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Encyclopedia > Carcinogenesis
Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.
Cancers are caused by a series of mutations. Each mutation alters the behavior of the cell somewhat.

Carcinogenesis (meaning literally, the creation of cancer) is the process by which normal cells are transformed into cancer cells This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... This image has been released into the public domain by the copyright holder, its copyright has expired, or it is ineligible for copyright. ... When normal cells are damaged or old they undergo apoptosis; cancer cells, however, avoid apoptosis. ... A cell is a single unit or compartment, enclosed by a border or wall. ...

Contents


Introduction

Cell division (proliferation) is a physiological process that occurs in almost all tissues and under many circumstances. Normally the balance between proliferation and cell death is tightly regulated to ensure the integrity of organs and tissues. Mutations in DNA that lead to cancer disrupt these orderly processes. Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... Biological tissue is a group of cells that perform a similar function. ... Mutations are permanent, sometimes transmissible (if the change is to a germ cell) changes to the genetic material (usually DNA or RNA) of a cell. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ...


Carcinogenesis is caused by this mutation, of the genetic material of normal cells, which upsets the normal balance between proliferation and cell death,. This results in uncontrolled cell division and tumor formation. The uncontrolled and often rapid proliferation of cells can lead to either a benign tumor or a malignant tumor (cancer). Benign tumors do not spread to other parts of the body or invade other tissues, and they are rarely a threat to life unless they compress vital structures or are physiologically active (for instance, producing a hormone). Malignant tumors can invade other organs, spread to distant locations (metastasize) and become life-threatening. Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. ... See the article about cancer for the main article about malignant tumors. ... yeaaaaaaaa poopsicle ... See the article about cancer for the main article about malignant tumors. ... In medicine, malignant is a clinical term that is used to describe a clinical course that progresses rapidly to death. ... A hormone (from Greek horman - to set in motion) is a chemical messenger from one cell (or group of cells) to another. ... Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ...


More than one mutation is necessary for carcinogenesis. In fact, a series of several mutations to certain classes of genes is usually required before a normal cell will transform into a cancer cell. Only mutations in those certain types of genes which play vital roles in cell division, cell death, and DNA repair will cause a cell to lose control of its proliferation. Mutations are permanent, sometimes transmissible (if the change is to a germ cell) changes to the genetic material (usually DNA or RNA) of a cell. ... Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... DNA damage resulting in multiple broken chromosomes DNA repair is a process constantly operating in each cell of a living being; it is essential to survival because it protects the genome from damage. ... The term cell growth is used in two different ways in biology. ...


Properties of malignant cells

Cells capable of forming malignant tumors exhibit many properties which distinguish them from the cells of healthy tissue.

  • They are resistant to apoptosis ("programmed" cell death).
  • They have an uncontrolled ability to divide (or, they are immortal), and they often divide at an increased rate.
  • These cells are self sufficient with respect to growth factors.
  • They are insensitive to anti-growth factors, and contact inhibition is suppressed.
  • These cells may exhibit altered differentiation.

More aggressive malignant cells may also show additional abilities. In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... Growth factor is any of about twenty small proteins that attach to specific receptors on the surface of stem cells in bone marrow and promote differentiation and maturation of these cells into morphotic constituents of blood. ... Cellular differentiation is a concept from developmental biology describing the process by which cells acquire a type. The morphology of a cell may change dramatically during differentiation, but the genetic material remains the same, with few exceptions. ...

Nearly all cancers originate from a single cell, but a cell that degenerates into a tumor cell does not usually acquire all these properties at once. With each carcinogenic mutation, a cell gains a slight selective advantage over its neighbors, resulting in a process known as clonal evolution. This leads to an increased chance that the descendents of the original mutant cell will acquire extra mutations, giving them even more selective advantage. Cells which acquire only some of the mutations necessary to become malignant are thought to be the source of benign tumors. However, when enough mutations accumulate, the mutant cells will become a malignant tumor. Biological tissue is a group of cells that perform a similar function. ... The metalloendopeptidases (also called metalloproteinases or metalloproteases) are a class of enzymes from the group of endopeptidases. ... In biology, extracellular matrix (ECM) is any material part of a tissue that is not part of any cell. ... Metastasis (Greek: change of the state) is the spread of cancer from its primary site to other places in the body. ... Angiogenesis is the physiological process involving the formation of new blood vessels from pre-existing vessels. ... Natural selection is a process by which biological populations are altered over time, as a result of the propagation of heritable traits that affect the capacity of individual organisms to survive and reproduce. ... yeaaaaaaaa poopsicle ... See the article about cancer for the main article about malignant tumors. ... In medicine, malignant is a clinical term that is used to describe a clinical course that progresses rapidly to death. ...


Mechanisms of carcinogenesis

Cancer is, ultimately, a disease of genes. Typically, a series of several mutations is required before a normal cell transforms into a cancer cell. The process involves both proto-oncogenes and tumor suppressor genes. Proto-oncogenes are involved in signal transduction by coding for a chemical "messenger", produced when a cell undergoes protein synthesis. These messengers, send signals based on the amount of them present to the cell or other cells, telling them to undergo mitosis, in order divide and reproduce. When mutated, they become oncogenes and overexpress the signals to divide, and thus cells have a higher chance to divide excessively. Frustratingly, the chance of cancer cannot be reduced by removing proto-oncogenes from the human genome as they are critical for growth, repair and homeostasis of the body. It is only when they become mutated, that the signals for growth become excessive. This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... Mutations are permanent, sometimes transmissible (if the change is to a germ cell) changes to the genetic material (usually DNA or RNA) of a cell. ... An oncogene is a gene that can cause a cell to develop into a tumor cell, possibly resulting in cancer. ... A tumor suppressor gene is a gene that reduces the probability that a cell in a multicellular organism will turn into a tumor cell. ... In biology, signal transduction is any process by which a cell converts one kind of signal or stimulus into another. ... A chemical substance is any material substance used in or obtained by a process in chemistry: A chemical compound is a substance consisting of two or more chemical elements that are chemically combined in fixed proportions. ... Biological and artificial methods for creation of proteins differ significantly. ... Light micrograph of a newt lung cell in early anaphase of mitosis. ... An oncogene is a gene that can cause a cell to develop into a tumor cell, possibly resulting in cancer. ... Gene expression (also protein expression or often simply expression) is the process by which a genes information is converted into the structures and functions of a cell. ... Homeostasis or homoeostasis is the property of an open system, especially living organisms, to regulate its internal environment so as to maintain a stable condition, by means of multiple dynamic equilibrium adjustments controlled by interrelated regulation mechanisms. ...


Tumor suppressor genes code for chemical messengers that command cells to slow or stop mitosis in order to allow DNA repair. This is done by special enzymes which detect any mutation or damage to DNA, such that the mistake is not carried on to the next generation. Tumor suppressor genes are usually triggered by signals that DNA damage has occurred. In addition to inhibiting mitosis, they can code for such enzymes themselves, or sending signals to activate such enzymes. However, a mutation can damage the tumor suppressor gene itself, or the signal pathway which activates it, "switching it off". The invariable consequence of this is that DNA repair is hindered or inhibited: DNA damage accumulates without repair, inevitably leading to cancer. DNA damage resulting in multiple broken chromosomes DNA repair is a process constantly operating in each cell of a living being; it is essential to survival because it protects the genome from damage. ... Neuraminidase ribbon diagram An enzyme (in Greek en = in and zyme = blend) is a protein, or protein complex, that catalyzes a chemical reaction and also controls the 3D orientation of the catalyzed substrates. ...


In general, mutations in both types of genes are required for cancer to occur. For example, a mutation limited to one oncogene would be suppressed by normal mitosis control (the Knudson or 1-2-hit hypothesis) and tumor suppressor genes. A mutation to only one tumor suppressor gene would not cause cancer either, due to the presence of many "backup" genes that duplicate its functions. It is only when enough proto-oncogenes have mutated into oncogenes, and enough tumor suppressor genes deactivated or damaged, that the signals for cell growth overwhelm the signals to regulate it, that cell growth quickly spirals out of control. The Knudson hypothesis is the hypothesis that cancer is the result of accumulated mutations to a cells DNA. It was first formulated by Alfred G. Knudson in 1971, and led indirectly to the identification of cancer-related genes. ... // Overview Backup in computer engineering refers to the copying of data for the purpose of having a second copy of an original source, in case of damage to the original data source. ...


Mutations can have various causes. Particular causes have been linked to specific types of cancer. Tobacco smoking is associated with lung cancer. Prolonged exposure to radiation, particularly ultraviolet radiation from the sun, leads to melanoma and other skin malignancies. Breathing asbestos fibers is associated with mesothelioma. In more general terms, chemicals called mutagens and free radicals are known to cause mutations. Other types of mutations can be caused by chronic inflammation, as neutrophil granulocytes secrete free radicals that damage DNA. Chromosomal translocations, such as the Philadelphia chromosome, are a special type of mutation that involve exchanges between different chromosomes. 1: cigar box 2: cigar 3: various pipes 4: waterpipe 5: joss stick 6: bong Various smoking equipment including different pipes, and cigars. ... The incidence of lung cancer is highly correlated with smoking. ... Radiation has a variety of different meanings. ... Note: Ultraviolet is also the name of a 1998 UK television miniseries about vampires. ... The Sun is the star at the centre of our Solar system. ... Skin cancer, close-up of level IV melanoma Melanoma is a malignant tumour of melanocytes . ... Asbestos (Greek a-, not; sbestos, extinguishable) is a group of fibrous metamorphic minerals. ... In biology, a mutagen (Latin, literally origin of change) is an agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ... In chemistry free radicals are uncharged atomic or molecular species with unpaired electrons or an otherwise open shell configuration. ... Inflammation is the first response of the immune system to infection or irritation and may be referred to as the innate cascade. ... Neutrophil granulocytes (commonly referred to as neutrophils) are a class of white blood cells and are part of the immune system. ... Chromosomal translocation of the 4th and 20th chromosome. ... Philadelphia chromosome or Philadelphia translocation is a specific genetic, chromosomal abnormality that is associated with chronic myelogenous leukemia (CML) and involves an exchange of material between chromosomes 9 and 22. ...


Many mutagens are also carcinogens, but some carcinogens are not mutagens. Examples of carcinogens that are not mutagens include alcohol and estrogen. These are thought to promote cancers through their stimulating effect on the rate cellular mitosis. Faster rates of mitosis increasingly leave less window space for repair enzymes to repair damaged DNA during DNA replication, increasingly the likelihood of a genetic mistake. A mistake made during mitosis can lead to the daughter cells receiving the wrong number of chromosomes, which leads to aneuploidy and may lead to cancer. In biology, a mutagen (Latin, literally origin of change) is an agent that changes the genetic information (usually DNA) of an organism and thus increases the number of mutations above the natural background level. ... In pathology, a carcinogen is any substance or agent that promotes cancer. ... In general usage, alcohol (from Arabic al-khwl الكحول, or al-ghawl الغول) refers almost always to ethanol, also known as grain alcohol, and often to any beverage that contains ethanol (see alcoholic beverage). ... Estrogens (or oestrogens) are a group of steroid compounds that function as the primary female sex hormone. ... Light micrograph of a newt lung cell in early anaphase of mitosis. ... DNA replication - Wikipedia /**/ @import /w/skins-1. ... This article is about the biological chromosome. ... Aneuploidy is a chromosomal state where abnormal numbers of specific chromosomes or chromosome sets exist within the nucleus. ...


Mutations can also be inherited. Inheriting certain mutations in the BRCA1 gene, a tumor suppressor gene, renders a woman much more likely to develop breast cancer and ovarian cancer. Mutations in the Rb1 gene predispose to retinoblastoma, and those in the APC gene lead to colon cancer. BRCA 1 (named for breast cancer 1) is a human gene located on the long arm of the 17th chromosome (17q21). ... Breast cancer is cancer of breast tissue. ... Ovarian cancer is a malignant ovarian neoplasm (an abnormal growth located on the ovaries). ... Retinoblastoma is a cancer of the retina. ... Familial adenomatous polyposis (FAP) is an inherited condition in which numerous polyps to form in the epithelium of the large intestine. ... Diagram of the stomach, colon, and rectum Colorectal cancer includes cancerous growths in the colon, rectum and appendix. ...


Some types of viruses can cause mutations. They play a role in about 15% of all cancers. Tumor viruses, such as some retroviruses, herpesviruses and papillomaviruses, usually carry an oncogene or a gene inhibits normal tumor suppression in their genome. Genera Alpharetrovirus Betaretrovirus Gammaretrovirus Deltaretrovirus Epsilonretrovirus Lentivirus Spumavirus A retrovirus is a virus which has a genome consisting of two plus sense RNA molecules, which may or may not be identical. ... Genera Subfamily Alphaherpesvirinae    Simplexvirus    Varicellovirus    Mardivirus    Iltovirus Subfamily Betaherpesvirinae    Cytomegalovirus    Muromegalovirus    Roseolovirus Subfamily Gammaherpesvirinae    Lymphocryptovirus    Rhadinovirus Unassigned    Ictalurivirus The Herpesviridae are a family of DNA viruses that cause diseases in humans and animals. ... Species See text Papillomaviruses are viruses that commonly cause warts. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ...


It is impossible to tell the initial cause for any specific cancer. However, with the help of molecular biological techniques, it is possible to characterize the mutations or chromosomal aberrations within a tumor, and rapid progress is being made in the field of predicting prognosis based on the spectrum of mutations in some cases. For example, up to half of all tumors have a defective p53 gene, a tumor suppressor gene also known as "the guardian of the genome". This mutation is associated with poor prognosis, since those tumor cells are less likely to go into apoptosis (programmed cell death) when damaged by therapy. Telomerase mutations remove additional barriers, extending the number of times a cell can divide. Other mutations enable the tumor to grow new blood vessels to provide more nutrients, or to metastasize, spreading to other parts of the body. Molecular biology is the study of biology at a molecular level. ... Prognosis (older Greek πρόγνωσις, modern Greek πρόγνωση - literally fore-knowing, foreseeing) is a medical term denoting the doctors prediction of how a patients disease will progress, and whether there is chance of recovery. ... Human p53 protein bound to a short DNA fragment. ... In biology, apoptosis (from the Greek words apo = from and ptosis = falling, pronounced ap-a-tow-sis[1]) is one of the main types of programmed cell death (PCD). ... Telomerase is an enzyme that adds specific DNA sequence repeats, (TTAGGG in all vertebrates) to the 3 (three prime) end of DNA strands, in the telomere regions at the ends of chromosomes. ... Angiogenesis is the physiological process involving the formation of new blood vessels from pre-existing vessels. ...


See also


  Results from FactBites:
 
BioMed Central | Full text | Suppression of colitis-related mouse colon carcinogenesis by a COX-2 inhibitor and PPAR ... (5556 words)
The precise mechanisms of the IBD-related carcinogenesis process are largely unclear, although it is generally assumed that IBD-related carcinogenesis occurs as a result of chronic inflammation [3].
Several agents, such as folic acid, short chain fatty acid (butyrate), ursodeoxycholic acid, and 5-aminosalicylic acid, have been suggested to be useful for prevention of CRC in UC Epidemiological studies have shown that prolonged use of aspirin is associated with a reduced risk of CRC [5].
The pathogenesis of IBD-associated colorectal carcinogenesis is widely believed to involve a step-wise progression from inflamed and hyperplastic epithelia through flat dysplasia to finally adenocarcinoma [30].
Carcinogenesis - Wikipedia, the free encyclopedia (2094 words)
Carcinogenesis (meaning literally, the creation of cancer) is the process by which normal cells are transformed into cancer cells.
Carcinogenesis is caused by this mutation of the genetic material of normal cells, which upsets the normal balance between proliferation and cell death.
There are a number of theories of carcinogenesis and cancer treatment which fall outside the mainstream of scientific opinion, due to lack of scientific rationale, logic, or evidence base.
  More results at FactBites »

 
 

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