  We study the tilt dependence of the pinning-depinning transition for an
interface described by the anisotropic quenched Kardar-Parisi-Zhang equation in
2+1 dimensions, where the two signs of the nonlinear terms are different from
each other. When the substrate is tilted by m along the positive sign
direction, the critical force F_c(m) depends on m as F_c(m)-F_c(0) \sim
-|m|^{1.9(1)}. The interface velocity v near the critical force follows the
scaling form v \sim |f|^{\theta}\Psi_{\pm}(m^2 /|f|^{\theta+\phi}) with \theta
= 0.9(1) and \phi= 0.2(1), where f \equiv F-F_c(0) and F is the driving force.
