response to injury or infection. Inflammation occurs when the body releases chemicals that trigger an immune response to fight off infection or heal damaged tissue. Once the injury or infection is healed, the inflammatory process ends. Chronic inflammation is an abnormal immune response in which the inflammatory process does not end when it should or may begin when there is no infection or injury. Over time, chronic inflammation can damage healthy cells, tissues, and organs. This can lead to diseases such as cancer, heart disease, diabetes, asthma, Alzheimer disease, and autoimmune conditions.
- inhibitor
- A molecule that "inhibits," or blocks, the biological action of another molecule.
- kinase
- A type of enzyme (a protein that speeds up chemical reactions in the body) that adds chemicals called phosphates to other molecules, such as sugars or proteins. This may cause other molecules in the cell to become either active or inactive. Kinases are a part of many cell processes. Some cancer treatments target certain kinases that are linked to cancer.
- liposome
- An oily, microscopic capsule designed to package and deliver biological cargo, such as drugs, to cells in the body.
- malignant
- A term used to describe cancer. Malignant cells grow in an uncontrolled way and can invade nearby tissues and spread to other parts of the body through the blood and lymph system.
- MAPK (MAP kinases)
- A family of mitogen-activated protein-serine/threonine kinases that are ubiquitous regulators of cell growth and differentiation.
- MDSCs (myeloid-derived suppressor cells)
- A diverse group of immature myeloid immune cells that suppress T-cell and other antitumour immune responses, particularly within the tumour microenvironment.
- MEK (MAPK/ERK kinase)
- A protein kinase that activates ERK and forms part of the RAS–RAF–MEK–ERK signalling pathway controlling cell growth and survival.
- metabolism
- The chemical changes that take place in a cell or an organism. These changes make energy and the materials cells and organisms need to grow, reproduce, and stay healthy. Metabolism also helps get rid of toxic substances.
- metabolite
- A substance made or used when the body breaks down food, drugs, or chemicals through metabolism.
- metastasis
- The spread of cancer cells from the place where they first formed to another part of the body. In metastasis, cancer cells break away from the original (primary) tumor, travel through the blood or lymph system, and form a new tumor in other organs or tissues of the body. The new, metastatic tumor is the same type of cancer as the primary tumor. For example, if breast cancer spreads to the lung, the cancer cells in the lung are breast cancer cells, not lung cancer cells.
- microRNA
- A short piece of RNA that binds to messenger RNA, blocking its ability to make proteins.
- monoclonal antibody
- A type of protein that is made in the laboratory and can bind to certain targets in the body, such as antigens on the surface of cancer cells. There are many kinds of monoclonal antibodies, and each monoclonal antibody is made so that it binds to only one antigen. Monoclonal antibodies are being used in the diagnosis and treatment of many diseases, including some types of cancer. They can be used alone or to carry drugs, toxins, or radioactive substances directly to cancer cells.
- mTOR
- A protein that helps control several cell functions, including cell division and survival, and binds to rapamycin and other drugs. mTOR may be more active in some types of cancer cells than it is in normal cells. Blocking mTOR may cause the cancer cells to die. It is a type of serine/threonine protein kinase. Also called mammalian target of rapamycin and mechanistic target of rapamycin.
- mutation
- Any change in the DNA sequence of a cell. Mutations may be caused by mistakes during cell division, or they may be caused by exposure to DNA-damaging agents in the environment. Mutations can be harmful, beneficial, or have no effect. If they occur in cells that make eggs or sperm, they can be inherited; if mutations occur in other types of cells, they are not inherited. Certain mutations may lead to cancer or other diseases. A mutation is sometimes called a variant.
- NADPH (reduced nicotinamide adenine dinucleotide phosphate)
- An electron-carrying coenzyme used in antioxidant defence and biosynthetic reactions, including fatty-acid production.
- natural product
- A molecule produced by a living organism—a plant, marine organism, or microorganism—that often has a medicinal use.
- necrosis
- Cell death caused by trauma or infection.
- NF-κB
- A group of proteins that help control many functions in a cell, including cell growth and survival. These proteins also control the body's immune and inflammatory responses. NF-kappa B may be overactive or found in higher than normal amounts in some types of cancer cells. This may lead to cancer cell growth. High levels or overactivity of NF-kappa B may also lead to inflammatory disorders, such as asthma and ulcerative colitis, and autoimmune disorders, such as rheumatoid arthritis. Also called NF-kB and nuclear factor-kappa B.
- NRF2 (nuclear factor erythroid 2–related factor 2)
- A transcription factor that activates genes involved in antioxidant defence, detoxification and cellular adaptation to oxidative or chemical stress.
- NSF
- An independent standards and certification organisation that audits facilities and certifies certain products or manufacturing operations against defined quality and safety standards.
- oncogene
- A mutated (changed) form of a type of gene called a proto-oncogene, which is involved in normal cell growth and division. When a proto-oncogene is changed so that too many copies are made or it becomes more active than normal, it is called an oncogene. Oncogenes may cause normal cells to become cancer cells and grow in the body. Mutations that lead to the conversion of proto-oncogenes to oncogenes usually occur during a person's lifetime and are not inherited from a parent.
- oxidative stress
- A condition that may occur when there are too many unstable molecules called free radicals in the body and not enough antioxidants to get rid of them. This can lead to cell and tissue damage. There are many factors that may lead to oxidative stress, including obesity, poor diet, smoking, drinking alcohol, taking certain medicines, and exposure to environmental factors such as radiation, toxins, air pollution, pesticides, and sunlight. Long-term oxidative stress may play a role in aging and the development of chronic inflammation, cancer, and other diseases.
- PARP
- A type of enzyme involved in many functions of the cell, including the repair of DNA damage. DNA damage may be caused by normal cell actions, UV light, some anticancer drugs, and radiation used to treat cancer. Inhibitors of one enzyme, PARP-1, are being studied in the treatment of cancer. Also called poly (ADP-ribose) polymerase.
- pharmacodynamics
- A branch of pharmacology studying how drugs act on their molecular targets and on the organs and tissues in the body.
- pharmacokinetics
- The activity of drugs in the body over a period of time, including the processes by which drugs are absorbed, distributed in the body, localized in the tissues, and excreted.
- phenotype
- The observable characteristics or traits in an individual based on the expression of their genes. The phenotype is determined by the individual's genotype and possibly influenced by other factors, such as environmental factors or other genetic modifiers.
- phytosome
- A delivery system in which a plant-derived compound or extract is complexed with phospholipids, usually to improve its solubility, membrane passage or oral absorption.
- PI3K
- A type of enzyme that transmits signals in cells and that helps control cell growth. Some tumors have higher-than-normal levels of PI3K. Also called phosphatidylinositol-3 kinase and PI3 kinase.
- placebo
- An inactive substance or other intervention that looks the same as, and is given the same way as, an active drug or treatment being tested. The effects of the active drug or other intervention are compared to the effects of the placebo.
- preclinical study
- Research using animals to find out if a drug, procedure, or treatment is likely to be useful. Preclinical studies take place before any testing in humans is done.
- proliferation
- An increase in the number of cells as a result of cell growth and cell division.
- prostaglandin
- One of several hormone-like substances made by the body. Different prostaglandins control blood pressure, contraction of smooth muscles, and other processes within tissues where they are made. Certain prostaglandins are being studied as cancer biomarkers. Also called PG.
- RAS
- A family of genes that make proteins involved in cell signaling pathways that control cell growth and cell death. Mutated (changed) forms of the RAS gene may be found in some types of cancer. These changes may cause cancer cells to grow and spread in the body. Members of the RAS gene family include KRAS, HRAS, and NRAS.
- RCT (randomized clinical trial)
- A study in which the participants are divided by chance into separate groups that compare different treatments or other interventions. Using chance to divide people into groups means that the groups will be similar and that the effects of the treatments they receive can be compared more fairly. At the time of the trial, it is not known which treatment is best.
- receptor
- A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific effect in the cell.
- ROS (reactive oxygen species)
- A type of unstable molecule that contains oxygen and that easily reacts with other molecules in a cell. A build up of reactive oxygen species in cells may cause damage to DNA, RNA, and proteins, and may cause cell death. Reactive oxygen species are free radicals.
- SEDDS (self-emulsifying drug-delivery system)
- A mixture of oils, surfactants and often co-solvents that forms a fine emulsion in gastrointestinal fluids to improve delivery of poorly water-soluble compounds.
- signal transduction
- The process by which a cell responds to substances outside the cell through signaling molecules found on the surface of and inside the cell. Most molecules that lead to signal transduction are chemical substances, such as hormones, neurotransmitters, and growth factors, that bind to a specific protein receptor (signaling molecule) on or in a cell. The signals are then passed from one molecule to another inside the cell, which results in a specific cell response, such as cell division or cell death. Signal transduction is important for cells to grow and work normally. Cells that have abnormal signaling molecules may become cancer cells. Also called cell signaling.
- siRNA (small interfering RNA)
- A short double-stranded RNA molecule that guides the cellular RNA-interference machinery to degrade a matching messenger RNA and reduce expression of its gene.
- SREBP-1c (sterol regulatory element-binding protein 1c)
- A transcription factor that activates genes involved in fatty-acid and triglyceride synthesis, including FASN.
- STAT3 (STAT proteins)
- Transcription factors that have an SH2 domain and are activated by tyrosine phosphorylation, which promotes their translocation from the cytoplasm to the nucleus.
- TCA cycle (citric acid cycle)
- A series of reactions in which acetyl CoA is oxidized to CO2. The central pathway of oxidative metabolism.
- TGF-β
- A polypeptide growth factor that generally inhibits animal cell proliferation.
- TNF-α (tumor necrosis factor)
- A protein made by white blood cells in response to an antigen (substance that causes the immune system to make a specific immune response) or infection. Tumor necrosis factor can also be made in the laboratory. It may boost a person's immune response, and also may cause necrosis (cell death) of some types of tumor cells. Tumor necrosis factor is being studied in the treatment of some types of cancer. It is a type of cytokine. Also called TNF.
- tumor microenvironment
- The normal cells, molecules, and blood vessels that surround and feed a tumor cell. A tumor can change its microenvironment, and the microenvironment can affect how a tumor grows and spreads.
- UPR (unfolded protein response)
- A cellular stress response activated when misfolded or unfolded proteins accumulate in the endoplasmic reticulum, initially working to restore protein-folding balance but potentially promoting cell death if the stress persists.
- VEGF
- A substance made by cells that stimulates new blood vessel formation. Also called vascular endothelial growth factor.
- wild-type
- The standard or non-mutated form of a gene, protein or organism used as the reference when comparing it with an altered variant.