OBJECTIVETo investigate the effect of triptolide(TPL) on proliferation and apoptosis of RPMI8226 cells and its mechanism.

METHODSMTT assay was used to measure the proliferation of RPMI8226 cells after treatment with different concentration (10, 20, 40, 80 and 160 nmol/L) of TPL for different incubation time (24 h, 48 h and 72 h). The cell apoptosis was detected by flow cytometry, the mRNA expressions of SMYD3 and MMP-9 were measured by quantitative real-time PCR, the protein level of H3K4me2 and H3K4me3 in RPMI8226 cells was assayed by Western blot.

RESULTSTPL inhibited RPMI8226 cell proliferation, and the inhibitory rate of cell proliferation increased significantly in a dose- and time-dependent manner(P<0.05), the RPMI8226 cell apoptosis was induced by treatment with 40, 80 and 160 nmol/L TPL (P<0.05), the qRT-PCR showed that treatment of RPMI8226 cells with TPL down-regulated the mRNA expression of SMYD3 in a dose-dependent manner(P<0.05). Compared with the blank group, the mRNA expression level of MMP-9 in RPMI8226 cells transfected by siRNA-SMYD3 was significantly depressed. Western blot showed that the protein levels of H3K4me2 and H3K4me3 were decreased in a dose-dependent manner after TPL treatment(P<0.05). Compared with the blank group and siRNA negative group, the protein level of H3K4me2 and H3K4me3 in RPMI8226 cells transfected by siRNA-SMYD3 also were significantly depressed(P<0.05).

CONCLUSIONTPL can significantly inhibit the proliferation of RPMI8226 cells and induce their apoptosis, which may be related to the inhibition of SMYD3 expression by TPL- down-regulating the H3K4 methylation and the activating the MMP-9 transcription.