Transcript Cancer
Cancer • Some cells, instead of leaving the cell cycle to die, divide repeatedly and excessively, forming a clump of cells called a tumour. • Cancer is a disease that eventually disrupts the body functions, whereas a tumour is a mass of cells with no apparent function in the body. • Cancer is the uncontrolled division and spread of abnormal cells. An estimated 171,000 new cases of cancer (excluding 75,100 nonmelanoma skin cancers), and 75,300 deaths from cancer are expected to occur in Canada in each year. About 40 per cent of Canadian women and 45 per cent of men will develop cancer during their lifetimes. About 24 per cent of women and 29 per cent of men, or approximately one out of four Canadians, is expected to die from cancer. Three Tumour Types • Benign: (non cancerous) harmless tumours that do not spread • Malignant: harmful tumours that have the potential to spread through the body • Metastatic: tumours that have travelled and grown in other areas Different Kinds of Cancer Some common carcinomas: Leukemias: Bloodstream Lung Lymphomas: Breast (women) Lymph nodes Colon Bladder Prostate (men) Some common sarcomas: Fat Bone Muscle Loss of Normal Growth Control Normal cell division Cell Suicide or Apoptosis Cell damage— no repair Cancer cell division First mutation Second mutation Third mutation Fourth or later mutation Uncontrolled growth Example of Normal Growth Dead cells shed from outer surface Epidermis Cell migration Dividing cells in basal layer Dermis The Beginning of Cancerous Growth Underlying tissue Invasion and Metastasis 1 Cancer cells invade surrounding tissues and blood vessels 2 Cancer cells are transported by the circulatory system to distant sites 3 Cancer cells reinvade and grow at new location Malignant versus Benign Tumors Benign (not cancer) tumor 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 Cancer Tends to Involve Multiple Mutations Benign tumor cells grow only locally and cannot spread by invasion or metastasis Malignant cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Time Mutation inactivates suppressor gene Cells proliferate Mutations Proto-oncogenes inactivate mutate to oncogenes DNA repair genes More mutations, more genetic instability, metastatic disease Q2: Why might cancer primarily affect older people rather than young people? A: Because the immune system of older people is not as effective in distinguishing normal cells from cancer cells. B: Because older people have been exposed to more carcinogens. C: Because cancer develops after multiple mutations have occurred which takes years to happen. D: None of the above. Why Cancer Is Potentially Dangerous Brain Melanoma cells travel through bloodstream Liver Melanoma (initial tumor) Microscopic Appearance of Cancer Cells What Causes Cancer? Some viruses or bacteria Some chemicals Radiation Heredity Diet Hormones Mutations •Cancer arises from the accumulation of genetic changes or mutations. Most cancers have a minimum of 6-9 genes involved. •People can be susceptible to cancer based on their genetic makeup, but cancer isn’t directly passed from parent to child. •Many genes that are involved in cancer are involved in regulating the cell cycle. Cancer cells generally have multiple mutations before control over cell division is lost. Tumour suppressor gene • A tumour supressor gene like P53 controls or slows the cell cycle and thus cell division. When it is mutated or absent, the cell will divide uncontrollably. • An oncogene is a gene that when mutated will lead to uncontrolled cell division. From Benign to Malignant •Cancer cells divide too quickly and can leave the original site and enter the blood, lymph, or tissues. •Most cells divide a set number (60-70) of times, then they stop dividing. •This usually limits benign tumors to small sizes. •Cancer cells can divide indefinitely. Treatment Options Radiation - Uses high-energy rays to kill cancer cells by damaging their DNA. Can come from gamma or X-rays from a machine or a radioactive substance ingested into the body. Chemotherapy - Uses cytotoxic (toxic to cells) drugs to prevent mitosis in rapidly dividing cells. This also kills normal rapidly-dividing cells (hair, bone marrow etc.) Surgery - Physically removes cancer cells Many patients will use combinations of these Taxol One common chemotherapy for ovarian cancer is Taxol, which was first isolated from Yew bark in 1962 by the National Cancer Institutes (NCI). Taxol blocks a cell's ability to break down the mitotic spindle during mitosis. With the spindle still in place, the cell can't divide into daughter cells and therefore the cancer can’t grow. Taxus Brevifolia 25 Cancer Detection and Treatment C hange in bowel or bladder habits A sore that does not heal Earlier detection and treatment of cancer greatly increase the odds of survival. Therefore, knowing the warning signs of cancer is important to health. U nusual bleeding or discharge T thickening or lump I ndigestion or difficulty swallowing O bvious change in wart or mole N agging cough or hoarseness 26 Population-Based Studies Regions of Highest Incidence U.K.: Lung cancer JAPAN: Stomach cancer CANADA: Leukemia U.S.: Colon cancer CHINA: Liver cancer AUSTRALIA: Skin cancer BRAZIL: Cervical cancer Heredity? Behaviors? Other Factors? Colon Cancer Stomach Cancer (Number of new cases per 100,000 people) (Number of new cases per 100,000 people) 100 100 70 50 7 0 5 0 Japan Japanese families in U.S. U.S. Japan Japanese families in U.S. U.S. Tobacco Use and Cancer Some Cancer-Causing Chemicals in Tobacco Smoke Lag Time 20-Year Lag Time Between Smoking and Lung Cancer Cigarette consumption (men) 4000 3000 Cigarettes Smoked per Person per Year Lung cancer (men) 2000 150 100 50 1000 1900 1920 1940 1960 1980 Year Lung Cancer Deaths (per 100,000 people) Avoid Tobacco Lung Cancer Risk Increases with Cigarette Consumption 15x 10x Lung Cancer Risk 5x 0 Non-smoker 15 Cigarettes Smoked per Day 30 Viruses Virus inserts and changes genes for cell growth Cancer-linked virus Examples of Human Cancer Viruses Some Viruses Associated with Human Cancers Avoid Cancer Viruses HPV Infection Increases Risk for Cervical Cancer High Cervical Cancer Risk Low Noninfected women Women infected with HPV Limit Alcohol and Tobacco Combination of Alcohol and Cigarettes Increases Risk for Cancer of the Esophagus 40x 30x Risk Increase 20x 10x Alcoholic Drinks Consumed per Day AND Packs of Cigarettes Consumed per Day Diet: Limit Fats and Calories Correlation Between Meat Consumption and Colon Cancer Rates in Different Countries 40 Number of Cases (per 100,000 people) 30 20 10 0 80 100 200 300 Grams (per person per day) Diet: Consume Fruits and Vegetables Protect Yourself From Excessive Sunlight Avoid Carcinogens Some Carcinogens in the Workplace