The cytotoxicty of 9,11-dehydroergosterol peroxide (DHEP) isolated from the fruiting bodies of Ganoderma lucidum on HeLa cells was studied. DHEP treatment for 48 h inhibited the proliferation of HeLa human cervical carcinoma cells with an IC50-value of 8.58 +/- 0.98 microM. Morphological changes of DHEP-treated cells indicated that DHEP induced apoptosis in HeLa cells. To identify the cellular targets of DHEP, two-dimensional electrophoresis analysis was performed to compare the protein expression profiles of DHEP-treated cells with that of control cells. Proteins altered in expressional level after DHEP exposure were identified by MALDI-TOF MS/MS. The cytotoxic effect of DHEP was associated with regulated expression of 6 proteins. Stathmin 1 might be an important target-related protein of DHEP. The regulation of stathmin 1 by DHEP treatment was also confirmed by Western blotting.