ISG15 and cancer: To elucidate the mechanisms of action of ISG15 in cancer, we utilized a proteomic approach and analyzed proteins retrieved from HEK293T cells expressing the E1 activating enzyme UBE1L, the E2 conjugating enzyme UbcH8, and Flag-tagged ISG15 (collectively henceforth referred to as the ISG15-conjugating system) by immunoaffinity purification using anti-Flag antibody-immobilized resin.