To whether the cancer risk arises from too much

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Unformatted text preview: have been identified • cancer-critical genes – genes whose alterations frequently contribute to causation of cancer • Grouped into two broad classes – according to whether the cancer risk arises from too much activity of the gene product, or too little • 1st class - Proto-oncogenes and Oncogenes • Genes, in which a gain-of-function mutation can drive a cell towards cancer, are called proto-oncogenes • Their mutant, overactive or overexpressed forms – oncogenes • 2nd class – tumour suppressor genes => a loss-of-function mutation can contribute to cancer Video • Proto-oncogenes and tumour suppressor genes are of many sorts, corresponding to the many different kinds of misbehaviour that cancer cells display • Some code for growth factors, for receptors, for components of intracellular signalling pathways that growth factors activate • Others code DNA repair proteins, for mediators of DNA damage response (like p53), for regulators of cell cycle or of apoptosis • Others code for adhesion molecules (like Cadherins) p53 pathway: G1 arrest via p21 transcription. The CDKI p21 will prevent cell cycle progression via inhibition of the G1/S-CDK and S-CDK kinases. Figure from Essential Cell Biology (© Garland Science 2010) Questions?...
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