We examined electroresistive effects of epitaxial thin films of La0.67Ca0.33MnO3 deposited on LaAlO3(100) substrates. To be noted here is that these oxides are considerably lattice-mismatched. Measurements of the resistivity, magnetoresistance effect, and current-voltage characteristics of these films revealed that they were inhomogeneous and composed of domains of the highly strained charge-ordered insulator (COI) and the less strained ferromagnetic metal (FMM). By using a microfabricating process, we obtained high current densities and observed a current-induced irreversible behavior at low temperature. The irreversibility became larger with increasing current density. Below the insulator-metal (ferromagnetic) transition temperature, spin-polarized electrons in the FMM domains were injected into the neighboring COI domains. There they forced antiferromagnetically ordered spins to align parallel, leading to a current-induced first-order transition from the COI to the FMM.