Which of the following processes characterizes an epigenetic contribution to oncogenesis?
A) A DNA repair mechanism is disrupted.
B) A tumor suppressor gene is present, but it is not expressed.
C) Cells lose their normal contact inhibition.
D) Regulation of apoptosis in impaired, resulting in accumulation of cancer cells.
Ans: B
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Epigenetic mechanisms of cancer growth involve changes in the patterns of gene expression without a change in the DNA. Epigenetic mechanisms may "silence" genes, such as tumor suppressor genes, so that even though the gene is present, it is not expressed and a cancer-suppressing protein is not made. Disruption of DNA repair may contribute to cancer, but this process is not particular to epigenetics. Similarly, loss of contact inhibition and impaired apoptosis are associated with cancer but are not specific manifestations of epigenetic mechanisms.
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