What is the role of viruses in cancer?
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Cancer causing viruses insert genetic material into infected cells that leads to uncontrolled growth which leads to cancer (such as the case with HPV - human papilloma virus).\n\nOther viruses can cause infections leading to chronic inflammation of an organ, which leads to mutations occuring in that organ (such as Hepatitis B Virus and Hepatitis C Virus, both of which can lead to a higher incidence of Hepatocellular Carcinoma).\n\nLastly, some viruses can cause immunesuppression of the T- and B-cells which mediate cellular immune response, and inhibit their ability to attack abnormal cells (Kaposi's Sarcoma and some lymphomas with HIV infection).
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The evillest thing about viruses is that they cannot really die, and retroviruses especially, they can inject their own DNA into yours, and your body won't realize it and will accept its DNA.
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To quote The Source of all knowledge - wikipedia - Cancer is a class of diseases characterized by uncontrolled cell division and the ability of these cells to invade other tissues, either by direct growth into adjacent tissue (invasion) or by migration of cells to distant sites (metastasis). This unregulated growth is caused by damage to DNA, resulting in mutations to vital genes that control cell division, among other functions. One or more of these mutations, which can be inherited or acquired, can lead to uncontrolled cell division and tumor formation. Tumor ("swelling" in Latin) refers to any abnormal mass of tissue, but may be either malignant (cancerous) or benign (noncancerous). Only malignant tumors are capable of invading other tissues or metastasizing.
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A virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism.They can't multiply on their own, so they have to invade a 'host' cell and take over its machinery in order to be able to make more virus particles. \nViruses consist of genetic materials (DNA or RNA) surrounded by a protective coat of protein. They are capable of latching onto cells and getting inside them. \n\nBacteria are organisms made up of just one cell. They are capable of multiplying by themselves, as they have the power to divide. Their shapes vary, and doctors use these characteristics to separate them into groups. \n\nBacteria exist everywhere, inside and on our bodies. Most of them are completely harmless and some of them are very useful. But some bacteria can cause diseases, either because they end up in the wrong place in the body, or simply because they are 'designed' to invade us. \n\nViral and bacterial infections are both spread in basically the same ways. \n   - A person with a cold can spread the infection by coughing and/or sneezing.\n   - Bacteria or viruses can be passed on by touching or shaking hands with another person.\n   - Touching food with dirty hands will also allow viruses or bacteria from the intestine to spread. \n   - Body fluids such as blood, saliva and semen can contain the infecting organisms and transmission of such fluids, for example by injection or sexual contact, is important, particularly for viral infections like hepatitis or AIDS.\n\n\nAn example of a viral infection would be Chickenpox (Varicella) and an example of a bacterial infection would be Pertussis (Whooping Cough) .
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As joseflip said, there are treatments to slow down viruses.  Do a study on viruses; it's fascinating.  They're not even alive!  Purely biologically mechanical (mindless and instinctless; they just do what they do), they do their work by invading cells, multiplying, and going out to other cells...very sneaky.  Because if you want to destroy the virus...you more than likely have to destroy cells as well, and that's where our problem lies.\nThe best example, I think, is HIV.  There are several treatments to keep this horrible disease "at bay," but I *don't think* there are *cures* for any viral diseases.
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Yes!  There is documented proof on this subject!  Scientists have re-worked the Measles virus so that it will attack cancer cells.  Oh, I wish I could give you a link, but I heard about this months ago.  Try searching the archives at this site:\n\nwww.advanceweb.com\n\nI'm pretty sure that's where I read about it.  Isn't that exciting.  It's one of those things that makes me happy for all of these technological marvels.
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The immune system is composed of many interdependent cell types that collectively protect the body from bacterial, parasitic, fungal, viral infections and from the growth of tumor cells. Many of these cell types have specialized functions. The cells of the immune system can engulf bacteria, kill parasites or tumor cells, or kill viral-infected cells. Often, these cells depend on the T helper subset for activation signals in the form of secretions formally known as cytokines, lymphokines, or more specifically interleukins. The purpose of this article is to review the organs, cell types and interactions between cells of the immune system as a commentary on their importance and interdependence on the T helper subset. Such an understanding may help comprehend the root of immune deficiencies, and perceive potential avenues that the immune system can be modulated in the case of specific diseases.
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No.  Viruses depend on a number of components of the host cell for basic functions like replicating DNA and producing proteins because they do not have these systems themselves.  Since they don't have these systems, they can't preform the necessary functions for another virus.\n\nWhen a virus infects a cell, it injects its viral DNA into the genome of the host cell, and the cell replicates and transcribes the viral DNA along with its own.  If a virus were to inject its DNA into another virus, that other virus wouldn't have the ability to replicate the DNA, so nothing would happen.  Also, viruses don't really have membranes (they just have protein), so it probably wouln't be able to inject its DNA in the first place.
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Genetics and environmental factors play a part, but why do some family members get it and not others, and why do some people exposed to a carcinogen develop cancer while others don't? As a cancer survivor, my own theory is that your immune system plays a role and that someday we will learn that viruses act as instigating agents.
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A viruses is a small structure that has a protein coat with a pieces of genetic material.  It invades the cell of its host and uses the hosts DNA to replicate its own genetic material.  Once the cell has replicated the viruses DNA the cell ruptures and the viral DNA is sent throughout the hosts body.  A virus is not technically classified as a living thing.  It is not able to replicate and reproduce with out a host.\nA bacteria is classified as a living thing.  It is a prokaryotic organism with the ability to reproduce using its own genetic material  DNA/ RNA.
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Cells have a lot of different genes that control their growth, and these genes are all copied when a cell divides.  Sometimes, there's a "typo" during the copying process, and there's a mutation in one of those genes controlling cell growth.  The cell can then become cancerous and grow out of control.  \n\nThe specifics may differ in different cases, but that's the general way.  Viruses can cause cancer by changing the DNA of a cell they are infecting, in a way that alters one of these growth-controlling genes.  Toxins can cause cancer by making a cell more likely to make a mistake, or "typo", in the genetic code.
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Proto-oncogenes are genes that are involved in normal cell developpement. We all have those genes in our cells and they are crucial for our survival. There are 5 classes of oncogenes. The genes that regulate the cell cycle, genes that code for transcription factors, second messengers, growth factors and cell surface receptors. The mutation of any of these "proto-oncogenes" turns on the "oncogene".\n\nThe problem is that when they get mutated, their normal function is affected and they cannot continue protecting the cell integrity/function. Without them, we would die anyway.\n\nDon't forget that cancer developpement is a multi-step process that is extremely complicated. It's not just one gene being mutated... it's a serie of events that lead to cell survival (blocking of cell apoptosis) and chaotic developpement.
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We can treat some diseases caused by viruses by vaccinations. Smallpox was eradicated through vaccination. Viruses use the host cell to replicate rather than cell division. They make many copies of themselves and in doing so mutate when a mistake is made in copying. Antiviral treatments try and stop the virus from replicating itself.\n\nThere are two types of mutation at least in influenza viruses: antigenic drift where the viruses mutate gradually and antigenic drift where the change is more sudden. Most viruses don't mutate all that often but HIV and flu viruses do.
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A virus is a microscopic parasite that infects cells in biological organisms. Viruses are obligate intracellular parasites; they can reproduce only by invading and controlling other cells as they lack the cellular machinery for self-reproduction. The term virus usually refers to those particles that infect eukaryotes (multi-celled organisms and many single-celled organisms), whilst the term bacteriophage or phage is used to describe those infecting prokaryotes (bacteria and bacteria-like organisms lacking a nucleus). Typically these particles carry a small amount of nucleic acid (either DNA or RNA, but not both) surrounded by some form of protective coat consisting of proteins, lipids, glycoproteins or a combination. Importantly, viral genomes code not only for the proteins needed to package its genetic material, but for proteins needed by the virus during its life cycle (the term "life cycle" is used loosely here—see #Living or non-living?).
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The Genetics of Cancer\n\n•Several types of genes play roles in cell growth and are particularly important in the development of cancer:\n•Oncogenes (mutated forms of proto-oncogenes) promote cancer.\n•Tumour suppressor genes/antioncogenes prevent cancer.\n•Mismatch repair genes function to repair mutated DNA.\n•For colon cancer to progress to its full malignancy, three tumour suppressor genes and one oncogene must be mutated in sequence.\n•Many cancers are now diagnosed by oligonucleotide probe hybridisation for identified mutations.\n\nOncogenes\n\n•Oncogenes are altered forms of proto-oncogenes, which are normal genes which promote cell growth and differentiation. The mutation may be acquired or inherited.\n•Proto-oncogenes are normally “switched off” in differentiated, non-dividing cells.\n•Some proto-oncogenes control apoptosis. Mutations in these genes may prevent apoptosis, causing a predisposition to cancer.\n\n•Oncogenes and proto-oncogenes are responsible for:\n•Growth factors\n•Growth factor receptors\n•Transducers (intracellular signalling proteins)\n•Transcription factors\n•Cell cycle control proteins\n\n•Mutant forms of the products of proto-oncogenes may signal cells to divide inappropriately and promote cell growth in inappropriate circumstances.\n•Only one oncogene is required for predisposition to cancer (as the mutation leads to an increase in function).\n•Signalling proteins are often mutated in human cancers. An important group of signalling proteins which are often mutated to become more active are tyrosine kinases. These are most commonly mutated in brain and breast cancers. – is it the growth factor or the receptor which changes?\n•Cellular signals can initiate cell proliferation or differentiation.\n\n•Proto-oncogenes may become oncogenes by translocation activating mutations or gene amplification.\n•Gene amplification means the gene is over-represented in the genome (up to 100 copies) and thus creates excess product. This is a common cause of breast and brain cancer.\n•Activating mutations result in increased activity of the gene product. eg.: epidermal growth factor receptor in breast cancer.\n•Translocation is seen in >90% (or 95%?) of leukaemias and many lymphomas. It is limited to somatic cells.\n•Oncogenes result in increased gene product activity or the production of more gene product of the same activity.\n•Tyrosine kinase (a growth factor) receptors are produced by proto-oncogenes, which often mutate to oncogenes causing increased tyrosine kinase activity.\n\nTumour Suppressor Genes/ Anti-Oncogenes\n\n•Tumour suppressor genes are found in all cells.\n•Tumour suppressor genes control critical checkpoints in the cell cycle, induce the transcription of inhibitory/regulatory genes, control for proteins that regulate signal delay mechanisms and generally negatively control cell growth.\n•Tumour suppressor genes code for cell cycle proteins, transcription factors, cell surface proteins, DNA repair proteins and apoptosis related proteins. They may code for cell adhesion and stop the cell cycle in G1 for DNA repair or other reasons (known as the G1-S checkpoint).\n•The loss of function of tumour suppressor genes can lead to cancer. This loss of function may be acquired or inherited.\n•The loss of function of one tumour suppressor gene may provide a slight cell progression advantage. The loss of both leads to a significant growth advantage and predisposition to cancer.\n•The “two hit hypothesis” states that both copies of the gene must be “lost” for cancer to develop.\n•Tumour suppressor genes prevent rapid cell cycling/growth.\n•An individual may be born with only one functioning copy of a tumour suppressor gene and may lose the second copy, becoming predisposed to cancer.\n\nAcquired Cancer\n\n•Acquired DNA damage can be induced by environmental factors such as chemical carcinogens, bacteria, viruses, radiation (ioni
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all viruses work by taking over the reproductive mechanism of cells and making them manufacture copies of themselves.  Frequently the viral cells put out toxins that cause various illnesses.  "Stomach" viruses do this in the GI tract.
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Cancer is uncontrolled cell growth.  Normally the cells in your body grow and divide along a fixed schedule, just enough to replace those that have died.  Sometimes, though, mutations occur within the cell in the pathway that controls growth.  These cells then begin growing and dividing without anything to keep them in check.  This is harmful because is destroys healthy tissue in the surrounding area and wastes valuable resources.