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Cancer treatment drugs pose a strong selective force on all types of cells in tumors, including cancer stem cells, which would be forced to evolve resistance to the treatment. Cancer stem cells do not always have to have the highest resistance among the cells in the tumor to survive chemotherapy and re-emerge afterwards.
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)).
Increased DNA damage tends to cause increased errors during DNA synthesis, leading to mutations that can give rise to cancer. If hypermethylation of a DNA repair gene is an early step in carcinogenesis, then it may also occur in the normal-appearing tissues surrounding the cancer from which the cancer arose (the field defect). See the table below.
A cancer syndrome or family cancer syndrome is a genetic disorder in which inherited genetic mutations in one or more genes predisposes the affected individuals to the development of cancers and may also cause the early onset of these cancers. Although cancer syndromes exhibit an increased risk of cancer, the risk varies.
Lung cancer is the second most common type of cancer and leading cause of death in men and women in the United States, it is estimated that there is about 216,000 new cases and 160,000 deaths due to lung cancer. [116] Initiation and progression of lung carcinoma is the result of the interaction between genetic, epigenetic and environmental factors.
An increase in the amount of a certain protein (protein concentration), caused by an increase of protein expression (through misregulation) an increase of protein (mRNA) stability, prolonging its existence and thus its activity in the cell; gene duplication (one type of chromosome abnormality), resulting in an increased amount of protein in the ...
Colon cancer provides one example of the mechanisms by which diet, the top factor listed in the table, is an external factor in cancer. The Western diet of African Americans in the United States is associated with a yearly colon cancer rate of 65 per 100,000 individuals, while the high fiber/low fat diet of rural Native Africans in South Africa is associated with a yearly colon cancer rate of ...
Among solid tumors, the clinical significance of the proliferation index on breast cancer has been extensively studied. Mitotic counting has also been shown in multiple studies to have prognostic value in breast cancer, where a lower count of mitotic cells correlates with a more favorable outcome, and thus has been incorporated into part of the ...