Neoplasia 3

Question 0

How do infections induce neoplasms indirectly?

Answer 0

• Chronic tissue injury and regeneration -> mutations
• Reduced immunity e.g. HIV
• Helicobacter pylori

Question 1

How do infections induce neoplasms directly?

Answer 1

• Directly: affects genes controlling cell growth
• HPV: E6 inhibits p53 (reparative/apoptosis)
  E7 inhibits pR6 (cell proliferation)

Question 2

What link is there between chemicals neoplasms?

Answer 2

• Long delay between carcinogen exposure and malignant neoplasm onset
• Risk depends on carcinogen dosage
• Sometimes organ specific

Question 3

What is meant by a complex carcinogen?

Answer 3

• It is both an initiator and promoter

- Smoking

Question 4

What sources of radiation are commonly the cause of some neoplasms?

Answer 4

• Radon gas
• Medical tests
• UV light
• Free radical damage
• Ionising radiation: radioactive (a,b,y)
  electromagnetic (y,X,UV)

Question 5

What types of damage can radiation cause?

Answer 5

• Indirect damage: free radicals

- Direct DNA damage: altered bases, single/double stranded DNA breaks

Question 6

Why is someone more likely to obtain cancer if they have a family history?

Answer 6

• First hit is inherited via germ line
• Affects all cells in the body
• Easier to obtain cancer with germline mutation already present

Question 7

What roles do RAS and RB genes have in neoplasia?

Answer 7

• RAS encodes for a small G protein
• This pushes cells past cell cycle restriction point
• Mutation causes this to be constant
• RB restricts cell passage through restriction point
• Mutation = no control

Question 8

What are the 6 main hallmark cellular behaviours?

Answer 8

• Self sufficient growth signals
• Resistance to anti-growth signals
• Grows indefinitely
• Induces new blood vessels
• Apoptosis resistance
• Invades and produces metastasise

Question 9

What do Proto-oncogenes do and what happens to them in neoplasia?

Answer 9

• Encode growth factors and receptors
• Plasma membrane signal transducers
• Intracellular kinases
• Transcription factors
• Only one of the POG alleles need to be activated for neoplastic growth

Question 10

What do tumour-suppressor genes do and how are they affected in neoplastic growth?

Answer 10

• TSG supply anti growth factor effects

- Needs both alleles to be inactivated hence 2 hit theory

Question 11

Outline the adenoma to carcinoma sequence

Answer 11

• Normal epithelium -> early adenoma -> intermediate adenoma -> late adenoma -> carcinoma -> metastasis