Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Genetics of Cancer [email protected] [email protected] Cancer in the media Human and Cancer Life and adaptation cell division cancer is a disease of the cell cycle Cont. Of RNA Synth. Of RNA & proteins G1 checkpoint DNA damage or broken Control system G1 M G2 Chromosomes are attached to the spindle M checkpoint In complete DNA replication G2 checkpoint S G0 G1 checkpoint G1 If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle. G1 If a cell does not receive a goahead signal at the G1 checkpoint, the cell exits the cell cycle and goes into G0, a nondividing state. Unlimited number of cell divisions. Growth without external signals. Failure to respond to 'stop' signals Avoidance of cell death. The ability to leave the original tumor location and form a new tumor, or metastasis. Cancer terminology Classification by tissue type: • carcinoma • Myeloid epithelial cell 90% of all tumours derived from ectoderm (mostly) or endoderm (some) • • sarcoma connective tissue 2% of all tumours derived from mesoderm • leukaemia circulatory or lymphatic 8% of all tumours derived from mesoderm blood cell Lymphoid lymphocytes or macrophages • Central nervous system cancers of the brain Main Features of Benign and Malignant Tumors Cancer Spreads Step-by-Step A Common Type of Colorectal Cancer May Develop by These Steps Types of genes which may mutate to cause cancer: • Tumor suppressor genes – Stop cell growth and division; prevent cancer formation – May prevent expression of oncogenes – Retinoblastoma: only one functional copy of a tumor suppressor gene on chromosome 13 – BRCA1 and BRCA2 – p53: codes for a regulatory protein that turns off cell division when the cell is stressed or damaged Types of cancer genes Type of gene Normal function Mutated function Types of proteins Oncogene Promotes division Promotes division abnormal time or cell type Growth factors Tumor Suppresses cell suppressor gene division Fails to suppress division Checkpoint molecules DNA repair gene mutation Fail to repair DNA mutations Enzymes for mismatch or excision repair Repair DNA mutations Tumour suppressor genes • The gene’s normal function is to regulate cell division. Both alleles need to be mutated or removed in order to lose the gene activity. • The first mutation may be inherited or somatic. • The second mutation will often be a gross event leading to loss of heterozygosity in the surrounding area. Oncogenes • Cellular oncogene c-onc • Viral oncogene v-onc • Proto-oncogene, activated by mutation to c-onc Proto-oncogene activation 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 • 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 Some Industrial Chemicals Linked to Cancer In the U.S., More than 1 Million People Are Diagnosed with Cancer Each Year Biopsy Is the Only Sure Way to Diagnose Cancer • Biopsy – Removal and microscopic examination of tissue 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 What mark have you thought to leave after? 29