Chapter 16 - Lecture 19 and 20 (2012)

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Department
Biological Sciences
Course
BIOB11H3
Professor
Dan Riggs
Semester
Winter

Description
Chapter 16 Cancer Lecture 19 - Biology of Cancer cancer is not a genetic disease it is not transmitted to the zygote. Instead it is from DNA in somatic cellb during lifetime of affected individual it is a genetic disease because it can be traced to alterations within specific genes cencer cells, because of changes can proliferate uncontrollably, producing malignant tumors invade surrounding tissue if they stay in one area then they can be treated, but malignant tumors tend to metastasize: spawn cells that break aaway from the parent mass and enter lyphatic or vascular circulation, and spread to other parts of body making secondary tumors called metastases Lung and colon cancer are the real killers, even though Prostate and Breast cancer have the highest cases per 100,000 people, lung and colon cancer have the highest deaths /100,000 people Characteristics of Normal Vs. Cancerous cells cancer cells can be studied by rremoving a tumor, separating it into its cells, and culturing the cells in vitro normal cells can also be made cancerous by treatment with carcinogenic chemicals, radiation, or tumor viruses Cancer Cells denisty independent growth. They grow regardless of is they covered the bottom of a culture dish or not no contact inhibition: growth inhibition arises from contact with surrounding cells in culture for normal cells, but for malignant cells, they grow in another layer on top forming a clump. They also tend to keep growing in the absence of growth medium. anchorage independent growth: they do not need to be anchored to the bottom layer of the culture dish. Characteristics of Normal and Cancerous Cells normal cells: require growth factor cancer cells: can continue to grow without growth factor in the medium because they produce their own normal cells: normal ploidy levels: maintain diploid chromosomal complement as they grow and divide. They also have a lower level of telomerase which keeps telomeres at the ends of chromosomes allowing continued division cancer cells: aneuploidy: genetically unstable and often have highly aberrant chromosome complements occurs due to defects in mititotic checkpoints. They also have higher levels of telomerase which keeps telomeres at the ends of chromosomes allowing continued division normal cells: apoptosis induced in aneupolids: when chromosomes content becomes deranged they undergo cell death. cancer cells: apoptotic failure: cant initiate apoptosis even when chromosome count is deranged. normal cells: form gap junctions for intercellular communication cancer cells: few gap junctions: dont need to communicate with adjacent cells. normal cells: normal proteinase secretion: proteinase breaks down extracellular matrix cancer cells: elevated levels of proteinase secretion: the excess proteinases allows loosening of tissue so cancer cells can detach and invade adjacent tissue (matastasize) after a finite number of mitotic disiviosn, they undergo aging and render them unfit leading to their apoptosis. Also undergo apoptosis if they are aneuploidy when cancer cells are mutated and they are immortal and continue to divide and grow indefinitely. This can be attributed to inc telomerase which allows the telomerease to remain at the ends. Benign tumor: unresponsive to growth control but lack ability to invade other tissue Malignant tumor: unresponsive to growth control and capable of invading other tissues and form secondary tumors 12.2 Three major causes of Cancer all of these agents must be able to alter the genome in order to cause cancer 1. Chemicals: caarcingogenic chemicals and other compounds shown to cause cancer. Found in soot, cigarette smoke, can be mutagenic or are converted to mutagenic compounds by cellular enzymes 2. Radiation: ionizing radiation, ultraviolet radiation, leading cause of skin cancer, strongly mutogenic. 3. Viruses: many viruses can infect mammalian cells and make them cancer cells. Oncogenes: encode proteins that promote the loss of growth control and conversion of tell to a malignant state. Act as accelerators of cell proliferation, may lead to genetic instability, prevent a cell from going through apoptosis, or promote metastasis. it was part of the genome. now we know cells have a variety of genes called proto-oncogenes: that have potential to subvert the cells own activities and push cell toward malignant state Importance of environmental Factors in Japanese immigrant coming to Hawaii the incidence of stomach cancer declines, whereas that of breast and colon cancer rises. Howeber, of the three types of cancer, only colon has reached rates equivalent to caucaisian Hawaiians by second generation people who move from Asia to US or Europe show the importance of environmental factos such as diet Asia usually has high level of gastric cancer, but once moving to these counties they are subject ot an elevated risk of colon and breast cancer, characteristic of Western countries Mutations accumulate 10,000 DNA bases are damaged or lost per cell per day there are many chemical reactions that occur, which can alter the DNA which are often corrected, but the few can accumulate, and indicden of cancer increases with age due to this The Genomic Landscape
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