Scientists may have discovered a way to lessen risk of cancer in stem cells... using a parasitic piece of DNA from insects known as "piggyBac" that'll cut and paste itself overwriting the disease.

British and Canadian scientists have reprogrammed piggyBac so that, instead of replicating itself into DNA sequences, it seeds genes to reprogram cancerous cells into more benign cells. Tests in human and mouse DNA have been successful to date, and follow-up testing has made it a potential possibility for piggyBac to leap back in to genes where the cancer reoccurs. Future tests will continue, but for now, Arnold Kriegstein, of the Institute for Regeneration Medicine at the University of California, San Francisco, believes that piggyBac holds a lot of potential:

This is an elegant method... It allows you to seamlessly excise the genes [of cancer].

Ethical stem cells stripped of 'cancer' genes [New Scientist]