• Kyodo


A team of researchers, including scientists from Hiroshima University, has identified a gene that acts to suppress the onset of leukemia and other blood cancers even after DNA damage caused by exposure to radiation, according to a study published in a U.S. scientific journal.

The team believes that the loss of the Samd9L gene through aging and other causes contributes to the triggering of leukemia decades after a person is exposed to radiation, according to the latest edition of the Cancer Cell magazine published Monday.

“Many atomic-bomb survivors develop leukemia more than half a century after the bombing. We have identified a reason why (radiation exposures) have a long-term effect,” said Toshiya Inaba, a Hiroshima University professor involved in the study.

The team focused on patients suffering from leukemia and myelodysplastic syndrome, also known as MDS, which affects blood cells.

The team examined patients who had developed symptoms of the diseases within a few years to several decades after the 1945 atomic bombing. It found that blood cells in many of the patients had only one copy of chromosome 7, instead of the usual two.

Based on the findings, the team assumed that a leukemia-suppressing gene is located within chromosome 7. After examining hundreds of genes, the team identified Samd9L, which has a role in suppressing cell proliferation.

The team produced a group of mice with a reduced number of Samd9L for observation. It found that 60 percent of the mice entirely deficient in the gene died from leukemia or MDS in about two years, as did the 53 percent possessing only one Samd9L gene as opposed to normal mice, which have two.

Among the normal group, 7 percent developed the blood cancer diseases, which was about the same rate as other types of cancers, it said. The findings prompted the team to conclude that the gene Samd9L is responsible for suppressing leukemia and MDS.

The researchers have yet to find out how the gene suppresses the blood cancer diseases. The team believes that the diseases develop when the DNA of blood-producing cells gets damaged by radiation exposure and other causes, leading affected people to lose chromosome 7 through subsequent cell divisions.

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