Objective Plants belonging to the genus Celastrus exhibit antitumor activity and the ability to reverse multidrug resistance in tumor cells; however, it remains unclear whether the compound oleanen from Celastrus hypoleucus also exhibits antitumor activity. The objective of this study was to explore the inhibitory effect of 12-oleanene-3β, 6α-diol (oleanen) on the proliferation of cervical cancer HeLa cells in vitro, as well as its relative mechanism.

Methods HeLa cells were treated with different concentrations of oleanen for different times. Cell proliferation was determined by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide assay. Cell apoptosis was evaluated by flow cytometry and caspases activities assay. The expression of several proapoptotic proteins belonging to the Bcl-2 family, such as Bax, Bim, and Bad, was detected by Western blot.

Results Oleanen mainly inhibited the proliferation of HeLa cells at the G₀ to G₁ and G₂ to M phases, and the IC₅₀ of oleanen for cells was significantly higher at 24 hours compared to 48 hours (17.45 ± 3.71 vs 9.02 ± 0.83 μg/mL, respectively; P < 0.05). The significant increase in activity of caspase 3/7, caspase 6 in oleanen-treated HeLa cells indicated that oleanen promoted the apoptosis of HeLa cells. The activity of caspase 9 representing the endogenous apoptotic pathways also increased obviously in oleanen treatment. Furthermore, the increase in the expression of Bim was the most significant among the Bcl-2 family after oleanen treatment.

Conclusion Oleanen up-regulates the expression of Bim and other proapoptotic molecules to activate the endogenous apoptosis pathway, thus promoting apoptosis and inhibiting proliferation of human cervical cancer HeLa cells in vitro.