Damage to Unirradiated Parts of Body Can Cause Cancer

August 22, 2008

Radiation damage can spread to unirradiated parts of the body and cause cancer in mice via a bystander effect that induces cellular damage and death, according to a report published online Aug. 18 in the Proceedings of the National Academy of Sciences Early Edition.

FRIDAY, Aug. 22 (HealthDay News) -- Radiation damage can spread to unirradiated parts of the body and cause cancer in mice via a bystander effect that induces cellular damage and death, according to a report published online Aug. 18 in the Proceedings of the National Academy of Sciences Early Edition.

Mariateresa Mancuso from l'Energia e l'Ambiente Centro Ricerche Casaccia in Rome, Italy, and colleagues treated neonatal mice missing one copy of the Patched-1 gene, which predisposes them to the childhood brain tumor medulloblastoma, with radiation to either the whole body or while their heads were shielded.

The researchers found that whole-body irradiated mice developed cerebellar tumors. However, mice with shielded brains had a 39 percent increase in medulloblastoma. Their cerebella had DNA double-stranded breaks and apoptotic cell death. Further experiments showed that inhibiting cell-cell communication via gap junctions reversed this bystander effect, suggesting that the genetic damage may have been initiated by gap-junctional intercellular communication in the central nervous system.

"These results represent the first proof-of-principle that bystander effects are factual in vivo events with carcinogenic potential, and implicate the need for re-evaluation of approaches currently used to estimate radiation-associated health risks," Mancuso and colleagues conclude.

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