Inactivation of ras and changes of mitochondrial membrane potential contribute to oridonin-induced autophagy in a431 cells

The Natural Product Oridonin as an Anticancer Agent: Current Achievements and Problems

Oridonin, an active diterpenoid isolated from traditional Chinese herbal medicine, has received a rising attention for its remarkable roles in cancer therapy. In recent years, increasing evidences have revealed that oridonin inhibits the occurrence and development of tumor cells through multiple mechanisms, including induction of apoptosis and autophagy, cell cycle arrest, and inhibition of angiogenesis as well as migration and invasion. In addition, several molecular signal targets have been identified, including ROS, EGFR, NF-κB, PI3K/Akt, and MAPK. In this paper, we review considerable knowledge about the molecular mechanisms and signal targets of oridonin, which has been studied in recent years. It is expected that oridonin may be developed as a novel anti-tumor herbal medicine in human cancer treatment.

Identification of Autophagy as a Functional Target Suitable for the Pharmacological Treatment of Mitochondrial Membrane Protein-Associated Neurodegeneration (MPAN) In Vitro

Mitochondrial membrane protein-associated neurodegeneration (MPAN) is a relentlessly progressive neurodegenerative disorder caused by mutations in the C19orf12 gene. C19orf12 has been implicated in playing a role in lipid metabolism, mitochondrial function, and autophagy, however, the precise functions remain unknown. To identify new robust cellular targets for small compound treatments, we evaluated reported mitochondrial function alterations, cellular signaling, and autophagy in a large cohort of MPAN patients and control fibroblasts. We found no consistent alteration of mitochondrial functions or cellular signaling messengers in MPAN fibroblasts. In contrast, we found that autophagy initiation is consistently impaired in MPAN fibroblasts and show that C19orf12 expression correlates with the amount of LC3 puncta, an autophagy marker. Finally, we screened 14 different autophagy modulators to test which can restore this autophagy defect. Amongst these compounds, carbamazepine, ABT-737, LY294002, oridonin, and paroxetine could restore LC3 puncta in the MPAN fibroblasts, identifying them as novel potential therapeutic compounds to treat MPAN. In summary, our study confirms a role for C19orf12 in autophagy, proposes LC3 puncta as a functionally robust and consistent readout for testing compounds, and pinpoints potential therapeutic compounds for MPAN.

Grandiflorenic acid from Wedelia trilobata plant induces apoptosis and autophagy cell death in breast adenocarcinoma (MCF7), lung carcinoma (A549), and hepatocellular carcinoma (HuH7.5) cells lines

INTRODUCTION

Wedelia trilobata (Sphagneticola trilobata) is a plant used in this popular medicine for treating infectious, sores and swellings in some rural communities, and their extract has antioxidant, anti-inflammatory, antitumor and hepatoprotective effect. Cancer is a molecularly heterogeneous disease caused by environmental and, genetic factors, among others. Since the complexity of the disease leads to low response rates to the different treatments used, it is necessary to find alternative drugs aimed at its control. The objective of our study was to assess whether grandiflorenic acid (GFA) has antitumor activity on breast (MCF7), liver (HuH7.5), and lung (A549) tumor cell lines.

METHODS

We used cell integrity assessment methods to assess whether (GFA) would be cytotoxic for tumor cell lines at doses ranging from and the pattern of death involved in this effect.

RESULTS

Treatment using GFA significantly inhibited cell proliferation in the three studied cells, followed by a decrease in cell size. The assessment of the death mechanisms showed the treatments increased the production of reactive oxygen species, caused exposure of phosphatidylserine, depolarization of the mitochondrial membrane, and, decrease plasma membrane integrity, indicating mechanisms related to apoptosis. Besides, we found the formation of autophagy vacuoles in our tests.

CONCLUSION

Finally, our study found the effect of GFA on breast (MCF7), lung (A549), and liver (HuH7.5) tumor cell lines induce cytotoxicity and patterns of death associated with apoptosis and autophagy, and oxidative stress generation plays a role in these two pathways of cell death. Thus, this study revealed GFA exhibits anti-cancer activity in vitro and could help future studies to improve strategies for cancer treatment with involving natural compounds.

Recent Progress of Oridonin and Its Derivatives for the Treatment of Acute Myelogenous Leukemia

First stage human clinical trial (CTR20150246) for HAO472, the L-alanine-(14-oridonin) ester trifluoroacetate, was conducted by a Chinese company, Hengrui Medicine Co. Ltd, to develop a new treatment for acute myelogenous leukemia. Two patents, WO2015180549A1 and CN201410047904.X, covered the development of the I-type crystal, stability experiment, conversion rate research, bioavailability experiment, safety assessment, and solubility study. HAO472 hewed out new avenues to explore the therapeutic properties of oridonin derivatives and develop promising treatment of cancer originated from naturally derived drug candidates. Herein, we sought to overview recent progress of the synthetic, physiological, and pharmacological investigations of oridonin and its derivatives, aiming to disclose the therapeutic potentials and broaden the platform for the discovery of new anticancer drugs.

Wheat germ agglutinin modification of lipid–polymer hybrid nanoparticles: enhanced cellular uptake and bioadhesion

WGA-modified lipid–polymer hybrid nanoparticles (WGA-LPNs) showed increased intestinal bioadhesion and cellular uptake and have the potential to improve the oral delivery of poorly water-soluble drugs.

Baicalein Triggers Autophagy and Inhibits the Protein Kinase B/Mammalian Target of Rapamycin Pathway in Hepatocellular Carcinoma HepG2 Cells

Baicalein (BA), isolated from the Chinese medicinal herb Scutellariae radix (Huangqin in Chinese), is a flavonoid with various pharmacological effects. Herein, we found that BA only slightly reduced the cell viability on HepG2 cells after 24-h treatment as determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. However, BA (50 μM) effectively blocked the colony formation. Meanwhile, BA remarkably induced the formation of autophagosomes after 24-h treatment as determined by immunofluorescence with monodansylcadaverine staining as well as transmission electron microscopy, respectively. Moreover, BA obviously up-regulated the expression of microtubule-associated protein 1A/1B-light chain 3-II in concentration-dependent and time-dependent manners in HepG2 cells. When combined with the autophagy inhibitor chloroquine and BA, the cell viability and colony formation were significantly decreased, indicating that BA triggered protective autophagy, which prevented cell death. Further study showed that BA concentration-dependently and time-dependently decreased the expression of p-AKT (S473), p-ULK1 (S757) and p-4EBP1 (T37 and S65), suggesting the involvement of protein kinase B (AKT)/mammalian target of rapamycin (mTOR) in BA-triggered autophagy.

Anti-proliferative effects of evodiamine in human lung cancer cells

BACKGROUND

Evodiamine, a compound isolated from the Evodia rutaecarpa Bentham (Rutaceae), is known to have a potential anti-proliferative activity in human cancer cells. However, the growth inhibitory activity against lung cancer cells and the underlying molecular mechanisms have been poorly determined. The present study was designed to examine the anti-proliferative effect of evodiamine in A549 human lung cancer cells.

METHODS

A549 cells were treated with the compounds from Evodia rutaecarpa, and the anti-proliferative activity was evaluated by the sulforhodamine B assay. The mechanisms of action for the growth inhibitory activity of evodiamine on A549 human lung cancer cells were evaluated using flow cytometry for cell cycle distribution, and Western blot for assessment of accumulation and phosphorylation of potential target proteins.

RESULTS

Evodiamine exhibited a potent anti-proliferative activity against A549 human lung cancer cells. Flow cytometric analysis revealed that evodiamine induced cell cycle arrest at G2/M phase and apoptosis in the A549 cells. The cell cycle arrest was well correlated with the inhibition of cyclin B1, cyclin A, cdk2 and p-cdc2 (Tyr15) and increase of p-chk1 (Ser345) and p-chk2 (Thr68). Evodiamine also significantly increased the ratio of Bax/Bcl-2 and decreased procaspase-3, suggesting evodiamine-induced apoptosis via the intrinsic apoptotic pathway. In addition, evodiamine inhibited the expression of p-ERK and ERK.

CONCLUSIONS

These findings suggest that the anti-proliferative effect of evodiamine was associated in part with the induction of G2/M phase cell cycle arrest and apoptosis, and down-regulation of ERK in human lung cancer cells.

Ouabain elicits human glioblastoma cells apoptosis by generating reactive oxygen species in ERK-p66SHC-dependent pathway

Excessive reactive oxygen species (ROS) generation has been implicated as one of main agents in ouabain-induced anticancer effect. Unfortunately, the signaling pathways under it are not very clarified. In the present study, we investigated the molecular mechanism involved in ouabain-induced ROS generation and cell apoptosis on human U373MG and U87MG glioma cells. Ouabain-induced glioblastoma cells apoptosis and increased ROS generation. Clearance ROS by three different ROS scavenger partly, but not totally, reversed ouabain's effect on cell apoptosis. Ouabain-induced ROS generation was not regulated by calcium overload, reduced nicotinamide adenine dinucleotide phosphate oxidation, but by p66Shc phosphorylation. Ouabain treatment increased p66Shc Ser36 phosphorylation. Knockdown of p66Shc by siRNA significantly inhibited ROS generations in response to ouabain. Ouabain-induced p66Shc phosphorylation through Src/Ras/extracellular signal-regulated kinase signal pathway. Our results uncovered a novel signaling pathway with p66Shc, ouabain-induced ROS generation, and glioblastoma cell apoptosis.

Hydroxyl radical (·OH) played a pivotal role in oridonin-induced apoptosis and autophagy in human epidermoid carcinoma A431 cells

Oridonin, a diterpenoid compound extracted and purified from Rabdosia rubescen, has been reported to induce tumor cell apoptosis through tyrosine kinase pathway. To further examine the mechanism of oridonin, we selected human epidermoid carcinoma A431 cell as a test object. Besides apoptosis, oridonin also induced A431 cell autophagy, and this autophagy antagonized apoptosis and played a protective role for A431 cells. Reactive oxygen species (ROS) played a pivotal role in induction of cytotoxicity. Therefore, a ROS scavenger, N-acetylcysteine (NAC) combined with oridonin was appiled. Results of morphologic observation, flow cytometric analysis and Western blot analysis showed that NAC could significantly reverse both ROS generation and down-regulation of mitochondrial membrane potential in oridonin treated cells. NAC inhibited oridonin induced apoptosis through both the intrinsic and extrinsic apoptotic pathways. NAC effectively inhibited both oridonin-induced apoptosis and autophagy by reducing intracellular oxidative stress. To further examine the mechanism of ROS, exogenous enzyme antioxidants (superoxide dismutase (SOD), catalase (CAT)) and non-enzyme antioxidants (glutathione (GSH)) were applied to detect the effect of oridonin on ROS generation. Only GSH exerted a similar role with NAC, suggesting that hydroxyl radical (·OH) played the major role in oridonin-induced cell death. Oridonin could decrease the GSH level in A431 cells in a dose-dependent manner. In addition, after treatment with ·OH donor, Fenton reagent, the changes in A431cells were similar to the results of oridonin treatment. All the results proved that ·OH played the pivotal role in oridonin induced apoptosis and autophagy in A431 cells.

Oridonin: targeting programmed cell death pathways as an anti-tumour agent

Oridonin, an active diterpenoid isolated from traditional Chinese herbal medicine, has drawn rising attention for its remarkable apoptosis- and autophagy-inducing activity and relevant molecular mechanisms in cancer therapy. Apoptosis is a well known type of cell death, whereas autophagy can play either pro-survival or pro-death roles in cancer cells. Accumulating evidence has recently revealed relationships between apoptosis and autophagy induced by oridonin; however, molecular mechanisms behind them remain to be discovered. In this review, we focus on highlighting updated research on oridonin-induced cell death signalling pathways implicated in apoptosis and autophagy, in many types of cancer. In addition, we further discuss cross-talk between apoptosis and autophagy induced by oridonin, in cancer. Taken together, these findings open new perspectives for further exploring oridonin as a potential anti-tumour agent targeting apoptosis and autophagy, in future anti-cancer therapeutics.

Oridonin induces apoptosis in gastric cancer through Apaf-1, cytochrome c and caspase-3 signaling pathway

AIM: To investigate the effect and mechanism of oridonin on the gastric cancer cell line HGC-27 in vitro.

METHODS: The inhibitory effect of oridonin on HGC-27 cells was detected using the 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. After treatment with 10 μg/mL oridonin for 24 h and 48 h, the cells were stained with acridine orange/ethidium bromide. The morphologic changes were observed under an inverted fluorescence microscope. DNA fragmentation (a hallmark of apoptosis) and lactate dehydrogenase activity were examined using DNA ladder assay and lactate dehydrogenase-release assay. After treated with oridonin (0, 1.25, 2.5, 5 and 10 μg/mL), HGC-27 cells were collected for anexin V-phycoerythrin and 7-amino-actinomycin D double staining and tested by flow cytometric analysis, and oridonin- induced apoptosis in HGC-27 cells was detected. After treatment with oridonin for 24 h, the effects of oridonin on expression of Apaf-1, Bcl-2, Bax, caspase-3 and cytochrome c were also analyzed using reverse-transcript polymerase chain reaction (RT-PCR) and Western blotting.

RESULTS: Oridonin significantly inhibited the proliferation of HGC-27 cells in a dose- and time-dependent manner. The inhibition rates of HGC-27 treated with four different concentrations of oridonin for 24 h (1.25, 2.5, 5 and 10 μg/mL) were 1.78% ± 0.36%, 4.96% ± 1.59%, 10.35% ± 2.76% and 41.6% ± 4.29%, respectively, which showed a significant difference (P < 0.05). The inhibition rates of HGC-27 treated with oridonin at the four concentrations for 48 h were 14.77% ± 4.21%, 21.57% ± 3.75%, 30.31% ± 4.91% and 61.19% ± 5.81%, with a significant difference (P < 0.05). The inhibition rates of HGC-27 treated with oridonin for 72 h at the four concentrations were 25.77% ± 4.85%, 31.86% ± 3.86%, 48.30% ± 4.16% and 81.80% ± 6.72%, with a significant difference (P < 0.05). Cells treated with oridonin showed typical apoptotic features with acridine orange/ethidium bromide staining. After treatment with oridonin, the cells became round, shrank, and developed small buds around the nuclear membrane while forming apoptotic bodies. Lactate dehydrogenase (LDH) release assay showed that after treated with 1.25 μg/mL and 20 μg/mL oridonin for 24 h, LDH release of HGC-27 caused by apoptosis increased from 22.94% ± 3.8% to 52.68% ± 2.4% (P < 0.001). However, the change in the release of LDH caused by necrosis was insignificant, suggesting that the major cause of oridonin-induced HGC-27 cell death was apoptosis. Flow cytometric analysis also revealed that oridonin induced significant apoptosis compared with the controls (P < 0.05). And the apoptosis rates of HGC-27 induced by the four different concentrations of oridonin were 5.3% ± 1.02%, 12.8% ± 2.53%, 28.5% ± 4.23% and 49.6% ± 3.76%, which were in a dose-dependent manner (P < 0.05). After treatment for 24 h, DNA ladder showed that oridonin induced a significant increase in DNA fragmentation in a dose-dependent manner. RT-PCR revealed that mRNA expression levels were up-regulated compared with the controls in caspase-3 (0.917 ± 0.103 vs 0.357 ± 0.019, P < 0.05), cytochrome c (1.429 ± 0.111 vs 1.002 ± 0.014, P < 0.05), Apaf-1 (0.688 ± 0.101 vs 0.242 ± 0.037, P < 0.05) and Bax (0.856 ± 0.101 vs 0.278 ± 0.027, P < 0.05) (P < 0.05), whereas down-regulated in Bcl-2 (0.085 ± 0.012 vs 0.175 ± 0.030, P < 0.05). Western blotting analysis also confirmed this result.

CONCLUSION: Apoptosis of HGC-27 induced by oridonin may be associated with differential expression of Apaf-1, caspase-3 and cytochrome c, which are highly dependent upon the mitochondrial pathway.

The tyrphostin AG1478 augments oridonin-induced A431 cell apoptosis by blockage of JNK MAPK and enhancement of oxidative stress

Oridonin, a diterpenoid compound, extracted and purified from Rabdosia rubescen has been reported to have cytotoxic effect on tumour cells through apoptosis, and tyrosine kinase pathways are involved in these processes. A specific epidermal growth factor receptor (EGFR) inhibitor AG1478 was used to examine the relationship between EGFR signal pathways and oridonin-induced apoptosis and autophagy in EGFR abundant human epidermoid carcinoma A431 cells. Inhibition of EGFRaugmented oridonin-induced A431 cell apoptosis, while the changes of expression of downstream proteins, Bcl-2, Bcl-xL, Bax, cytochrome c, pro-caspase-3, Fas, FADD and pro-caspase-8 suggested that both the intrinsic and extrinsic apoptotic pathways are involved in these processes. Pretreatment with AG1478 aggravated oridonin-induced loss of mitochondrial membrane potential (MMP) and increased ROS generation in A431 cells, while a ROS scavenger, N-acetylcysteine (NAC) completely reversed oridonin- and AG1478-induced ROS generation and apoptosis. Therefore, AG1478 augmented oridonin-induced apoptosis by enhancing oxidative stress. Pretreatment with AG1478 decreased the expression of downstream MAPK proteins ERK, JNK and P38 and their phosphorylated forms to varying degrees compared with oridonin alone treatment. Then after administration of ERK, JNK and P38 inhibitors, only JNK inhibitor SP600125 effectively augmented oridonin-induced apoptosis and ROS generation. Therefore, in EGFR downstream pathways, JNK played a major role in preventing oridonin-induced apoptosis. Autophagy antagonised apoptosis and exerted a protective effect in A431 cells, and both AG1478 and SP600125 decreased oridonin-induced autophagy. Inhibition of EGFR augmented oridonin-induced apoptosis and this was caused by enhanced oxidative stress, and JNK played a major protective role by increasing autophagy, leading to antagonising apoptosis and ROS generation.

Oridonin up-regulates expression of P21 and induces autophagy and apoptosis in human prostate cancer cells

Background: Oridonin (ORI) could inhibit the proliferation and induce apoptosis in various cancer cell lines. However, the mechanism is not fully understood.

Methods: Human prostate cancer (HPC) cells were cultured in vitro and cell viability was detected by the CCK-8 assay. The ultrastructure changes were observed under transmission electron microscope (TEM). Chemical staining with acridine orange (AO), MDC or DAPI was used to detect acidic vesicular organelles (AVOs) and alternation of DNA. Expression of LC3 and P21 was detected by Western Blot. Apoptotic rates and cell cycle arrest were detected by FACS.

Results: Our study demonstrated that after ORI treatment, the proliferations of human prostate cancer (HPC) cell lines PC-3 and LNCaP were inhibited in a concentration and time-dependent manner. ORI induced cell cycle arrest at the G2/M phase. A large number of autophagosomes with double-membrane structure and acidic vesicular organelles (AVOs) were detected in the cytoplasm of HPC cells treated with ORI for 24 hours. ORI resulted in the conversion of LC3-I to LC3-II and recruitment of LC3-II to the autophagosomal membranes. Autophagy inhibitor 3-methyladenine (3-MA) reduced AVOs formation and inhibited LC3-I to LC3-II conversion. At 48 h, DNA fragmentation, chromatin condensation and disappearance of surface microvilli were detected in ORI-treated cells. ORI induced a significant increase in the number of apoptotic cells (PC-3: 5.4% to 27.0%, LNCaP: 5.3% to 31.0%). Promoting autophagy by nutrient starvation increased cell viability, while inhibition of autophagy by 3-MA promoted cell death. The expression of P21 was increased by ORI, which could be completely reversed by the inhibition of autophagy.

Conclusions: Our findings indicated that autophagy occurred before the onset of apoptosis and protected cancer cells in ORI-treated HPC cells. P21 was involved in ORI-induced autophagy and apoptosis. Our results provide an experimental basis for understand the anti-tumor mechanism of ORI as treatment for prostate cancer.

RGD-modified poly(D,L-lactic acid) nanoparticles enhance tumor targeting of oridonin

Objective

The purpose of this study was to develop an active targeting strategy to improve the therapeutic antitumor efficacy of oridonin (ORI), the main active ingredient in the medicinal herb Rabdosia rubescens.

Methods

A modified spontaneous emulsification solvent diffusion method was used to prepare the ORI-loaded atactic poly(D,L-lactic acid) nanoparticles (ORI-PLA-NPs). Surface cross-linking with the peptide Arg-Gly-Asp (RGD) further modified the ORI-PLA-NPs, generating ORI-PLA-RGD-NPs. The NPs were characterized and release experiments were performed in vitro. The pharmacokinetics, tissue distribution, and antitumor activity of the NPs were studied in mice bearing hepatocarcinoma 22 (H22)-derived tumors.

Results

The ORI-PLA-NPs and ORI-PLA-RGD-NPs were smooth, sphere-like, and relatively uniform in size. The RGD surface modification slightly increased the mean particle size (95.8 nm for ORI-PLA-NPs versus 105.2 nm for ORI-PLA-RGD-NPs) and considerably altered the surface electrical property (−10.19 mV for ORI-PLA-NPs versus −21.95 mV for ORI-PLA-RGD-NPs), but it had no obvious influence on ORI loading (8.23% ± 0.35% for ORI-PLA-NPs versus 8.02% ± 0.38% for ORI-PLA-RGD-NPs), entrapment efficiency (28.86% ± 0.93% for ORI-PLA-NPs versus 28.24% ± 0.81% for ORI-PLA-RGD-NPs), or the release of ORI. The pharmacokinetic properties of free ORI were improved by encapsulation in NPs, as shown by increased area under the concentration-time curve (11.89 ± 0.35 μg·mL⁻¹ · h for ORI solution versus 22.03 ± 0.01 μg · mL⁻¹ · h for ORI-PLA-RGD-NPs) and prolonged mean retention time (2.03 ± 0.09 hours for ORI solution versus 8.68 ± 0.66 hours for ORI-PLA-RGD-NPs). In the tissue distribution study, more ORI targeted tumor tissue in the mice treated with ORI-PLA-RGD-NPs than with ORI-PLA-NPs or ORI solution. Consistent with these observations, ORI-PLA-RGD-NPs showed greater antitumor efficacy than ORI-PLA-RGD-NPs or ORI solution, as reflected by the decreased tumor growth and the prolonged survival time of mice bearing H22 tumors.

Conclusion

The tumor-targeting efficiency and subsequent antitumor efficacy of ORI is increased by incorporation into ORI-PLA-RGD-NPs.

Autophagy counteracts apoptosis in human multiple myeloma cells exposed to oridonin in vitro via regulating intracellular ROS and SIRT1

AIM

To explore the mechanisms underlying the oridonin-induced apoptosis and autophagy in human multiple myeloma cells in vitro.

METHODS

Human multiple myeloma RPMI8266 cells were used. The cell viability was assessed using MTT assay. Morphological changes of apoptosis and autophagy were observed under transmission electron microscope. TUNEL and annexin V-FITC/PI dual staining assays were used to measure apoptosis. Autophagy was analyzed using Western blot analysis and immunofluorescence staining with a QDs(605 nm)-Anti-LC3 fluorescent probe. Intracellular ROS was estimated with flow cytometry using DCFH-DA fluorescent probe. Protein levels of active caspase 3, Beclin 1 and SIRT1 were determined with Western blot analysis.

RESULTS

Exposure to oridonin (1-64 μmol/L) inhibited the proliferation of RPMI8266 cells in a concentration-dependent manner with an IC(50) value of 6.74 μmol/L. Exposure to oridonin (7 μmol/L) simultaneously induced caspase 3-mediated apoptosis and Beclin 1-dependent autophagy of RPMI8266 cells. Both the apoptosis and autophagy were time-dependent, and apoptosis was the main effector pathway of cell death. Exposure to oridonin (7 μmol/L) increased intracellular ROS and reduced SIRT1 nuclear protein in a time-dependent manner. The blockade of intracellular generation of ROS by NAC (5 mmol/L) abrogated apoptosis, autophagy and the decrease of SIRT1 in the cells exposed to oridonin (7 μmol/L). The inhibition of autophagy by 3-MA (5 mmol/L) sensitized the cells to oridonin-induced apoptosis, which was accompanied by increased intracellular ROS and decreased SIRT1.

CONCLUSION

Oridonin simultaneously induces apoptosis and autophagy of human multiple myeloma RPMI8266 cells via regulation of intracellular ROS generation and SIRT1 nuclear protein. The cytotoxicity of oridonin is mainly mediated through the apoptotic pathway, whereas the autophagy protects the cells from apoptosis.

Study on the autophagy of prostate cancer PC-3 cells induced by oridonin

To investigate the mechanism of oridonin (ORI)-induced autophagy in prostate cancer PC-3 cells, PC-3 cells cultured in vitro were treated with ORI, and the inhibitory ratio of ORI on PC-3 cells was assayed by 3-4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide. The ultrastructural changes of the cells were observed under light microscope, scanning electron microscope (SEM), and transmission electron microscope (TEM). Acridine orange (AO) staining was used to observe the acidic vesicular organelles (AVOs). The level of autophagy-related proteins, MAP1-LC3, was detected by Western Blot, and RT-PCR was used to detect the level of mRNA of beclin 1. After ORI treatment, the proliferation of PC-3 cells was inhibited significantly in a concentration and time-dependent manner. SEM examination revealed cellular shrinkage and disappearance of surface microvilli in ORI-treated cells. Under TEM examination, the nuclei exhibited chromatin condensation and the appearance of a large number of autophagosomes with double-membrane structure in cytoplasm. AO staining showed the existence of AVOs. The expression of LC3 and the mRNA level of beclin 1 was increased by ORI. Furthermore, autophagy inhibitor 3-methyladenine reversed the increase of beclin 1 mRNA. The growth of PC-3 cells was inhibited, and autophagy was induced by ORI, indicating ORI may have a potential antitumor effect.

Increases in mitochondrial biogenesis impair carcinogenesis at multiple levels

Although mitochondrial respiration is decreased in most cancer cells, the role of this decrease in carcinogenesis and cancer progression is still unclear. To better understand this phenomenon, instead of further inhibiting mitochondrial function, we induced mitochondrial biogenesis in transformed cells by activating the peroxisome proliferator-activated receptors (PPARs)/peroxisome proliferator-activated receptor gamma co-activator 1α (PGC-1α) pathways. This was achieved by treating the cells with bezafibrate, a PPARs panagonist that also enhances PGC-1α expression. We confirmed that bezafibrate treatment led to increased mitochondrial proteins and enzyme functions. We found that cells with increased mitochondrial biogenesis had decreased growth rates in glucose-containing medium. In addition, they became less invasive, which was directly linked to the reduced lactate levels. Surprisingly, even though bezafibrate-treated cells had higher levels of mitochondrial markers, total respiration was not significantly altered. However, respiratory coupling, and ATP levels were. Our data show that by increasing the efficiency of the mitochondrial oxidative phosphorylation system, cancer progression is hampered by decreases in cell proliferation and invasiveness.

Anti-cancer natural products isolated from chinese medicinal herbs

In recent years, a number of natural products isolated from Chinese herbs have been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, retard metastasis and enhance chemotherapy, exhibiting anti-cancer potential both in vitro and in vivo. This article summarizes recent advances in in vitro and in vivo research on the anti-cancer effects and related mechanisms of some promising natural products. These natural products are also reviewed for their therapeutic potentials, including flavonoids (gambogic acid, curcumin, wogonin and silibinin), alkaloids (berberine), terpenes (artemisinin, β-elemene, oridonin, triptolide, and ursolic acid), quinones (shikonin and emodin) and saponins (ginsenoside Rg3), which are isolated from Chinese medicinal herbs. In particular, the discovery of the new use of artemisinin derivatives as excellent anti-cancer drugs is also reviewed.

Anti-cancer natural products isolated from chinese medicinal herbs

In recent years, a number of natural products isolated from Chinese herbs have been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, retard metastasis and enhance chemotherapy, exhibiting anti-cancer potential both in vitro and in vivo. This article summarizes recent advances in in vitro and in vivo research on the anti-cancer effects and related mechanisms of some promising natural products. These natural products are also reviewed for their therapeutic potentials, including flavonoids (gambogic acid, curcumin, wogonin and silibinin), alkaloids (berberine), terpenes (artemisinin, β-elemene, oridonin, triptolide, and ursolic acid), quinones (shikonin and emodin) and saponins (ginsenoside Rg₃), which are isolated from Chinese medicinal herbs. In particular, the discovery of the new use of artemisinin derivatives as excellent anti-cancer drugs is also reviewed.

Stimulation of suicidal erythrocyte death by oridonin

Oridonin triggers apoptosis of cancer cells and was suggested as anticancer agent. Oridonin is partially effective through mitochondrial depolarization and partially by modifying gene expression. Erythrocytes lack mitochondria and nuclei but may undergo eryptosis, a suicidal cell death characterized by cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+)-activity, ATP depletion and ceramide formation. The present study explored, whether oridonin triggers eryptosis. Cytosolic Ca(2+)-concentration was estimated from Fluo3-fluorescence, cell volume from forward scatter in FACS analysis, phosphatidylserine exposure from binding of fluorescent annexin V, hemolysis from hemoglobin release, ATP concentration utilizing a luciferin-luciferase assay and ceramide abundance utilizing fluorescent anti-ceramide antibodies. A 48 h exposure to oridonin (≥25μM) significantly increased cytosolic Ca(2+)-concentration, increased ceramide formation, decreased forward scatter and triggered annexin V-binding (the latter in >20% of the erythrocytes). Oridonin didn't decrease ATP concentration and hemolysed <5% of erythrocytes. The effects of oridonin on annexin V binding were partially reversed in the nominal absence of Ca(2+) and by the addition of amiloride (1mM). The present observations reveal a completely novel effect of oridonin, i.e. triggering of Ca(2+) entry and ceramide formation as well as suicidal death of erythrocytes.

Oridonin: An active diterpenoid targeting cell cycle arrest, apoptotic and autophagic pathways for cancer therapeutics

It is well-known that cell cycle arrest and/or death play a pivotal role in tumor progression, which has drawn a rising attention for cancer biologists due to their complex and intricate relationships. In this review, we demonstrate the recent research on oridonin, an active diterpenoid with remarkable anti-proliferative activities, and then further explore its molecular mechanisms of cell cycle arrest, apoptosis, autophagy and their cross-talks in various cancer cells, which may provide a new perspective of oridonin as a candidate anti-neoplastic drug for future cancer therapeutics.

Role and regulation of autophagy in cancer

Autophagy is an evolutionarily conserved process whereby cytoplasm and cellular organelles are degraded in lysosomes for amino acid and energy recycling. Autophagy is a survival pathway activated in response to nutrient deprivation and other stressful stimuli, such as metabolic stress and exposure to anticancer drugs. However, autophagy may also result in cell death, if it proceeds to completion. Defective autophagy is implicated in tumorigenesis, as the essential autophagy regulator beclin 1 is monoallelically deleted in human breast, ovarian and prostate cancers, and beclin 1(+/-) mice are tumor-prone. How autophagy suppresses tumorigenesis is under intense investigation. Cell-autonomous mechanisms, involving protection of genome integrity and stability, and a non-cell-autonomous mechanism, involving suppression of necrosis and inflammation, have been discovered so far. The role of autophagy in treatment responsiveness is also complex. Autophagy inhibition concurrently with chemotherapy or radiotherapy has emerged as a novel approach in cancer treatment, as autophagy-competent tumor cells depend on autophagy for survival under drug- and radiation-induced stress. Alternatively, autophagy stimulation and preservation of cellular fitness by maintenance of protein and organelle quality control, suppression of DNA damage and genomic instability, and limitation of necrosis-associated inflammation may play a critical role in cancer prevention.

Involvement of PKC signal pathways in oridonin-induced autophagy in HeLa cells: a protective mechanism against apoptosis

Our previous studies showed that oridonin could induce both apoptosis and autophagy in HeLa cells, and this autophagy might be a protective mechanism against apoptosis. In this study, the roles of PKC signal pathways in oridonin-induced HeLa cell autophagy and apoptosis were further investigated. We found that inhibition of PKC significantly reduced oridonin-induced autophagy whereas markedly increased apoptosis, while pretreatment with PKC activator caused opposite results. Subsequently, the oridonin-induced autophagy was also suppressed by Raf-1 or JNK inhibition accompanied by the increase of apoptosis, but it was not affected by ERK or p38 inhibition. In addition, oridonin-induced protein levels of Raf-1, JNK and p-JNK were sharply downregulated by PKC inhibitor, and they were enhanced by PKC activator. Taken together, these results demonstrate that PKC enhances oridonin-induced autophagy against apoptosis through regulating its downstream factors Raf-1 and JNK in HeLa cells.

Fas-mediated autophagy requires JNK activation in HeLa cells

Fas has been reported to play an important role in apoptosis; however, Fas-mediated autophagy and its mechanism are still unclear. Here, we found that Fas agonistic antibody CH11-induced autophagy in HeLa cells, and inhibition of autophagy by 3-MA increased CH11-induced apoptosis. A Fas antagonistic antibody (UB2) suppressed both CH11-induced autophagy and apoptosis. In addition, the CH11-induced autophagy was blocked by JNK inhibitor (SP600125), but it was not affected by caspase 8 inhibitor (Z-IETD); whereas the CH11-induced apoptosis was increased by SP600125, and it was suppressed by Z-IETD. Further experiments confirmed that JNK was activated by CH11 dose-dependently, and the activation was suppressed when autophagy was blocked by 3-MA. Together, our results suggest that JNK, but not caspase 8, involves in Fas-mediated CH11-induced autophagy in HeLa cells, and this autophagy plays a protective role in CH11-induced cell death.

Diet, autophagy, and cancer: a review

A host of dietary factors can influence various cellular processes and thereby potentially influence overall cancer risk and tumor behavior. In many cases, these factors suppress cancer by stimulating programmed cell death. However, death not only can follow the well-characterized type I apoptotic pathway but also can proceed by nonapoptotic modes such as type II (macroautophagy-related) and type III (necrosis) or combinations thereof. In contrast to apoptosis, the induction of macroautophagy may contribute to either the survival or death of cells in response to a stressor. This review highlights current knowledge and gaps in our understanding of the interactions among bioactive food constituents, autophagy, and cancer. Whereas a variety of food components including vitamin D, selenium, curcumin, resveratrol, and genistein have been shown to stimulate autophagy vacuolization, it is often difficult to determine if this is a protumorigenic or antitumorigenic response. Additional studies are needed to examine dose and duration of exposures and tissue specificity in response to bioactive food components in transgenic and knockout models to resolve the physiologic implications of early changes in the autophagy process.