  In String Theory compactification, branes are often invoked to get the
desired form of the radion effective potential. Current popular way of doing
this assumes that the introduction of branes will not modify the background
geometry in an important way. In this paper, we show by an explicit example
that at least in the codimension 2 case, the gravitational backreaction of the
brane cannot be neglected in deriving the radion effective potential. Actually,
in this case, the presence of branes will have no effect on the dynamics of
radion.
