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The central role of DNA damage and epigenetic defects in DNA repair genes in carcinogenesis. DNA damage is considered to be the primary cause of cancer. [17] More than 60,000 new naturally-occurring instances of DNA damage arise, on average, per human cell, per day, due to endogenous cellular processes (see article DNA damage (naturally occurring)).
For some of these diseases, cancer is not the primary feature and is a rare consequence. Many of the cancer syndrome cases are caused by mutations in tumor suppressor genes that regulate cell growth. Other common mutations alter the function of DNA repair genes, oncogenes and genes involved in the production of blood vessels. [12]
Mutations are the immediate cause of cancer and define the tumor phenotype. Access to cancerous and normal tissue samples from the same patient and the fact that most cancer mutations represent somatic events, allow the identification of cancer-specific mutations. Cancer mutations are cumulative and sometimes are related to disease stage.
Illustration of how a normal cell is converted to a cancer cell, when an oncogene becomes activated. An oncogene is a gene that has the potential to cause cancer. [1] In tumor cells, these genes are often mutated, or expressed at high levels. [2]
Hereditary non-polyposis colon cancer, also known as Lynch syndrome, is an autosomal dominant cancer syndrome that increases the risk of colorectal cancer. It is caused by genetic mutations in DNA mismatch repair (MMR) genes, notably MLH1, MSH2, MSH6 and PMS2. In addition to colorectal cancer many other cancers are increased in frequency.
An example of a disease that is caused by a dominant lethal mutation is Huntington's disease. Null mutations, also known as Amorphic mutations, are a form of loss-of-function mutations that completely prohibit the gene's function. The mutation leads to a complete loss of operation at the phenotypic level, also causing no gene product to be formed.
Scientist Otto Warburg, whose research activities led to the formulation of the Warburg hypothesis for explaining the root cause of cancer.. The Warburg hypothesis (/ ˈ v ɑːr b ʊər ɡ /), sometimes known as the Warburg theory of cancer, postulates that the driver of carcinogenesis (cancer formation) is insufficient cellular respiration caused by insult (damage) to mitochondria. [1]
Other carcinogens may cause cancer through a variety of mechanisms without producing mutations, such as tumour promotion, immunosuppression that reduces the ability to fight cancer cells or pathogens that can cause cancer, disruption of the endocrine system (e.g. in breast cancer), tissue-specific toxicity, and inflammation (e.g. in colorectal ...