ß-Elemene inhibits proliferation of human glioblastoma cells and causes cell-cycle G0/G1 arrest via mutually compensatory activation of MKK3 and MKK6.

ß-elemene, a natural plant drug extracted from Curcuma wenyujin, has shown a strong anti-glioblastoma effect. However, the antitumor mechanism of ß-elemene remains unclear. Mitogen-activated protein kinase kinase-3 (MKK3) and -6 (MKK6) can regulate cellular growth, fission, differentiation and apoptosis. To illustrate the role of MKK3 and MKK6 in the anti-glioblastoma proliferation effect of ß-elemene, U87 cells were treated with ß-elemene at various doses or for different times, and then phosphorylated MKK3 (p-MKK3), phosphorylated MKK6 (p-MKK6), MKK3 and MKK6 were detected by Western blot assay. After transient transfection with dominant-negative mutant plasmids of MKK3 and MKK6, cell viability and cell cycle stage were determined by methyl thiazolyl tetrazolium assay and flow cytometry, respectively. Results showed that ß-elemene inhibited the proliferation of U87 glioblastoma cells and arrested them in G0/G1 phase through up-regulating p-MKK3 and p-MKK6 levels. In contrast, inhibition of MKK3 and MKK6 reversed the antitumor effect of ß-elemene. Furthermore, when either MKK3 or MKK6 was inhibited by a dominant-negative plasmid, the other was compensatorily activated in the presence of ß-elemene. Taken together, our findings indicate that mutually compensatory activation of MKK3 and MKK6 mediates the anti-glioblastoma effect of ß-elemene. MKK3 and MKK6 might be two putative targets for molecular therapy against glioblastoma.