Surveillance team against cancer

摘要

Variations in the control of a phenomenon known as parental imprinting influence the likelihood of tumour development. These new findings may tie in with an earlier concept of 'two-phase' carcinogenesis. Cancer is often viewed as a genetic disease —one that results when the DNA sequence of key genes is mutated, leading to the removal of protective roadblocks and/or to the unchecked proliferation of cells. In recent years, however, it has become clear that 'epigenetic' malfunctions can also contribute to cancer development. These malfunctions can be defined as being due to relatively stable changes in gene expression without changes in the DNA sequence of the gene. They are often detected by the chemical addition or removal of methyl or acetyl groups that cause, or signal, a change in the structure of chromatin, the DNA-protein complex that forms chromosomes. When their normal modifying effects on gene expression are deregulated, tumours can arise.