A new study published in PNAS shows that some chemotherapy drugs may be having epigenetic effects on the genomes of patients who take them, reports Nature News' Heidi Ledford. In the study, the researchers gave mice three common chemotherapy drugs, and found that not only did they cause mutations in the mice' genomes, but also in the genomes of their offspring. "The results suggest that the genome in treated mice became destabilized yielding new mutations long after exposure to the drugs has ceased. A similar phenomenon has been observed in mice exposed to radiation," Ledford says. "The work emphasizes the importance of looking at the effects of chemotherapy not only on recipients, but also on their descendants."
However, the researchers who led the study say the results may not be completely applicable in humans. Many adults that are treated for cancer don't have children because they're either too old or the treatment renders them sterile, Ledford says. So the group that may see epigenetic effects from cancer treatment is childhood cancer survivors. But those children who survive cancer don't have children of their own for many years, Ledford adds. In contrast, mice live for a much shorter time and the mice in the study had offspring only a few months after their exposure to the medications.
"In recent years, researchers have begun to investigate the ‘bystander effect’, in which cells that do not directly receive radiation show signs of radiation-induced changes," Ledford says. "It’s possible that some of these effects — perhaps linked to signalling between cells — could contribute to the heritable genomic instability seen in response to radiation and, now, chemotherapy." Patients who have undergone chemotherapy are often asked to wait at least a year before attempting to have children, and, experts note, this study may provide some evidence to back up the logic of that suggestion.