Chapter 7: Etiologic Factors in Neoplastic Disease

Question 1

What are the 5 broad categories of causes of cancer?

Answer 1

1) Viruses
2) Gene and chromosome abnormalities
3) Failure of immunological defense
4) Heredity
5) Chemical carcinogens

Question 2

Which virus causes some types of leukemias and lymphomas?

Answer 2

Human T cell leukemia-lymphoma virus (HTLV-1)

Question 3

Which virus causes Kaposi’s sarcoma?

Answer 3

Human herpesvirus 8 (HHV-8) (occurs in AIDS patients)

Question 4

Which strains of the papilloma virus predispose one to cervical carcinoma and squamous carcinomas of the mouth, throat, larynx, and skin not exposed to sunlight?

Answer 4

HPV 16 or 18

Question 5

Warts caused by HPV

Answer 5

genital condylomas

Question 6

Which viruses predispose one to primary liver carcinoma?

Answer 6

Chronic viral hepatitis B or C

Question 7

What virus appears to predispose one to nasopharyngeal carcinomas and some lymphomas?

Answer 7

Epstein Barr virus

Question 8

Mutations or derangements of what three types of genes are associated with loss of growth control and tumor formation?

Answer 8

1) Proto-oncogenes
2) Tumor suppressor genes
3) DNA repair genes

Question 9

What are three means by which a proto-oncogene can become an oncogene?

Answer 9

1) Mutation
2) Amplification
3) Translocation

Question 10

Abnormally functioning gene that stimulates cell growth excessively, leading to unrestricted cell proliferation

Answer 10

Oncogene

Question 11

How many mutations do you need to create an oncogene?

Answer 11

One (only one of the chromosomal pairs has to be mutated; gain of function mutation)

Question 12

Normal genes that function to suppress cell proliferation/mitosis, and prevent
replication of cells with damaged DNA (act at cell cycle checkpoints)

Answer 12

Tumor suppressors

Question 13

How many mutations do you need to deactivate a tumor suppressor?

Answer 13

2 (they exist in pairs on homologous chromosomes, so both genes must cease to function before the cell malfunctions)

Question 14

What is the most common genetic defect in human cancer?

Answer 14

p53

Question 15

What percentage of human cancers have a defective p53 tumor suppressor?

Answer 15

Half

Question 16

The guardian of the genome

Answer 16

p53

Question 17

How does p53 function in a normal cell?

Answer 17

Prevents cell cycle progression of DNA damaged cells which allows time for DNA repair or promotes their apoptosis if they are sufficiently damaged.

Question 18

What is the result of loss of p53?

Answer 18

1) Continued growth of damaged cells
2) Reduced chemotherapy effectiveness
3) Permits angiogenesis

Question 19

What are the 3 genes most frequently mutated in cancer

Answer 19

1) p53 (TS)
2) Myc (onc)
3) Ras (onc)

Question 20

What was the first human oncogene discovered?

Answer 20

Ras

Question 21

Mutations in this important tumor suppressor are associated with drug resistance and treatment failure.

Answer 21

p53

Question 22

Mutations in these 2 oncogenes are associated with increased cell proliferation.

Answer 22

Myc and Ras

Question 23

What percentage of human cancers have a mutated Myc?

Answer 23

40%

Question 24

What percentage of all cancers have a mutated Ras?

Answer 24

20-30%

Question 25

Which types of genes regulate normal processes that monitor and repair any errors in DNA duplication during cell division?

Answer 25

DNA repair genes

Question 26

What is the result of failure of DNA repair genes to function?

Answer 26

Increased likelihood of mutations, including proto-oncogenes and tumor suppressors, leading to unrestrained cell growth.

Question 27

How many of the genes of the chromosomal pair must become non-functional for DNA repair function to be lost?

Answer 27

Both genes

Question 28

What is the result of inactivated DNA repair genes?

Answer 28

Increased mutation rate

Question 29

These genes inhibit cell proliferation

Answer 29

Tumor suppressor genes

Question 30

These genes correct errors in DNA duplication

Answer 30

DNA repair genes

Question 31

What is the name of the reciprocal translocation between chromosomes 9 and 22 that forms a composite bcr/abl gene with overactive Tyr kinase activity that affects cell growth

Answer 31

Philadelphia chromosome