Trimeric and Tetrameric A-Type Procyanidins from Peanut Skins.

Peanut skins are a rich source of oligomeric and polymeric procyanidins. The oligomeric fractions are dominated by dimers, trimers, and tetramers. A multistep chromatographic fractionation led to the isolation of four new A-type procyanidins of tri- and tetrameric structures. The structures of the new trimers were defined by NMR, electronic circular dichroism, and MS data as epicatechin-(4ß→8,2ß→O→7)-epicatechin-(4ß→8,2ß→O→7)-catechin, peanut procyanidin B (3), and epicatechin-(4ß→8,2ß→O→7)-epicatechin-(4ß→6)-catechin, peanut procyanidin C (4). The new tetramers were defined as epicatechin-(4ß→8,2ß→O→7)-epicatechin-(4ß→6)-epicatechin-(4ß→8,2ß→O→7)-catechin, peanut procyanidin E (1), and epicatechin-(4ß→8,2ß→O→7)-epicatechin-(4ß→6)-epicatechin-(4ß→8,2ß→O→7)-epicatechin, peanut procyanidin F (2). In addition, both A-type dimers A1, epicatechin-(4ß→8,2ß→O→7)-catechin, and A2, epicatechin-(4ß→8,2ß→O→7)-epicatechin, as well as two known peanut trimers, ent-epicatechin-(4ß→6)-epicatechin-(4ß→8,2ß→O→7)-catechin, peanut procyanidin A (5), and epicatechin-(4ß→8)-epicatechin-(4ß→8,2ß→O→7)-catechin, peanut procyanidin D (6), were also isolated. Dimer A1, the four trimers, and two tetramers were evaluated for anti-inflammatory activity in an in vitro assay, in which LPS-stimulated macrophages were responding with secretion of TNF-α, a pro-inflammatory cytokine. Tetramer F (2) was the most potent, suppressing TNF-α secretion to 82% at 8.7 µM (10 µg/mL), while tetramer E (1) at the same concentrations caused a 4% suppression. The results of the TNF-α secretion inhibition indicate that small structural differences, as in peanut procyanidin tetramers E and F, can be strongly differentiated in biological systems.

BreastDefend enhances effect of tamoxifen in estrogen receptor-positive human breast cancer in vitro and in vivo.

BACKGROUND: Tamoxifen (TAM) has been widely used for the treatment of estrogen receptor (ER)-positive breast cancer and its combination with other therapies is being actively investigated as a way to increase efficacy and decrease side effects. Here, we evaluate the therapeutic potential of co-treatment with TAM and BreastDefend (BD), a dietary supplement formula, in ER-positive human breast cancer. METHODS: Cell proliferation and apoptosis were determined in ER-positive human breast cancer cells MCF-7 by MTT assay, quantitation of cytoplasmic histone-associated DNA fragments and expression of cleaved PARP, respectively. The molecular mechanism was identified using RNA microarray analysis and western blotting. Tumor tissues from xenograft mouse model were analyzed by immunohistochemistry. RESULTS: Our data clearly demonstrate that a combination of 4-hydroxytamoxifen (4-OHT) with BD lead to profound inhibition of cell proliferation and induction of apoptosis in MCF-7 cells. This effect is consistent with the regulation of apoptotic and TAM resistant genes at the transcription and translation levels. Importantly, TAM and BD co-treatment significantly enhanced apoptosis, suppressed tumor growth and reduced tumor weight in a xenograft model of human ER-positive breast cancer. CONCLUSION: BD sensitized ER-positive human breast cancer cells to 4-OHT/TAM treatment in vitro and in vivo. BreastDefend can be used in an adjuvant therapy to increase the therapeutic effect of tamoxifen in patients with ER-positive breast cancer.

Ganodermanontriol (GDNT) exerts its effect on growth and invasiveness of breast cancer cells through the down-regulation of CDC20 and uPA.

Ganoderma lucidum is a medicinal mushroom that has been recognized by Traditional Chinese Medicine (TCM). Although some of the direct anticancer activities are attributed to the presence of triterpenes-ganoderic and lucidenic acids-the activity of other compounds remains elusive. Here we show that ganodermanontriol (GDNT), a Ganoderma alcohol, specifically suppressed proliferation (anchorage-dependent growth) and colony formation (anchorage-independent growth) of highly invasive human breast cancer cells MDA-MB-231. GDNT suppressed expression of the cell cycle regulatory protein CDC20, which is over-expressed in precancerous and breast cancer cells compared to normal mammary epithelial cells. Moreover, we found that CDC20 is over-expressed in tumors when compared to the tissue surrounding the tumor in specimens from breast cancer patients. GDNT also inhibited invasive behavior (cell adhesion, cell migration, and cell invasion) through the suppression of secretion of urokinase-plasminogen activator (uPA) and inhibited expression of uPA receptor. In conclusion, mushroom GDNT is a natural agent that has potential as a therapy for invasive breast cancers.

Semisynthesis and biological evaluation of ganodermanontriol and its stereoisomeric triols.

The first synthesis of ganodermanontriol, a bioactive lanostane triterpene from the medicinal mushroom Ganoderma lucidum, has been achieved in 15.3% yield over nine steps, along with its three stereoisomeric triols and ganoderol A. The key steps leading to this family of isomers involve the reconstruction of the trisubstituted alkene by stereoselective and chemoselective phosphonate reactions and the formation of the unusual Δ7,9(11)-diene core by the mild acidic opening of a lanosterone-derived epoxide. Ganodermanontriol showed promising activity on the inhibition and proliferation of breast cancer cells. The effect of ganodermanontriol and its isomers on cell proliferation was assayed; IC50 values of 5.8 and 9.7 µM on breast cancer cell lines MCF-7 and MDA-MB-231, respectively, were found for ganodermanontriol.

Anti-inflammatory activity of edible oyster mushroom is mediated through the inhibition of NF-κB and AP-1 signaling.

BACKGROUND: Mushrooms are well recognized for their culinary properties as well as for their potency to enhance immune response. In the present study, we evaluated anti-inflammatory properties of an edible oyster mushroom (Pleurotus ostreatus) in vitro and in vivo. METHODS: RAW264.7 murine macrophage cell line and murine splenocytes were incubated with the oyster mushroom concentrate (OMC, 0-100 µg/ml) in the absence or presence of lipopolysacharide (LPS) or concanavalin A (ConA), respectively. Cell proliferation was determined by MTT assay. Expression of cytokines and proteins was measured by ELISA assay and Western blot analysis, respectively. DNA-binding activity was assayed by the gel-shift analysis. Inflammation in mice was induced by intraperitoneal injection of LPS. RESULTS: OMC suppressed LPS-induced secretion of tumor necrosis factor-α (TNF-α, interleukin-6 (IL-6), and IL-12p40 from RAW264.7 macrophages. OMC inhibited LPS-induced production of prostaglandin E2 (PGE2) and nitric oxide (NO) through the down-regulation of expression of COX-2 and iNOS, respectively. OMC also inhibited LPS-dependent DNA-binding activity of AP-1 and NF-κB in RAW264.7 cells. Oral administration of OMC markedly suppressed secretion of TNF-α and IL-6 in mice challenged with LPS in vivo. Anti-inflammatory activity of OMC was confirmed by the inhibition of proliferation and secretion of interferon-γ (IFN-γ), IL-2, and IL-6 from concanavalin A (ConA)-stimulated mouse splenocytes. CONCLUSIONS: Our study suggests that oyster mushroom possesses anti-inflammatory activities and could be considered a dietary agent against inflammation. The health benefits of the oyster mushroom warrant further clinical studies.

ReishiMax, mushroom based dietary supplement, inhibits adipocyte differentiation, stimulates glucose uptake and activates AMPK.

BACKGROUND: Obesity is a health hazard which is closely associated with various complications including insulin resistance, hypertension, dyslipidemia, atherosclerosis, type 2 diabetes and cancer. In spite of numerous preclinical and clinical interventions, the prevalence of obesity and its related disorders are on the rise demanding an urgent need for exploring novel therapeutic agents that can regulate adipogenesis. In the present study, we evaluated whether a dietary supplement ReishiMax (RM), containing triterpenes and polysaccharides extracted from medicinal mushroom Ganoderma lucidum, affects adipocyte differentiation and glucose uptake in 3T3-L1 cells. METHODS: 3T3-L1 pre-adipocytes were differentiated into adipocytes and treated with RM (0-300 µg/ml). Adipocyte differentiation/lipid uptake was evaluated by oil red O staining and triglyceride and glycerol concentrations were determined. Gene expression was evaluated by semi-quantitative RT-PCR and Western blot analysis. Glucose uptake was determined with [³H]-glucose. RESULTS: RM inhibited adipocyte differentiation through the suppresion of expression of adipogenic transcription factors peroxisome proliferator-activated receptor-γ (PPAR-γ), sterol regulatory element binding element protein-1c (SREBP-1c) and CCAAT/enhancer binding protein-α (C/EBP-α). RM also suppressed expression of enzymes and proteins responsible for lipid synthesis, transport and storage: fatty acid synthase (FAS), acyl-CoA synthetase-1 (ACS1), fatty acid binding protein-4 (FABP4), fatty acid transport protein-1 (FATP1) and perilipin. RM induced AMP-activated protein kinase (AMPK) and increased glucose uptake by adipocytes. CONCLUSION: Our study suggests that RM can control adipocyte differentiation and glucose uptake. The health benefits of ReishiMax warrant further clinical studies.

Role of Rho kinase in sphingosine 1-phosphate-mediated endothelial and smooth muscle cell migration and differentiation.

The role of sphingosine 1-phosphate (S1P)-induced Rho kinase (ROCK) activation in the angiogenic responses of pulmonary artery-derived endothelial cells (PAEC) and smooth muscle cells (PASMC) was examined. S1P, a biologically active phospholipid that regulates angiogenesis, promoted PAEC chemotaxis and capillary morphogenesis; furthermore, this activity was unaltered by pretreatment with the pharmacological inhibitor of ROCK, H1152. In contrast, S1P (500 nM) significantly inhibited spontaneous PASMC chemotaxis and differentiation; however, this inhibition was eradicated upon H1152 pretreatment. Similarly, PASMCs transfected with ROCK II siRNA diminished S1P-induced inhibition of the development of multi-cellular structures. Analysis by RT-PCR identified the presence of S1P(1) and S1P(3) receptors on both PAECs and PASMCs, while S1P(2) receptor expression was confined to only PASMCs. Consistent with this observation, the S1P(1) and S1P(3) receptor antagonist, VPC23019, virtually abolished the S1P-initiated PAEC differentiation but did not impede the S1P-induced inhibition of PASMC differentiation. However, the S1P(2) receptor antagonist, JTE013, had no effect on S1P-mediated differentiation of PAECs but abolished the S1P-induced inhibition of PASMC function. Co-cultured endothelial and smooth muscle cells differentiated into "neovascular-like" networks, which were significantly inhibited by S1P. The inhibition of co-culture differentiation in both PAECs and PASMCs was negated by H1152 pretreatment. However, when smooth muscle cells were added to S1P-initiated endothelial cell networks, additional S1P treatment did not inhibit the cellular networks generated by these cells. In conclusion, S1P-induced PAEC angiogenic responses are regulated by S1P(1) and/or S1P(3) receptors independent of Rho kinase activation, whereas S1P(2) receptor-mediated curtailment of PASMC function by S1P.

Triterpenes from Ganoderma Lucidum induce autophagy in colon cancer through the inhibition of p38 mitogen-activated kinase (p38 MAPK).

Medicinal mushroom Ganoderma lucidum is one of the most esteemed natural products that have been used in the traditional Chinese medicine. In this article, we demonstrate that G. lucidum triterpene extract (GLT) suppresses proliferation of human colon cancer cells HT-29 and inhibits tumor growth in a xenograft model of colon cancer. These effects of GLT are associated with the cell cycle arrest at G0/G1 and the induction of the programmed cell death Type II-autophagy in colon cancer cells. Here, we show that GLT induces formation of autophagic vacuoles and upregulates expression of Beclin-1 (1.3-fold increase) and LC-3 (7.3-fold increase) proteins in colon cancer cells and in tumors in a xenograft model (Beclin-1, 3.9-fold increase; LC-3, 1.9-fold increase). Autophagy is mediated through the inhibition of p38 mitogen-activated protein kinase (p38 MAPK) because p38 MAPK inhibitor, SB202190, induces autophagy and expression of Beclin-1 (1.2-fold increase) and LC-3 (7.4-fold increase), and GLT suppresses phosphorylation of p38 MAPK ( approximately 60% inhibition) in colon cancer cells. Taken together, our data demonstrate a novel mechanism responsible for the inhibition of colon cancer cells by G. lucidum and suggest GLT as natural product for the treatment of colon cancer.

Development of a new method for improved identification and relative quantification of unknown metabolites in complex samples: determination of a triterpenoid metabolic fingerprint for the in situ characterization of Ganoderma bioactive compounds.

Ganoderma lucidum is a mushroom with a long history of medical applications. Research has demonstrated chemotherapeutic effects of G. lucidum in tissue culture, and bioactive fractions of the mushroom have been shown to contain high levels of triterpenoids and polysaccharides. In this study, we developed a new method for the detection of ganoderic acids and other triterpenes in Ganoderma mushroom extracts based on a post-biosynthetic stable isotope encoding technique. Overall, 57 doublets were identified as potential ganoderic acids and 11 of those matched with the database. Ganoderic acid A, F and H were confirmed by standards and their absolute concentrations were measured in GLT (GA A: 3.88 mg/g; GA F: 0.95 mg/g and GA H: 1.74 mg/g) and ReishiMax (GA A: 2.32 mg/g; GA F: 0.43 mg/g and GA H: 0.85 mg/g) extracts. The method was also used for the evaluation of bioavailability of triterpenes after an oral application and demonstrated the presence of G. lucidum triterpenes in plasma.

CDC20 associated with cancer metastasis and novel mushroom­derived CDC20 inhibitors with antimetastatic activity.

Aberrant expression of cell division cycle 20 (CDC20) is associated with malignant progression and poor prognosis in various types of cancer. The development of specific CDC20 inhibitors may be a novel strategy for the treatment of cancer with elevated expression of CDC20. The aim of the current study was to elucidate the role of CDC20 in cancer cell invasiveness and to identify novel natural inhibitors of CDC20. The authors found that CDC20 knockdown inhibited the migration of chemoresistant PANC­1 pancreatic cancer cells and the metastatic MDA­MB­231 breast cancer cell line. By contrast, the overexpression of CDC20 by plasmid transfection promoted the metastasizing capacities of the PANC­1 cells and MCF­7 breast cancer cells. It was also identified that a triterpene mixture extracted from the mushroom Poria cocos (PTE), purified triterpenes dehydropachymic acid, and polyporenic acid C (PPAC) downregulated the expression of CDC20 in PANC­1 cells dose­dependently. Migration was also suppressed by PTE and PPAC in a dose­dependent manner, which was consistent with expectations. Taken together, the present study is the first, to the best of our knowledge, to demonstrate that CDC20 serves an important role in cancer metastasis and that triterpenes from P. cocos inhibit the migration of pancreatic cancer cells associated with CDC20. Further investigations are in progress to investigate the specific mechanism associated with CDC20 and these triterpenes, which may have future potential use as natural agents in the treatment of metastatic cancer.

Ganoderma Lucidum induces oxidative DNA damage and enhances the effect of 5-Fluorouracil in colorectal cancer in vitro and in vivo.

The first-line chemotherapy of colorectal cancer (CRC), besides surgery, comprises administration of 5-Fluorouracil (5FU). Apart from cytotoxic effect on cancer cells, 5FU may also cause adverse side effects. Ganoderma Lucidum (GLC) is a mushroom used in Traditional Eastern Medicine. We propose that natural compounds, particularly GLC extracts, may sensitize cancer cells to conventional chemotherapeutics. This combination therapy could lead to more selective cancer cell death and may improve the response to the therapy and diminish the adverse effects of anticancer drugs. Here we demonstrate that GLC induced oxidative DNA damage selectively in colorectal cancer cell lines, whereas it protected non-malignant cells from the accumulation of reactive oxygen species. Accumulation of DNA damage caused sensitization of cancer cells to 5FU resulting in improved anticancer effect of 5FU. The results obtained in colorectal cell lines were confirmed in in vivo study: GLC co-treatment with 5FU increased the survival of treated mice and reduced the tumor volume in comparison with group treated with 5FU alone. Combination of conventional chemotherapeutics and natural compounds is a promising approach, which may reduce the effective curative dose of anticancer drugs, suppress their adverse effects and ultimately lead to better quality of life of CRC patients.

Pleurotus ostreatus inhibits proliferation of human breast and colon cancer cells through p53-dependent as well as p53-independent pathway.

In spite of the global consumption of mushrooms, only two epidemiological studies demonstrated an inverse correlation between mushroom intake and the risk of cancer. Therefore, in the present study we evaluated whether extracts from edible mushrooms Agaricus bisporus (portabella), Flammulina velutipes (enoki), Lentinula edodes (shiitake) and Pleurotus ostreatus (oyster) affect the growth of breast and colon cancer cells. Here, we identified as the most potent, P. ostreatus (oyster mushroom) which suppressed proliferation of breast cancer (MCF-7, MDA-MB-231) and colon cancer (HT-29, HCT-116) cells, without affecting proliferation of epithelial mammary MCF-10A and normal colon FHC cells. Flow cytometry revealed that the inhibition of cell proliferation by P. ostreatus was associated with the cell cycle arrest at G0/G1 phase in MCF-7 and HT-29 cells. Moreover, P. ostreatus induced the expression of the tumor suppressor p53 and cyclin-dependent kinase inhibitor p21(CIP1/WAF1), whereas inhibited the phosphorylation of retinoblastoma Rb protein in MCF-7 cells. In addition, P. ostreatus also up-regulated expression of p21 and inhibited Rb phosphorylation in HT-29 cells, suggesting that that P. ostreatus suppresses the proliferation of breast and colon cancer cells via p53-dependent as well as p53-independent pathway. In conclusion, our results indicated that the edible oyster mushroom has potential therapeutic/preventive effects on breast and colon cancer.

Suppression of cancer invasiveness by dietary compounds.

Tumor invasion and cancer metastasis are interrelated processes involving cell growth, cell adhesion, cell migration and proteolytic degradation of tissue barriers, which are mediated by aberrant intracellular signaling in cancer cells. Natural (green tea polyphenols, soy isoflavones) or dietary compounds (mushroom G. lucidum) markedly decreased AP-1 and NF-kappaB signaling and suppressed invasiveness of cancer cells. This review will summarize alternative approaches for the inhibition of invasive behavior of cancer cells by dietary compounds, which can be considered in adjuvant or combination therapy for the prevention and treatment of cancer metastasis.

Ganoderic acids suppress growth and invasive behavior of breast cancer cells by modulating AP-1 and NF-kappaB signaling.

Structurally related lanostane-type triterpenes, ganoderic acid A, F and H (GA-A, GA-F, GA-H), were identified in an oriental medicinal mushroom Ganoderma lucidum. In the present study we evaluated the effect of GA-A, GA-H and GA-F on highly invasive human breast cancer cells. We showed that GA-A and GA-H suppressed growth (cell proliferation and colony formation) and invasive behavior (adhesion, migration and invasion) of MDA-MB-231 cells. Our results suggest that GA-A and GA-H mediate their biological effects through the inhibition of transcription factors AP-1 and NF-kappaB, resulting in the down-regulation of expression of Cdk4 and the suppression of secretion of uPA, respectively. Furthermore, the activity of ganoderic acids is linked to the hydroxylation in the position 7 and 15 (GA-A) and 3 (GA-H) in their triterpene lanostane structure. In conclusion, hydroxylated triterpenes from G. lucidum could be promising natural agents for the therapy of invasive breast cancers.

Combined effect of green tea and Ganoderma lucidum on invasive behavior of breast cancer cells.

Epidemiological studies have suggested that consumption of green tea may decrease the risk of a variety of cancers. In addition, mushroom Ganoderma lucidum has been used for the promotion of health, longevity and treatment of cancer in traditional Chinese medicine. In the present study we show that extract from green tea (GTE) increased the anticancer effect of G. lucidum extract (GLE) on cell proliferation (anchorage-dependent growth) as well as colony formation (anchorage-independent growth) of breast cancer cells. This effect was mediated by the down-regulation of expression of oncogene c-myc in MDA-MB-231 cells. Although individual GTE and GLE independently inhibited adhesion, migration and invasion of MDA-MB-231 cells, their combination demonstrated a synergistic effect, which was mediated by the suppression of secretion of urokinase plasminogen activator (uPA) from breast cancer cells. Our study suggests the potential use of combined green tea and G. lucidum extracts for the suppression of growth and invasiveness of metastatic breast cancers.

Ganoderma lucidum inhibits proliferation of human breast cancer cells by down-regulation of estrogen receptor and NF-kappaB signaling.

Ganoderma lucidum, an oriental medical mushroom, has been used in Asia for the prevention and treatment of a variety of diseases, including cancer. We have previously demonstrated that G. lucidum inhibits growth and induces cell cycle arrest at G0/G1 phase through the inhibition of Akt/NF-kappaB signaling in estrogen-independent human breast cancer cells. However, the molecular mechanism(s) responsible for the inhibitory effects of G. lucidum on the proliferation of estrogen-dependent (MCF-7) and estrogen-independent (MDA-MB-231) breast cancer cells remain to be elucidated. Here, we show that G. lucidum inhibited the proliferation of breast cancer MCF-7 and MDA-MB-231 cells by the modulation of the estrogen receptor (ER) and NF-kappaB signaling. Thus, G. lucidum down-regulated the expression of ERalpha in MCF-7 cells but did not effect the expression of ERbeta in MCF-7 and MDA-MB-231 cells. In addition, G. lucidum inhibited estrogen-dependent as well as constitutive transactivation activity of ER through estrogen response element (ERE) in a reporter gene assay. G. lucidum decreased TNF-alpha-induced (MCF-7) as well as constitutive (MDA-MB-231) activity of NF-kappaB. The inhibition of ER and NF-kappaB pathways resulted in the down-regulation of expression of c-myc, finally suppressing proliferation of estrogen-dependent as well as estrogen-independent cancer cells. Collectively, these results suggest that G. lucidum inhibits proliferation of human breast cancer cells and contain biologically active compounds with specificity against estrogen receptor and NF-kappaB signaling, and implicate G. lucidum as a suitable herb for chemoprevention and chemotherapy of breast cancer.

Synthesis and screening of N-alkyl hydroxamates for inhibition of cancer cell proliferation.

A small library of N-alkylated amino acid-derived sulfonamide hydroxamates was synthesized on solid phase and tested for inhibition of proliferation of the highly invasive breast cancer cell line MDA-MB-231. The most active compound 4317 inhibited cell growth at IC(50) 30 microM. N-alkylation of N-H hydroxamate-based MMP inhibitors, a modification known to eliminate MMP activity, enhanced cell proliferation inhibition potency.

Inhibition of oxidative stress-induced invasiveness of cancer cells by Ganoderma lucidum is mediated through the suppression of interleukin-8 secretion.

Epidemiological studies suggest that the intake of natural/nutrient products is inversely related to cancer risk. While oxidative stress, generating reactive oxygen species, has been linked to cancer initiation and progression, dietary antioxidants have reduced the risk of certain cancers. Experimental studies have demonstrated that antioxidants and phytochemicals could prevent cancer metastasis, and antioxidants were suggested as adjuvants in cancer therapy. Ganoderma lucidum is an Asian medicinal mushroom that has been used for the past two thousand years for the treatment of various diseases, including cancer. G. lucidum is currently popular as a dietary supplement in the form of tea, powder or extract. We have previously demonstrated that G. lucidum suppresses growth, angiogenesis and invasiveness of highly invasive and metastatic breast cancer cells. The present study was undertaken to evaluate the effect of G. lucidum on oxidative stress-induced metastatic behavior of poorly-invasive MCF-7 breast cancer cells. We show that G. lucidum inhibits oxidative stress-induced migration of MCF-7 cells by the down-regulation of MAPK signaling. G. lucidum suppressed oxidative stress stimulated phosphorylation of extracellular signal-regulated protein kinases (Erk1/2), which resulted in the down-regulation of expression of c-fos, and in the inhibition of transcription factors AP-1 and NF-kappaB. The biological effect of G. lucidum on cell migration was mediated by the suppression of secretion of interleukin-8 from MCF-7 cells exposed to oxidative stress. In summary, our results suggest that G. lucidum inhibits the oxidative stress-induced invasive behavior of breast cancer cells by modulating Erk1/2 signaling and can be potentially considered as an antioxidant in adjuvant cancer therapy.

Honokiol inhibits migration of renal cell carcinoma through activation of RhoA/ROCK/MLC signaling pathway.

Honokiol, a biologically active compound isolated from Magnolia bark, has been shown to possess promising anticancer effect through induction of apoptosis. However, there is a relative lack of information regarding its anti­metastatic activity. Renal cell carcinoma (RCC) is the most common malignancy of the adult kidney and is known for high risk of metastasis. Clinically, therapeutic methods for metastatic RCC cases are limited and efforts to exploit new treatments are still ongoing. The results of our current investigation first revealed that honokiol suppressed the proliferation of different human RCCs without affecting cell viability. In addition, honokiol inhibited migration of highly metastatic RCC 786­0 cells and stimulated the activity of small GTPase, RhoA. Furthermore, phosphorylated myosin light chain (MLC) and excessive formation of actin stress fibers were identified in 786­0 cells treated with honokiol. Interestingly, the pharmacological Rho­associated protein kinase (ROCK) inhibitor Y­27632 attenuated contraction of actin stress fibers induced by honokiol and abrogated honokiol­mediated inhibition of cell migration. Together these important findings suggest that honokiol suppresses the migration of highly metastatic RCC through activation of RhoA/ROCK/MLC signaling and warrants attention in the treatment of RCC metastasis as a novel therapeutic approach.

Signaling pathways responsible for cancer cell invasion as targets for cancer therapy.

Migration of cancer cells is one of the key factors responsible for cancer metastasis. The elucidation of mechanisms responsible for the highly invasive potential of cancer cells can help to identify specific targets for the treatment of cancer patients. Highly invasive cancers are usually characterized by aberrant activity of specific intra- or extracellular molecules such as protein kinases, phosphatases, transcriptional factors, proteolytic enzymes, and others. Protein kinase C (PKC) and phosphatidylinositol 3-kinase (PI3K) are responsible for the constitutive activity of transcriptional factors NF-kappaB and AP-1 in some of the highly invasive cancers. Furthermore, NF-kappaB and AP-1 control the expression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR), and expression of both uPA and uPAR correlates with invasive cancer cell phenotype and poor prognosis. The inhibition of PKC and PI3K signaling (through NF-kappaB and AP-1) suppressed the secretion of uPA, resulting in the inhibition of motility of highly invasive breast cancer cells. Therefore, inhibition of specific target molecules in common signaling pathway(s) responsible for metastatic spread can have potential clinical relevance. This review will summarize different approaches to targeting distinct signaling molecules involved in cancer invasion and metastasis.