Honokiol, a hydroxylated biphenyl compound isolated from the Chinese herb Magnolia officinalis, has been reported to have anticancer activities in a variety of cancer cell lines. The present study aimed to evaluate the anticancer effect and possible molecular mechanisms of honokiol in a glioblastoma multiforme (GBM) cell line. The anticancer activities of honokiol were investigated in the DBTRG-05MG GBM cell line. The effect of honokiol on cell growth was determined using a sulforhodamine B assay. Flow cytometry and immunoblotting were used to measure honokiol-induced apoptosis (programmed cell death type I) and autophagy (programmed cell death type II). Honokiol was observed to reduce DBTRG-05MG cell viability in a dose-dependent manner. At a dose of 50 μM, honokiol markedly decreased the expression of Rb protein and led to the cleavage of poly(ADP-ribose) polymerase and Bcl-xL to promote apoptosis in the cancer cells. In addition, markers of autophagy, including Beclin-1 and LC3-II, were also significantly increased. In addition to apoptosis, honokiol was also able to induce autophagy in the DBTRG-05MG cells. The mechanisms that are responsible for the correlation between honokiol-induced apoptosis and autophagy require further investigation. Such efforts may provide a potential strategy for improving the clinical outcome of GBM treatment.
