Devita, Hellman, and Rosenberg's Cancer

LWBK1006-04 LWW-Govindan-Review November 24, 2011 11:19

64 DeVita, Hellman, and Rosenberg’s CANCER: Principles and Practice of Oncology Review

Answer 4.6. The answer is C.

Carcinogenesis is a multistage process involving several genetic events at

each stage. There is a wide interindividual variation in humans to carcino-

gen exposure. Herein lies the difficulty in using in vitro models to mimic

human cellular response. Experimental studies that involve a single clone

being exposed to a particular carcinogen to study a particular gene might

not be representative of the population. It does allow the investigation of

specific mechanisms that may be involved in carcinogenesis.

Answer 4.7. The answer is D.

There are four components in the estimation of dose and effect in epidemi-

ologic studies. Measurements of internal and external exposure, markers

of the biologically effective dose, and markers of damage are all impor-

tant, and these components help quantify the exposure at the cellular

level. When assessing these surrogate markers, their sensitivity and speci-

ficity, reproducibility, and general applicability for human use should be

taken into appropriate consideration.

Answer 4.8. The answer is D.

Benzene is metabolized in the liver by CYP2E1 into active metabolites.

These metabolites are known to bind to DNA in the bone marrow

cells. Myeloperoxidase is involved in the production of active metabo-

lites of benzene (benzoquinone). Functional polymorphisms in myeloper-

oxidase might play a protective role by reduced enzyme expression in

some individuals. Currently, the dose response of benzene needs further

evaluation.

Answer 4.9. The answer is C.

UVC light, the most damaging to DNA, has most of its emission from the

sun absorbed by the ozone layer, with living organisms exposed mainly to

UVA and UVB. UVB and UVC induce predominantly covalent pyrimidine

dimers, whereas UVA induces reactive oxygen species.

Answer 4.10. The answer is A.

Proliferating skin cells are very vulnerable to UV light because UV lesions

block DNA replication. Although there is a strong link between UV expo-

sure and skin cancers, the mechanism appears to be different, with the

risk of melanoma linked to childhood exposure and nonmelanomas to

cumulative lifetime exposure.

Answer 4.11. The answer is D.

All the disease conditions listed above were treated with radiation in the

past. Other examples include tinea capitis, tonsillar enlargement, benign

breast, and gynecologic disease. Studies in these cohorts have contributed

toward the understanding of radiation-related acute and chronic toxicity,

as well as the development of radiation-related cancers such as thyroid

cancer and breast cancer.