Epidemiologic and Environmental Aspects of Cancer

Question 1

What percent of malignant neoplasms are caused by environment?

Answer 1

80%

Question 2

T or F, migrants and their descendants adopt the relative risk of the country that they move to. What does this imply?

Answer 2

T.can’t attribute everything to genetics. Matters where you came from and where you go.

Question 3

Identify the three most common types of cancer (other than skin cancer) among men (incidence).

Answer 3

Prostate- 26%
Lung- 14%
Colon/Rectum- 14%

Question 4

Identify the three most common types of cancer (other than skin cancer) among women (incidence)

Answer 4

Breast- 29%
Lung-13%
Colon/Rectum- 8%

Question 5

Identify the three most common types of cancer (other than skin cancer) among men (death).

Answer 5

Lung-28%
Prostate-9%
Colon/Rectum-8%

Question 6

Identify the three most common types of cancer (other than skin cancer) among women (death).

Answer 6

Lung-26%
Breast-15%
Colon/Rectum-9%

Question 7

An environmental chemical must be activated by what molecule to be considered carcinogenic?

Answer 7

P450

Question 8

What are the four groups of chemical carcinogens?

Answer 8

1. Polycyclic aromatic hydrocarbons (benzo(a)pyrene)
2. Aromatic amines (anilines)
3. Nitrosamines
4. Aflatoxins

Question 9

What are some examples of Polycyclic aromatic hydrocarbon carcinogens?

Answer 9

-benzo(a)pyrene-anything with a diol or epoxide group-at risk any time you burn stuff

Question 10

What are some facts of Aromatic amine carcinogens?

Answer 10

• aniline
• requires N-hydroxylation and sulfation
• industrial and consumer products

Question 11

What are some facts of nitrosamine carcinogens?

Answer 11

-carbonium intermediate-in preservatives in food (cheetohs)-2 amines in food react with nitrous acid in stomach

Question 12

Where do aflatoxins come from?

Answer 12

• moldy grains, nuts, corn especially in tropics
• produced by aspergillus flavus
• microsomal epoxidation is required to be a carcinogen

Question 13

If an epoxide is formed during a P450 reaction, _____

Answer 13

the product becomes cytotoxic and mutagenic.

Question 14

Outline Miller’s theory of carcinogenesis

Answer 14

• CYP450 turns chemicals into active forms
• metabolites become strong electrophiles
• electrophilic species can chemically modify proteins, RNA, DNA
• The bases can be attacked and cause frameshifts and mispairings

P450 generates electrophiles which screw with RNA/DNA.

Question 15

What is the Ames test?

Answer 15

A rapid and inexpensive test for mutagens. Tests ability to mutagenize Salmonella typhimurium.

Question 16

Generally all carcinogens are mutagens but not all mutagens are carcinogens, T or F?

Answer 16

False:

Mutagens are carcinogens but not all carcinogens are mutagens.

Question 17

A positive Ames test says what about the chemical?

Answer 17

it is mutagenic. It is assumed that it is already proven to be carcinogenic.

Question 18

How does the Ames test work?

Answer 18

Media is lacking His and the is plated with lots of His negative bacteria. The bacteria needs His to grow. Apply carcinogen to central disk on agar; if some His+ bacteria start to grow it is assumed that the carcinogen did this and thus it is mutagenic.

Question 19

T or F. Effect of a carcinogen is non-dose dependent in causing cancer

Answer 19

F

Question 20

Is carcinogenesis a quick or lengthy process

Answer 20

lengthy, requires time

Question 21

Carcinogens are specific to one type of cancer T or F?

Answer 21

T

Question 22

Which tissues are at the most risk of carcinogenesis?

Answer 22

tissues that continually divide (epithelium, bone marrow)

Question 23

The cellular triggers of carcinogenesis are _______. what does this mean?

Answer 23

stably inherited. Tumors are proliferations of clones of a malignant cell

Question 24

T or F, only stem cells can become malignant.

Answer 24

T. Fully differentiated cells cannot become malignant

Question 25

What are the two steps through which cancers develop?

Answer 25

1. initiation | 2. promotion

Question 26

What is initiation?

Answer 26

the irreversible effect of the carcinogen

Question 27

What is promotion?

Answer 27

A reversible step that requires the repeated application of a promoter (i.e. something that causes inflammation)

Question 28

What is the difference between a carcinogen and a tumor promoter?

Answer 28

carcinogens cause mutations, tumor promoters drive proliferation without causing more mutations.

Question 29

What happens if you reverse the order of cancer initiation and promotion.

Answer 29

Nothing. Think about the definitions of each.

Question 30

Smoking is a carcinogen or promoter?

Answer 30

Promoter. it has phenols that cause inflammation?

Question 31

How much time can be between initiation and promotion?

Answer 31

A long time. Skin cancer sometimes takes years to proliferate after it has mutated.

Question 32

What are some common promoters?

Answer 32

urethan, phorbol esters, bile acids, saccharin, phenobarbitol, butylated hydroxytoluene phenols.

Question 33

How do bile salts supports the idea that tumor promotion plays a role in development of human cancer?

Answer 33

they promote cancer in benign colon polyps in rats

Question 34

What is evidence that tumor promotion plays a role in development of human cancers?

Answer 34

Former smokers lose increased risk of cancer after 14 yrs smoke free. if only apply carcinogen, don't get proliferation of cancer.

Question 35

Why is cancer more common among the elderly?

Answer 35

- 2 hit hypothesis (LoH) - Lose tumor suppressors or gain oncogenes over time - Cancers take time to develop - Most are epithelial cancers (being old doesn't put you at higher risk of every kind of cancer)

Question 36

What is the difference between somatic and germline mutations?

Answer 36

S can't be passed on while G mutations can be transmitted to offspring

Question 37

Define epigenetic mutations.

Answer 37

These are not coded for in the DNA but are modifications that are added to proteins or DNA (as in methylation) that repress genes. They

Question 38

How can epigenetic mutations cause cancer?

Answer 38

- methylation inactivates - messes with reading - they can silence a tumor suppressor - loss of methylation can activate an oncogene.