Transcript cancer pp
Genes and Cancer Prof. Arnaldo Ferreira Impacts, Issues: Between You and Eternity Cancer strikes one in three people in the United States • Kills one in four Overall more males than females get cancer • Pattern varies depending upon the type of cancer Gene mutations and cancer • BRCA1 and BRCA2: “breast cancer susceptibility genes” The Characteristics of Cancer As genes switch on and off, they determine when and how fast the cell will grow and divide, when it will stop dividing, and even when it will die Cancer can result when controls over cell division are lost Some Tumors Are Cancer, Others Are Not Hyperplasmia Cells in a tissue overgrow Resulting defined mass: tumor (neoplasm) • Benign, e.g., moles • Slow growth • Expands in the same tissue; does not spread • Cells look nearly normal • Malignant • Rapid growth • Invades surrounding tissue and metastasizes • Cell differentiation usually poor Some Tumors Are Cancer, Others Are Not Dysplasia Abnormal change in the size, shape, and organization of cells in a tissue Often an early step toward cancer • Microscopic characteristics of cancer cells • Behave differently from normal cells Cancer Cells Are Abnormal in Their Growth and Appearance Normal Moles Are Common Examples of Benign Growths Main Features of Benign and Malignant Tumors A Cancer Cell’s Structure Is Abnormal Cancer is a result of a series of mutations in the cell’s genes • • • • Larger cell nucleus and less cytoplasm Loss of structural specialization Cytoskeleton shrinks Plasma membrane proteins could be lost or altered • New plasma membrane proteins may appear • Changes passed on to cell’s descendants Cancer Cells Also Do Not Divide Normally Cancer cells don’t necessarily divide faster than normal cells; more cancer cells are dividing than dying Cancer cells do not respond to crowding; loss of contact inhibition • Leads to a disorganized mass; cells may have extensions • May produce HCG and angiogenin • Metastasis: makes a cancer malignant Threadlike “False Feet” Are a Common Feature of Cancerous Cells Cancer Spreads Step-by-Step Cancer is a Genetic Disease Cancer is a genetic disease that develops in a predictable sequence of steps Carcinogenesis • Transformation of a normal cell into a cancerous cell • Step-by-step transformation Carcinogenesis Occurs in Predictable Steps A Common Type of Colorectal Cancer May Develop by These Steps Colon cancer results from genetic alterations in multiple genes Inherited mutations in the APC gene dramatically increase risk of colon cancer Cancer Usually Involves Several Genes Proto-oncogenes • In normal cells • Code for proteins involved in the stimulus of cell division • If altered, may form oncogenes • Alone, do not cause malignant cancer • Require other mutations, including one in a tumor suppressor gene Cancer Usually Involves Several Genes Tumor suppressor genes • Stop cell growth and division; prevent cancer formation • May prevent expression of oncogenes Types of cancer genes Type of gene Normal function Mutated function Types of proteins Oncogene Promotes division Promotes division Growth factors - abnormal time or cell type Tumor suppressor gene Suppresses cell division DNA repair Repair DNA gene mutation mutations Fails to suppress division Checkpoint molecules Fail to repair DNA mutations Enzymes for mismatch or excision repair Other Factors Also May Lead to Cancer Inherited susceptibility to cancer • ~5% of cancers Viruses • Viral DNA may be inserted into a host cell’s DNA • May switch on a proto-oncogene • May carry oncogenes Other Factors Also May Lead to Cancer Chemical carcinogens • Carcinogens: cancer-causing substances that can lead to a mutation in DNA • Asbestos, vinyl chloride, and benzene • Hydrocarbons in cigarette smoke • Aflatoxin: fungal product Radiation • UV from the sun and tanning lamps • X-rays: medical and dental • Radon, cosmic rays, and gamma radiation Cruciferous vegetables can lower cancer risk Other Factors Also May Lead to Cancer Breakdowns in immunity • Healthy immune system can target and destroy cancer cells • When cancer cells have altered proteins at its surface, cells are not destroyed • Risk of cancer increases: • With age • When an immune system has been suppressed for a long time • HIV infection • Immunosuppressant drugs • Anxiety and depression Focus on Environment: Cancer Risk from Environmental Chemicals Exposure to pesticides • Agricultural chemicals in food and airborne chemicals due to spraying programs • Reduce exposure; how? Industrial chemicals Ames test • Assess chemical’s ability to cause mutations Some Industrial Chemicals Linked to Cancer Some Major Types of Cancer In general, a cancer is named according to the type of tissue in which it first forms Sarcomas: cancer of connective tissue Carcinomas: cancer arising from epithelium Lymphomas: cancer of lymphoid tissue Leukemias: cancer of stem cells Gliomas: cancer of brain glial cells Cancer Is Named for the Site in the Body Where It First Develops In the U.S., More than 1 Million People Are Diagnosed with Cancer Each Year Cancer Screening and Diagnosis Early and accurate diagnosis of cancer is important to maximize the chances that a cancer can be cured Blood Tests Can Detect Chemical Indications of Cancer Tumor markers • Produced by particular types of cancer cells • Produced by certain cells in response to cancer • Detected by blood tests • HCG • PSA: prostate-specific antigen Medical Imaging Can Reveal the Site and Size of Tumors Medical imaging • MRI (magnetic resonance imaging): reveals tumors obscured by bone • X-rays • Ultrasound • CT (computerized tomography) Medical Imaging Can Reveal the Site and Size of Tumors Radioactive tracers • Tracked using a PET scanner • Diagnosis of thyroid cancer using radioactive iodine Radioactively labeled monoclonal antibodies • Useful in the location and size of certain tumors in the colon, brain, and bone DNA probe: locates mutated genes, e.g., p53 Radioactive Tracers Also Can Reveal Cancer Tumors Biopsy Is the Only Sure Way to Diagnose Cancer Biopsy • Removal and microscopic examination of tissue Seven common cancer signs: CAUTION Light Microscope Image Shows Cancerous Cells in Breast Tissue Cancer Treatment and Prevention When a person is diagnosed with cancer, a variety of weapons are available to combat it Chemotherapy drugs Radiation therapy Surgery Chemotherapy and Radiation Kill Cancer Cells Chemotherapy • Drugs used to kill cancer cells; disrupt some aspect of cell division • Toxic to healthy cells; hair, bone marrow, lymphocytes, and epithelial cells of intestinal lining • Side effects include hair loss, nausea, vomiting, and reduced immune responses • Genetic approach to chemo in the future Chemotherapy and Radiation Kill Cancer Cells Radiation therapy • Used when cancer is small or has not spread • Radioisotopes used, e.g., Ra-226 and Co-60 Chemotherapy and radiation destroy healthy cells More precise treatments • Monoclonal antibody treatment • Interferon treatment; limited at present Good Lifestyle Choices Can Limit Cancer Risk Avoid tobacco completely Maintain a desirable weight; eat a low-fat diet with plenty of fruits and vegetables Drink alcohol in moderation Make sure your living and work environment is safe from carcinogens Protect your skin from the sun’s UV rays This Cancer Cell Is Surrounded by White Blood Cells Cancer Causes and Contributing Factors Types of Cancer • Skin Cancer • Colon Cancer • Prostate Cancer • Lung Cancer • Liver Cancer • Brest Cancer • Bladder Cancer