A method of producing a tumorigenic mouse cell, the tumorigenicity of which depends on a recombinant gene of interest is disclosed. The method involves: (a) providing a conditionally tumorigenic mouse cell containing a recombinant oncogene operably linked to an inducible promoter, wherein (i) expression of the recombinant oncogene is necessary and sufficient for the tumorigenicity of the tumorigenic mouse cell, and (ii) the inducible promoter is in the uninduced state; and (b) introducing into the cell a recombinant gene of interest that functionally complements the oncogene, thereby restoring tumorigenicity without expression of the inducible recombinant oncogene. Also disclosed is a method of testing a compound for anti-tumor effects. The method includes producing tumorigenic mouse cells the tumorigenicity depends on expression of a recombinant gene of interest, implanting the cells in mice and obtaining tumors from the implanted cells, administering test compounds to the mice, and determining anti-tumor effects, if any, of the compounds.