Lec 16 - Oncogenic viruses Flashcards
List the features of transformation.
- Uncontrolled growth
- No contact inhibition = cells grow on top of each other
- No anchoring dependence
- Form colonies on semi-solid media
- Altered GF and nutrient requirements = don’t need as much
What is carcinogenesis?
Complex multistage process by which cancer develops
What is cancer?
- Group of diseases caused by abnormal cell growth
- Potential to metastasise = interferes with normal organ function
What is a tumour?
Swelling from abnormal growth of tissue
What is the difference between benign and malignant cancers?
Benign = restricted to 1 site
Malignant = uncontrolled growth with invasion and metastasis by blood and/or lymph
Where does each of the following types of cancer originate from?
- Carcinoma
- Sarcoma
- Leukaemia
- Lymphoma and multiple myeloma
- CNS cancer
- Carcinoma = skin/epithelia
- Sarcoma = connective tissue
- Leukaemia = blood forming tissue ie bone marrow
- Lymphoma and multiple myeloma = immune cells
- CNS cancer = brain and spinal cord
What is metastasis?
Secondary growth at a distance from primary cancer site
What percentage of human cancers do viruses cause and what cancers?
20%
Liver and cervical cancers
What cancers do the following viruses cause?
- Epstein Barr virus
- HBV
- Human T lymphotropic virus 1
- Human papillomavirus
- HCV
- Kaposi sarcoma associated herpesvirus
- Merkel cell polyomavirus
- Epstein Barr virus = Hodgkin and Burkitt lymphomas, carcinoma, sarcoma
- HBV = hepatocellular carcinoma
- Human T lymphotropic virus 1 = T cell leukaemia
- Human papillomavirus (HPV) = hepatocellular carcinoma, lymphoma, squamous cell carcinoma (cervical)
- HCV - hepatocellular carcinoma, lymphoma
- Kaposi sarcoma associated herpesvirus = Kaposi sarcoma, lymphoma
- Merkel cell polyomavirus = Merkel cell carcinoma (skin)
What is the difference between RNA and DNA viruses in how they activate the cell cycle?
RNA viruses = encoded oncogenes to activate growth signalling pathways
DNA viruses = have tumour suppressor proteins to disrupt inhibitory pathways for proliferation
What are proto-oncogenes and oncogenes?
- Proto-oncogenes = normal cellular proteins promoting regulation and proliferation of normal cells
- Oncogenes = mutated proto-oncogene allowing uncontrolled growth
How do oncogenes and tumour suppressor genes induce abnormal cell growth? How many mutations are needed for each and what type of functional mutation is involved with each?
- Oncogenes = recessive (1 copy) gain of function stimulating proliferation
- Tumour suppressors = dominant (2 copies) loss of function allowing proliferation
How do retroviruses convert proto-oncogenes to oncogenes?
Integration of viral genome
What 2 processes do retroviruses use to induce transformation? Describe each.
- Acutely transforming retrovirus = tumour in weeks; incorporates host genome into viral genome to make oncogenes then integrate oncogene into next cell
- Slowly transforming retrovirus = tumour in months; integrates promoter into host genome’s proto-oncogene to convert it to oncogene
What step in the HIV replication cycle - or any retrovirus replication cycle - causes transformation?
When viral integrase inserts cDNA into host genome