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Viruses to Cancer What is cancer? R Loss of Normal Growth Control Normal cell division Cell Suicide or Apoptosis Cell damage— no repair Cancer cell division First mutation Second mutation Third Fourth or mutation later mutation R Uncontrolled growth Example of Normal Growth Dead cells shed from outer surface Epidermis Dividing cells in basal layer Cell migration Dermis R The Beginning of Cancerous Growth Underlying tissue R Tumors (Neoplasms) Underlying tissue R 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 R Malignant versus Benign Tumors Benign (not cancer) tumor cells grow only locally and cannot spread by invasion or metastasis Malignant (cancer) cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Time R Microscopic Appearance of Cancer Cells R What Causes Cancer? Some viruses or bacteria Some chemicals Radiation Heredity Diet Hormones R Viruses Virus inserts and changes genes for cell growth Cancer-linked virus R Examples of Human Cancer Viruses Some Viruses Associated with Human Cancers R Replication & Variety of DNA Viruses SV40 Virion Figure 3.3 The Biology of Cancer (© Garland Science 2007) HPV 16 Virion R AIDS and Kaposi’s Sarcoma Without disease HIV infection Depressed immune system KSHV infection Kaposi’s sarcoma R Genes and Cancer Viruses Chemicals Radiation Heredity Chromosomes are DNA molecules R Proto-Oncogenes and Normal Cell Growth Normal Growth-Control Pathway Growth factor Receptor Signaling enzymes Transcription factors Cell nucleus DNA Cell proliferation R Oncogenes are Mutant Forms of Proto-Oncogenes Inactive growth factor receptor Inactive intracellular signaling protein Signaling protein from active oncogene Activated gene regulatory protein Transcription Cell proliferation driven by internal oncogene signaling R Tumor Suppressor Genes Normal genes prevent cancer Normal cell Remove or inactivate tumor suppressor genes Cancer cell Damage to both genes leads to cancer Mutated/inactivated tumor suppressor genes R Tumor Suppressor Genes Act Like a Brake Pedal Tumor Suppressor Gene Proteins Growth factor Receptor Signaling enzymes Cell nucleus Transcription factors DNA Cell proliferation R RNA Tumor Viruses – The Rous Sarcoma Virus Story R Figure 3.2 The Biology of Cancer (© Garland Science 2007) R Figure 3.22 The Biology of Cancer (© Garland Science 2007) Viruses and Their Oncogenes Virus Rous sarcoma virus Simian sarcoma virus Avian erythroblastosis Kirsten murine sarcoma Moloney murine sarcoma MC29 avian myelocytoma Oncogene v-src v-sis v-erbA/B v-kRas v-mos v-myc R Retroviral Insertion Has the Potential to Transform by Activation of Oncogenes R Figure 3.23b The Biology of Cancer (© Garland Science 2007) Many Types of HPVs Different HPVs–Different Infections Harmless No warts or cancer Warts-Linked Genital warts Cancer-Linked Most clear up Some persist, but no abnormalities in cervix Some persist, some abnormalities in cervix A few persist and progress to cervical cancer R Common Infection Infected with HPV R Virus Penetrates Cervix Papillomavirus Uterus Layers of epithelial cells Cervix HPV infection Vagina R Virus Uncoats Nucleus Viral DNA enters nucleus mRNAs for viral proteins E6 and E7 Virus “uncoats” Epithelial cell interior R Virus Disables Suppressors Mucus Healthy cells E6 viral protein Suppressor protein 1 Degraded suppressors Cancerous epithelial cells E7 viral protein Suppressor protein 2 R The Vaccination R Antibodies Prevent Infection Papillomavirus = Antibodies No DNA strands can escape the capsid R
