Devita, Hellman, and Rosenberg's Cancer

LWBK1006-01 LWW-Govindan-Review November 24, 2011 11:17

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

ANSWERS

Answer 1.1. The answer is B.

One of the surprising findings of analysis of the sequenced human genome

is the presence of only approximately 25,000 expressed genes in human

cells. However, only a few thousand of these seem to be expressed at

any given time. Previous estimates, based on the known approximate size

of human chromosomes, were that there were up to 100,000 or more

individual genes expressed in human cells.

Answer 1.2. The answer is B.

Preclinical and clinical studies into cancer cell pathogenesis and response

to potential treatments can be guided initially with cell culture experi-

ments because these experiments can be manipulated in a reproducible

manner. However, cell culture experiments do not allow for evaluation

of the interaction between cancer cells and the tumor microenvironment.

Some techniques such as cellular assays that evaluate for cellular migra-

tion and invasion through a Matrigel can mimic the tumor microenviron-

ment, but they cannot replicate all of the cellular–environmental inter-

actions. In addition, cancer cells can acquire genetic changes through

multiple passages in culture such that they may not completely reflect in

vivo cancer cell–host interactions.

Answer 1.3. The answer is D.

Ninety percent of germ line mutations in familial cancer syndromes are

in tumor suppressor genes. It is thought that many dominant oncogene

mutations likely cause fetal demise and therefore do not arise in familial

cancer syndromes. Dominant mutations in cancer genes denote oncogenes

and make up 90% of all cancer genes.

Answer 1.4. The answer is C.

The cell cycle is composed of the phases G0, G1, S, G2 and M. Reg-

ulation of the cell cycle depends on an interplay of multiple proteins.

Cyclin-dependent kinases are serine/threonine kinases that are ubiqui-

tous in the cell cycle. They generally require phosphorylation and associ-

ation with cyclins for activity. Cyclin-dependent kinase 4 phosphorylates

retinoblastoma protein, allowing depression of transcription factors (of

which E2F is an example) essential to progression of the cell cycle. A

series of inhibitors (INK4 family) act to decrease the activity of cyclins,

of which p16INK4a is a member.

Answer 1.5. The answer is D.

Angiogenesis encompasses a cascade of events that allow a tumor’s vascu-

lar supply to be enhanced, thereby increasing cellular proliferation. Apop-

tosis and autophagy are two distinct mechanisms of cell death. Apoptosis