Carcinogenesis requires that a single cell or one of its descendents undergo a s
ID: 214491 • Letter: C
Question
Carcinogenesis requires that a single cell or one of its descendents undergo a series of rare genetic and epigenetic changes that permanently alter the expression of at least five to eight genes. Thus, it is not surprising that many cancer cells assayed in cell culture dishes were found to have a very high rate of mutagenesis.
A. What are three systems that are often defective in cancer cells whose role is to ensure the integrity of the genome?
B. The increased mutation rate speeds cancer progression by increasing the likelihood that a cell will acquire additional properties that contributes to carcinogenesis. Name four of the eight typical properties of cancer cells.
C. UV and ionizing radiation are known to cause cancer because they are mutagens that damage DNA. How, then, are the many anticancer therapies that act by damaging DNA, including ionizing radiation and many drugs, so effective at shrinking tumors?
Explanation / Answer
A.
i. DNA repair system
ii. Cell cycle checkpoints
iii. Tumor suppressors and oncogenes
B. Hallmarks of cancer cells
i. Self-sufficiency of growth signals
ii. Insensitivity to anti-growth signals
iii. Evasion of apoptosis
iv. Limitless replicative potential
v. Sustained angiogenesis
vi. Tissue invasion
vii. Genome instability
viii. Abnormal metabolism
C. Anti-cancer drugs and radiotherapy are specifically targetted to the cancer cells so that they mutate further leading to their death. However many of these drugs have several side effects as they sometimes affect the normal cells as well.