Chemical Carcinogenesis Flashcards
There is evidence that certain dietary components are carcinogenic. Which of the following
is NOT tabbed as a dietary carcinogen?
a. excessive caloric intake.
b. excessive alcohol consumption.
c. aflatoxin B1 (a food contaminant).
d. insufficient caloric intake.
e. nitrites (found in some lunchmeats)
Correct answer: d. insufficient caloric intake
a. Excessive caloric intake – TRUE. Obesity and high caloric intake are linked to several cancers.
b. Excessive alcohol consumption – TRUE. Alcohol is a known carcinogen.
c. Aflatoxin B1 – TRUE. It’s a potent liver carcinogen from contaminated food.
d. Insufficient caloric intake – FALSE. While it affects health, it is not associated with carcinogenesis.
e. Nitrites – TRUE. Found in processed meats, linked to colorectal cancer.
Which of the following statements regarding mechanisms of chemical carcinogenesis is
FALSE?
a. Procarcinogens require metabolism in order to exert their carcinogenic effect.
b. Free radicals are highly reactive molecules that have a single, unpaired electron.
c. DNA adducts interfere with the DNA replication machinery.
d. Mutations in the DNA and failure to repair those mutations can be highly carcinogenic.
e. Biological reduction of molecular oxygen is the only way free radicals can be formed.
Correct answer: e. Biological reduction of molecular oxygen is the only way free radicals can be formed.
a–d – TRUE. All describe accurate processes in carcinogenesis.
e – FALSE. Free radicals can be formed in multiple ways, including radiation and metabolic processes—not just molecular oxygen reduction.E
In addition to being necessary for transcription to occur, which of the following transcription
factors also plays a crucial role in nucleotide excision repair?
a. TFIIA.
b. TFIIB.
c. TFIID.
d. TFIIF.
e. TFIIH.
Correct answer: e. TFIIH
a–d – Incorrect. These transcription factors are involved in general transcription initiation but not directly in DNA repair.
e. TFIIH – TRUE. It is crucial in both transcription and NER because it helps unwind DNA at damaged sites.
Which of the following statements regarding DNA repair is true?
a. Base excision repair requires the removal of a longer piece of DNA in comparison with
nucleotide excision repair.
b. The repair of double-stranded DNA breaks is more prone to error than is base excision
repair.
c. Dimerization of pyrimidines is repaired via base excision repair.
d. Mismatch repair can only recognize normal nucleotides that are paired with a
noncomplementary nucleotide.
e. Nucleotide excision and base excision are tolerance mechanisms used to respond to
DNA damage.
Correct answer: b. The repair of double-stranded DNA breaks is more prone to error than is base excision repair.
a. FALSE – NER removes longer DNA stretches than BER.
b. TRUE. DSB repair (via NHEJ) is error-prone.
c. FALSE – Pyrimidine dimers are repaired by NER, not BER.
d. FALSE – Mismatch repair recognizes base mismatches, not just “normal” bases.
e. FALSE – NER and BER are repair, not tolerance mechanismsB
Which of the following statements is a characteristic of the initiation stage of
carcinogenesis?
a. Initiation is reversible in viable cells.
b. The dose–response exhibits an easily measurable threshold.
c. Cell division is required for the fixation of the process.
d. All initiated cells survive over the lifespan of the organism.
e. Spontaneous initiation of cells is a rare occurrence.
Correct answer: c. Cell division is required for the fixation of the process.
a. FALSE – Initiation is irreversible once DNA is damaged.
b. FALSE – Initiation can occur without a threshold.
c. TRUE. Cell division is necessary to “fix” mutations.
d. FALSE – Not all initiated cells survive or cause tumors.
e. FALSE – Spontaneous initiation is not rare.C
Tumor suppressor genes are mutated in a majority of cancers. Which of the following is
NOT a characteristic of a tumor suppressor gene?
a. A mutation in a tumor suppressor gene is dominant.
b. Germ line inheritance of a mutated tumor suppressor gene is often involved with cancer
development.
c. There is considerable tissue specificity for cancer development.
d. The p53 gene is a tumor suppressor gene that also acts as a transcription factor.
e. Mutations in tumor suppressor genes can result in loss of cell cycle control.
Correct answer: a. A mutation in a tumor suppressor gene is dominant.
a. FALSE. Tumor suppressor gene mutations are usually recessive (both alleles must be inactivated).
b–e – TRUE. All are accurate characteristics of tumor suppressor genes.A
Which of the following molecules does NOT play an important role in cell cycle regulation?
a. p53.
b. cyclin-D.
c. MAPK.
d. MHC.
e. E2F.
Correct answer: d. MHC
a. p53 – TRUE. Key regulator and tumor suppressor.
b. cyclin-D – TRUE. Promotes progression through the G1 phase.
c. MAPK – TRUE. Signal transduction in cell proliferation.
d. MHC – FALSE. Major histocompatibility complex is related to immune recognition, not cell cycle.
e. E2F – TRUE. Regulates progression into S-phase.D
Which of the following environmental factors is proportionally responsible for the LEAST
amount of cancer deaths?
a. tobacco.
b. infection.
c. diet.
d. sexual behavior.
e. alcohol.
Correct answer: e. alcohol
(This aligns with the book.)
Explanation:
Here’s the ranking of major modifiable risk factors by contribution to global cancer deaths, based on epidemiologic data:
Tobacco – Highest contributor (~30%).
Diet and obesity – Significant contributors.
Infection – Notable in developing countries (e.g., HPV, HBV, H. pylori).
Sexual behavior – Linked to infections like HPV, thus indirectly contributes.
Alcohol – Does contribute to cancer risk, but proportionally less than the others above.
So, while sexual behavior can lead to cancer-causing infections (especially HPV), alcohol contributes to several cancers (e.g., liver, esophageal, breast), but accounts for a lower overall proportion of cancer deaths compared to others on this list.
The evidence of the carcinogenicity of dietary intake is sufficient to include one’s diet as
associated with neoplasms of all of the following EXCEPT:
a. colon.
b. breast.
c. pancreas.
d. endometrium.
e. gallbladder.
Correct Answer (based on the book): c. pancreas
Explanation:
Diet has been strongly linked with cancers of the colon, breast, endometrium, and even gallbladder due to the role of fats, obesity, and chronic inflammation. However, although pancreatic cancer has some dietary links (e.g., processed meats, obesity), the direct evidence of diet as a primary driver is less conclusive compared to the others listed.
Thus, pancreas is the correct “EXCEPT” option — meaning it’s the one least supported by strong evidence linking dietary intake to cancer risk.
Which of the following is the correct definition of a complete carcinogen?
a. a chemical capable only of initiating cells.
b. a chemical possessing the ability of inducing cancer from normal cells, usually
possessing properties of initiating, promoting, and progression agents.
c. a chemical capable of converting an initiated cell or a cell in the stage of promotion to a
potentially malignant cell.
d. a chemical capable of causing the expansion of initiated cell clones.
e. a chemical that will cause cancer 100% of the time that it is administered.
Correct answer: b. a chemical possessing the ability of inducing cancer from normal cells, usually possessing properties of initiating, promoting, and progression agents.
a. FALSE – That describes initiators only.
b. TRUE. Complete carcinogens both initiate and promote cancer development.
c. FALSE – Describes promotion, not complete carcinogenicity.
d. FALSE – Expansion of clones is part of promotion, not complete.
e. FALSE – No chemical causes cancer 100% of the time in every individual.
