LWBK1006-04 LWW-Govindan-Review November 24, 2011 11:19
Chapter 4•Etiology of Cancer Part 2 63ANSWERS
Answer 4.1. The answer is C.
The development of cancer is a multistage process. It depends not only
on genetic predispositions but is also influenced by the environment, diet,
occupation, and lifestyle of an individual. Therefore, cancer results from a
combination of hereditary susceptibility and individual exposure to either
endogenous or exogenous factors.Answer 4.2. The answer is D.
All of the listed factors are implicated in cancer development. Exposure
to chemicals can result in DNA damage and mutations. These genotoxic
events can occur directly from exposure or indirectly through the gener-
ation of intermediate compounds that disrupt normal cellular function.
Tobacco and alcohol are well known to predispose humans to numerous
cancers, including cancers of the oral cavity, oropharynx, larynx, lung,
and esophagus. Common examples of diet-related carcinogenesis include
smoked or pickled foods (stomach cancer) and red meat (colon cancer).
The relationship between human papilloma virus and cancer of the cervix
is an example of cancer associated with sexual behavior.Answer 4.3. The answers are (A) 3, (B) 1, (C) 6, (D) 7, (E) 2, (F) 4, (G) 5.
Tobacco is the single most important risk factor in lung cancer. Although
it does increase the risk of lung cancer, asbestos is a major risk factor in the
development of pleural mesothelioma. Studies have shown the association
between liver cancer and exposure to aflatoxins. Benzene has been well
studied in the causation of leukemia. UV light exposure directly correlates
to the development of skin cancer.Answer 4.4. The answer is B.
Genotoxic carcinogens are potent mutagens. They interact with DNA
and cause base mispairing, deletions, both small and large, and are capa-
ble of causing direct chromosomal breaks. Each class of genotoxic agent
reacts selectively with purine and pyrimidine targets within a nucleotide
sequence. The mechanism of action of nongenotoxic carcinogens is less
clear and believed to be mediated through direct cell death, deregulated
hyperplasia, induction of endogenous toxic radical production, and so
forth.Answer 4.5. The answer is D.
Studies in animal models have shown that carcinogenic agents act in a
variety of different ways. They can activate oncogenes directly and inac-
tivate tumor suppressor genes. They cause genomic changes that help
propagate the malignant phenotype that manifests as unregulated growth,
resistance to apoptosis, and potential for metastatic spread.