Lecture 5 Profile of a cancer cell Characteristics of a normal cell Reproduce themselves exactly Stop reproducing at the right time Stick together in the right place specific manner Self destruct if they are damages apoptosis Become specialized or mature well differentiated Characteristics of a cancer cell Do not reproduce themselves exactly Do not stop reproducing at the right time Do not stick together in the right place Do not self destruct if they are damaged evade apoptosis Do not become specialized or mature do not differentiate The cell cycle Cells spend most of their life in G1 When a cell is big enough it begins the process of cell division Growth in G2 only occurs if the cell notices that it does not have all the required components to divide Mitotic M phase actual cell division Checkpoints Cells have checkpoints to regulate the cell cycle Each of these checkpoints has a set of questions If the answer is no the cell cycle pauses until there are enough changes that the answer becomes yes If yes is not possible the cell can exit cell cycle begin apoptosis G1 checkpoint is the cell big enough Is the environment favorable G2 checkpoint is all DNA replicated Is the environment favorable Is the cell big enough Metaphase checkpoint are all the chromosomes aligned on spindle Cancer begins with DNA damage Possible causes of cancer DNA damage or mutation exposure to radiation toxins hormonal abnormalities inherited abnormalities nutrition and diet tobacco use viral infection Cancer incidences increases with age We re accumulating incidences of DNA damage Immune system is more active when you re younger How cancer develops Develops when you have accumulation of mutations The first mutation seems normal In the 2nd mutation the cell divides a bit more quickly The 3rd mutation divides more quickly and undergoes structural changes 4th mutation cell grows uncontrollably and looks deranged every cancer cell has around 60 mutations abnormal DNA causes the cancer Hallmarks of cancer cells Cancer cells exhibit a decreased dependence on external growth factors Decreased density dependent growth inhibition Don t rely on substance cellular material to grow Able to evade apoptosis There s no end to their ability to divide become immortal Blood sustains feeds any kind of tumor Involved in tissue invasion and metastasis Growth factors Growth factors are proteins that stimulate cell growth and division Can be self produced or come from another cell Bind to growth receptor and start a signal cascade Results in transcription factor activation which results in transcription of growth related genes Decreased dependence on external growth factors Either produce their own growth factors or alter growth receptors their always stay on or overexpressed Cancer cells exhibit less density dependent inhibition of growth Cancer cells attached to the bottom of a flask continue dividing and pile up on one another Cancer cells exhibit anchorage independent growth Anoikis homelessness Normal cells grow poorly when shaking the flask Cancer cells grow well when shaking the flask they don t need to be anchored Telomeres DNA unlaced Telomeres helps protect cells from age related damage They seal off the ends of chromosomes with contain the cells genetic information Telomerase enzyme Normally expressed in early embryo Mis expression cancer cell Telomerase make cancer cells immortal Presence of telomerase allows cancer cells to continue diving and indefinitely grow Summary of cancer cells
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