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Download Cancer cells grow and divide when they should not
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The Cell cycle: Mitosis http://www.youtube.com/watch?v=C6hn3sA0ip0 At what stage do the chromosomes line up in the center of the cell? 25% A. B. C. D. 25% 25% B. C. 25% Prophase Metaphase Anaphase Telophase A. D. When do the microtubules retract and pull the sister chromatids to opposite poles of the cell? 25% A. B. C. D. 25% 25% B. C. 25% Prophase Telophase Metaphase Anaphase A. D. Cell cycle control and mutation • Normal cells halt at checkpoints – proteins survey the condition of the cell • Cancer cells skip these checkpoints Cancer cells skip checkpoints due to DNA damage • DNA can be physically damaged, or undergo mutation – changes the structure and function of the protein coded by the DNA – mutations may be inherited, spontaneous or caused by carcinogens How can DNA damage happen? 25% A. B. C. D. 25% 25% B. C. 25% Exposure to carcinogens Exposure to radiation Replication errors All of the above A. D. • Mutations often occur in proto-oncogenes – genes that code for cell cycle control proteins and regulatory proteins Stimulates cell division when conditions are RIGHT OVER-stimulates cell division when conditions are WRONG • Tumor suppressor genes – stop cell division if conditions are not favorable – When mutated, can allow cells to override checkpoints Stops cell division Fails to stop cell division Example proto-oncogene: • HER2: senses growth factors and activates cell division – Mutations that activate HER2 are found in many aggressive breast cancers Example tumor suppressor gene: • BRCA1: repairs DNA breaks – mutations that inactivate BRCA1 are associated with breast and ovarian cancers Mutations in these are associated with Hereditary Cancers A single mutation is not sufficient for the development of cancer • Multiple hit model – process of cancer development requires multiple mutations • may be inherited (familial risk), most are probably acquired Cancer progression • Loss of contact inhibition – cells will now pile up on each other • Angiogenesis – tumor gets its own blood supply by making blood vessles • Loss of anchorage dependence – enables a cancer cell to move to another location Metastasis of cancer cells 1. Cancer cells build their own blood vessels 2. invade surrounding blood vessels 3. transported by the circulatory system to distant sites 4. invade new tissue and grow in a new location
