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publicado em 22/10/2013 às 09h14:00
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Cancer caused by mutations affecting the X chromosome in women

The researchers said the discovery helps to understand how cellular stress accelerates the process of carcinogenesis fatal

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All cancers arise from changes in the genetic material of a person .. These changes usually occur as "somatic mutations" into individual cells throughout the life of an individual. "Over time, the original cell damage accumulates additional mutations, a process still poorly understood," says Professor Roland Eils, who conducted the study at the University of Heidelberg.

In this international study, the researchers analyzed the first time, the exact distribution of somatic mutations in the genome of tumor cells of various types of cancer. According to study results, the changes do not affect all regions of the genome to the same extent. It is known, for example, the number of somatic mutations is dependent on the base sequence of a gene which form the frequency with which is transcribed into RNA molecules.

The researchers analyzed the genome sequences of more than 400 tumors from patients suffering from twelve kinds of cancer, including brain cancer in children and adults, leukemias and breast cancer.

Scientists were surprised to find that the mutations were extremely frequent in women X chromosome responsible for sex determination. In many cancers, this chromosome exhibited two to four times the number of mutations observed in other chromosomes. Another finding from the study was that the rate of change was not the same in the two copies. Since embryonic development, one copy is inactivated in cells. The highest mutation rate affects just copying inactive.

This phenomenon was not found in patients with cancer of the male, whose cells carry only one X chromosome or inactive X chromosomes of the cells healthy female. The researchers also found that the accumulation of mutations occurs at a very early stage of carcinogenesis.

Before each cell division, the DNA of the original cell is duplicated. The inactive X chromosome is always the last to be duplicated. "Our theory is that cells that have undergone this double experience a state of stress caused by rapid cell division," says Natalie Jäger. "They may not have enough time to repair the errors."

"This discovery helps us understand how cellular stress accelerates the fatal process of carcinogenesis and therefore contributes to an accumulation of more and more mutations in a cancer cell, complete scientists.

   Palavras-chave:   Carcinogenesis    Mutations caused by cancer    Chromosome X    Cancer    Roland Eils    Health   
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