cancer inducing bacteria

Question 1

describe the Rous

experiment

Answer 1

in 1910 peyton Rous discovered that healthy chickens can be inected with cell free extract of the tumor of a sick chichen.

1. he removed sarcoma from a sick chicken.
2. ground up the tissue finely with sand
3. he passed it thorugh a fine-pore filter.
4. collected the filtrate and injected it into into a young healthy chicken.
5. he observed the chicken develop sarcoma.

Question 2

the hallmarks of cancer define the prerequisites and properties common to all cancers. name 4 of these hallmarks and how they contribute to cancer .

Answer 2

1. Genome instability- DNA damamge is a frequent consequence of infection
2. Tumor promoting inflammation- Inflammation is can be a consequence of chronic infection.
3. Evading cell death- preventing immune eradication
   - protection of replication niches.
4. Avoiding immune desctruction- prevent immune eradication
   - protection of replication niches
5. Angiogenesis- Nutrient supply
6. induction of proliferation/evading growth suppression- get acces to replication machinery

Question 3

Salmonella typhi has been considered as the cause of gallbladder cancer.
Which of the prerequisites to consider infectious agents as cause of
cancers are fulfilled in this case? Name three of them and explain the link to salmonella typhi- gallbladder cancer connection.

Answer 3

1. Resisting cell death-
2. Tumor promoting inflammation- during chronic infection or carrier stage. presistent exposure to bacteria canuse infalmmation.
   3

Ask.

Question 4

Microbiota can play a major role in colon cancer (CRC). Explain two different possible connections and the mechanisms of cancer induction.

Answer 4

E. coli produces colibactin which causes an increase in double strand breaks. The results of this genomic instability may lead to oncogenic mutations.

Fusobacterium play a role in carcinogenesis by deriecly and specifically inducing Epithelial cadherin. Mutations in the E Cadherin is correlated with

Question 5

Name three mechanisms modulated by bacteria that are hallmarks of carcinogenesis.

Answer 5

Resisting cell death
Modulating growth suppressors
Promoting inflammation
Genomic instability and mutation
Avoiding immune desruction

Question 6

describe the difference between genotoxicity and cytotoxicity. Further, give two examples of bacteria for each type of toxicity.

Answer 6

An agent is said to be cytotoxic if it has the ability to destroy cell but does not necessarily affect genes. Genotoxic agents however are able to destroy genetic material and cause mutations and cytotoxicity.
cytotoxic cells cannot cause heritable damage but genotoxic agents do.
Cytotoxic bacteria- H. Pylori, chlamydia trachomatis, pseudomonas aeruginosa, strep. Pneumonia
Genotoxic bacteria- E. coli, H. Pylori, klebsiella pneumonea

Question 7

How does Chlamydia induce DNA damage and which DNA repair pathway is inhibited?

Answer 7

causing double strand breaks by inhibiting p35 pathway
Inhibits dna damage repair by promoting interation between pp2a and ATM
Promotes error prone dna repair
Induced hyperproliferation

Question 8

Which bacteria cause distinct genomic mutational signatures that correspond to cancers mutations?

Answer 8

E. coli
Shigella flexneri
Neiserria gonorrhoeae
H. pylori

Question 9

List four markers that define epithelial and four markers that define the mesenchymal phenotype.

Answer 9

Epithelial- Laminin, E-cadherin, Syndecan-1, MUC-1, desmoglein-3, beta CATENIN
Mesenchymal- Fibronectin, twist, N-Cdherin, alpha-SMA, slug,snail

Question 10

Are the Koch’s postulates fulfilled in case of Helicobacter pylori as the cause of gastric
cancer? Explain your answer.

Answer 10

H. pylori does not fulfil the kock’s postulates in he case of gastric cancer because for koch’s postulates to be fulfiled:
1. the organism should only be found in sick individuals and not healthy ones. There are people who carry H. pylori but will have not developed gastric cancer.

2. Must be isolated from diseased organisms and be cultured: gastric cancer is not specific for H. pylori. therefore not every organism with gastric cancer will have H. pylori or gastric cancer from H. pylori will not be reversed after eradication of H. pylori.
3. cultured isolates should be cause the disease:
   Not all organisms inoculated with H. pylori will develop gastric cancer.