Bum Sang Shim

Irreversible Inhibition of CD13/Aminopeptidase N by the Antiangiogenic Agent Curcumin

CD13/aminopeptidase N (APN) is a membrane-bound, zinc-dependent metalloproteinase that plays a key role in tumor invasion and angiogenesis. Here, we show that curcumin, a phenolic natural product, binds to APN and irreversibly inhibits its activity. The direct interaction between curcumin with APN was confirmed both in vitro and in vivo by surface plasmon resonance analysis and an APN-specific antibody competition assay, respectively. Moreover, curcumin and other known APN inhibitors strongly inhibited APN-positive tumor cell invasion and basic fibroblast growth factor-induced angiogenesis. However, curcumin did not inhibit the invasion of APN-negative tumor cells, suggesting that the antiinvasive activity of curcumin against tumor cells is attributable to the inhibition of APN. Taken together, our study revealed that curcumin is a novel irreversible inhibitor of APN that binds to curcumin resulting in inhibition of angiogenesis.

Embelin suppresses STAT3 signaling, proliferation, and survival of multiple myeloma via the protein tyrosine phosphatase PTEN

Even though embelin, an inhibitor of the XIAP, is known to exhibit anti-inflammatory and anti-cancer activities, very little is known about its mechanism of action. Here, we investigated whether embelin mediates its effect through interference with the signal transducer and activator of transcription 3 (STAT3) pathway. We found that embelin inhibited constitutive STAT3 activation in a variety of human cancer cell lines such as U266, DU-145, and SCC4 cells. The suppression of STAT3 was mediated through inhibition of the activation of JAK2 and c-Src. Pervanadate treatment also reversed the embelin-induced down-regulation of STAT3, suggesting the involvement of a protein tyrosine phosphatase. Indeed, we found that embelin-induced the expression of the tyrosine phosphatase PTEN and deletion of the PTEN gene by small interfering RNA abolished the ability of embelin to inhibit STAT3 activation. Besides, embelin failed to suppress STAT3 activation in PTEN-null PC3 cells, thus indicating that the inhibitory effect of embelin on STAT3 is PTEN-dependent. Embelin down-regulated the expression of STAT3-regulated gene products; this correlated with the suppression of cell proliferation and invasion, and the induction of apoptosis through the activation of caspase-3. Overall, our results indicate that the anti-inflammatory and anti-cancer activities previously assigned to embelin may be mediated in part through the suppression of the STAT3 pathway.

Ocimum sanctum induces apoptosis in A549 lung cancer cells and suppresses the in vivo growth of Lewis lung carcinoma cells.

Although Ocimum sanctum has been used extensively for its medicinal values in India and China, its antitumor activity against human nonsmall cell lung carcinoma (NSCLC) A549 cells has not been investigated until now. Therefore, the antitumor mechanism of ethanol extracts of Ocimum sanctum (EEOS) was elucidated in A549 cells in vitro and the Lewis lung carcinoma (LLC) animal model. EEOS exerted cytotoxicity against A549 cells, increased the sub‐G1 population and exhibited apoptotic bodies in A549 cells. Furthermore, EEOS cleaved poly(ADP‐ribose)polymerase (PARP), released cytochrome C into cytosol and simultaneously activated caspase‐9 and ‐3 proteins. Also, EEOS increased the ratio of proapoptotic protein Bax/antiapoptotic protein Bcl‐2 and inhibited the phosphorylation of Akt and extracellular signal regulated kinase (ERK) in A549 cancer cells. In addition, it was found that EEOS can suppress the growth of LLC inoculated onto C57BL/6 mice in a dose‐dependent manner. Overall, these results demonstrate that EEOS induces apoptosis in A549 cells via a mitochondria caspase dependent pathway and inhibits the in vivo growth of LLC, suggesting that EEOS can be applied to lung carcinoma as a chemopreventive candidate. Copyright

Cinnamomum cassia Bark in Two Herbal Formulas Increases Life Span in Caenorhabditis elegans via Insulin Signaling and Stress Response Pathways

Background Proving the efficacy and corresponding mode of action of herbal supplements is a difficult challenge for evidence-based herbal therapy. A major hurdle is the complexity of herbal preparations, many of which combine multiple herbs, particularly when the combination is assumed to be vitally important to the effectiveness of the herbal therapy. This issue may be addressed through the use of contemporary methodology and validated animal models. Methods and Principal Findings In this study, two commonly used traditional herbal formulas, Shi Quan Da Bu Tang (SQDB) and Huo Luo Xiao Ling Dan (HLXL) were evaluated using a survival assay and oxidative stress biomarkers in a well-established C. elegans model of aging. HLXL is an eleven herb formula modified from a top-selling traditional herbal formula for the treatment of arthritic joint pain. SQDB consists of ten herbs often used for fatigue and energy, particularly in the aged. We demonstrate here that SQDB significantly extend life span in a C. elegans model of aging. Among all individual herbs tested, two herbs Cinnamomum cassia bark (Chinese pharmaceutical name: Cinnamomi Cortex, CIN) and Panax ginseng root (Chinese pharmaceutical name: Ginseng Radix, GS) significantly extended life span in C. elegans. CIN in both SQDB and HLXL formula extended life span via modulation of multiple longevity assurance genes, including genes involved in insulin signaling and stress response pathways. All the life-span-extending herbs (SQDB, CIN and GS) also attenuated levels of H2O2 and enhanced small heat shock protein expression. Furthermore, the life span-extending herbs significantly delayed human amyloid beta (Aβ)-induced toxicity in transgenic C. elegans expressing human Aβ. Conclusion/Significance These results validate an invertebrate model for rapid, systematic evaluation of commonly used Chinese herbal formulations and may provide insight for designing future evidence-based herbal therapy(s).

A Hexane Fraction of Guava Leaves (Psidium guajava L.) Induces Anticancer Activity by Suppressing AKT/Mammalian Target of Rapamycin/Ribosomal p70 S6 Kinase in Human Prostate Cancer Cells

This study was carried out to evaluate the anticancer effects of guava leaf extracts and its fractions. The chemical compositions of the active extracts were also determined. In the present study, we set out to determine whether the anticancer effects of guava leaves are linked with their ability to suppress constitutive AKT/mammalian target of rapamycin (mTOR)/ribosomal p70 S6 kinase (S6K1) and mitogen-activated protein kinase (MAPK) activation pathways in human prostate cancer cells. We found that guava leaf hexane fraction (GHF) was the most potent inducer of cytotoxic and apoptotic effects in PC-3 cells. The molecular mechanism or mechanisms of GHF apoptotic potential were correlated with the suppression of AKT/mTOR/S6K1 and MAPK signaling pathways. This effect of GHF correlated with down-regulation of various proteins that mediate cell proliferation, cell survival, metastasis, and angiogenesis. Analysis of GHF by gas chromatography and gas chromatography-mass spectrometry tentatively identified 60 compounds, including β-eudesmol (11.98%), α-copaene (7.97%), phytol (7.95%), α-patchoulene (3.76%), β-caryophyllene oxide (CPO) (3.63%), caryophylla-3(15),7(14)-dien-6-ol (2.68%), (E)-methyl isoeugenol (1.90%), α-terpineol (1.76%), and octadecane (1.23%). Besides GHF, CPO, but not phytol, also inhibited the AKT/mTOR/S6K1 signaling pathway and induced apoptosis in prostate cancer cells. Overall, these findings suggest that guava leaves can interfere with multiple signaling cascades linked with tumorigenesis and provide a source of potential therapeutic compounds for both the prevention and treatment of cancer.

Cellular Uptake of Ginsenosides in Korean White Ginseng and Red Ginseng and Their Apoptotic Activities in Human Breast Cancer Cells

Panax ginseng has been reported to have cancer-preventive properties and, through anti-inflammatory, antioxidant, and pro-apoptotic mechanisms, to influence gene expression. However, the comparison of Korean white ginseng (WG) and red ginseng (RG) in their apoptotic effects and the identification of the selective cellular uptake of the ginsenosides in human breast cancer cells have not yet been fully understood. In the present study, the relative nonpolar and protopanaxadiol (PPD) class ginsenosides exhibited more cytotoxic and efficient cellular uptake on MCF-7 cells compared with the relative polar and protopanaxatriol (PPT) class compounds. PPD class ginsenosides were present in RG in a 2.5 times higher concentration as compared to WG, while PPT class ginsenosides were only present in WG. Thus, RG exerted more potent cytotoxicity than WG against MCF-7 and MDA-MB231 cells. RG also increased the sub-G1 DNA contents of the cell cycle and Annexin V-positive apoptotic bodies undergoing apoptosis through the caspase-3 activation in MCF-7 cells. In addition, RG downregulated the proliferative and anti-apoptotic gene products and potentiated paclitaxel-induced apoptosis in MCF-7 cells. Overall, RG contained a higher concentration of PPD class ginsenosides as compared to WG; the greater cellular uptake of PPD resulted in more substantial antiproliferative activity in human breast cancer cells.

Bergamottin, a natural furanocoumarin obtained from grapefruit juice induces chemosensitization and apoptosis through the inhibition of STAT3 signaling pathway in tumor cells

Persistent activation of signal transducers and activator of transcription 3 (STAT3) has been closely related to growth, survival, proliferation, metastasis, and angiogenesis of various cancer cells, and thus its inhibition can be considered a potential therapeutic strategy. In this study, we investigated the role of bergamottin (BGM) obtained from grapefruit juice in abrogating the constitutive STAT3 activation in multiple myeloma (MM) cells. This suppression was mediated through the inhibition of phosphorylation of Janus-activated kinase (JAK) 1/2 and c-Src. Pervanadate reversed the BGM induced down-regulation of STAT3 activation, suggesting the involvement of a protein tyrosine phosphatase (PTP). Furthermore, BGM induced the expression of the tyrosine phosphatase SHP-1, and gene silencing of the SHP-1 by small interfering RNA abolished the ability of BGM to inhibit STAT3 activation, suggesting a critical role for SHP-1 in the action of BGM. BGM also downregulated the expression of STAT3-regulated gene products such as COX-2, VEGF, cyclin D1, survivin, IAP-1, Bcl-2, and Bcl-xl in MM cells. This correlated with induction of substantial apoptosis as indicated by an increase in the sub-G1 cell population and caspase-3 induced PARP cleavage. Also, this agent significantly potentiated the apoptotic effects of bortezomib and thalidomide in MM cells. Overall, these results suggest that BGM is a novel blocker of STAT3 activation pathway thus may have a potential in therapy of MM and other cancers.

Embelin inhibits growth and induces apoptosis through the suppression of Akt/mTOR/S6K1 signaling cascades†‡

Akt/mTOR/S6K1 signaling cascades play an important role both in the survival and proliferation of tumor cells.

Brassinin Induces Apoptosis in PC‐3 Human Prostate Cancer Cells through the Suppression of PI3K/Akt/mTOR/S6K1 Signaling Cascades

The oncogenic PI3K/Akt/mammalian target of rapamycin (mTOR) signaling axis and its downstream effector, the ribosomal protein S6 kinase 1 (S6K1) play a key role in mediating cell survival in various tumor cells. Here, we investigated the effects of brassinin (BSN), a phytoalexin first identified as a constituent of cabbage, on the PI3K/Akt/mTOR/S6K1 activation, cellular proliferation, and apoptosis in PC‐3 human prostate cancer. BSN exerted a significant dose‐dependent cytotoxicity and reduced constitutive phosphorylation of Akt against androgen‐independent PC‐3 cells as compared to androgen‐dependent LNCaP cells. Moreover, knockdown of androgen receptor (AR) by small interfering RNA enhanced the potential effect of BSN on induction of apoptosis in LNCaP cells. BSN clearly suppressed the constitutive activation of PI3K/Akt/mTOR/S6K1 signaling cascade, which correlated with the induction of apoptosis as characterized by accumulation of cells in subG1 phase, positive Annexin V binding, TUNEL staining, loss of mitochondrial membrane potential, down‐regulation of antiapoptotic and proliferative proteins, activation of caspase‐3, and cleavage of PARP. Additionally, BSN could block broad‐spectrum inhibition of PI3K/Akt/mTOR/S6K1 axes, and aberrant Akt activation by pcDNA3‐myr‐HA‐Akt1 plasmid could not prevent the observed suppressive effect of BSN on constitutive mTOR activation. Finally, overexpression of Bcl‐2 also attenuated BSN‐mediated apoptosis in PC‐3 cells. Taken together, our findings suggest that BSN can interfere with multiple signaling cascades involved in tumorigenesis and might be provided as a potential therapeutic candidate for both the prevention and treatment of prostate cancer. Copyright

Emodin inhibits invasion and migration of prostate and lung cancer cells by downregulating the expression of chemokine receptor CXCR4

Emodin (ED), an anthraquinone derivative, has been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, impede metastasis, and enhance chemotherapy. However, the detailed mechanism of ED related to the regulation of CXC chemokine receptor-4 (CXCR4) gene expression that affects cellular migration and invasion in prostate and lung cancer cells are not fully understood. Recent evidence indicates that the CXCR4/CXCL12 axis is involved in promoting invasion and metastasis in tumors. Thus, novel agents that can downregulate CXCR4 expression have therapeutic potential in repressing cancer metastasis. Among ED and its derivatives, it is found that ED downregulated the expression of both CXCR4 and HER2 without affecting cell viability in tumor cells. The suppression of CXCR4 expression by ED was found to correlate with the inhibition of CXCL12-induced migration and invasion of both DU145 and A549 cells. Besides, neither proteasome inhibition nor lysosomal stabilization had any effect on ED-induced decrease in CXCR4 expression. The basic molecular mechanisms unveiled that the downregulation of CXCR4 was at the transcriptional level, as indicated by downregulation of mRNA expression and suppression of NF-κB activation. Overall, our findings suggest that ED is a novel blocker of CXCR4 expression and, thus, has enormous potential as a powerful therapeutic agent for metastatic cancer.