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.