Magnetoresistance measurements have been performed on a gated two-dimensional electron system (2DES) separated by a thin barrier layer from a layer of InAs self-assembled quantum dots (QDs). Clear features of the quantum Hall effect were observed despite the proximity of the QDs layer to the 2DES. However, the magnetoresistance ($rho_{xx}$) and Hall resistance ($rho_{xy}$) are suppressed significantly in the magnetic field range of filling factor $ u<1$ when a positive voltage is applied to the front gate. The influence of the charge state in QDs was observed on the transport properties of the nearby 2DES only in the field range of $ u < 1$. It is proposed that the anomalous suppression of $rho_{xx}$ and $rho_{xy}$ is related to spin excitation, which is induced by spin-flip processes involving electrons in the QDs and the 2DES.
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