Exam #2: Neoplasia VI Flashcards
(66 cards)
What is the mechanism of UVB tumorigenesis?
- UVB (280-320 nm) causes the formation of pyrimidine dimers
- Pyrimidine dimers cause DNA damage
What is the pathway of DNA repair following UVB damage?
NER pathway i.e. nucleotide excision repair
What is Xeroderma Pigementosum?
This is a condition in which infected individuals have enzyme defect in DNA repair (NER pathway), making the patient highly susceptible to radiation damage
What is ionizing radiation?
Ionizing radiation is radiation with enough energy so that during an interaction with an atom, it can remove tightly bound electrons from the orbit of an atom, causing the atom to become charged or ionized. Types of ionizing radiation include:
- Alpha rays
- Beta rays
- Gamma rays
- Neutrons
- X-ray
Note that alpha, beta, and neutrons are worse than gamma & x-rays; these are particulates
What are the two ways that ionizing radiation can cause DNA damage?
1) Direct effect i.e. direct damage to DNA
2) Indirect effect= free radical generation, which then damage DNA
What are the mechanisms of DNA damage that lead to tumorigenesis in ionizing radiation?
1) Chromosome breakage
2) Translocation
3) Point mutation
What are the most common cancers caused by radiation?
Leukemia, except CLL
Thyroid papillary cancer
Breast/ lung
In response to atomic bomb radiation, is skin cancer likely?
No–skin is most sensitive to UV radiation
What cancers are associated with x-rays workers?
Radiation dermatitis
Skin cancer
For workers that commonly work with radium, what cancer is most common? What occupation is associated with radium exposure?
Osteosarcoma
–This is associated with factory workers that dials of watches that contain “luminous radium”
How do Hepatitis B & C lead to liver cancer?
Chronic liver damage leads to chronic regeneration and regenerative hyperplasia, which can transform to dysplasia & eventually malignancy
B= Hepatitis B also produces HBX protein
- Stimulates insulin-like growth factor
- Binds & inhibits p53
What cancers are associated with EBV?
- Burkitt Lymphoma
- Hodgkin Lymphoma
- B-cell Lymphoma in immunosuppressed patients
- Nasopharyngeal carcinoma
Which subtypes of HPV are associated with cancer? What are the mechanisms of carcinogenesis?
- HPV 16, 18, & 31 are “high risk” b/c they INTEGRATE their DNA into host DNA
- E6= p53 inhibitor
- E7= Rb, p53, & p21 inhibitor
What subtypes of HPV are “low risk” & why?
- HPV 6 & 11 only cause benign tumors
- These subtypes of HPV do NOT integrate into the genome of the host
Not integrated= “episomal”
What is the primary cancer causing RNA virus?
Human T-cell Leukemia Virus Type 1 (HTLV-1)
HTLV-1 is a retrovirus of the human T-lymphotropic virus (HTLV) family that has been implicated in several kinds of diseases including very aggressive adult T-cell lymphoma (ATL)
Where is HTLV-1 endemic?
Japan
Caribbean basin
What is the mode of transmission for HTLV-1?
Intercourse
Blood
Breast feeding
What is the mechanism of HTLV-1?
Virus contains Tax gene that:
1) Stimulates transcription of viral mRNA
2) Activates c-FOS, IL-2, and GM-CSF in the host
- IL-2 is a growth factor for T-cells that is activated by the virus
- c-FOS 7 GM-CSF are both growth factors
3) Inactivates p16INK4a
What is p16INK4a?
Tumor suppressor
What is HHV-8 & what cancer is it associated with?
HHV-8= Human Herpes Virus; this is an HIV-associated virus that leads to the development of Kaposi sarcoma
What are the symptoms of Kaposi Sarcoma?
Red-purple macules, papules, or nodules
What tumors are associated with H. pylori infection?
1) Gastric carcinoma
2) Gastric Lymphoma (MALT)
How does H. pylori cause cancer?
H. pylori encodes CagA (Cytotoxin associated gene A), which is a toxin stimulates growth factor pathways
What hormones are carcinogeneic?
Estrogen
Contraceptive hormones
Anabolic steroids
