Complex sentence: One major problem with the iPS cells currently is that they way in which the cells are reprogrammed, using gene-carrying viruses, has the potential to cause the iPS cells to develop into cancerous cells.
Split into simpler sentences: One major problem with the iPS cells currently is that they way in which the cells are reprogrammed. Using gene-carrying viruses, has the potential to cause the iPS cells to develop into cancerous cells.