Not quite sure why you think a priest trumps primary literature, but here ya go:
The technical challenges that we need
to overcome to be able to use iPS cells
for therapy include: the use of retroviral
vectors to introduce reprogramming factors
into cells; the need to use a selection
marker (either inserted into the starting
cell by homologous recombination or
included as part of the vector) to identify
reprogrammed cells; the use of the oncogene
MYC to achieve reprogramming; and
the integration of retroviral vectors into the
genome. These manipulations genetically
modify the starting cells, and genetically
modified cells face significant regulatory
hurdles for therapeutic applications
from:
http://www.nature.com/nrm/journal/v9/n9/pdf/nrm2466.pdf