The genetic signature of cancer - Reuters

stride to understand cancer and move into prevention . This time experts from around the world involved in searching the genome cancer analyzed the mutational signatures, mutation processes in the DNA of cells (which are always at the origin of cancer) and follow a fixed pattern. They have found that 20 patterns explain most of the mutations found in the 30 most common cancers. Some of these are very common patterns are repeated in most tumors but are cancers such as leukemia and lymph nodes, which have unique patterns.

The study on cancer signatures published mutational today in the journal Nature and was performed by an endless list of researchers included in the International Consortium Cancer Genome (ICGC), one of the most ambitious international projects for the understanding of cancer. This is the first comprehensive compendium of these mutational processes that generate tumors.

They analyzed almost f ive million mutations from 7,042 cancer samples. The number is important, because the results are much safer. They found more than twenty different patterns, these mutational signatures. Mutational signature is a genetic alteration mechanism which always occurs in the same way. For example, an error might be: if the cell DNA is disrupted the letter A and the letter T in front of him, that A is changed to a C. And there begins to create a tumor.

This important finding is the result of international collaboration research teams from 14 countries, including Spain, and was coordinated by Dr. Michael Stratton of Sanger Institute ( Cambridge, United Kingdom). Spain is responsible leukemia genome and its contribution to this study has been the identification of two fundamental mechanisms that cause mutations in chronic lymphocytic leukemia. The scientists who run it, Dr. Elias Campo, the Hospital Clinic-IDIBAPS and UB, and Carlos Lopez-Otin, the University Institute of Oncolog y, University of Oviedo, have discovered a mutational signature linked to age and another, the own DNA repair system. “The error occurs just when introduces an enzyme to repair damage to the DNA of the cell, the organism does something continuously. But one of every so often, the system makes a mistake and does not perform well this repair. And always wrong with the same pattern, “said Dr. Elias Campo. And then the change starts and cancer.

In this case and in many other mutational signatures described in this investigation, which causes the mutation, and thus cancer is not a external action, a cause exogenous. But endogenously. Thus appears a kind of inevitability in a significant percentage of tumors. “The genomic damage by exogenous agents often arise, such as snuff or ultraviolet light, and are therefore perhaps avoidable genomic damage or at least minimizable” Spanish scientists argue. “But also arise from endogenous changes arising, f or example, of the imperfection of the biological mechanisms of replication or DNA repair. Such imperfections have allowed biological evolution, but also we have focused on developing processes such as cancer.” And that is the case of at least one of the mutational signatures chronic lymphocytic leukemia: no agent that generates outside, not a familial defect. Only malfunction of DNA repair system.

The ICGC want to launch in a few months PanCancer Genome, a new project to compare the genomes of different cancers and define common genomic alterations the specific. “A challenge to manage and understand the vast genomic information being generated,” says Dr. Field.