W5-Lec 5: Carcinogenesis

Question 1

What is carcinogenesis?

Answer 1

Is the process where normal cells transform into cancerous cells

Question 2

What is required for a successful carcinogenesis to take place?

Answer 2

• Multiple mutations leading to damaged genes

Question 3

What are carcinogens?

Answer 3

Environmental agent that causes cancer.

*acts on DNA in which genes are encoded.

Question 4

What are the causes of cancer?

Answer 4

• Occupational and behavioural factors
• Carcinogenic agents:
  *Chemicals
  *Viruses
  *Ionising and non-ionising radiation
  *Hormones
  *Bacteria, fungi and parasites
  *Miscellaneous agents (abestos causing mesothelioma)

Question 5

What are the 3 types of chemical carcinogens and their MOA?

Answer 5

• Direct carcinogens: act directly
• Procarcinogens : require metabolic conversion into active carcinogens
• Electrophiles (electron deficient atoms) react with nucleophilic (electron rich) sites in cells

Question 6

What cancer types are caused by occupational and behavioural factors?

Answer 6

• Scrotal carcinoma: In 1777 Percival Pott observed a high incidence of scrotal carcinoma in
  chimney sweeps.
• Lung carcinoma: atmospheric pollutants, smoking
• Carcinoma of the cervix: increased sexual partners, early age at first intercourse
• Bladder carcinoma: is due to exposure to B-naphthylamine in men employed in rubber industries

Question 7

On the aspect of carcinogenic agents, which RNA viruses cause cancer, and what cancers do they cause?

Answer 7

• HTLV-1: T cell lymphoma/leukaemia
• Hepatitis C virus: causes chronic inflammation and injury, linked to Hepatocellular Carcinoma

Question 8

Which DNA viruses are considered carcinogenic? And what cancers do they cause?

Answer 8

• Human papillomavirus: (cervical cancer) ,
• Epstein-Barr virus: (Nasopharyngeal carcinoma)
• Hepatitis B virus: (HCC)
• Human herpesvirus 8: (kaposi sacorma)(Primary effusion lymphoma)

Question 9

It’s type ___and______of Human papilloma virus that can cause cervical cancer. They are the high risk types.

Answer 9

16 & 18

These two types cause:
- cervical cancer,
- Squamous cell carcinoma of cervix,
- anogenital region cancer (anal, vulvar, and penile cancers)
- oropharyngeal (throat) cancer

Question 10

What is the low risk types of Human papilloma virus which causes genital warts?

Answer 10

6 & 11

Question 11

How do the human papilloma virus escape cell cycle restrains and heed with proliferation?

Answer 11

HPV proteins E6 and E7.
- E6 enhances degradation of p53 and block apoptosis.
- E7 binds to RB gene (Retinoblastoma)

Question 12

How does human papilloma virus infect human cells and initiate malignancy?

Answer 12

-Integrates its genome into the host cell’s genome

Question 13

What cancer is caused by the aspergillus fungi which releases aflatoxin?

Answer 13

HepatoCellular Carcinoma

*In Afrika

Question 14

What’s a parasite strongly implicated in bladder squamous cell carcinoma in Egypt?

Answer 14

Schistosoma

Question 15

What is the cancer caused by a chinese liver fluke, Clonorchis sinensis?

Answer 15

Cholangiocarcinoma

Question 16

A bacteria causing gastric adenocarcinoma?

Answer 16

helicobacter pylori

Question 17

What are the host factors that might have impact in carcinogenesis?

Answer 17

• Race
• Diet
• Age
• Genetic predisposition
• Gender

Question 18

What are the 3 members of RAS oncogenes and the cancers they cause?

Answer 18

• K ras: pancreatic and colonic adenocarcinoma
• N ras: melanoma
• H ras: bladder carcinoma

*C myc: Burkitt lymphoma

Question 19

What are the 3 genetic predisposition to cancer?

Answer 19

• Autosomal dominant inherited cancer syndromes (eg. Rb and APC)
• Familial cancers (the Autosomal Dorminant ones) eg. Rb and APC)
• Defective DNA repair syndromes (are autosomal recessive) eg. HNPCC