14 - Neoplasia 3 Flashcards
What is carcinogenesis and what are the factors involved in this?
Extrinsic: prolonged life span
What are the five behaviours that we undertake that can lead to cancer?
- High BMI
- Low fruit and veg intake
- Lack of physical activity
- Tobacco use
- Alcohol use
What are the categories of extrinsic carcinogens?
- Infections
- Chemicals
- Radiation
How is neoplasia multifactorial?
What is 2-Napthylamine and what lessons does it teach us?
- Chemical carcinogen used in the dye industry
1. There is a long delay between carcinogen exposure and malignant neoplasm onset
2. Risk of cancer depends on carcinogen dosage
3. Carcinogens can be organ specific, e.g this carcinogen causes bladder carcinoma
Why is it mainly roof workers that develop cancer from asbestos exposure?
Dosage of carcinogen highest in these populations, industrial scale
What does the Ames test teach us about carcinogenesis?
- Initiators are mutagens
- Promoters cause prolonged proliferation
Initiators must be followed by promoters, leading to progression as there is a monoclonal expansion of mutant cells
How can chemical carcinogens be classified?
What are pro-carcinogens?
Chemicals that are not carcinogenic until they are converted into carcinogens by cytochrome P450 enzymes in the liver e.g nitrites
What is a complete carcinogen?
Acts as both an initiator and a promoter
What is radiation?
Any type of energy travelling through space.
What are the properties of the following radiation?
- UV radiation
- Ionising radiation
- Nuclear radiation
Where do people’s radiation exposure come from?
How does radiation damage DNA in general?
How are infections carcinogenic?
Directly: affect genes that control cell growth
Indirectly: chronic tissue injury where the resulting regeneration acts either as a promoter for pre-existing mutations / initiator for new mutations
How do the following pathogens act as carcinogens?
- Human Papilloma Virus
- Hepatitis B & C Viruses
- Helicobacter pylori
- Parasitic flukes
- Human Immunodeficiency Virus
- HPV expresses E6 and E7 proteins which directly inhibit p53 and pRB protein function in cell proliferation (cervical carcinoma)
- Hepatitis B,C act indirectly and cause chronic liver cell injury and regeneration
- Helicobacter pylori causes chronic gastric inflammation (gastric carcinoma)
- Parasitic flukes act indirectly to cause inflammation in bile ducts and bladder mucosa (cholangio- and bladder carcinomas)
- HIV acts indirectly by lowering immunity and allowing other potentially carcinogenic infections to occur