  We study the top quark portal dominated dark matter interactions, and its
implications for the gamma ray line searches. In this picture, the dark matter
interactions with photons and gluons are loop induced by the axial anomaly of
the top quark current. We show there can be a natural suppression of the
tree-level annihilation of dark matter, and the photon channel in turn has a
substantial rate when the main annihilation proceeds into gluons. We observe a
competition between the indirect detection of gamma ray line and the search
with monojet plus missing energy events at LHC, and the 7 TeV data already set
an upper bound of ~ 10^{-28} cm^3/s on the photonic annihilation cross section.
This upper limit is compatible with a thermal WIMP scenario.
