Honokiol exhibits enhanced antitumor effects with chloroquine by inducing cell death and inhibiting autophagy in human non-small cell lung cancer cells

Abstract

Abstract. Honokiol (HNK), a potential antitumor compound, has been widely studied in recent years. It induces apoptosis and affects autophagy in cancer cells, yet the mechanism of its antitumor efficacy remains obscure. Chloroquine (CQ), an autophagy inhibitor, is often applied to sensitize antitumor drugs in clinical trials. Here, we investigated the antitumor effect of HNK or CQ alone or in combination in non-small cell lung cancer (NSCLC) cells. Using an experimental approach, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) or sulforhodamine B (SRB) was used to determine the cytotoxicity of the agents. The expression levels of proteins were detected by western blotting. Apoptosis was examined via Annexin V-FITC and PI staining. H460 cell xenografts in nude mice were used to study the effects of HNK and/or CQ in vivo. Transfection with siRNA was applied to knock down cathepsin D. The results demonstrated the enhanced effects of HNK combined with CQ on the inhibition of proliferation, induction of apoptosis in vitro and the reduction in growth in vivo. It was confirmed that HNK and/or CQ triggered apoptosis via a caspase-dependent manner. Furthermore, HNK significantly increased the expression of p62 and LC3-Ⅱ in the A549 and H460 cells and inhibited autophagy and induced apoptosis in a cathepsin D-involved manner. In conclusion, an enhanced antitumor effect was demonstrated following treatment with HNK combined with CQ by inhibiting autophagy and inducing apoptosis via a caspase-dependent and cathepsin D-involved manner. This combination may be a novel and useful antitumor approach for chemotherapy in NSCLC. IntroductionHonokiol (HNK) (Fig. 1A), a biphenolic compound isolated from the leaves, bark, and root of Magnolia officinalis is used in traditional Chinese and Japanese medicine (1). It was reported that HNK effectively reduces the growth of cancer in vitro and in vivo in cell and animal xenograft models (2). It also induces caspase-dependent apoptosis of cancer cells through downregulation of survivin, c-FLIP, Bcl-xL and upregulation of . Recent studies have demonstrated that HNK increases the expression levels of the two hallmarks of autophagy, Beclin-1 and LC3-II, and induces autophagy in glioblastoma multiforme (GBM) DBTRG-05MG cells, yet the role of autophagy in the anti-GBM effects requires further research (6). In addition, HNK was found to induce autophagy in prostate cancer cells (7). However, another study indicated that w007B, a newly synthesized derivative of honokiol, exerted neuroprotective effects through inhibition of autophagy (8). As suggested above, the role of autophagy in the antitumor effects of HNK requires further research and combined treatment of HNK with an autophagy inhibitor or activator may result in enhanced antitumor effects.Autophagy is a conserved, lysosomal-dependent membrane process to maintain cellular homeostasis under metabolic stress. During this process, autophagosomes engulf damaged proteins and defective organelles and then fuse with lysosomes f...

Honokiol inhibits EMT-mediated motility and migration of human non-small cell lung cancer cells in vitro by targeting c-FLIP

“…In the experiment, the cells were exposed to 25 ng/mL TNF-α and 5 ng/mL TGF-β1 combined with the indicated concentrations of HNK ( Figure 1B, 1C). The results showed that HNK reduced the growth of A549 and H460 cells in a dose-dependent manner, as previously reported [18] . At the same time, TNF-α+TGF-β1 enhanced the inhibitory effects exerted by HNK on the proliferation of A549 cells, but there was no significant difference in cell growth for H460 cells between the three agents and HNK alone.…”

“…HNK has been applied to treat neurodegenerative diseases, such as Alzheimer's disease [22] , and has potential anti-diabetic [23] , anti-acnegenic [24] , anti-viral [25] , anti-tumoral [26] and other activities. Our previous study showed that HNK effectively inhibits the proliferation of NSCLC cells through the induction of apoptosis and inhibition of autophagy and also at least partially promotes the apoptosis of NSCLC cells induced by TRAIL by reducing c-FLIP expression levels [15,18] . Given that EMT is a major biological process that results in malignancy [27] , EMT could be an effective target for drugs by inhibiting cancer and distant metastases and improving disease conditions [28] .…”

Combination of an Autophagy Inducer and an Autophagy Inhibitor: A Smarter Strategy Emerging in Cancer Therapy

“…Honokiol is isolated from the bark, seed cones, and leaves of trees belonging to the genus Magnolia and is a kind of lignan. Honokiol-induced cell death increased with CQ by inhibiting autophagy that finally exhibits augmented antitumor effects in human nonsmall cell lung cancer cells (Lv et al, 2015). Combretastatin A-4 (CA-4) is a drug isolated from combretum caffrum which has been applied in clinical trials for solid tumors therapy in past over ten years.…”

Honokiol: A Review of Its Anticancer Potential and Mechanisms

“…Moreover, honokiol has been shown to effectively induce apoptosis in p53-deficient cancer cells, such as MDA-MD-231 breast cancer cells, as well as lung and bladder cancer cell lines by inhibiting the activation of ras-phospholipase D [39,99,100]. Besides p53, other tumour suppressor genes that will be activated in honokiol treatment include p21 [53], p21/waf1 [101], p27 [53], p38 MAPK [102,103], and p62 [26,46].…”