WHY THE IMPACT OF CANCER INCREASES WITH AGE
Life NK AHCC
Scientists have known for years that age is a major risk factor for the development of many types of cancer, but because aging increases the risk of cancer remains unclear. The researchers suspect that the methylation of DNA, or bonds of chemical tags called methyl groups on the DNA , may be involved .
The term methylation is used in chemistry to define the addition or substitution of a methyl group on various substrates. Methylation is the event that is the basis of epigenetic modifications of the genome. The changes made by specific enzymes, DNA and protein, help to define specific markers , inheritable from the parent generation to the next , that distinguish one individual from another . According to the types of epigenetic modifications in fact, two individuals who have the same genotype , are different in some respects , such as the predisposition to the development of specific diseases . These mechanisms leading to the modification of the state of expression of the genes have been identified as key differential expression of genes in real tissues in the human body , as well as in the development of various diseases.
The tumor is characterized by a " methylation imbalance " where genome hypomethylation is accompaganata from local ipermetilazioni and an increase in the expression of DNA methyltransferase . The overall status of methylation in a cell can also be an accelerating factor in carcinogenesis as evidence suggests that genomic hypomethylation can lead to chromosomal instability and increased mutation rates .
Zongli Xu and Jack Taylor, researchers from the National Institute of Environmental Health Sciences ( NIEHS) have identified the sites of DNA methylation throughout the human genome that have changed with increasing age . They showed that a subset of these sites - the ones that become increasingly methylated with age - are also disproportionately methylated in a variety of human tumors . " You can think of methylation as the dust settles on an unused switch , which then prevents the cell to turn on genes ," Taylor said , "If a cell can no longer activate critical development programs , can easily become a cancer cell "
Xu and Taylor made the discovery using blood samples from thousands of women over the course of time a national search to find the environmental and genetic causes of breast cancer and other diseases. More than 50,000 sisters of women who have had breast cancer participating in the study .
Taylor argues that the DNA methylation seems to be part of the normal aging process and occurs in genes involved in cell development . Cancer cells often have altered DNA methylation , but the researchers were surprised to find that 70-90 percent of the sites associated with age showed a significant increase in methylation in all seven types of cancer. Taylor suggests that the age-related methylation can disable the expression of certain genes , making it easier for the transition to the cancer cells .
" The longer you live, the more you will have methylation " say the authors.
Xu and Taylor will face in the future, the question of whether environmental exposures during childhood and adulthood affect the methylation profiles . These additional studies will help scientists to better understand why the methylation occurs at a faster pace over the years .
DNA methylation is one of several epigenetic mechanisms that can control gene expression without changes in DNA sequence.
Source: Worldhealth
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