To make an iPSC, scientists must reprogram an adult cell, such as a skin cell, to express a different set of genes, which can be accomplished using viruses as delivery vehicles or with molecules called messenger RNAs (mRNAs).

The researchers looked at three popular methods of iPSC production (integrating retroviral vectors, non-integrating Sendai virus and synthetic mRNAs), assessing each for the potential to trigger cancer-causing mutations. They used whole-genome sequencing and de novo genome mapping to identify single-nucleotide variants, insertions and deletions, and structural variants.

While the researchers noted some minor alterations in the iPSCs, none of the methods led to significant mutations. Most importantly, a thorough genomic analysis showed that the variants were generally benign.The researchers repeated the experiments two more times and again found no significant risk.
"The methods we're using to make pluripotent stem cells are safe," said the author.

The scientists do warn that even though iPSCs don't gain cancer-causing mutations during reprogramming, potentially harmful mutations can accumulate later on as iPSCs multiply in lab cultures. Author said scientists must analyze their cells for these mutations before using them in therapies.

"We need to move on to developing these cells for clinical applications," said the author. "The quality control we're recommending is to use genomic methods to thoroughly characterize the cells before you put them into people."

http://www.scripps.edu/news/press/2016/20160219loring.html