Unformatted text preview: Genes and Cancer
Chapter 12 Cancer Cancer= Causes: genetic and environmental What types of cancer are there? Metastasize = Metastasis of Cancer Cells Fig. 12.2 Cancer Is a Sporadic Event Most cancers are sporadic Environmental factors causing mutation In some inherited cancers: mutant allele can increase risk 100,000X Depends on the gene and the cancer How does age affect cancer rates? Evidence that cancer has a genetic origin: 50+ cancers have some gene basis Carcinogens can be mutagens Cancer Is a Genetic Disorder Evidence that cancer has a genetic origin: Viruses carry oncogenes Cancer Is a Genetic Disorder What is an oncogene? Can be spread by viruses Cancers and chromosomal changes Inherited Susceptibilities Beginnings of Cancer Tumor cells come from single cell Single cell accumulates mutations over time Mutations cause uncontrolled cell division Cancer Cells Cell cycle controls get turned off Cancer cells become invasive What is this called? Further mutations = aggressive cancer Several Mutations May Cause Cancer Fig. 12.3 Cell Cycle Out of Control Cancer = uncontrolled cell division Cells have abnormal shapes Fig. 12.4 G1 Cell Division Signals S Pr op io divis ic plasm Cyto e has e p s elo T ha ase p na ph A a et M
se ha n MI G2 Cell Division Signals TO SI S Fig. 12-5 Checkpoint Genes Tumor suppressor genes = Act at either G1/S or G2/M control points Protooncogenes = Onocogenes = Cancer of the retina Retinoblastoma Early onset: 13 years of age 40% of cases = autosomal dominant 60% = sporadic Fig. 12.6 Retinobastoma Need 2 copies of gene to get disease Fig. 12.7 Fig. 12.7 Fig. 12.7 Retinoblastoma
Inherited: 90% chance of disease with the RB1 gene Both eyes Increased risk of other cancer Retinoblastoma
Sporatic: Need two mutations to get disease Only one eye No increase risk for other cancers The RB1 Gene Controls the cell cycle Present in most cells Controls transition from G1 to S Without gene, cell divides uncontrollably ProtoOncogenes to Oncogenes Protooncogenes do what? Mutation in protooncogene oncogene Cell cycle permanently switched on Ex.: ras protooncogene receives and transfers signal for cell divsion Fig. 12.9 Breast Cancer In women most common form of cancer Also found in men 40,000 deaths/year; 180,000 new cases Most cases are sporadic Breast Cancer About 5% of cases due to gene mutation BRCA1 gene Autosomal domiant 1/200 women inherit the allele Women with BRCA1 90% will develop breast cancer Linked to ovarian cancer BRCA1 and BRCA2 Second breast cancer gene: BRCA2 Also autosomal dominant BRCA1 and BRCA2 = 1015% of breast cancer Both are DNA repair genes Tumor suppressor genes Most (~84%) are sporadic Colon Cancer Multiple mutations cancer formation Two genes: ~ 1% Familial adenomatous polypoisis (FAP) ~15% Hereditary nonpolyposis colon cancer (HNPCC) ; increased risk of other cancers Colon Cancer Mutations cause Start benign formation of polyps (meaning?) can become malignant (meaning?)
Fig. 12.11 Model for Colon Cancer Fig. 12.12 Chromosome Instability and Cancer Susceptibility Translocations and Cancer Translocation = Chromosomal breaks: convert proto oncogenes to oncogenes New proteins cause unchecked cell division Translocation and Cancer Causes form of leukemia: Chronic Meylogenous Leukemia (CML) Adult onset leukemia Translocation between chromosomes 9 & 22 Creates hybrid gene cell division Philladelphia Chromosome Chronic Myelogenous Leukemia Fig. 12.15 Cancer Treatment Chemotherapy target rapidly dividing cells Radiation kill off cells Cancer drugs block proteins ...
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- Fall '07