Honokiol causes the p21WAF1-mediated G(1)-phase arrest of the cell cycle through inducing p38 mitogen activated protein kinase in vascular smooth muscle cells

Honokiol and its analogues as anticancer compounds: Current mechanistic insights and structure-activity relationship

Lignans are plant-derived polyphenolic compounds with a plethora of biological applications. Also, regarded as phytoestrogens, the lignans offer a variety of health benefits of which the anti-cancer effects are the most attractive. Honokiol is a lignan isolated from various parts of trees belonging to the genus Magnolia. The bioactivity of honokiol is attributed to its characteristic physical properties, which include small size and the presence of two phenolic groups that may interact with proteins in cell membranes via hydrophobic interactions, aromatic pi orbital co-valency, and hydrogen bonding. The hydrophobicity of honokiol enables its rapid dissolution in lipids and the crossing of physiological barriers, including the blood-brain barrier and cerebrospinal fluid. These factors contribute towards the high bioavailability of honokiol which further support its candidature in medicinal research. Therefore, the anticancer properties of honokiol are of particular interest as many of the contemporary anticancer drugs suffer from bioavailability drawbacks, which necessitates the identification and development of novel candidate molecules directed as anticancer chemotherapeutics. The antioncogenic profile of honokiol also arises from the regulation of various signalling pathways associated with oncogenesis, arresting of the cell cycle by regulation of cyclic proteins, upregulation of epithelial markers and downregulation of mesenchymal markers leading to the inhibition of epithelial-mesenchymal transition, and preventing the metastasis by restricting cell migration and invasion due to the downregulation of matrix-metalloproteinases. In this review, we discuss the anticancer properties of honokiol.

Clinical Potential of Fruit in Bladder Cancer Prevention and Treatment

Bladder cancer (BC) is the most common tumor of the urinary system in the world. Moreover, despite using anticancer therapies, BC is also characterized by a high recurrence risk. Among numerous risk factors, cigarette smoking, occupational exposure to certain aromatic compounds, and genetic factors contribute most strongly to BC development. However, the epidemiological data to date suggests that diet quality may influence some carcinogenic factors of BC and, therefore, might have a preventative effect. Adequate consumption of selected fruits with scientifically proven properties, including pomegranates and cranberries, can significantly reduce the risk of developing BC, even in those at risk. Therefore, in this article, we aim to elucidate, using available literature, the role of fruits, including pomegranates, cranberries, citrus fruits, cactus pears, and apples, in BC prevention and treatment. Previous data indicate the role of compounds in the above-mentioned fruits in the modulation of the signaling pathways, including cell proliferation, cell growth, cell survival, and cell death.

Anti-Atherosclerotic Effect of Gossypetin on Abnormal Vascular Smooth Muscle Cell Proliferation and Migration

Gossypetin (GTIN), known as 3,5,7,8,3′,4′-hexahydroxyflavone, has been demonstrated to exert anti-atherosclerotic potential against apoptotic injury in oxidized low-density lipoprotein-incubated endothelial cells, and atherosclerotic lesions of cholesterol-fed rabbits. However, the effect and underlying mechanism of GTIN on abnormal vascular smooth muscle cells (VSMCs) proliferation and migration, a major event in the pathogenesis of atherosclerosis, is still unknown. In this study, non-cytotoxic doses of GTIN abolished the VSMCs A7r5 proliferation and cell-cycle S phase distribution. The GTIN-arrested G0/G1 phase might be performed by increasing the expressions of phosphorylated p53 and its downstream molecules that inhibit the activation of cyclin E/cyclin-dependent kinase (cdk)-2, blocking retinoblastoma protein (Rb) phosphorylation and the subsequent dissociation of Rb/transcription factor E2F1 complex. In addition, the results indicated that GTIN inhibited VSMCs wound-healing and migratory abilities through reducing matrix metalloproteinase (MMP)-9 activity and expression, as well as down-regulating protein kinase B (PKB)/nuclear factor-kappaB (NF-κB) signaling. GTIN also revealed potential in diminishing reactive oxygen species (ROS) generation. These findings suggested the inhibitory effects of GTIN on VSMCs dysfunction could likely lead to the containment of atherosclerosis and other cardiovascular illness.

Upregulated NTF4 in colorectal cancer promotes tumor development via regulating autophagy

Autophagy plays a key role in colorectal cancer (CRC) development and reduces the sensitivity of CRC cells to treatment. The present study reported a novel tumor‑suppressive role for autophagy, which was demonstrated to be regulated through the novel oncogene neurotrophin‑4 (NTF4). NTF4 was significantly overexpressed in tumor tissue compared with non‑tumor mucosa, and the upregulation of NTF4 in CRC was associated with poor overall survival and advanced TNM stage. The genetic knockdown of NTF4 using short hairpin RNA in CRC cells prevented epithelial‑to‑mesenchymal transition and activated autophagy; this was regulated through the interaction between autophagy‑associated gene 5 (Atg5) and the mitogen‑activated protein kinase pathway. In addition, the knockdown of NTF4 inhibited cell invasion, migration, proliferation and colony formation, and promoted cell cycle arrest. Treatment of the cells with the autophagy inhibitor chloroquine (CQ) rescued these functions and promoted cell invasion, migration, proliferation and colony formation. Finally, the knockdown of NTF4 inhibited the growth of subcutaneous xenografts in Balb/c‑nu mice. In conclusion, these findings suggested that NTF4 may be a diagnostic marker associated with the overall survival and progression of patients with CRC. NTF4 was found to promote tumorigenesis and CRC development through autophagy regulation.

Cardiovascular Modulating Effects of Magnolol and Honokiol, Two Polyphenolic Compounds from Traditional Chinese Medicine-Magnolia Officinalis

Honokiol and its isomer magnolol are poly-phenolic compounds isolated from the Magnolia officinalis that exert cardiovascular modulating effects via a variety of mechanisms. They are used as blood-quickening and stasis-dispelling agents in Traditional Chinese Medicine and confirmed to have therapeutic potential in atherosclerosis, thrombosis, hypertension, and cardiac hypertrophy. This comprehensive review summarizes the current data regarding the cardioprotective mechanisms of those compounds and identifies areas for further research.

Anti-Atherosclerotic Effect of Hibiscus Leaf Polyphenols against Tumor Necrosis Factor-alpha-Induced Abnormal Vascular Smooth Muscle Cell Migration and Proliferation

The proliferation and migration of vascular smooth muscle cells (VSMCs) are major events in the development of atherosclerosis following stimulation with proinflammatory cytokines, especially tumor necrosis factor-alpha (TNF-α). Plant-derived polyphenols have attracted considerable attention in the prevention of atherosclerosis. Hibiscus leaf has been showed to inhibit endothelial cell oxidative injury, low-density lipoprotein oxidation, and foam cell formation. In this study, we examined the anti-atherosclerotic effect of Hibiscus leaf polyphenols (HLPs) against abnormal VSMC migration and proliferation in vitro and in vivo. Firstly, VSMC A7r5 cells pretreated with TNF-α were demonstrated to trigger abnormal proliferation and affect matrix metalloproteinase (MMP) activities. Non-cytotoxic doses of HLPs abolished the TNF-α-induced MMP-9 expression and cell migration via inhibiting the protein kinase PKB (also known as Akt)/activator protein-1 (AP-1) pathway. On the other hand, HLP-mediated cell cycle G0/G1 arrest might be exerted by inducing the expressions of p53 and its downstream factors that, in turn, suppress cyclin E/cdk2 activity, preventing retinoblastoma (Rb) phosphorylation and the subsequent dissociation of Rb/E2F complex. HLPs also attenuated reactive oxygen species (ROS) production against TNF-α stimulation. In vivo, HLPs improved atherosclerotic lesions, and abnormal VSMC migration and proliferation. Our data present the first evidence of HLPs as an inhibitor of VSMC dysfunction, and provide a new mechanism for its anti-atherosclerotic activity.

High Glucose with Insulin Induces Cell Cycle Progression and Activation of Oncogenic Signaling of Bladder Epithelial Cells Cotreated with Metformin and Pioglitazone

Metformin and pioglitazone are two commonly prescribed oral hypoglycemic agents for diabetes. Recent evidence suggests that these drugs may contribute to bladder cancer. This study investigated molecular mechanism underlying effects of metformin and pioglitazone in bladder epithelial carcinogenesis in type 2 diabetes. The cells derived from human bladder epithelial cells (HBlEpCs) were treated with metformin or pioglitazone with high glucose and insulin. Cell viability and proliferation were evaluated using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and a bromodeoxyuridine incorporation assay, respectively, while cell cycle regulatory factors and oncogene expression were analyzed using western blotting. Metformin or pioglitazone suppressed cell viability concentration and time dependently, which was reversed by exposure to high glucose with or without insulin. Prolonged exposure to high glucose and insulin enhanced cyclin D, cyclin-dependent kinase 4 (Cdk4), and Cdk2 expression and suppressed cyclin-dependent kinase inhibitors p21 and p15/16 in HBlEpC cotreated with pioglitazone and metformin. Levels of tumor suppressor proteins p53 and cav-1 were downregulated while those of the oncogenic protein as c-Myc were upregulated under high glucose and insulin supplementation in HBlEpC cotreated with pioglitazone and metformin. Prolonged exposure to high glucose with or without insulin downregulated B cell lymphoma 2-associated X (Bax) and failed to enhance the expression of extracellular signal-regulated kinase (ERK) and p38 mitogen-activated protein kinase (p38MAPK) in drug-treated cells. These results suggest that hyperglycemic and insulinemic conditions promote cell cycle progression and oncogenic signaling in drug-treated bladder epithelial cells and uncontrolled hyperglycemia and hyperinsulinemia are probably greater cancer risk factors than diabetes drugs.

Local honokiol application inhibits intimal thickening in rabbits following carotid artery balloon injury

Honokiol is a natural bioactive product with anti-tumor, anti-inflammatory, anti-oxidative, anti-angiogenic and neuroprotective properties. The present study aimed to investigate the effects of honokiol treatment on intimal thickening following vascular balloon injury. The current study determined that perivascular honokiol application reduced intimal thickening in rabbits 14 days after carotid artery injury, it may inhibit vascular smooth muscle cell (VSMCs) proliferation and reduce collagen deposition in local arteries. The findings of the presents study also suggested that honikiol may increase the mRNA expression levels of matrix metalloproteinase‑1 (MMP‑1), MMP‑2 and MMP‑9 and decrease tissue inhibitor of metalloproteinase‑1 (TIMP‑1) mRNA expression in the rabbit arteries. Additionally, perivascular honokiol application inhibited intimal thickening, possibly via inhibition of the phosphorylation of SMAD family member 2/3.

Biological activity and toxicity of the Chinese herb Magnolia officinalis Rehder & E. Wilson (Houpo) and its constituents

Traditional Chinese herbal drugs have been used for thousands of years in Chinese pharmacopoeia. The bark of Magnolia officinalis Rehder & E. Wilson, known under the pinyin name "Houpo", has been traditionally used in Chinese and Japanese medicines for the treatment of anxiety, asthma, depression, gastrointestinal disorders, headache, and more. Moreover, Magnolia bark extract is a major constituent of currently marketed dietary supplements and cosmetic products. Much pharmacological activity has been reported for this herb and its major compounds, notably antioxidant, anti-inflammatory, antibiotic and antispasmodic effects. However, the mechanisms underlying this have not been elucidated and only a very few clinical trials have been published. In vitro and in vivo toxicity studies have also been published and indicate some intriguing features. The present review aims to summarize the literature on M. officinalis bark composition, utilisation, pharmacology, and safety.

Anti-atherosclerotic plants which modulate the phenotype of vascular smooth muscle cells

BACKGROUND

Cardiovascular disease (CVD) remains the leading cause of global death, with atherosclerosis being a major contributor to this mortality. Several mechanisms are implicated in the pathogenesis of this disease. A key element in the development and progression of atherosclerotic lesions is the phenotype of vascular smooth muscle cells. Under pathophysiologic conditions such as injury, these cells switch from a contractile to a synthetic phenotype that often possesses high proliferative and migratory capacities.

PURPOSE

Despite major advances made in the management and treatment of atherosclerosis, mortality associated with this disease remains high. This mandates that other approaches be sought. Herbal medicine, especially for the treatment of CVD, has been gaining more attention in recent years. This is in no small part due to the evidence-based values associated with the consumption of many plants as well as the relatively cheaper prices, easier access and conventional folk medicine "inherited" over generations. Sections: In this review, we provide a brief introduction about the pathogenesis of atherosclerosis then we highlight the role of vascular smooth muscle cells in this disease, especially when a phenotypic switch of these cells arises. We then thoroughly discuss the various plants that show potentially beneficial effects as anti-atherosclerotic, with prime attention given to herbs and plants that inhibit the phenotypic switch of vascular smooth muscle cells.

CONCLUSION

Accumulating evidence provides the justification for the use of botanicals in the treatment or prevention of atherosclerosis. However, further studies, especially clinical ones, are warranted to better define several pharmacological parameters of these herbs, such as toxicity, tolerability, and efficacy.

Preclinical effects of honokiol on treating glioblastoma multiforme via G1 phase arrest and cell apoptosis

BACKGROUND

Our previous study showed that honokiol, a bioactive polyphenol, can traverse the blood-brain barrier and kills neuroblastoma cells.

PURPOSE

In this study, we further evaluated the preclinical effects of honokiol on development of malignant glioma and the possible mechanisms.

METHODS

Effects of honokiol on viability, caspase activities, apoptosis, and cell cycle arrest in human glioma U87 MG or U373MG cells were assayed. As to the mechanisms, levels of inactive or phosphorylated (p) p53, p21, CDK6, CDK4, cyclin D1, and E2F1 were immunodetected. Pifithrin-α (PFN-α), a p53 inhibitor, was pretreated into the cells. Finally, our in vitro findings were confirmed using intracranial nude mice implanted with U87 MG cells.

RESULTS

Exposure of human U87 MG glioma cells to honokiol decreased the cell viability. In parallel, honokiol induced activations of caspase-8, -9, and -3, apoptosis, and G1 cell cycle arrest. Treatment of U87 MG cells with honokiol increased p53 phosphorylation and p21 levels. Honokiol provoked signal-transducing downregulation of CDK6, CDK4, cyclin D1, phosphorylated (p)RB, and E2F1. Pretreatment of U87 MG cells with PFN-α significantly reversed honokiol-induced p53 phosphorylation and p21 augmentation. Honokiol-induced alterations in levels of CDK6, CDK4, cyclin D1, p-RB, and E2F1 were attenuated by PFN-α. Furthermore, honokiol could induce apoptotic insults to human U373MG glioma cells. In our in vivo model, administration of honokiol prolonged the survival rate of nude mice implanted with U87 MG cells and induced caspase-3 activation and chronological changes in p53, p21, CDK6, CDK4, cyclin D1, p-RB, and E2F1.

CONCLUSIONS

Honokiol can repress human glioma growth by inducing apoptosis and cell cycle arrest in tumor cells though activating a p53/cyclin D1/CDK6/CDK4/E2F1-dependent pathway. Our results suggest the potential of honokiol in therapies for human malignant gliomas.

Naringin suppresses cell metastasis and the expression of matrix metalloproteinases (MMP-2 and MMP-9) via the inhibition of ERK-P38-JNK signaling pathway in human glioblastoma

Naringin (4',5,7-trihydroxyflavanone 7-rhamnoglucoside), a natural flavonoid, has pharmacological properties. In the present study, we investigated the anti-metastatic activity of naringin and its molecular mechanism(s) of action in human glioblastoma cells. Naringin exhibits inhibitory effects on the invasion and adhesion of U87 cells in a concentration-dependent manner by Matrigel Transwell and cell adhesion assays. Naringin also inhibited the migration of U87 cells in a concentration-dependent manner by wound-healing assay. Additional experiments showed that naringin treatment reduced the enzymatic activities and protein levels of matrix metalloproteinase (MMP)-2 and MMP-9 using a gelatin zymography assay and western blot analyses. Furthermore, naringin was able to reduce the protein phosphorylation of extracellular signal-regulated kinase ERK, p38 mitogen-activated protein kinase and c-Jun N-terminal kinase by western blotting. Collectively, our data showed that naringin attenuated the MAPK signaling pathways including ERK, JNK and p38 and resulted in the downregulation of the expression and enzymatic activities of MMP-2, MMP-9, contributing to the inhibition of metastasis in U87 cells. These findings proved that naringin may offer further application as an antimetastatic agent.

The antioxidant paradox: what are antioxidants and how should they be used in a therapeutic context for cancer

So-called antioxidants have yet to make a clinical impact on the treatment of human cancer. The reasons for this failure are several. First, many agents that are called antioxidants are truly antioxidants at a given dose, but this dose may not have been given in clinical trials. Second, many agents are not antioxidants at all. Third, not all tumors use reactive oxygen as a signaling mechanism. Finally, reactive oxygen inhibition is often insufficient to kill or regress a tumor cell by itself, but requires sequential introduction of a therapeutic agent for maximal effect. We hope to provide a framework for the logical use of these agents in cancer.

Honokiol ameliorates endothelial dysfunction through suppression of PTX3 expression, a key mediator of IKK/IκB/NF-κB, in atherosclerotic cell model

Pentraxin 3 (PTX3) was identified as a marker of the inflammatory response and overexpressed in various tissues and cells related to cardiovascular disease. Honokiol, an active component isolated from the Chinese medicinal herb Magnolia officinalis, was shown to have a variety of pharmacological activities. In the present study, we aimed to investigate the effects of honokiol on palmitic acid (PA)-induced dysfunction of human umbilical vein endothelial cells (HUVECs) and to elucidate potential regulatory mechanisms in this atherosclerotic cell model. Our results showed that PA significantly accelerated the expression of PTX3 in HUVECs through the IκB kinase (IKK)/IκB/nuclear factor-κB (NF-κB) pathway, reduced cell viability, induced cell apoptosis and triggered the inflammatory response. Knockdown of PTX3 supported cell growth and prevented apoptosis by blocking PA-inducted nitric oxide (NO) overproduction. Honokiol significantly suppressed the overexpression of PTX3 in PA-inducted HUVECs by inhibiting IκB phosphorylation and the expression of two NF-κB subunits (p50 and p65) in the IKK/IκB/NF-κB signaling pathway. Furthermore, honokiol reduced endothelial cell injury and apoptosis by regulating the expression of inducible NO synthase and endothelial NO synthase, as well as the generation of NO. Honokiol showed an anti-inflammatory effect in PA-inducted HUVECs by significantly inhibiting the generation of interleukin-6 (IL-6), IL-8 and monocyte chemoattractant protein-1. In summary, honokiol repaired endothelial dysfunction by suppressing PTX3 overexpression in an atherosclerotic cell model. PTX3 may be a potential therapeutic target for atherosclerosis.

Honokiol inhibits tumor necrosis factor-α-stimulated rat aortic smooth muscle cell proliferation via caspase- and mitochondrial-dependent apoptosis

This study aims to investigate the effects of honokiol on proliferation, cell cycle, and apoptosis in tumor necrosis factor (TNF)-α-induced rat aortic smooth muscle cells (RASMCs). We found that honokiol treatment showed potent inhibitory effects on TNF-α-induced RASMC proliferation, which were associated with G0/G1 cell cycle arrest and downregulation of cell cycle-related proteins, including cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2 and CDK4. Furthermore, honokiol treatment led to the release of cytochrome c into cytosol and a loss of mitochondrial membrane potential (ΔΨm), as well as a decrease in the expression of Bcl-2 and an increase in the expression of Bax. Treatment with honokiol also reduced TNF-α-induced phosphorylation of p38, extracellular signal-regulated kinase 1/2, and c-Jun N-terminal kinase. Taken together, our results suggest that honokiol suppresses TNF-α-stimulated RASMC proliferation via caspase- and mitochondria-dependent apoptosis and highlight the therapeutic potential of honokiol in the prevention of cardiovascular diseases.

Honokiol, a constituent of Magnolia species, inhibits adrenergic contraction of human prostate strips and induces stromal cell death

Purpose

Smooth muscle contraction and prostate growth are important targets for medical therapy of lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia. Honokiol and Magnolol are lignan constituents of Magnolia species, which are used in traditional Asian medicine. Here, we examined effects of honokiol and magnolol on contraction of human prostate tissue and on growth of stromal cells.

Methods

Prostate tissues were obtained from radical prostatectomy. Contraction of prostate strips was examined in organ bath studies. Effects in stromal cells were assessed in cultured immortalized human prostate stromal cells (WPMY-1). Ki-67 mRNA was assessed by reverse transcription-polymerase chain reaction, and proliferation by a fluorescence 5-ethynyl-2′-deoxyuridine assay.

Results

Honokiol (100μM) reduced noradrenaline-induced contractions, which was significant at 10 to 100μM noradrenaline. Honokiol reduced phenylephrine-induced contractions, which was significant at 3 to 100μM phenylephrine. Honokiol reduced electric field stimulation-induced contractions very slightly. In WPMY-1 cells, honokiol (24 hours) induced cell death. Magnolol (100μM) was without effects on contraction, and cellular viability.

Conclusions

Honokiol inhibits smooth muscle contraction in the human prostate, and induces cell death in cultured stromal cells. Because prostate smooth muscle tone and prostate growth may cause LUTS, it appears possible that honokiol improves voiding symptoms.

Honokiol suppresses TNF-α-induced migration and matrix metalloproteinase expression by blocking NF-κB activation via the ERK signaling pathway in rat aortic smooth muscle cells

Honokiol, a small-molecule polyphenol derived and isolated from the Chinese medicinal herb Magnolia officinalis, has been shown to possess a wide range of pharmacological activities. In the present study, we aimed to investigate the effects of honokiol on tumor necrosis factor-α (TNF-α)-induced migration in rat aortic smooth muscle cells (RASMCs). We found that honokiol inhibited TNF-α-induced RASMC proliferation and migration in a dose-dependent manner. At the molecular level, pretreatment with honokiol blocked TNF-α-induced protein expression of matrix metalloproteinase (MMP)-2 and MMP-9, nuclear factor (NF)-κB activation, and extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation. Moreover, NF-κB inhibitor (BAY 11-7028) and ERK inhibitor (U0126) also mimicked the inhibitory effects of honokiol in TNF-α-treated RASMCs. In conclusion, these results indicate that honokiol suppresses TNF-α-induced migration and MMP expression by blocking NF-κB activation via the ERK signaling pathway in RASMCs. Our findings support honokiol as a promising novel agent for the prevention and treatment of atherosclerosis.

Sequential treatment of HPV E6 and E7-expressing TC-1 cells with bortezomib and celecoxib promotes apoptosis through p-p38 MAPK-mediated downregulation of cyclin D1 and CDK2

Interruption of the cell cycle is accompanied by changes in several related molecules that result in the activation of apoptosis. The present study was performed to verify the apoptotic effects of sequential treatment with bortezomib and celecoxib in TC-1 cells expressing the human papillomavirus (HPV) E6 and E7 proteins. In TC-1 cells sequentially treated with bortezomib and celecoxib, apoptosis was induced through decreased expression of signal transducer and activator of transcription-3 (STAT3), cyclin D1 and cyclin-dependent kinase (CDK) 2, which are major regulators of the G0/G1 cell cycle checkpoint. In addition, increased levels of p21, CHOP, BiP and p-p38 MAPK were identified in these cells. The treatment-induced apoptosis was effectively inhibited by treatment with SB203580, an inhibitor of p-p38. Moreover, the growth of tumors sequentially treated with bortezomib and celecoxib was retarded compared to the growth of tumors exposed to a single treatment with either bortezomib or celecoxib in vivo. We demonstrated that sequential treatment with bortezomib and celecoxib induced apoptosis via p-p38-mediated G0/G1 cell cycle arrest and endoplasmic reticulum (ER) stress. Sequential treatment with these two drugs could therefore be a useful therapy for cervical cancer.

O-desmethylangolensin inhibits the proliferation of human breast cancer MCF-7 cells by inducing apoptosis and promoting cell cycle arrest

The aim of the present study was to investigate the anticancer effect of O-desmethylangolensin (O-DMA) by assessing cell proliferation, apoptosis and cell cycle distribution, as well as exploring the mechanisms underlying these effects in breast carcinoma MCF-7 cells. The cells were exposed to O-DMA (5–200 μM) for 24, 48 and 72 h. The results revealed that cell proliferation was significantly inhibited in a dose-dependent manner following treatment for 48 and 72 h, but not after 24 h, and resulted in the significant induction of apoptosis and the promotion of cell cycle arrest at the G₁/S and G₂/M phases. To elucidate these effects of O-DMA, the expression levels of cell cycle regulators were measured in the cells exposed to O-DMA at 150 μM for 72 h. Of the G₁/S phase-related proteins, O-DMA modulated the cyclin-dependent kinases (CDKs), with a decrease in CDK2 and CDK4 and an increase in CDK6, and downregulated cyclin D and E. With respect to the G₂/M-related proteins, O-DMA caused a reduction in CDK1, together with a slight increase in cyclin A and B. In addition, O-DMA downregulated p21^Cip1 and p27^Kip1, but not p16^INK4a and p15^INK4b, and interacted with the CDK6-cyclin D and CDK1-cyclin B complexes. In conclusion, these results indicate for the first time that the regulation of the CDK4/6-cyclin D and CDK1-cyclin B complexes may participate in the anticancer activity pathway of O-DMA in MCF-7 cells.

Gene silencing of claudin‑6 enhances cell proliferation and migration accompanied with increased MMP‑2 activity via p38 MAPK signaling pathway in human breast epithelium cell line HBL‑100

Disruption or loss of tight junction structure and function is associated with tumor growth, invasion and metastasis in tumors of human epithelial origin. Since claudin is the most important backbone protein of tight junctions, the downregulation or loss of claudin expression is hypothesized to be important for tumor development and metastasis. In the current study, RNA interference (RNAi) was used to knock down the expression of claudin‑6 to investigate the effect of claudin‑6 downregulation on the malignant phenotype in the human breast epithelium cell line HBL‑100. The junctional function was investigated by measuring the transepithelial electrical resistance across the confluent epithelial cell layer. Manual cell counting and wound healing assays were performed to examine cell proliferation and migration. Changes in matrix metalloproteinase‑2 (MMP‑2) expression and activity were examined by reverse transcription polymerase chain reaction (RT‑PCR) and gelatin zymography. The expression of p38 mitogen‑activated protein kinases (MAPKs) and phosphorylated p38 MAPK were measured by western blot analysis. Claudin‑6 knockdown resulted in significantly lower transepithelial electrical resistance (P<0.001), higher growth rate (P<0.001) and migratory ability (P<0.001) accompanied with an increased MMP‑2 expression and activity (P<0.001). Furthermore, a decreased expression of phosphorylated p38 MAPK (P<0.001) was detected in HBL‑100 cells. These observations support the hypothesis that a decreased expression of claudin‑6 contributes to the malignant progression of human breast cancer.

Modulating testosterone pathway: a new strategy to tackle male skin aging?

In men, the level of testosterone decreases with age. At the skin level, the result is observed as a decrease in density and in a lower elasticity. Identifying compounds that are able to increase the level of testosterone appears to be an attractive strategy to develop new antiaging bioactive ingredients for men. Reverse pharmacognosy was successfully applied to identify new natural compounds able to modulate testosterone levels. Among several in silico hits, honokiol was retained as a candidate as it has the greatest potential to become an active ingredient. This result was then validated in vitro on aromatase and 5-alpha-reductase type 1 and 2, which are two types of enzymes implicated in the degradation of free testosterone. Indeed, honokiol was identified as an inhibitor of aromatase, with a half-maximal inhibitory concentration (IC(50)) of about 50 μM. In addition, honokiol was shown to be an inhibitor of 5-alpha-reductase type 1, with an IC(50) of about 75 μM. Taken together, these data indicate that honokiol modulates testosterone levels, and its structure has the potential to serve as a lead for future designs of highly selective inhibitors of 5-alpha-reductase type 1.

In vitro growth inhibition of human cancer cells by novel honokiol analogs

Honokiol possesses many pharmacological activities including anti-cancer properties. Here in, we designed and synthesized honokiol analogs that block major honokiol metabolic pathway which may enhance their effectiveness. We studied their cytotoxicity in human cancer cells and evaluated possible mechanism of cell cycle arrest. Two analogs, namely 2 and 4, showed much higher growth inhibitory activity in A549 human lung cancer cells and significant increase of cell population in the G0-G1 phase. Further elucidation of the inhibition mechanism on cell cycle showed that analogs 2 and 4 inhibit both CDK1 and cyclin B1 protien levels in A549 cells.

Curcumin enhanced antiproliferative effect of mitomycin C in human breast cancer MCF-7 cells in vitro and in vivo

AIM

To investigate the efficacy of mitomycin C (MMC) in combination with curcumin in suppressing human breast cancer in vitro and in vivo.

METHODS

Human breast cancer MCF-7 cells were used. Cell viability was measured using MTT assay. The cell cycle phase was detected with flow cytometric analysis. Cell cycle-associated proteins were examined using Western blot analysis. MCF-7 breast cancer xenografts were established to monitor tumor growth and cell cycle-associated protein expression.

RESULTS

Curcumin inhibited MCF-7 breast cancer cell viability in a concentration-dependent manner (IC(50) value=40 μmol/L). Similarly, MMC inhibited the cell viability with an IC(50) value of 5 μmol/L. Combined treatment of MMC and curcumin showed a synergistic antiproliferative effect. In the presence of curcumin (40 μmol/L), the IC(50) value of MMC was reduced to 5 μmol/L. In MCF-7 xenografts, combined administration of curcumin (100 mg/kg) and MMC (1-2 mg/kg) for 4 weeks produced significantly greater inhibition on tumor growth than either treatment alone. The combined treatment resulted in significantly greater G(1) arrest than MMC or curcumin alone. Moreover, the cell cycle arrest was associated with inhibition of cyclin D1, cyclin E, cyclin A, cyclin-dependent kinase 2 (CDK2) and CDK4, along with the induction of the cell cycle inhibitor p21 and p27 both in MCF-7 cells and in MCF-7 xenografts. These proteins were regulated through p38 MAPK pathway.

CONCLUSION

The results suggest that the combination of MMC and curcumin inhibits MCF-7 cell proliferation and cell cycle progression in vitro and in vivo via the p38 MAPK pathway.

G1 arrest and caspase-mediated apoptosis in HL-60 cells by dichloromethane extract of Centrosema pubescens

Cell division and apoptosis are two crucial components of tumor biology and the importance of increased cell proliferation and reduced cell death have made them valid therapeutic targets. The plant kingdom is a relatively underexploited cache of novel drugs, and crude extracts of plants are known for their synergistic activity. The present study assessed the anti-proliferative activity of the medicinal plant Centrosema pubescens Benth. Centrosema pubescens dichloromethane extract (CPDE) inhibited the proliferation of HL-60 (promyelocytic acute leukaemia) cells with an IC₅₀ value of 5 μg/ml. Further studies also showed that CPDE induces growth arrest at the G1 phase and specifically down-regulates the expressions of cyclin E and CDK2 and up-regulates p27(CKI) levels. These events apparently lead to the induction of apoptosis, which was demonstrated qualitatively by a DNA fragmentation assay and propidium iodide staining. Quantitative assessment of the effective arrest of the cell cycle and of apoptosis was confirmed by flow cytometry. CPDE exhibited negligible cytotoxicity even at the highest dose tested (100 μg/ml) in both normal peripheral blood mononuclear cells and in an in vitro model (HL-60). Our results strongly suggest that CPDE arrests the cell cycle at the G1 phase and triggers apoptosis by caspase activation.

p38 MAPK-Mediated Bmi-1 down-regulation and defective proliferation in ATM-deficient neural stem cells can be restored by Akt activation

A-T (ataxia telangiectasia) is a genetic disease caused by a mutation in the Atm (A-T mutated) gene that leads to neurodegeneration. Despite an increase in the numbers of studies in this area in recent years, the mechanisms underlying neurodegeneration in human A-T are still poorly understood. Previous studies demonstrated that neural stem cells (NSCs) isolated from the subventricular zone (SVZ) of Atm(-/-) mouse brains show defective self-renewal and proliferation, which is accompanied by activation of chronic p38 mitogen-activated protein kinase (MAPK) and a lower level of the polycomb protein Bmi-1. However, the mechanism underlying Bmi-1 down-regulation and its relevance to defective proliferation in Atm(-/-) NSCs remained unclear. Here, we show that over-expression of Bmi-1 increases self-renewal and proliferation of Atm(-/-) NSCs to normal, indicating that defective proliferation in Atm(-/-) NSCs is a consequence of down-regulation of Bmi-1. We also demonstrate that epidermal growth factor (EGF)-induced Akt phosphorylation renders Bmi-1 resistant to the proteasomal degradation, leading to its stabilization and accumulation in the nucleus. However, inhibition of the Akt-dependent Bmi-1 stabilizing process by p38 MAPK signaling reduces the levels of Bmi-1. Treatment of the Atm(-/-) NSCs with a specific p38 MAPK inhibitor SB203580 extended Bmi-1 posttranscriptional turnover and H2A ubiquitination in Atm(-/-) NSCs. Our observations demonstrate the molecular basis underlying the impairment of self-renewal and proliferation in Atm(-/-) NSCs through the p38 MAPK-Akt-Bmi-1-p21 signaling pathway.

Therapeutic applications of compounds in the Magnolia family

The bark and/or seed cones of the Magnolia tree have been used in traditional herbal medicines in Korea, China and Japan. Bioactive ingredients such as magnolol, honokiol, 4-O-methylhonokiol and obovatol have received great attention, judging by the large number of investigators who have studied their pharmacological effects for the treatment of various diseases. Recently, many investigators reported the anti-cancer, anti-stress, anti-anxiety, anti-depressant, anti-oxidant, anti-inflammatory and hepatoprotective effects as well as toxicities and pharmacokinetics data, however, the mechanisms underlying these pharmacological activities are not clear. The aim of this study was to review a variety of experimental and clinical reports and, describe the effectiveness, toxicities and pharmacokinetics, and possible mechanisms of Magnolia and/or its constituents.

Intracellular chloride regulates cell proliferation through the activation of stress-activated protein kinases in MKN28 human gastric cancer cells

Recently, we reported that reduction of intracellular Cl(-) concentration ([Cl(-)](i)) inhibited proliferation of MKN28 gastric cancer cells by diminishing the transition rate from G(1) to S cell-cycle phase through upregulation of p21, cyclin-dependent kinase inhibitor, in a p53-independent manner. However, it is still unknown how intracellular Cl(-) regulates p21 expression level. In this study, we demonstrate that mitogen-activated protein kinases (MAPKs) are involved in the p21 upregulation and cell-cycle arrest induced by reduction of [Cl(-)](i). Culture of MKN28 cells in a low Cl(-) medium significantly induced phosphorylation (activation) of MAPKs (ERK, p38, and JNK) and G(1)/S cell-cycle arrest. To clarify the involvement of MAPKs in p21 upregulation and cell growth inhibition in the low Cl(-) medium, we studied effects of specific MAPKs inhibitors on p21 upregulation and G(1)/S cell-cycle arrest in MKN28 cells. Treatment with an inhibitor of p38 or JNK significantly suppressed p21 upregulation caused by culture in a low Cl(-) medium and rescued MKN28 cells from the low Cl(-)-induced G(1) cell-cycle arrest, whereas treatment with an ERK inhibitor had no significant effect on p21 expression or the growth of MKN28 cells in the low Cl(-) medium. These results strongly suggest that the intracellular Cl(-) affects the cell proliferation via activation of p38 and/or JNK cascades through upregulation of the cyclin-dependent kinase inhibitor (p21) in a p53-independent manner in MKN28 cells.

Molecular determinants of the antitumor effects of trichostatin A in pancreatic cancer cells

AIM: To gain molecular insights into the action of the histone deacetylase inhibitor (HDACI) trichostatin-A (TSA) in pancreatic cancer (PC) cells.

METHODS: Three PC cell lines, BxPC-3, AsPC-1 and CAPAN-1, were treated with various concentrations of TSA for defined periods of time. DNA synthesis was assessed by measuring the incorporation of 5-bromo-2’-deoxyuridine. Gene expression at the level of mRNA was quantified by real-time polymerase chain reaction. Expression and phosphorylation of proteins was monitored by immunoblotting, applying an infrared imaging technology. To study the role of p38 MAP kinase, the specific enzyme inhibitor SB202190 and an inactive control substance, SB202474, were employed.

RESULTS: TSA most efficiently inhibited BrdU incorporation in BxPC-3 cells, while CAPAN-1 cells displayed the lowest and AsPC-1 cells an intermediate sensitivity. The biological response of the cell lines correlated with the increase of histone H3 acetylation after TSA application. In BxPC-3 cells (which are wild-type for KRAS), TSA strongly inhibited phosphorylation of ERK 1/2 and AKT. In contrast, activities of ERK and AKT in AsPC-1 and CAPAN-1 cells (both expressing oncogenic KRAS) were not or were only modestly affected by TSA treatment. In all three cell lines, but most pronounced in BxPC-3 cells, TSA exposure induced an activation of the MAP kinase p38. Inhibition of p38 by SB202190 slightly but significantly diminished the antiproliferative effect of TSA in BxPC-3 cells. Interestingly, only BxPC-3 cells responded to TSA treatment by a significant increase of the mRNA levels of bax, a pro-apoptotic member of the BCL gene family. Finally, in BxPC-3 and AsPC-1 cells, but not in the cell line CAPAN-1, significantly higher levels of the cell cycle inhibitor protein p21^Waf1 were observed after TSA application.

CONCLUSION: The biological effect of TSA in PC cells correlates with the increase of acetyl-H3, p21^Waf1, phospho-p38 and bax levels, and the decrease of phospho-ERK 1/2 and phospho-AKT.

Carbon monoxide releasing molecule-2 inhibits pancreatic stellate cell proliferation by activating p38 mitogen-activated protein kinase/heme oxygenase-1 signaling

Proliferation of pancreatic stellate cells (PSCs) plays a cardinal role during fibrosis development. Therefore, the suppression of PSC growth represents a therapeutic option for the treatment of pancreatic fibrosis. It has been shown that up-regulation of the enzyme heme oxygenase-1 (HO-1) could exert antiproliferative effects on PSCs, but no information is available on the possible role of carbon monoxide (CO), a catalytic byproduct of the HO metabolism, in this process. In the present study, we have examined the effect of CO releasing molecule-2 (CORM-2) liberated CO on PSC proliferation and have elucidated the mechanisms involved. Using primary rat PSCs, we found that CORM-2 inhibited PSC proliferation at nontoxic concentrations by arresting cells at the G(0)/G(1) phase of the cell cycle. This effect was associated with activation of p38 mitogen-activated protein kinase (MAPK) signaling, induction of HO-1 protein, and up-regulation of the cell cycle inhibitor p21(Waf1/Cip1). The p38 MAPK inhibitor 4-(4-flurophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)imidazole (SB203580) abolished the inhibitory effect of CORM-2 on PSC proliferation and prevented both CORM-2-induced HO-1 and p21(Waf1/Cip1) up-regulation. Treatment with tin protoporphyrin IX, an HO inhibitor, or transfection of HO-1 small interfering RNA abolished the inductive effect of CORM-2 on p21(Waf1/Cip1) and reversed the suppressive effect of CORM-2 on PSC growth. The ability of CORM-2 to induce cell cycle arrest was abrogated in p21(Waf1/Cip1)-silenced cells. Taken together, our results suggest that CORM-2 inhibits PSC proliferation by activation of the p38/HO-1 pathway. These findings may indicate a therapeutic potential of CO carriers in the treatment of pancreatic fibrosis.

Anti-inflammatory bioactivities of honokiol through inhibition of protein kinase C, mitogen-activated protein kinase, and the NF-kappaB pathway to reduce LPS-induced TNFalpha and NO expression

Much recent research has demonstrated that honokiol, a phenolic compound originally isolated from Magnolia officinalis, has potent anticancer activities; however, the detailed molecular mechanism of its anti-inflammatory activity has not yet been fully addressed. In this study we demonstrated that honokiol inhibited lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha secretion in macrophages, without affecting the activity of the tumor necrosis factor-alpha converting enzyme. At the same time, honokiol not only inhibited nitric oxide expression in LPS-stimulated murine macrophages but also inhibited the LPS-induced phosphorylation of ERK1/2, JNK1/2, and p38. By means of confocal microscope analysis we demonstrated that phosphorylation and membrane translocation of protein kinase C-alpha, as well as NF-kappaB activation, were inhibited by honokiol in LPS-stimulated macrophages. Furthermore, it was found that honokiol neither antagonizes the binding of LPS to cells nor alters the cell surface expression of toll-like receptor 4 and CD14. Our current results have exhaustively described the anti-inflammatory properties of honokiol, which could lead to the possibility of its future pharmaceutical application in the realm of immunomodulation.

Inhibition of epidermal growth factor receptor signaling by Saussurea involucrata, a rare traditional Chinese medicinal herb, in human hormone-resistant prostate cancer PC-3 cells

Prostate carcinoma is the most frequently diagnosed malignancy and the second leading cause of death of men in the United States. To date, no effective therapeutic treatment allows abrogation of the progression of prostate cancer to more invasive forms. In this study, we identified Saussurea involucrata Kar. et Kir., a rare traditional Chinese medicinal herb, as a potential agent for androgen-independent prostate cancer patients and investigated its biological mechanism as an antineoplastic agent. S. involucrata caused a concentration- and time-dependent inhibition of cell proliferation in human hormone-resistant prostate cancer PC-3 cells. Moreover, in vitro studies in a panel of several types of human cancer cell lines revealed that S. involucrata inhibited cell proliferation with high potency. To evaluate the bioactive compounds, we successively extracted the S. involucrata with fractions of methanol (SI-1), ethyl acetate (SI-2), n-butanol (SI-3), and water (SI-4). Among these extracts, SI-2 contains the most effective bioactivity. SI-2 treatment resulted in significant time-dependent growth inhibition together with G1 phase cell cycle arrest and apoptosis in PC3 cells. In addition, SI-2 treatment strongly induced p21WAF1/CIP and p27KIP1 expression, independent of the p53 pathway, and downregulated expression of cyclin D1 and cyclin-dependent kinase 4 (CDK4). SI-2 treatment increased levels of Bax, cytochrome c, activated caspase-3, and active caspase-9 and decreased Bcl-2 expression level. One of the major targets for the therapy in prostate cancer can be epidermal growth factor receptor (EGFR). SI-2 markedly reduced phosphorylation of EGFR and inhibited activation of AKT and STAT3. Moreover, p.o. administration of SI-2 induced a dose-dependent inhibition of PC-3 tumor growth in vivo. In summary, our study identifies S. involucrata as an effective inhibitor of EGFR signaling in human hormone-resistant prostate cancer PC-3 cells. We suggest that S. involucrata could be developed as an agent for the management of EGFR-positive human cancers.

Polyphenol-rich extract from mulberry leaf inhibits vascular smooth muscle cell proliferation involving upregulation of p53 and inhibition of cyclin-dependent kinase

This study was carried out to investigate the impact of polyphenol-rich extract from mulberry leaf on the proliferation of vascular smooth muscle cell (VSMC) and verify its mechanism in vitro. VSMC proliferation is an important pathophysiological process in the development of atherosclerosis, which is the major cause of coronary artery disease (CAD). Polyphenol-rich foods, such as mulberry leaf, have been reported to reduce the risk of CAD. The effect of mulberry leaf extract (MLE) on cell growth was measured by a growth curve assay, on distribution of cells in the cell cycle by flow cytometry, and on cyclin-dependent kinase (CDK) activity and cell-cycle regulatory proteins by Western blot, immunoblotting, and immunoprecipitation analyses. The results showed that MLE induced phosphorylation of p53, promoted expression of p21 and p27, decreased CDK2/4 activity, inhibited phosphorylation of Rb, and thereby blocked the G1 to S transition in the cell cycle.

Gold (III) porphyrin complexes induce apoptosis and cell cycle arrest and inhibit tumor growth in colon cancer

BACKGROUND

Gold (III) compounds have exhibited favorable antitumor properties both in vitro and in vivo. In a previous study, the authors reported that the novel gold (III) complex 1a (gold 1a) exhibited strong cytotoxicity in some tumor cell lines. In the current study, the effect of gold 1a was investigated on colon cancer cells.

METHODS

The cytotoxicity of gold 1a was determined by using the 3-(4,5-dimethyl-2-thihazyl)-2,5-diphenyl-2H-tetrazolium bromide method. Flow cytometry was used to detect apoptosis and cell cycle. The expression of protein was evaluated by Western blot assay. Tumor growth in vivo was evaluated in nude mice.

RESULTS

Gold 1a exhibited marked cytotoxic effects in vitro to human colon cancer, and the concentration of drug required to inhibit cell growth by 50% compared with control (IC(50)) values ranged from 0.2 muM to 3.4 muM, which represented 8.7-fold to 20.8-fold greater potency than that of cisplatin. Gold 1a significantly induced apoptosis and cell cycle arrest and cleaved caspase 3, caspase 7, and poly(ADP-ribose) polymerase; released cytochrome C, and up-regulated p53, p21, p27, and Bax. In vivo, intraperitoneal injection of gold 1a at doses of 1.5 mg/kg and 3.0 mg/kg significantly inhibited tumor cell proliferation, induced apoptosis, and suppressed colon cancer tumor growth. An acute toxicology study indicated that gold 1a at effective antitumor concentrations did not cause any toxic side effects in mice.

CONCLUSIONS

The current results suggested that gold 1a may be a new potential therapeutic drug for colon cancer.

Antigrowth properties of BAY 41-2272 in vascular smooth muscle cells

Vascular smooth muscle (VSM) growth is integral in the pathophysiology of blood vessel diseases, and identifying approaches that have capacity to regulate VSM growth is critically essential. Cyclic nucleotide signaling has been generally considered protective in cardiac and vascular tissues and has been the target of numerous basic science and clinical studies. In this project, the influence of BAY 41-2272 (BAY), a recently described soluble guanylate cyclase stimulator and inducer of cyclic guanosine monophosphate (cGMP) synthesis, on VSM cell growth was analyzed. In rat A7R5 VSM cells, BAY significantly reduced proliferation in a dose- and time-dependent fashion. BAY activated cGMP and cyclic adenosine monophosphate (cAMP) signaling evidenced through elevated cGMP and cAMP content, increased expression of cyclic nucleotide-dependent protein kinases, and differential vasodilator-stimulated phosphoprotein phosphorylation. BAY significantly elevated cyclin E expression, decreased expression of the regulatory cyclin-dependent kinases -2 and -6, increased expression of cell cycle inhibitory p21 WAF1/Cip1 and p27 Kip1, and reduced expression of phosphorylated focal adhesion kinase. These comprehensive findings provide first evidence for the antigrowth cell cycle-regulatory properties of the neoteric agent, BAY 41-2272, in VSM and lend support for its continued study in the clinical and basic cardiovascular sciences.

Leoligin, the major lignan from Edelweiss, inhibits intimal hyperplasia of venous bypass grafts

Aims

Despite the lower patency of venous compared with arterial coronary artery bypass grafts, ∼50% of grafts used are saphenous vein conduits because of their easier accessibility. In a search for ways to increase venous graft patency, we applied the results of a previous pharmacological study screening for non-toxic compounds that inhibit intimal hyperplasia of saphenous vein conduits in organ cultures. Here we analyse the effects and mechanism of action of leoligin [(2S,3R,4R)-4-(3,4-dimethoxybenzyl)-2-(3,4-dimethoxyphenyl)tetrahydrofuran-3-yl]methyl (2Z)-2-methylbut-2-enoat, the major lignan from Edelweiss (Leontopodium alpinum Cass.).

Methods and results

We found that leoligin potently inhibits vascular smooth muscle cell (SMC) proliferation by inducing cell cycle arrest in the G1-phase. Leoligin induced cell death neither in SMCs nor, more importantly, in endothelial cells. In a human saphenous vein organ culture model for graft disease, leoligin potently inhibited intimal hyperplasia, and even reversed graft disease in pre-damaged vessels. Furthermore, in an in vivo mouse model for venous bypass graft disease, leoligin potently inhibited intimal hyperplasia.

Conclusion

Our data suggest that leoligin might represent a novel non-toxic, non-thrombogenic, endothelial integrity preserving candidate drug for the treatment of vein graft disease.

Involvement of p38 mitogen-activated protein kinase pathway in honokiol-induced apoptosis in a human hepatoma cell line (hepG2)

BACKGROUND

Honokiol has been known to have antitumour activity. This study was conducted to evaluate the antiproliferative potential of honokiol against the hepG2 heptocellular cell line and its mechanism of action.

METHODS

hepG2 cells were treated with honokiol of 0-40 microg/ml concentration. The cytotoxic effect of honokiol was determined by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The apoptosis was evaluated by flow cytometry. Western blots were used to analyse the expression of various proteins (procaspase-9, procaspase-3, cleaved caspase-3, cytochrome c, Bcl-2, Bax, Bad, Bcl-X(L) and p38).

RESULTS

Honokiol induced apoptosis with a decreased expression of procaspase-3 and -9 and an increased expression of active caspase-3. Exposure of hepG2 cells to honokiol resulted in the downregulation of Bcl-X(L) and Bcl-2 expression and the release of mitochondrial cytochrome c to the cytosol. In addition, honokiol activated the p38 mitogen-activated protein kinase (MAPK) pathway, and the inhibition of this pathway by SB203580 reduced honokiol-induced apoptosis and activation of caspase-3.

CONCLUSION

Honokiol induces apoptosis of hepG2 human hepatocellular carcinoma cells through activation of the p38 MAPK pathway, and, in turn, activation of caspase-3.

Anti-tumor effect of beta-elemene in glioblastoma cells depends on p38 MAPK activation

beta-Elemene, a natural plant drug extracted from Curcuma wenyujin, has been used as an antitumor drug for different tumors, including glioblastoma. However, the mechanism of its anti-tumor effect is largely unknown. Here we report that anti-proliferation of glioblastoma cells induced by beta-elemene was dependent on p38 MAPK activation. Treatment of glioblastoma cell lines with beta-elemene, led to phosphorylation of p38 MAPK, cell-cycle arrest in G0/G1 phase and inhibition of proliferation of these cells. Inhibition of p38 MAPK reversed beta-elemene-mediated anti-proliferation effect. Furthermore, the growth of glioblastoma cell-transplanted tumors in nude mice was inhibited by intraperitoneal injection of beta-elemene. Taken together, our findings indicate that activation of p38 MAPK is critical for the anti-proliferation effect of beta-elemene and that p38 MAPK might be a putative pharmacological target for glioblastoma therapy.

Combination of PTEN and gamma-ionizing radiation enhances cell death and G(2)/M arrest through regulation of AKT activity and p21 induction in non-small-cell lung cancer cells

PURPOSE

To identify the role of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) during gamma-ionizing radiation (gamma-IR) treatment for non-small-cell lung cancer cells.

METHODS AND MATERIALS

Wild-type PTEN or mutant forms of PTEN plasmids were transfected to construct stable transfectants of the NCI-H1299 non-small-cell lung cancer cell line. Combined effects of PTEN expression and IR treatment were tested using immunoblot, clonogenic, and cell-counting assays. Related signaling pathways were studied with immunoblot and kinase assays.

RESULTS

At steady state, stable transfectants showed almost the same proliferation rate but had different AKT phosphorylation patterns. When treated with gamma-IR, wild-type PTEN transfectants showed higher levels of cell death compared with mock vector or mutant transfectants, and showed increased G(2)/M cell-cycle arrest accompanied by p21 induction and CDK1 inactivation. NCI-H1299 cells were treated with phosphosinositide-3 kinase (PI3K)/AKT pathway inhibitor (LY29002), resulting in reduced AKT phosphorylation levels. Treatment of NCI-H1299 cells with LY29002 and gamma-IR resulted in increased cell-cycle arrest and p21 induction. Endogenous wild-type PTEN-containing NCI-H460 cells were treated with PTEN-specific siRNA and then irradiated with gamma-IR: however reduced PTEN levels did not induce cell-cycle arrest or p21 expression.

CONCLUSIONS

Taken together, these findings indicate that PTEN may modulate cell death or the cell cycle via AKT inactivation by PTEN and gamma-IR treatment. We also propose that a PTEN-PI3K/AKT-p21-CDK1 pathway could regulate cell death and the cell cycle by gamma-IR treatment.

Honokiol, a natural therapeutic candidate, induces apoptosis and inhibits angiogenesis of ovarian tumor cells

OBJECTIVES

To observe the anti-tumor activities of honokiol on human ovarian tumor in vitro and in vivo.

STUDY DESIGN

Cells were treated with honokiol, and the effects on proliferation and apoptosis were examined by MTT, DNA ladder, Hoechst staining, and flow cytometry assays. Expression of Bcl-2 members and caspase-3 were assessed. Measurements of tumor volume and microvessel densities (MVDs) were performed.

RESULTS

Honokiol significantly inhibited proliferation and induced apoptosis, with alteration of Bcl-2 members and caspase-3. Administration of honokiol to tumor-bearing animals decreased MVD and resulted in inhibition of tumor growth.

CONCLUSIONS

Honokiol could induce apoptosis and inhibit angiogenesis in vitro and in vivo, suggesting a novel and attractive therapeutic candidate for ovarian tumor treatment.

c-Jun NH2-terminal kinase activating kinase 1/mitogen-activated protein kinase kinase 4-mediated inhibition of SKOV3ip.1 ovarian cancer metastasis involves growth arrest and p21 up-regulation

In many patients without clinical metastases, cancer cells have already escaped from the primary tumor and entered a distant organ. A long-standing question in metastasis research is why some disseminated cancer cells fail to complete steps of metastatic colonization for extended periods of time. Our laboratory identified c-Jun NH(2)-terminal kinase activating kinase 1/mitogen-activated protein kinase kinase 4 (JNKK1/MKK4) as a metastasis suppressor protein in a mouse xenograft model of experimental i.p. ovarian cancer metastasis. In this model, expression of JNKK1/MKK4 via activation of p38 delays formation of >or=1-mm implants and prolongs animal survival. Here, we elucidate the time course of this delay as well as the biological mechanisms underpinning it. Using the Gompertz function to model the net accumulation of experimental omental metastases, we show that MKK4-expressing implants arise, on average, 30 days later than controls. Quantitative real-time PCR shows that MKK4 expression does not have a substantial effect on the number of cancer cells initially adhering to the omentum, and terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling analysis shows that there is no increase in apoptosis in these cells. Instead, immunohistochemical quantitation of cell cycle proteins reveals that MKK4-expressing cells fail to proliferate once they reach the omentum and up-regulate p21, a cell cycle inhibitor. Consistent with the time course data, in vitro kinase assays and in vivo passaging of cell lines derived from macroscopic metastases show that the eventual outgrowth of MKK4-expressing cells is not due to a discrete selection event. Rather, the population of MKK4-expressing cells eventually uniformly adapts to the consequences of up-regulated MKK4 signaling.

Requirement for Ras/Raf/ERK pathway in naringin-induced G1-cell-cycle arrest via p21WAF1 expression

Naringin, an active flavonoid found in citrus fruit extracts, has pharmacological utility. The present study identified a novel mechanism of the anticancer effects of naringin in urinary bladder cancer cells. Naringin treatment resulted in significant dose-dependent growth inhibition together with G(1)-phase cell-cycle arrest at a dose of 100 microM (the half maximal inhibitory concentration) in 5637 cells. In addition, naringin treatment strongly induced p21WAF1 expression, independent of the p53 pathway, and downregulated expression of cyclins and cyclin dependent kinases (CDKs). Moreover, treatment with naringin induced phosphorylation of extracellular signal-regulated kinase (ERK), p38 mitogen-activated protein kinase and c-Jun N-terminal kinase. Among the pathways examined, only PD98059, an ERK-specific inhibitor, blocked naringin-dependent p21WAF1 expression. Consistently, blockade of ERK function reversed naringin-mediated inhibition of cell proliferation and decreased cell-cycle proteins. Furthermore, naringin treatment increased both Ras and Raf activation. Transfection of cells with dominant-negative Ras (RasN17) and Raf (RafS621A) mutant genes suppressed naringin-induced ERK activity and p21WAF1 expression. Finally, the naringin-induced reduction in cell proliferation and cell-cycle proteins also was abolished in the presence of RasN17 and RafS621A mutant genes. These data demonstrate that the Ras/Raf/ERK pathway participates in p21WAF1 induction, subsequently leading to a decrease in the levels of cyclin D1/CDK4 and cyclin E-CDK2 complexes and naringin-dependent inhibition of cell growth. Overall, these unexpected findings concerning the molecular mechanisms of naringin in 5637 cancer cells provide a theoretical basis for the therapeutic use of flavonoids to treat malignancies.

Anti-inflammatory effect of honokiol is mediated by PI3K/Akt pathway suppression

AIM

In this study, we investigated the regulatory effects of honokiol on various inflammatory events mediated by monocytes/macrophages (U937/RAW264.7 cells) and lymphocytes (splenic lymphocytes and CTLL-2 cells) and their putative action mechanism.

METHODS

In order to investigate the regulatory effects, various cell lines and primary cells (U937, RAW264.7, CTLL-2 cells, and splenic lymphocytes) were employed and various inflammatory events, such as the production of inflammatory mediators, cell adhesion, cell proliferation, and the early signaling cascade, were chosen.

RESULTS

Honokiol strongly inhibited various inflammatory responses, such as: (i) the upregulation of nitric oxide (NO), prostaglandin E2 and TNF-alpha production and costimulatory molecule CD80 induced by lipopolysaccharide (LPS); (ii) the functional activation of beta1-integrin (CD29) assessed by U937 cell-cell and cell-fibronectin adhesions; (iii) the enhancement of lymphocytes and CD8+CTLL-2 cell proliferation stimulated by LPS, phytohemaglutinin A (PHA), and concanavalin A or interleukin (IL)-2; and (iv) the transcriptional upregulation of inducible NO synthase, TNF-alpha, cyclooxygenase-2, IL-12, and monocyte chemoattractant protein (MCP)-1. These anti-inflammatory effects of honokiol seem to be mediated by interrupting the early activated intracellular signaling molecule phosphoinositide 3-kinase (PI3K)/Akt, but not Src, the extracellular signal-regulated kinase, and p38, according to pharmacological, biochemical, and functional analyses.

CONCLUSION

These results suggest that honokiol may act as a potent anti-inflammatory agent with multipotential activities due to an inhibitory effect on the PI3K/Akt pathway.

Paclitaxel enhanced radiation sensitization for the suppression of human prostate cancer tumor growth via a p53 independent pathway

BACKGROUND

This study investigated the influence of p53 status on treatment using combined paclitaxel and irradiation for human prostate cancer (PC) in vitro and in vivo.

METHODS

Enhancement of the radiation response by paclitaxel was determined by MTT and clonogenic assays in four sublines of the human PC cell line, LNCaP, stably transfected to express different p53 mutations found in PC patients. Suppression of xenograft growth by combined paclitaxel and radiation was assessed in NOD.SCID mice in vivo. Expression of p53 and downstream functional proteins, p21 and Bax, was assessed by Western blotting.

RESULTS

Paclitaxel (8-10 nM) suppressed cell proliferation by 50% by inducing G2M mitotic arrest in LNCaP cell lines transfected to overexpress wild-type or mutant p53. Exposure to 20 nM paclitaxel before radiation therapy enhanced cytotoxicity in clonogenic assays. The dose and duration of paclitaxel exposure were important in inducing both G2M arrest and cell growth suppression and were critical factors in paclitaxel/irradiation combination therapy. Western blotting indicated that combination therapy increased p21 protein expression to varying degrees in all cell lines. In vivo studies indicated that paclitaxel pre-treatment followed by irradiation significantly suppressed tumor growth compared with either treatment alone.

CONCLUSIONS

Pre-treatment with paclitaxel enhances radiation efficacy on cell killing and suppression of growth of human PC cell lines in vitro and in vivo via p53 independent pathways. Paclitaxel has potential for use as a radiosensitizer in the treatment of patients with PC with either wild-type or mutant p53 genetic status.