Oncoretroviruses

Oncoretroviruses, the first vectors developed for gene therapy, get their name
from oncogenes, which turn the cell cycle permanently on — one of the precursors
to development of full-blown cancer. Most of the oncoretrovirus vectors in
use for gene therapy trace their history back to a virus that causes leukemia in
monkeys (it’s called Moloney murine leukemia virus, or MLV). MLV has proven
an effective vector, but it’s not without problems; MLV’s propensity to cause
cancer has been difficult to keep in check. Oncoretroviruses work well as vectors
only if they’re used to treat cells that are actively dividing.