ObjectiveTo observe the inhibitory effects of pseudolaric acid B (PAB) on the proliferation of rat glioma C6 cells in vivo and in vitro. MethodsMTT assay was used to examine the inhibitory effect of 0, 0.1, 0.2, 0.4, 0.8, 1.6, 8, and 16 μg/ml PAB on C6 cells; the distribution of cell cycle was determined by flow cytometry. C6 cells were injected subcutaneously to establish glioma-bearing rat model and the tumor volume was measured. The expression of proliferating cell nuclear antigen (PCNA) was detected immunohistochemically in the implanted glioma. ResultsIn vitro results showed that PAB inhibited C6 cell growth in a dose-dependent manner, with the IC50 being 0.03 μg/ml. It also arrested the cells in G2/M phase. In vivo results showed that the tumor size of PAB group was decreased compared with the control group; moreover, PCNA expression was also decreased by PAB. ConclusionPAB can inhibit rat glioma C6 cell growth, which might be associated with cell arrest in G2/M phase and down-regulation of PCNA expression.