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The BCERF program on the Cancer Risks of Environmental Chemicals in the Home and Workplace closed on March 31, 2010. No further updates will be made to this web site. Please go Cornell University’s eCommons web site to access BCERF’s archived research and educational materials (http://ecommons.library.cornell.edu/handle/1813/14300).

Glossary

If you would like to see a term added to the glossary, please let us know. Send an email to breastcancer@cornell.edu

2,4-D : 2,4-dichlorophneoxyacetic acid (2,4-D) is a chemical used to control the growth of unwanted weeds, (an herbicide). It is one of the most widely used herbicides in the United States. 2,4-D belongs to a family of herbicides called, "chlorophenoxy herbicides." The chemical structure of 2,4-D resembles a naturally occurring chemical produced by plants and used to regulate their own growth. The resemblance allows 2,4-D to artificially regulate plant growth.

Agent Orange : A chemical mixture of two synthetic herbicides, 2,4-D and 2,4,5-T. Agent Orange was used as a chemical agent to remove leaves from plants in the Vietnamese jungle during the Vietnam War. One of the chemicals in Agent Orange, 2,4,5-T has the potential to cause cancer and other harmful affects. The use of 2,4,5-T was banned by the U.S. Environmental Protection Agency (EPA) in 1983, 2,4-D is a weed killer that is still manufactured and used in the U.S.

Anti-estrogens : Chemicals that interfere with the interaction between the hormone estrogen (a chemical messenger) and it's binding site in the cell, the estrogen receptor. If an anti-estrogen binds to the estrogen receptor, it can then block a strong estrogen (key) from binding to the receptor (lock). It can block the action of estrogen by occupying the receptor in the same way that bubble gum could block up a key hole and prevent a key (estrogen) from entering and turning the lock (estrogen receptor).

Apoptosis : The self-destruction of a cell, also called "cell suicide."

Ataxia Telangiectasia : A rare genetic disorder in which cells in the body don't have the ability to repair damage to DNA caused by ionizing radiation (like X-rays).

Basement membrane : this membrane defines the area that contains the contents of the cell. Cells are contained in their proper location by a "curb" called the basement membrane.

Benign tumor : Although the cells in a benign tumor are not normal, a benign tumor poses no immediate threat to the patient. However, in some cases a benign tumor may undergo further changes and may become a life-threatening aggressive tumor.

Birth control pill : Pills which are able to prevent pregnancy. Currently, the most commonly used birth control pills contain small amounts of the female hormones estrogen and progesterone.

Blood clotting : The coagulation of blood. This process protects against blood loss from harm to blood vessels but can also occur abnormally and deprive tissues of normal blood flow.

Blood vessel disease : A disease which is characterized by abnormal growth of cells and blockage of the arteries or veins through which the blood circulates.

Brain astrocytoma : A type of tumor of the brain. This type of tumor is malignant. It invades and destroys healthy cells. The cells that this type of tumor invades are those of the nerves in the brain.

BRCA1 and BRCA2 : These are two genes that are known to play a part in breast cancer risk. Women who inherit a defective BRCA1 or BRCA2 gene from either or both of their parents may have a higher chance of developing breast cancer than women who have not inherited one of these defective genes. Women who have a high rate of breast cancer in their families can have a test done that can tell them if they have a defective BRCA1 or BRCA2 gene.

Breakdown product : A breakdown product is the result of a chemical breaking apart into smaller pieces. For instance, the hormone estrogen can be broken down several different ways in the liver to form other estrogen-like chemicals.
    Synthetic chemicals can also form breakdown products. Some kinds of pesticides break down when exposed to the sun, rain or to bacteria found in soil. Certain pesticide breakdown products are monitored in our food supply and in our drinking water.

Breast tumor progression : A normal cell must go through a series of changes before it becomes a cancer. These changes or stages that a cell passes through are: * a normal cell, a cell with a mistake in its DNA, a cell that looks normal but grows too much * a cell (or cells) which grow too much AND look abnormal * a benign tumor * in situ cancer - cells look more abnormal in growth and appearance but the tumor cells have not spread into surrounding tissues * invasive cancer (primary tumor): some cells in the tumor have broken through the boundary and invade nearby tissues * metastatic cancer, cells from the primary tumor have moved to somewhere else in the body where they form new tumors.

Brush-1 : A gene that has been shown to have a tumor-suppressing function in some breast cancer cells. This gene is absent, or does not work in some primary breast tumors.

c-myc oncogene : Researchers believe that this oncogene may work with other genes to promote cancer formation.

Cadherins and integrins : A group of functionally related cell surface proteins responsible for cell-to-cell adhesion. These proteins play an important role in the construction of tissues throughout the body.

Cancer : An uncontrolled growth of abnormal cells. Cancer cells can invade and destroy surrounding tissues, and can travel to other parts of the body and invade other vital organs.

Canine lymphoma : A disease found in dogs. These are cancerous tumors arising in tissue of the lymph system of the body. The lymph system is a second circulatory system in the body whose function is to maintain the fluid balance and aid in elimination of infections.

Carcinogens : Substances found in nature or made by man than can start or help the growth of cancer cells.

Cell adhesion protein : Cells are cemented in position by cell adhesion proteins, which act like the mortar between bricks or cobblestones. These proteins direct cell-to-cell adhesion. They play an important role in maintaining tissues in the body and healing wounds. They can also be responsible for the movement of cells from one part of the body to another and metastasis.

Cell cycle : The series of steps that a cell passes through to duplicate its genetic material and split into two new cells. The model of this process is often drawn as a circle. It is divided into five events in which each previous phase needs to be completed before the next phase can start. The phases are called: Mitosis, G1, Synthesis (S-phase) and G2. . Errors in regulation of the cell cycle can lead to uncontrolled growth and cancer.

Certified pesticide applicator : Any individual who is trained and certified to use or supervise the use of pesticides. Different categories of certification exist and the applicator must be certified in the category of pesticide they use or supervise.

Cervical mucus : A secretion of the cervix which moistens and protects this region of the body. The consistency of cervical mucus changes during a woman's menstrual cycle and can hinder the travel of sperm to the uterus.

Chemically-induced mutations : An error in the genetic code of a cell resulting from a chemical found in nature or a synthetic chemical.

Chlorophenoxy herbicides : Herbicides are chemicals that are used to kill or control the growth of unwanted plants. Chlorophenoxy herbicides are a specific chemical family of herbicides that are commercially produced. This class of herbicides is used on lawns and gardens, on crops, beside roadways, or on recreational areas to control broad leaf weeds.

Conception : The beginning of a pregnancy marked by the fertilization of an egg by a sperm cell.

Coumestan phytoestrogens : A class of chemicals from plants that behave like estrogen in the body. Coumestan phytoestrogens are found in beans such as , pinto beans, lima beans and split peas. Alfalfa, and clover sprouts contain high amounts of these phytoestrogens

Cyclins : Cyclins are molecules that help control the cell cycle. There are multiple cyclins, each with a specific role. They function as on switches for the active phase of the cell cycle.

Cyclin D-1 : This substance, which is a protein, is one of the chemicals the body makes to signal a cell to divide. Researchers think that cyclin D-1 and estrogen somehow work together to tell a breast cell when to divide.

Cyclin regulator CDK-1 : Cdk (cyclin dependent kinase) is an important control switch for the cell cycle. It causes the cell to move from a resting phase to an active phase of the cell division process. Errors in this regulator of the cell cycle can lead to uncontrolled cell growth and cancer.

Daughter cells : When a cell divides, it copies its DNA and produces two new daughter cells that have identical DNA.

Differentiated cells : In the breast differentiated cells are those mature cells which make milk. Hormonal influences during the first full term pregnancy change the cells of the breast from immature to mature cells.

Dioxins : There are 75 known varieties of dioxin. Each known variety has a unique chemical structure. These chemicals can have effects at extremely low levels. Health problems related to dioxin exposure include: some types of cancer, immune disorders, lowered sperm counts, diabetes, malformations and other reproductive and developmental effects, and endocrine disruption. The largest current sources of dioxins are industries producing chemicals, pesticides and paper products. Another suspected source are emissions from trash and toxic waste incinerators, particularly those burning plastic.

DNA : is the short way to say "deoxyribonucleic acid." It is the genetic blueprint that tells the cell how to grow, function, divide, and die.

Ducts : Tubes that transport the product of a gland. Ducts in the breast (also called the mammary gland) have a tree-like structure. When a mother makes breast milk, the branch-like ducts gather the milk, moving it to larger ducts and then to the nipple.

Environmental estrogens : Estrogen is a hormone produced by a woman's ovaries. It is a chemical messenger which is important for the normal growth and development of a woman's breast, uterus and ovaries, and is important for healthy bones and heart. An environmental estrogen is a chemical found in the things around us: air, water, chemical products, that mimics the action of the hormone estrogen.

erb-B2 receptor gene : One example of a cancer gene (oncogene) is the erb-B2 receptor gene. The erb-B2 receptor in normal cells must be bound to another molecule before it can cause the cell to enter the cell cycle and divide. But in faulty versions of this gene, the erb-B2 receptors can release signals to stimulate increased cell division without being bound to their partner molecule.

Estrogen-receptor positive : Breast tumors can also have estrogen receptors. About one- to two-thirds of all breast tumors have estrogen receptors and depend on estrogen for growth. These receptors can be seen under a microscope by looking at thin sections of breast tissue that have been prepared with a special stain.

Estrogen Receptors : The part of a cell which allows it to recognize the hormone estrogen (a chemical messenger). The hormone can be thought of as a "key" and the receptor as a "lock." In order for the hormone (key) to deliver its message to the cell (like divide) it must first bind to the receptor (lock). In this way, the chemical messenger has an effect only on the tissues that have the specific hormone receptor.

Estrogen : A hormone which is produced by a woman's ovaries. It is a chemical messenger that is important for the normal growth and development of a woman's breast, uterus, and ovaries. Estrogen is also important for childbearing and for maintaining a healthy heart and bones.

Estrogenic : Acting like the hormone estrogen which is produced by a woman's ovaries. Estrogen is a chemical messenger which can affect the normal growth and development of a woman's breasts, uterus, and ovaries, and is important for healthy bones and heart.

Fertilization : The union of sperm and egg which marks conception and the beginning of a pregnancy.

Flaxseeds : Seeds of the flax plant. These seeds contain high amounts of lignan phytoestrogens.

Gallbladder disease : Disease of the gallbladder in which there can be inflammation, infection, the formation of stones, or the obstruction of bile flow from this organ.

G1 Checkpoint : The period in the cell cycle between mitosis and the duplication of the DNA. It is also called the decision period of the cell, because the cell decides to divide when it enters the next phase, also called the S phase.

Genes : The functional units of a cell's genetic code. Genes provide information to the cell that controls and directs its activities.

Genistein : One of the most studied of the soy isoflavone phytoestrogens.

Growth factor TGF-alpha : One example of a growth factor is the growth factor TGF-alpha (transforming growth factor alpha). Researchers have shown that having too much TGF-alpha may cause a high rate of growth and cell division. Some tumor cells can make TGF-alpha which signals the cancerous cell to grow and divide.

Growth factors : Local chemical messengers in many tissues in the body that can control the growth of cells. Some growth factors can tell breast cells to grow and divide. Other growth factors can act as brakes, stopping or slowing down the growth of breast cells. "Transforming growth factor-alpha" is an example of a growth factor that is known to stimulate the growth of normal breast cells and some types of breast tumors.

Heart disease : an abnormal medical condition of the heart and circulation.

Herbicide : A chemical that is used to kill or control the growth of unwanted plants. Herbicides can occur in nature or they can be created synthetically. Herbicides can be used on lawns and gardens, on crops, beside roadways, or on recreational areas.

Hormones : Chemical messengers made by the body. Hormones released by one part of the body travel in the blood to other parts of the body to tell cells how to function or when to grow, divide or die. Some examples of hormones are estrogen, progesterone, testosterone, and insulin.

Hormone dependent : Cancer, the uncontrolled growth of abnormal cells in the body, can be stimulated or encouraged by certain chemical messengers in the body. Tumors which only grow in the presence of specific chemical messengers (either natural ones or chemical mimics) are said to be hormone dependent. An example would be a breast tumor that depends on the hormone estrogen for growth.

Hormone replacement therapy : Can be prescribed by a doctor to replace the estrogen that a woman stops producing after she goes through menopause. It is sometimes called "HRT."

Hysterectomy : A surgical operation which removes the uterus.

Immune system : Composed of organs and cells in the body that recognize and neutralize viruses, foreign cells and other disease-causing organisms. The immune system of the body plays an important role in the body's defense system against cancer. There is concern that damage to the immune system may affect cancer risk.

Incontinence : A loss of the ability to control urine flow.

Ionizing radiation : Ionizing radiation is radiation with a very high level of energy. It has so much energy that when it interacts with an atom, the energy can remove electrons from their orbits. This causes the atom to become charged or ionized. An example of radiation with enough energy to form ions is x-rays. Other types of energy, like visible light, radio and television waves, ultra violet (UV) and microwaves do not cause ionization of atoms because they do not carry enough energy to separate molecules or remove electrons from atoms.

Isoflavavones : Plant compounds that are found in soy products that have estrogen-like actions in the body.

Leukemia : A type of cancer that affects the blood.

Lignan phytoestrogens : One of the three classes of plant chemical compounds that have estrogen-like actions in the bidy. Lignan phytoestrogens are found in high fiber foods such as cereal brans and beans.

Lymphomas : Cancerous tumors that are found in the lymph system

Mammary gland : Another name for the system of cells and tubes that make and deliver breast milk to the nipple. In experimental animals, often the name used for breast tissue is the mammary gland.

Maspin : Maspin has been shown to have a tumor-suppressing function in breast cancer. In many breast cancers the level of Maspin may be lower than in normal cells.

Maximum contaminant level : The legal limit set by the U.S. Environmental Protection Agency and each individual state for the maximum amount of a chemical that is allowed to be in the public water supply. Each state can create stricter levels of control, but cannot lower the levels of control set by the EPA.

MCPA : Stands for "4-chloro-2-methyl phenoxy acetic acid." It is used to control weeds in crops like rice, peas, potatoes, asparagus, and on lawns. It is in the class of herbicides called "chloro-phenoxy herbicides."

Menarche : The age at which a girl has her first period. It marks the beginning of her childbearing years.

Menopause : Also known as "the change of life." It is the time when the ovaries stop producing the hormone estrogen and a woman stops having menstrual periods. Menopause marks the end of a woman's childbearing years.

Menstrual cycle : Occurs about every 28 days during a woman's reproductive years. During this cycle an egg (ovum) from the ovary matures and enters the uterus (womb). If the egg is not fertilized and pregnancy does not occur, then the lining of the womb sloughs off and appears as a bloody discharge. The time when the discharge is visible is commonly called a woman's "period."

Metastatic cancer : A second cancer that forms in the body as a result of an original (primary) tumor is called a metastatic cancer. It is caused when cells break away from the primary tumor and form another tumor at another site in the body. These secondary tumors are called metastases. Metastatic tumors can become fatal if they disrupt the function of vital organs.

Metastasis : The process by which cancerous cells break away from a tumor and form cancers at other sites in the body.

Micrograms : One microgram is one-millionth of a gram. 1/1,000,000

Milk duct : The tubular passages in the breast which carry milk to the nipple.

Mitosis : The process of cell division. The term can also mean specifically the division of the nucleus of the cell into two separate nuclei in preparation for cell division.

MPF (Maturation Promoting Factor) : Includes the CdK and cyclins that triggers the cells progression through the cell cycle. During mitosis MPF plays a role in moving the cell through the G2 to M phase transition. MPF is activated by cyclins, and directs the production of two new nuclei from the original single nucleus of the cell.

Mutation : Any change in the genetic code of a cell. Units of genetic code are called genes. A mutation can be spontaneous, inherited from parent(s), or caused by something in the environment. A mutation can have no effect, cause minor effects or cause major effects. Over many years, the accumulation of mutations in genes that control a cell's ability to divide, mature, or die can result in cancer cells.

Myeloma : A type of cancer that occurs in blood-making cells found in the bone marrow.

nm23 :This gene is thought to work in cells to suppress the progression of a tumor to metastasis (spread of a primary tumor to a new site in the body).

Non-Hodgkin's lymphoma : A type of cancer that affects the lymph system

Nucleus : The central core of a cell that regulates the cell's function. The nucleus holds all of the cell's genetic information.

Occupational Safety and Health Administration : This government agency helps to protect the health and welfare of workers in the United States. Known as "OSHA", this agency determines and regulates the practices that must be followed to make sure workers are not exposed to harmful levels of chemicals.

Oncogene : This is a mutated form of a proto-oncogene. In this form the gene can cause the cell to divide uncontrollably. This change, by itself or with other mutations, can cause a cell to become cancerous.

Osteoporosis : A medical condition in which there is a decrease in bone density, producing fragile bones.

Ovarian hormones : Chemical messengers produced and released by a woman's ovaries. Ovarian hormones control a woman's sexual development, reproduction, and the development of the breast. Estrogen and progesterone are two examples of ovarian hormones.

Ovarian cancer : Cancer that occurs a woman's ovary.

Ovaries : An important part of a woman's reproductive system. Women have two ovaries. During each monthly menstrual cycle an egg (ovum) matures and is released from one of the ovaries. Ovaries also produce chemical messengers called "ovarian hormones" which are important for normal sexual development, reproduction and the development of the breast.

Overiectomy (oophorectomy) : A surgical operation which removes one or both ovaries.

Ovulation : The release of a mature egg from the ovary.

p53 gene : The role of tumor suppressor genes is to maintain the integrity of the genetic code, DNA, in cells. An example of an important tumor suppressor gene is the p53 gene. In cancer cells, the p53 gene recognizes damaged DNA and tells the cell to "commit suicide" (apoptosis). If the p53 gene is damaged and loses its function, cells with damaged DNA continue to pass on the damage, called mutations, to daughter cells.

Placebo : An inactive substance which is administered during a clinical trial to determine the effectiveness of a drug. Patients receiving the placebo serve as the reference for comparison to the patients who received the drug under examination.

Phytoestrogens : Chemicals found in plant foods that can act like estrogen in the body.

Postmenopausal : A term which refers to the time period following menopause.

Pituitary gland : Sometimes called the "master gland." This small bundle (gland) located at the base of the brain acts as a supervisor over all the other glands in the body.

Progesterone : A hormone (chemical messenger) produced by a woman's ovaries. This hormone plays an important role in childbearing. It helps by preparing the womb (uterus) for the fertilized egg, and is important in keeping the womb healthy during pregnancy. It is also important for the normal growth and development of the breast.

Proto-oncogenes : Genes that tell a cell to enter the cell cycle and control when a cell should divide. If a proto-oncogene loses the ability to regulate the cell cycle, the cell may divide uncontrollably. Proto-oncogenes can become damaged and become a cancer gene (oncogene).

Puberty : The process of changing from a child into an adult. This series of changes are caused by chemical messages that tell the body to grow and become physically and sexually mature.

Randomized clinical trial : A scientific study to compare different medical treatments. In these studies, patients are assigned to the different treatment groups by chance. This design allows for the unbiased comparison of the treatments. If the study is also 'double-blinded' neither the patients nor the researchers know who is receiving the treatments under study.

Receptors : Part of a cell that allows it to recognize a chemical messenger. A hormone is an example of a chemical messenger. The hormone can be thought of as a "key" and the receptor as the "lock." For the hormone (key) to deliver its message to the cell (like divide, grow or die), it must first bind to the receptor (lock). In this way, the chemical messenger has an effect only on the tissues that have the specific hormone receptor.

Receptor protein : A substance that lets a cell recognize a chemical messenger. Receptors and chemical messengers, such as hormones, work like a lock and key. The key is the hormone and the lock is the receptor. A receptor will only link up with a chemical that has a certain shape that allows it to bind to the receptor.

Retinoblastoma : A malignant tumor of the retina. Retinoblastoma is caused by a mutation in a gene and can affect the entire body, not just the retina of the eye. The product of the retinoblastoma gene is a tumor suppressor that works with transcription proteins such as E2F to block the formation of growth regulating genes. It is also called the Rb gene.

SDG : Secoisolaricirescinol diglycoside, a lignan phytoestrogen found in flaxseed.

Soft-tissue sarcoma : A type of malignant tumor found in the soft-tissues of the human body.

Stem cells : Stem cells are immature cells. The chemical messengers (hormones) that the body releases during pregnancy can cause stem cells in the breast to change into mature, milk-producing cells. It is believed that stem cells in the breast are particularly susceptible to damage that can be caused by cancer-causing substances (carcinogens). That is why it is especially important to limit exposure to cancer-causing chemicals in young girls and women who have not yet had a full-term pregnancy.

Tamoxifen : A drug that acts as an anti-estrogen in some types of breast tumors. In breast tumors that depend on estrogen for growth, tamoxifen can prevent breast cancer cells from dividing and multiplying further by blocking the action of estrogen.

Tissue culture : Growth of cells in the laboratory for scientific studies.

Tolerance : The maximum level of a chemical (for example - a pesticide, and its breakdown products) that are allowed in human food and animal feed. These levels are set by the U.S. Environmental Protection Agency.

Transcribed : This chemical process takes place in the nucleus of the cell during cell division. A strand of messenger RNA is constructed by a chemical messenger that moves along the unwound portion of DNA, using it as a template.

Translation : The molecular process that converts the information in a strand of messenger RNA into a corresponding sequence of protein building blocks called amino acids.

TSG101 : A gene that is suspected to have a tumor-suppressing function in breast cancer cells. In many primary breast tumors this gene may be mutated or damaged.

tumor "promoter" : A chemical in the body, whether natural or synthetic, that aids or stimulates the growth of cancerous cells.

Tumor suppressor genes : The role of tumor suppressor genes is to maintain the integrity of the DNA in cells. The activation of a tumor suppressor gene at certain "check points" puts on the "brakes" and allows the cell to check for any damage in its DNA. Usually repairs are made before the cell is allowed to go on and divide. Without these brakes, cells with damaged DNA would copy the damage and pass damage on to daughter cells. The damage becomes a permanent mutation in future generations of new cells.

Tyrosine kinase family : These cellular chemicals play a major role in the cell division process. They signal the section of the cell cycle known as mitosis to begin, and how to progress.

Undifferentiated cells : Cells in the breast that have not matured into milk producing cells. The breast cells become fully mature only after a woman's first full term pregnancy will

Uterine (endometrial) cancer : Cancerous growth in the lining of the uterus (endometrium).

Uterus : is also called the womb. It houses and protects the baby during pregnancy.

Venous thromboembolism : Formation of a blood clot in the veins which can travel from the site where it formed and block blood flow at another location.