Testable Deviation from Exact Tribimaximal Mixing

A simple relation U_{MNS}=V_{CKM}^\dagger U_{TB} between the lepton and quark mixing matrices (U_{MNS} and V_{CKM}) is speculated under an ansatz that U_{MNS} becomes an exact tribimaximal mixing U_{TB} in a limit V_{CKM}={\bf 1}. By using the observed CKM mixing parameters, possible values of neutrino oscillation parameters are estimated: \sin^2 \theta_{13}=0.024-0.028, \sin^2 2\theta_{23}=0.94-0.95 and \tan^2 \theta_{12}=0.24-1.00 depending on phase conventions of U_{TB}. Those values are testable soon by precision measurements in neutrino oscillation experiments.