Cont a mutation may give a cell a selective advantage

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Unformatted text preview: n trouble for a multicellular organism How does cancer develop? – cont’ • A mutation may give a cell a selective advantage, allowing it to grow and divide more vigorously and survive better than its neighbours, and produce daughter cells in same asocial way • The organisation of the tissue and, and eventually the body as a whole, may then become disrupted by a relentlessly expanding clone of abnormal cells • => problem that happens in cancer • Cancer cells are defined by two heritable properties: • They reproduce in defiance of the normal restraints on cell growth and division • They invade and colonize territories normally reserved for other cells • Combination of these properties makes cancers dangerous Benign or malignant • An abnormal cell that grows and proliferates out of control will give rise to a tumour, or neoplasm • If the neoplastic cells do not become invasive -> benign tumour • A tumour is considered a cancer only if it is malignant - cells have acquired ability to invade surrounding tissue • Invasiveness – essential characteristics of cancer • Cancer cells can break loose, enter blood or lymphatic vessels, and form secondary tumours at other sites in the body Metastasis Malignant versus Benign Tumors Benign (not cancer) tumour cells grow only locally and cannot spread by invasion or metastasis Time Malignant (cancer) cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Cancers develop by an accumulation of mutations • Cancer is a genetic disease • It arises as a consequence of pathological changes in the information carried by DNA • A single mutation is not enough to cause cancer • Most identified agents known to contribute to causing cancer (ionizing radiation and chemical carcinogens) are mutagens • Even in an environment free of tobacco smoke, radioactivity and other external mutagens, mutations will occur spontaneously (limit on accuracy of DNA replication and DNA repair) • Cancers develop by an accumulation of mutations (genetic changes and epigenetic changes) • The concept that development of cancer requires a gradual accumulation of mutations in a number of diff genes (diff for diff cancers, but usually at least 5) • -helps to explain the phenomenon of tumour progression (an initial mild disorder of cell behaviour evolves gradually into a fullblown cancer) • cancer is most often a disease of old age -it takes time for an individual line of c...
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This note was uploaded on 05/22/2013 for the course SCI 987 taught by Professor Joh during the Spring '13 term at University of Massachusetts Boston.

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