American Association for Cancer Research

Glossary of Cancer Research Terms

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Click below to browse a glossary of cancer-related terms and their definitions. You can use your web browser's Find function to search for specific terms on either page.


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A


ABC drug transporters: A family of membrane proteins that mediate the efflux of drugs from cells in an energy (ATP)-dependent manner.

acinus (plural acini): One of the small sac-like pouches composing some glands.

acquired resistance: A term used to describe drug resistance in tumors that are initially responsive to drugs, but are resistant at relapse. Acquired resistance is likely due to the accumulation of random mutations in tumor cells that allowed survival following the first round of therapy.

adjuvant therapy: Treatment given after the primary therapy, which is usually surgery. Adjuvant therapy for cancer may include immune therapy, chemotherapy, radiation therapy or hormone therapy.

adenoma: A benign or noncancerous tumor made up of glandular tissue.

adverse effects: Problems that occur when treatment affects healthy cells. Common adverse effects of cancer treatment are fatigue, nausea, vomiting, decreased blood cell counts, hair loss, and mouth sores. Also called side effects.

agent: In a cancer clinical trial, an agent is a substance that produces, or is capable of producing, an effect that fights cancer.

allele: One of the alternate forms of a gene that may occupy a given locus (position on the chromosome).

amino acids: The building blocks of proteins.

angiogenesis: Blood vessel formation. Angiogenesis that occurs in cancer is the growth of blood vessels from surrounding tissue to a solid tumor. Angiogenesis is necessary for a tumor to grow larger and for metastases to grow at secondary sites. It is stimulated by growth factors such as VEGF (vascular endothelial growth factor).

angiogenesis inhibitor: A substance that may prevent the formation of blood vessels. In anticancer therapy, an angiogenesis inhibitor prevents the growth of blood vessels from surrounding tissue to a solid tumor. Some naturally occurring inhibitors are thrombospondin, angiostatin and endostatin.

anti-angiogenesis: Prevention of the growth of new blood vessels.

antibody: An antigen-specific receptor, also called an immunoglobulin, made by B-lymphocytes. Antibodies are a critical component of the immune system that circulate in the blood and bind to foreign antigens and tumor cells, marking them for destruction by immune proteins or other immune cells. Monoclonal antibodies (mAb) are laboratory-produced antibodies that can locate and bind to cancer cells wherever they are in the body. Each one recognizes a different protein on certain cancer cells. They are used in cancer detection or therapy, and can be administered alone or used to deliver drugs, toxins or radioactive material directly to a tumor.

antibody therapy: Treatment with an antibody, a substance that can directly kill specific tumor cells or stimulate the immune system to kill tumor cells.

antigens: Substances that cause the immune system to make a specific immune response. An example would be a protein only found on tumor cells. Another example would be a murine antibody, which is derived solely from mouse proteins and therefore is viewed as foreign by the host (human) body.

antigen presenting cells (APC): Specialized cells that "sample" the proteins in a tissue (for example by ingesting dying cells and debris), have the machinery to cut proteins into small fragments (antigens) and load them into MHC molecules, and express other molecules (co-stimulatory proteins) that are necessary for T helper cells to be activated to mount an immune response. B cells, macrophages, dendritic cells and Langerhans cells are all antigen-presenting cells.

antioxidant: Any substance that delays or inhibits oxidative damage to a target molecule. Antioxidants protect cells from free radical damage or oxidation by preventing free radical formation, by scavenging the free radicals before they can cause damage, and by repairing damaged molecules. Vitamin E is an example of an antioxidant.

apoptosis: A normal series of events in a cell that leads to its death. Also called cell-suicide.

 

B


B cells or B-lymphocytes: White blood cells that make antibodies and are an important part of the immune system.

basement membrane: A specialized, sheet-like structure of the extracellular matrix that separates cells from the surrounding connective tissue, and thereby serves as a boundary of a tissue. The basement membrane must be broken down in order for cancer cells to invade surrounding tissue.

benign: A swelling or growth that is not cancerous and does not spread from one part of the body to another.

biological therapy: Treatment to stimulate or restore the ability of the immune system to fight infection and disease. Biological therapy is also used to lessen side effects that may be caused by some cancer treatments. Also known as immunotherapy, biotherapy or biological response modifier (BRM) therapy.

biomarker: A substance sometimes found in the blood, other body fluids or tissues. A high level of biomarker may mean that a certain type of cancer is in the body. Examples of biomarkers include CA 125 (ovarian cancer), CA 15-3 (breast cancer), CEA (ovarian, lung, breast, pancreas and gastrointestinal tract cancers), and PSA (prostate cancer). Also called tumor marker.

biospecimens: Samples of tissue that can be used to study various aspects of cancer.

bone marrow: The soft, sponge-like tissue in the center of bones that produces white blood cells, red blood cells and platelets.

bone marrow toxicity: The destruction of bone marrow using radiation or drugs.

breast cancer: A malignant tumor that has developed from cells in the breast. It is the most common form of cancer in women and is the second leading cause of cancer death in women, exceeded only by lung cancer.

C


cancer: A term for diseases in which abnormal cells divide without control. Cancer cells can invade nearby tissues and can spread through the bloodstream and lymphatic system to other parts of the body. Cancers are classified according to the tissue and cell type from which they arise. Also called a malignant tumor or neoplasm.

cancer in situ: The stage where the cancer is still confined to the tissue in which it started.

cancer stem cells: A small population of cells inside tumors that have the ability to self-renew while giving rise to different types of cells. It is thought that cancer stem cells might be resistant to many cancer drugs and reconstitute a tumor after chemotherapy has eradicated the bulk of the tumor cells.

cancer vaccine: A form of biological therapy which may help a person's immune system to recognize cancer cells. These vaccines may help the body reject tumors and prevent cancer from recurring.

carcinogen: A substance that increases the risk of developing cancer. Chemical carcinogens such as tobacco smoke typically cause simple local changes in the DNA sequence. Physical carcinogens such as ionizing radiation typically cause chromosome breaks and translocations.

carcinogenesis: The process by which normal cells are transformed into malignant cells. Multiple genetic and environmental factors are involved in the generation of cancer.

carcinoma: A type of cancer that arises in epithelial cells such as those in the skin or lining of organs. About 90 percent of human cancers are carcinomas.

CCSS: Childhood cancer survivor study.

cell: The fundamental living unit of animals and plants. Cells vary in appearance, structure and function. Examples of types of cells are epithelial cells, endothelial cells, squamous cells and stromal cells.

cell cycle: The sequence of events by which a cell enlarges, duplicates it DNA and divides. The cell cycle consists of four successive phases (G1, S, G2 and M), and involves many genes including cyclins and cyclin dependent kinases (CDKs). Access to growth factors, adhesion to extracellular matrix, and cell cycle checkpoints are some of the many factors that regulate the cell cycle. Disregulation of the cell cycle can lead to the uncontrolled growth characteristic of cancer cells.

cell division: The process by which two daughter cells are produced from one parent cell.

chemoprevention: The use of drugs, vitamins or other agents to try to reduce the risk of or delay the development or recurrence of cancer.

chemotherapy: Treatment with anticancer drugs.

chimeric antibody: An antibody that is made of segments of both mouse and human antibodies, usually a 30/70 percent split, respectively.

chondroma: A benign tumor of cartilage.

chromosome: A long, tightly packaged DNA molecule that contains the genetic instructions essential for the life of a cell and allows the transmission of genetic information from generation to generation.

clinical trial: A research study that tests how well new medical treatments or other interventions work in people. Each study is designed to test new methods of screening, prevention, diagnosis or treatment of a disease.

codon: A triplet of three bases or nucleotides that specify a single amino acid. Nucleic acid sequences (DNA and RNA) are read three nucleotides at a time to reveal the genetic code.

colorectal cancer: A disease in which malignant (cancer) cells are found in the colon or rectum.

combination therapy: Treatment using more than one anticancer drug.

complete remission: The disappearance of all detectable signs of cancer. This does not mean the cancer has been cured. Also called a complete response.

concurrent therapy: A treatment that is given at the same time as another.

consolidation therapy: Chemotherapy treatments given after induction chemotherapy to further reduce the number of cancer cells.

control group: In a randomized clinical trial, the group that receives standard treatment.

cytokines: Secreted proteins that are important for interactions between immune cells and help orchestrate an immune response. Some cytokines stimulate or suppress the activity of immune cells. Others, such as lymphotoxin and tumor necrosis factor, are cytotoxic. T cells, B cells, macrophages, fibroblasts, endothelial cells and many other types of cells make cytokines. Cytokines can also be produced in the laboratory by recombinant DNA technology and given to people to affect immune responses. Also called interleukins or lymphokines.

cytoplasm: The part of the cell between the cell membrane and the nucleus.

cytotoxic: Has the ability to kill a cell.

D


dendritic cell: A type of antigen presenting cell named for its long arms or dendrites that is important for initiating and controlling the overall immune response. These cells exist in many tissues including the skin and mucous membranes and can travel to lymph nodes or spleen to interact with other immune cells. In a sense, dendritic cells are the sentinels that alert other immune cells of an attack.

disease-free survival: The length of time after treatment during which no cancer is found. It can be reported for an individual patient or for a study population.

disease progression: Cancer that continues to grow or spread.

DNA (deoxyribonucleic acid): A nucleic acid made of deoxyribose and four different types of bases or nucleotides (A, T, G, C) that pair with each other to form a linear, double-stranded DNA helix. The order of the bases in a gene is called the DNA sequence. DNA is the molecule that encodes genes.

DNA methylation: A type of epigenetic mark. Changes in methylation affect gene expression; the more methylated a stretch of DNA, the less likely it is to be transcribed to RNA.

DNA repair:
The process through which mutations in DNA are repaired. The basic DNA repair mechanism involves nucleases that cut out the damaged area of DNA, polymerases that fill in the gap with the correct nucleotides, and ligases that seal the nick between the new segment of DNA and the original DNA strand.

DNA replication: The copying or duplication of a DNA molecule. DNA in a cell is replicated in preparation for cell division so that the two daughter cells will each receive a complete copy of the DNA of the parent cell. While this process is extremely accurate, errors do occur. The cell has proofreading and DNA repair mechanisms to fix these mistakes.

double-blind: A clinical trial in which the method for analyzing data has been specified in the protocol before the study has begun (prospective), the patients have been randomly assigned to receive either the study drug or alternative treatment, and in which neither the patient nor the physician(s) conducting the study know which treatment is being given to the patient.

drug resistance: The ability of a tumor cell to survive in the presence of drugs that are normally toxic.

duration of response: The length of time between anticancer treatments where a patient's cancer shrinks, disappears or remains stable.

dysplasia: Condition in which cells proliferate excessively and appear abnormal in shape and orientation.

E


EGFR (epidermal growth factor receptor): The protein found on the surface of some cells and to which epidermal growth factor binds, causing the cells to divide. It is found at abnormally high levels on the surface of many types of cancer cells, so these cells may divide excessively in the presence of epidermal growth factor. Also known as ErbB1 or HER1.

eligibility criteria: Participant eligibility criteria for clinical trials can range from general (age, sex, type of cancer) to specific (prior treatment, tumor characteristics, blood cell counts, organ function). Eligibility criteria may also vary with trial phase. In phase I and II trials, the criteria often focus on making sure that people who might be harmed because of abnormal organ function or other factors are not put at risk. Phase II and III trials often add criteria regarding disease type and stage, and number of prior treatments.

endpoint:
What researchers measure to evaluate the results of a new treatment being tested in a clinical trial. Research teams establish the endpoints of a trial before it begins. Examples of endpoints include toxicity, tumor response, survival time and quality of life.

epidemiology: The study of the incidence, distribution, causes and control of disease in a population.

epigenetic: Having to do with the chemical attachments to DNA or the histone proteins around which it coils. Epigenetic marks change the pattern of genes expressed in a given cell or tissue by amplifying or muting the effect of a gene, but do not alter the actual DNA sequence. Unlike mutations to DNA sequence, epigenetic modifications are typically reversible. Epigenetic markers include acetyl groups, methyl groups, phosphate groups and the peptide ubiquitin. Tumor cells often contain epigenetic abnormalities.

epithelium: The most common cell of origin for human cancer.

etiology: The study of the cause or origin of a disease.

extensive-stage small cell lung cancer: Cancer that has spread outside the lung to other tissues in the chest or to other parts of the body.

extracellular: Outside of the cell.

extracellular matrix: A complex network of fiber-forming proteins interwoven in a hydrated polysaccharide gel that helps hold cells and tissues together and provides a meshwork for cells to migrate on and interact with one another. The extracellular matrix influences cell development, migration, proliferation, shape and metabolic functions.

F


Fast Track status: Under the FDA Modernization Act of 1997, the Fast Track Program of the FDA is designed to facilitate the development and expedite the review of a new drug that is intended for the treatment of a serious or a life-threatening condition, and demonstrates the potential of a drug candidate to address unmet medical needs for such a condition.

first-line therapy: The first therapy given in the treatment for cancer.

Food and Drug Administration (FDA): An agency of the U.S. Department of Health and Human Services whose mission is to promote and protect the public health by ensuring that medical products are proven safe and effective before they can be used by patients and by monitoring products for continued safety after they are in use.

free radical: An atom or group of atoms that has at least one unpaired electron and is therefore unstable and highly reactive. Free radicals are produced by the body as part of its normal activity (e.g., during an immune response) and are also present in the environment (e.g., cigarette smoke, asbestos). In animal tissues, excess free radicals can damage cells by stealing electrons from the lipids, proteins and/or DNA of the cell (a process called oxidation or oxidative damage). They are believed to accelerate the progression of many diseases including cancer and cardiovascular disease. Also referred to as reactive species (e.g., reactive oxygen species, reactive nitrogen species).

G


gamete: A reproductive cell that contains a single set of unpaired chromosomes (egg or sperm). Mutations in the DNA of a gamete are inherited by next generation of offspring. Also called germ cells.

gene: The functional and physical unit of heredity passed from parent to offspring. Genes are segments of DNA, and most genes contain the information for making a specific protein. The DNA sequence of a gene determines the amino acid sequence of a protein.

genetic: Inherited, or having to do with information that is passed from parents to offspring through genes in sperm and egg cells.

genetic testing:
Analyzing DNA to look for a genetic alteration that may indicate an increased risk for developing a specific disease or disorder.

genetics research: Research that focuses on how someone's genetic makeup can assist in the early detection, diagnosis or treatment of cancer. Genetics research may be a part of screening or treatment trials.

genome: The total genetic information that is stored in the chromosomes and that governs how an organism develops.

genotype: The genetic makeup of an organism, or the combination of alleles located on homologous chromosomes that determines a specific characteristic or trait.

germ line: Genetic material that is passed down through the gametes (sperm and egg).

glioma: Cancer of non-neuronal brain cells.

growth factors: Substances made by the body that function to regulate cell division and cell survival. Some growth factors are also produced in the laboratory and used in biological therapy. Growth factors bind specific receptors expressed on the surface of the cells they affect.

H


hazard ratio: A summary of the difference between two survival curves, representing the reduction in the risk of death on treatment compared to control. A control experiment is an experiment where the variable that is being investigated is kept constant.

HER1 (human epidermal growth factor receptor-1): See EGFR.

HER2 (human epidermal growth factor receptor-2): The HER2 gene is responsible for making HER2 protein, which plays an important role in normal cell growth and development.

HER2 overexpression: A genetic alteration in the HER2 gene that produces an increased amount of the growth factor receptor protein on the tumor cell surface, causing cells to divide, multiply and grow more rapidly than normal. Women whose tumors overexpress the HER2 protein are likely to have a more aggressive type of breast cancer with a poorer prognosis, shorter time to disease progression, increased relapse rate, shortened survival, and disease that is not as responsive to standard therapies, including certain chemotherapy regimens.

HER2 tumor marker test: Detects overproduction of HER2 protein and/or gene amplification, both of which contribute to aggressive growth of the cancer and its spread to other parts of the body. HER2 overexpression occurs in approximately 25 percent of women with breast cancer.

histones: Proteins that bind DNA and help wrap it into tightly packaged chromatin. Histones and other DNA-binding proteins can affect the pattern of gene expression in different cell types by controlling access to the DNA.

humanized antibody: An antibody that contains over 90 percent human material.

hyperplasia: An overgrowth of cells.

I


investigational group: In a clinical trial, the group that receives the new agent being tested. The investigational group is typically compared to a control group.

imaging: Tests that produce pictures of areas inside the body.

immune response: The activity of the immune system against foreign substances called antigens.

immune system: The complex group of organs and cells that defends the body against infection or disease.

immunotherapy: See biological therapy.

in situ cancer: A tumor that has not broken through the basement membrane to invade surrounding tissue.

induction therapy: Treatment designed to be used as a first step toward shrinking the cancer and in evaluating response to drugs and other agents. Induction therapy is followed by additional therapy to eliminate whatever cancer remains.

infection: Up to one third of the world's cancers are associated with infectious diseases caused by pathogens such as Helicobacter pylori (stomach cancer) or viruses such as the human papillomavirus (HPV, cervical cancer), hepatitis B virus (HBV, liver), Epstein-Barr virus (EBV, lymphoma) and HIV (Kaposi's sarcoma).

inflammation: The cellular and vascular changes that occur after tissue injury. Chronic inflammation may promote tumor growth and progression.

informed consent:
The process of providing all relevant information about the trial's purpose, risks, benefits, alternatives and procedures to a potential participant, who then, consistent with his or her own interests and circumstances, makes an informed decision about whether to participate.

institutional review board (IRB):
A board designed to oversee the research process in order to protect participant safety. Made up of researchers, ethicists and lay people from the community, the board must review the trial protocols and the informed consent forms participants sign. Only after an IRB has approved a study can a researcher submit a proposal for funding.

intracellular: Inside of the cell.

intrinsic resistance: A term used to describe tumor types that are drug resistant at presentation. In this case, resistance likely arises from a characteristic of the tissue of origin (e.g., colon tumors may express high levels of drug transport proteins because these proteins are expressed and play a role in normal colon cells), or from changes that occur during oncogenesis (e.g., mutations in p53 are involved in cancer development as well as drug resistance).

investigational new drug (IND):
A drug that the Food and Drug Administration (FDA) allows.

irreversible toxicity: Side effects that are caused by toxic substances or something harmful to the body and do not go away.



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This glossary was compiled by scientific mentors of the ScientistSurvivor Program® and AACR staff. The definitions used were provided by the mentors and AACR staff, or were adapted from Alberts B, Bray D, Lewis J, Raff M, Roberts K, and Watson JD. Molecular Biology of the Cell, 2nd Edition, New York: Garland Publishing Inc., 1989, or were adapted or copied directly from the NCI website's Dictionary of Cancer Terms (www.cancer.gov/dictionary), Medicine OnLine's Cancer Glossary (www.meds.com/glossary.html), Merriam Webster's Collegiate Dictionary: 11th Edition or the American Heritage® Dictionary of the English Language: Fourth Edition, 2000.

July 7, 2006