Leonurine ameliorates the STAT3 pathway through the upregulation of SHP-1 to retard the growth of hepatocellular carcinoma cells.

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that directs the transcription of genes involved in the promotion of cell survival and proliferation, inflammation, angiogenesis, invasion, and migration. Overactivation of STAT3 is often witnessed in human cancers, thereby making it a good target in oncology. Herein the efficacy of Leonurine (Leo), a bioactive alkaloid present in Herba leonuri, was investigated for its STAT3-inhibitory potential in hepatocellular carcinoma (HCC) cells. Leo downregulated the persistent as well as IL-6-driven activation of STAT3. Leo abrogated the nuclear localization and DNA interacting ability of STAT3. Leo was also found to impart STAT3 inhibition by mitigating the activation of upstream kinases such as JAK1, JAK2, and Src both in constitutive and IL-6 inducible systems. Leo curbed the STAT3-driven luciferase gene expression and the depletion of STAT3 resulted in the reduced responsiveness of HCC cells to Leo. Pervanadate exposure counteracted Leo-induced STAT3 inhibition suggesting the involvement of a protein tyrosine phosphatase. SHP-1 was significantly elevated upon Leo exposure whereas the depletion of SHP-1 was found to revert the effect of Leo on STAT3. Leo induced apoptosis and also significantly potentiated the cytotoxic effect of paclitaxel, doxorubicin, and sorafenib. Leo was found to be non-toxic up to the dose of 10 mg/kg in NCr nude mice. In conclusion, Leo was demonstrated to induce cytotoxicity in HCC cells by mitigating the persistent of activation of STAT3 pathway.

Effects of Tributyltin-Contaminated Aquatic Environments and Remediated Water on Early Development of Sea Urchin (Hemisentrotus pulcherrimus).

In this study, gametotoxicity and embryotoxicity experiments were performed using Hemicentrotus pulcherrimus to investigate the toxic effects of tributyltin (TBT). The effects of TBT on fertilization and embryogenesis were assessed at various concentrations (0, 0.02, 0.05, 0.09, 0.16, 0.43, 0.73, 4.68, and 9.22 ppb). The fertilization rates decreased in a concentration-dependent manner, with significant reduction following treatment with TBT at 0.05 ppb. Embryos exhibited developmental impairment after TBT exposure at each tested concentration. The frequency of developmental inhibition delay that treatment with TBT delayed embryonic development in a dose-dependent manner, with 100% of embryos exhibiting developmental impairment at 4.68 ppb. During developmental recovery tests, embryos cultured in fresh media without TBT showed advanced embryonic development. Although the observed normal development after transferring the developmentally delayed embryos to fresh media without TBT offers prospects for the restoration of contaminated environments, embryonic development remained incomplete. These results suggest that TBT adversely affects the early embryonic development of H. pulcherrimus.

BBT-176, a Novel Fourth-Generation Tyrosine Kinase Inhibitor for Osimertinib-Resistant EGFR Mutations in Non-Small Cell Lung Cancer.

PURPOSE: Resistance to third-generation EGFR inhibitors including osimertinib arises in part from the C797S mutation in EGFR. Currently, no targeted treatment option is available for these patients. We have developed a new EGFR tyrosine kinase inhibitor (TKI), BBT-176, targeting the C797S mutation. PATIENTS AND METHODS: Recombinant EGFR proteins and Ba/F3 cell lines, patient-derived cells, and patient-derived xenografts expressing mutant EGFRs were used to test the inhibitory potency and the anticancer efficacy of BBT-176 both in vitro and in vivo. Patient case data are also available from an ongoing phase I clinical trial (NCT04820023). RESULTS: The half maximal inhibitory concentration (IC50) of BBT-176 against EGFR 19Del/C797S, EGFR 19Del/T790M/C797S, and EGFR L858R/C797S proteins were measured at 4.36, 1.79, and 5.35 nmol/L, respectively (vs. 304.39, 124.82, and 573.72 nmol/L, for osimertinib). IC50 values of BBT-176 against Ba/F3 cells expressing EGFR 19Del/C797S, EGFR 19Del/T790M/C797S, EGFR L858R/C797S, and EGFR L858R/T790M/C797S were 42, 49, 183, and 202 nmol/L, respectively (vs. 869, 1,134, 2,799, and 2,685 nmol/L for osimertinib). N-ethyl-N-nitrosourea mutagenesis suggested that BBT-176 treatment does not introduce any secondary mutations in the EGFR gene but increases EGFR expression levels. Combined with the EGFR antibody cetuximab, BBT-176 effectively suppressed the growth of BBT-176-resistant clones. BBT-176 strongly inhibited the tumor growth, and in some conditions induced tumor regression in mouse models. In the clinical trial, two patients harboring EGFR 19Del/T790M/C797S in blood showed tumor shrinkage and radiologic improvements. CONCLUSIONS: BBT-176 is a fourth-generation EGFR inhibitor showing promising preclinical activity against NSCLC resistant to current EGFR TKI, with early clinical efficacy and safety.

Crocetin imparts antiproliferative activity via inhibiting STAT3 signaling in hepatocellular carcinoma.

STAT3 is a key oncogenic transcription factor, often overactivated in several human cancers including hepatocellular carcinoma (HCC). STAT3 modulates the expression of genes that are connected with cell proliferation, antiapoptosis, metastasis, angiogenesis, and immune evasion in tumor cells. In this study, we investigated the effect of crocetin on the growth of HCC cells and dissected its underlying molecular mechanism in imparting a cytotoxic effect. Crocetin suppressed proliferation, promoted apoptosis, and counteracted the invasive capacity of HCC cells. Besides, crocetin downregulated the constitutive/inducible STAT3 activation (STAT3Y705 ), nuclear accumulation of STAT3 along with suppression of its DNA binding activity in HCC cells with no effect on STAT5 activation. Crocetin suppressed the activity of upstream kinases such as Src, JAK1, and JAK2. Sodium pervanadate treatment terminated the crocetin-propelled STAT3 inhibition suggesting the involvement of tyrosine phosphatases. Crocetin increased the expression of SHP-1 and siRNA-mediated SHP-1 silencing resulted in the negation of crocetin-driven STAT3 inhibition. Further investigation revealed that crocetin treatment inhibited the expression of STAT3 regulated genes (Bcl-2, Bcl-xL, cyclin D1, survivin, VEGF, COX-2, and MMP-9). Taken together, this report presents crocetin as a novel abrogator of the STAT3 pathway in HCC cell lines.

Pyrimethamine Modulates Interplay between Apoptosis and Autophagy in Chronic Myelogenous Leukemia Cells.

Pyrimethamine (Pyri) is being used in combination with other medications to treat serious parasitic infections of the body, brain, or eye and to also reduce toxoplasmosis infection in the patients with HIV infection. Additionally, Pyri can display significant anti-cancer potential in different tumor models, but the possible mode of its actions remains unclear. Hence, in this study, the possible anti-tumoral impact of Pyri on human chronic myeloid leukemia (CML) was deciphered. Pyri inhibited cell growth in various types of tumor cells and exhibited a marked inhibitory action on CML cells. In addition to apoptosis, Pyri also triggered sustained autophagy. Targeted inhibition of autophagy sensitized the tumor cells to Pyri-induced apoptotic cell death. Moreover, the activation of signal transducer and activator of transcription 5 (STAT5) and its downstream target gene Bcl-2 was attenuated by Pyri. Accordingly, small interfering RNA (siRNA)-mediated STAT5 knockdown augmented Pyri-induced autophagy and apoptosis and promoted the suppressive action of Pyri on cell viability. Moreover, ectopic overexpression of Bcl-2 protected the cells from Pyri-mediated autophagy and apoptosis. Overall, the data indicated that the attenuation of STAT5-Bcl-2 cascade by Pyri can regulate its growth inhibitory properties by simultaneously targeting both apoptosis and autophagy cell death mechanism(s).

Formononetin Regulates Multiple Oncogenic Signaling Cascades and Enhances Sensitivity to Bortezomib in a Multiple Myeloma Mouse Model.

Here, we determined the anti-neoplastic actions of formononetin (FT) against multiple myeloma (MM) and elucidated its possible mode of action. It was observed that FT enhanced the apoptosis caused by bortezomib (Bor) and mitigated proliferation in MM cells, and these events are regulated by nuclear factor-κB (NF-κB), phosphatidylinositol 3-kinase (PI3K)/AKT, and activator protein-1 (AP-1) activation. We further noted that FT treatment reduced the levels of diverse tumorigenic proteins involved in myeloma progression and survival. Interestingly, we observed that FT also blocked persistent NF-κB, PI3K/AKT, and AP-1 activation in myeloma cells. FT suppressed the activation of these oncogenic cascades by affecting a number of signaling molecules involved in their cellular regulation. In addition, FT augmented tumor growth-inhibitory potential of Bor in MM preclinical mouse model. Thus, FT can be employed with proteasomal inhibitors for myeloma therapy by regulating the activation of diverse oncogenic transcription factors involved in myeloma growth.

Fermented dried Citrus unshiu peel extracts exert anti-inflammatory activities in LPS-induced RAW264.7 macrophages and improve skin moisturizing efficacy in immortalized human HaCaT keratinocytes.

Context: Citrus unshiu Markovich (Rutaceae) peel is known to contain high concentrations of flavonoids and exerts pharmacological effects on antioxidant, anti-inflammation, allergies, diabetes and viral infections. Objective: Very little is known about potential activity of fermented dried Citrus unshiu peel extracts (FCU) using Bacillus subtilis, as well as its mechanism of action. We investigated the effects of FCU on the anti-inflammatory activities in murine macrophages and moisturizing effects in human keratinocytes. Materials and methods: We isolated the Bacillus subtilis from Cheonggukjang and FCU using these Bacillus subtilis to prepare samples. The cells were pre-treated with various extracts for 2 h and then induced with LPS for 22 h. We determined the NO assay, TNF-α, IL-6 and PGE2 in RAW 264.7 ells. The expression of SPT and Filaggrin by FCU treatment was measured in HaCaT cells. Result: We found that two types of FCU highly suppressed LPS-induced nitric oxide (NO) without exerting cytotoxic effects on RAW 264.7 cells (21.9 and 15.4% reduction). FCU inhibited the expression of LPS-induced iNOS and COX-2 proteins and their mRNAs in a concentration-dependent manner. TNF-α (59 and 30.9% reduction), IL-6 (39.1 and 65.6% reduction), and PGE2 secretion (78.6 and 82.5% reduction) were suppressed by FCU in LPS-stimulated macrophages. Furthermore, FCU can induce the production of hyaluronic acid (38 and 38.9% induction) and expression of Filaggrin and SPT in HaCaT keratinocyte cells. Discussion and conclusion: FCU potentially inhibits inflammation, improves skin moisturizing efficacy, and it may be a therapeutic candidate for the treatment of inflammation and dry skin.

Cycloastragenol can negate constitutive STAT3 activation and promote paclitaxel-induced apoptosis in human gastric cancer cells.

BACKGROUND: Cycloastragenol (CAG), a triterpene aglycone is commonly prescribed for treating hypertension, cardiovascular disease, diabetic nephropathy, viral hepatitis, and various inflammatory-linked diseases. HYPOTHESIS: We investigated CAG for its action on signal transducer and activator of transcription 3 (STAT3) activation cascades, and its potential to sensitize gastric cancer cells to paclitaxel-induced apoptosis. METHODS: The effect of CAG on STAT3 phosphorylation and other hallmarks of cancer was deciphered using diverse assays in both SNU-1 and SNU-16 cells. RESULTS: We observed that CAG exhibited cytotoxic activity against SNU-1 and SNU-16 cells to a greater extent as compared to normal GES-1 cells. CAG predominantly caused negative regulation of STAT3 phosphorylation at tyrosine 705 through the abrogation of Src and Janus-activated kinases (JAK1/2) activation. We noted that CAG impaired translocation of STAT3 protein as well as its DNA binding activity. It further decreased cellular proliferation and mediated its anticancer effects predominantly by causing substantial apoptosis rather than autophagy. In addition, CAG potentiated paclitaxel-induced anti-oncogenic effects in gastric tumor cells. CONCLUSIONS: Our results indicate that CAG can function to impede STAT3 activation in human gastric tumor cells and therefore it may be a suitable candidate agent for therapy of gastric cancer.

Casticin-Induced Inhibition of Cell Growth and Survival Are Mediated through the Dual Modulation of Akt/mTOR Signaling Cascade.

The Akt/mTOR signaling cascade is a critical pathway involved in various physiological and pathological conditions, including regulation of cell proliferation, survival, invasion, and angiogenesis. In the present study, we investigated the anti-neoplastic effects of casticin (CTC), identified from the plant Vitex rotundifolia L., alone and/or in combination with BEZ-235, a dual Akt/mTOR inhibitor in human tumor cells. We found that CTC exerted a significant dose-dependent cytotoxicity and reduced cell proliferation in a variety of human tumor cells. Also, CTC effectively blocked the phosphorylation levels of Akt (Ser473) and mTOR (Ser2448) proteins as well as induced substantial apoptosis. Additionally treatment with CTC and BEZ-235 in conjunction resulted in a greater apoptotic effect than caused by either agent alone thus implicating the anti-neoplastic effects of this novel combination. Overall, the findings suggest that CTC can interfere with Akt/mTOR signaling cascade involved in tumorigenesis and can be used together with pharmacological agents targeting Akt/mTOR pathway.

Arctiin is a pharmacological inhibitor of STAT3 phosphorylation at tyrosine 705 residue and potentiates bortezomib-induced apoptotic and anti-angiogenic effects in human multiple myeloma cells.

BACKGROUND: Arctiin is a main component from the fruits of Arctium lappa L., that can be prescribed for cold or flu in East Asian countries; it has also been found to exert chemopreventive actions against various tumor cells. HYPOTHESIS: In view of this evidence, we examined arctiin for its ability to trigger apoptosis and inhibit the activation of signal transducer and activator of transcription 3 (STAT3) in human multiple myeloma (MM) cells. METHODS: We evaluated the effect of arctiin on STAT3 signaling cascades and its regulated functional responses in MM cells. RESULTS: Arctiin effectively blocked the constitutive activation of STAT3 phosphorylation in the residue of tyrosine 705. Arctiin also abrogated the constitutive activation of Src phosphorylation and Janus-activated kinases (JAKs) 1/2. Furthermore, it was found that arctiin treatment clearly enhanced the mRNA and protein levels of protein tyrosine phosphatase ε (PTPε), and the silencing of PTPε caused a reversal of the arctiin-induced PTPε expression and the blockadge of STAT3 phosphorylation. Interestingly, arctiin could not repress IL-6-induced STAT3 activation in serum-starved U266 cells and when arctiin was incubated with a complete culture medium in RPMI 8226 and MM.1S cells. Arctiin suppressed cell proliferation, accumulated cells in the G2/M cell-cycle phase, and induced apoptosis within U266 cells, although the knockdown of PTPε prevented PARP cleavage and caspase-3 activation induced by the arctiin. In addition, arctiin exerted cytotoxicity in MM cells, but did not do so in peripheral blood mononuclear cells. Arctiin down-modulated diverse oncogenic gene products regulated by STAT3, although the induction of apoptosis by arctiin was abrogated upon transfection with pMXs-STAT3C in mouse embryonic fibroblast (MEF) cells. Arctiin also potentiated bortezomib-induced antitumor effects in U266 cells. CONCLUSION: On the whole, our results indicate that arctiin is a potentially new inhibitor of constitutive STAT3 activation through the induction of PTPε in MM, cells and therefore has great value in treating various tumors sheltering constitutively activated STAT3.

Oxymatrine Attenuates Tumor Growth and Deactivates STAT5 Signaling in a Lung Cancer Xenograft Model.

Oxymatrine (OMT) is a major alkaloid found in radix Sophorae flavescentis extract and has been reported to exhibit various pharmacological activities. We elucidated the detailed molecular mechanism(s) underlying the therapeutic actions of OMT in non-small cell lung cancer (NSCLC) cells and a xenograft mouse model. Because the STAT5 signaling cascade has a significant role in regulating cell proliferation and survival in tumor cells, we hypothesized that OMT may disrupt this signaling cascade to exert its anticancer effects. We found that OMT can inhibit the constitutive activation of STAT5 by suppressing the activation of JAK1/2 and c-Src, nuclear localization, as well as STAT5 binding to DNA in A549 cells and abrogated IL-6-induced STAT5 phosphorylation in H1299 cells. We also report that a sub-optimal concentration of OMT when used in combination with a low dose of paclitaxel produced significant anti-cancer effects by inhibiting cell proliferation and causing substantial apoptosis. In a preclinical lung cancer mouse model, OMT when used in combination with paclitaxel produced a significant reduction in tumor volume. These results suggest that OMT in combination with paclitaxel can cause an attenuation of lung cancer growth both in vitro and in vivo.

Casticin inhibits growth and enhances ionizing radiation-induced apoptosis through the suppression of STAT3 signaling cascade.

Casticin (CTC), one of the major components of Vitex rotundifolia L., has been reported to exert significant beneficial pharmacological activities and can function as an antiprolactin, anticancer, anti-inflammatory, neuroprotective, analgesic, and immunomodulatory agent. This study aimed at investigating whether the proapoptotic effects of CTC may be mediated through the abrogation of signal transducers and activators of transcription-3 (STAT3) signaling pathway in a variety of human tumor cells. We found that CTC significantly decreased cell viability in a concentration-dependent manner and suppressed cell proliferation in 786-O, YD-8, and HN-9 cells. CTC also induced programmed cell death that was found to be mediated via caspase-3 activation and induction of poly(ADP-ribose) polymerase cleavage. Interestingly, CTC repressed both constitutive and interleukin-6-induced STAT3 activation in 786-O and YD-8 cells but only affected constitutive STAT3 phosphorylation in HN-9 cells. Moreover, CTC could potentiate ionizing radiation-induced apoptotic effects leading to the downregulation of STAT3 activation and thus may be used in combination with radiation against diverse malignancies.

Ophiopogonin D, a Steroidal Glycoside Abrogates STAT3 Signaling Cascade and Exhibits Anti-Cancer Activity by Causing GSH/GSSG Imbalance in Lung Carcinoma.

Natural medicinal plants are multi-targeted in nature and their anti-cancer activities are also complex and varied, thus requiring a more systematic analysis of their modes of action. Since the activation of signal transducer and activator of transcription 3 (STAT3) is often deregulated in non-small cell lung carcinoma (NSCLC) cells and tissue specimens, its negative regulation can form the basis for identification of targeted therapy. In this report, we analyzed the possible anti-cancer effects of ophiopogonin D (OP-D) and the underlying mechanisms by which OP-D exerts its actions in NSCLC. OP-D exhibited substantial suppressive activity on STAT3 signaling and this effect was found to be mediated via oxidative stress phenomena caused by disturbance in GSH/GSSG ratio. In addition, OP-D induced apoptosis, activated caspase mediated apoptotic cascade and decreased expression of various oncogenic genes. Consistently, OP-D treatment significantly reduced NSCLC tumor growth in preclinical mouse model with via decreasing levels of p-STAT3. OP-D was also found to attenuate the expression of STAT3-regulated anti-apoptosis, cell cycle regulator, and angiogenesis biomarkers. Our findings suggest that OP-D can induce apoptosis and exert anti-tumor effects by inhibition of STAT3 signaling pathways in NSCLC.

Formononetin-induced oxidative stress abrogates the activation of STAT3/5 signaling axis and suppresses the tumor growth in multiple myeloma preclinical model.

Aberrant reactions of signal transducer and transcriptional activator (STAT) are frequently detected in multiple myeloma (MM) cancers and can upregulate the expression of multiple genes related to cell proliferation, survival, metastasis, and angiogenesis. Therefore, agents capable of inhibiting STAT activation can form the basis of novel therapies for MM patients. In the present study, we investigated whether the potential anti-cancer effects of Formononetin (FT), a naturally occurring isoflavone derived from Astragalus membranaceus, Trifolium pratense, Glycyrrhiza glabra, and Pueraria lobata, against MM cell lines and human multiple myeloma xenograft tumors in athymic nu/nu mice model are mediated through the negative regulation of STAT3 and STAT5 pathways. Data from the in vitro studies indicated that FT could significantly inhibit cell viability, and induce apoptosis. Interestingly, FT also suppressed constitutive STAT3 (tyrosine residue 705 and serine residue 727) and STAT5 (tyrosine residue 694/699) activation, which correlated with the suppression of the upstream kinases (JAK1, JAK2, and c-Src) in MM cells, and this effect was found to be mediated via an increased production of reactive oxygen species (ROS) due to GSH/GSSG imbalance. Also, FT abrogated STAT3 and STAT5 DNA binding capacity and nuclear translocation. FT induced cell cycle arrest, downregulated the expression of STAT3-regulated anti-apoptotic, angiogenetic, and proliferative gene products; and this correlated with induction of caspase-3 activation and cleavage of PARP. Intraperitoneal administration of FT significantly suppressed the tumor growth in the multiple myeloma xenograft mouse model without exhibiting any significant adverse effects. Overall, our findings indicate that FT exhibits significant anti-cancer effects in MM that may be primarily mediated through the ROS-regulated inhibition of the STAT3 and STAT5 signaling cascade.

Ophiopogonin D modulates multiple oncogenic signaling pathways, leading to suppression of proliferation and chemosensitization of human lung cancer cells.

BACKGROUND: Ophiopogonin D (OP-D), a steroidal glycoside obtained from the Chinese medicinal plant Ophiopogonin japonicas (the root portion), has been traditionally used to treat fever, inflammation, cough, sputum etc. However, the detailed molecular mechanism(s) underlying its therapeutic actions is still unknown. HYPOTHESIS: Because nuclear factor-κB (NF-κB), PI3K/AKT, and activator protein-1 (AP-1) signaling cascades have significant functions in cell proliferation, inflammation, and angiogenesis in tumor cells, we hypothesized that OP-D may disrupt these signaling cascades to exert its anticancer effects in human lung-cancer cells. METHODS: We evaluated the effect of OP-D on multiple signaling cascades and its regulated functional responses in lung cancer cells. RESULTS: OP-D blocked both basal and cytokine-induced proliferation of human lung-cancer cells and caused down-regulation of the expression of diverse oncogenic gene products through the suppression of NF-κB, PI3K/AKT, and AP-1 pathways; but did not affect JNK, p38 and ERK MAP kinases. Interestingly, OP-D suppressed constitutive NF-κB activation in lung cancer cells via interfering with the IκB kinase activation, which inhibited phosphorylation and caused degradation of IκB-α. OP-D also blocked phosphorylation and the nuclear translocation of p65, thereby suppressing NF-κB reporter activity in lung cancer cells. Besides, OP-D could augment cell death induced by paclitaxel in lung-cancer cells. CONCLUSION: Overall, the data indicates that OP-D may abrogate diverse signaling cascades linked to tumorigenesis, and can be used in combination with chemotherapeutic agents for cancer therapy.

Korean Red Ginseng Extract Enhances the Anticancer Effects of Sorafenib through Abrogation of CREB and c-Jun Activation in Renal Cell Carcinoma.

Although application of sorafenib in the treatment of human renal cell carcinoma (RCC) remains one of the best examples of successful targeted therapy, majority of RCC patients suffer from its side effects as well as develop resistance to this targeted therapy. Thus, there is a need to promote novel alternative therapies for the treatment of RCC. In this study, we investigated whether Korean red ginseng extract (KRGE) could inhibit the proliferation and induce chemosensitization in human renal cancer cells. Also, we used a human phospho-antibody array containing 46 antibodies against signaling molecules to examine a subset of phosphorylation events after KRGE and sorafenib combination treatment. Korean red ginseng extract suppressed the proliferation of two RCC cell lines; activated caspase-3; caused poly(ADP-ribose) polymerase cleavage; abrogated the expression of B-cell lymphoma 2, B-cell lymphoma extra large, survivin, inhibitors of apoptosis proteins-1/2, cyclooxygenase-2, cyclin D1, matrix metallopeptidase-9, and vascular endothelial growth factor; and upregulated pro-apoptotic gene products. Interestingly, KRGE enhanced the cytotoxic and apoptotic effects of sorafenib in RCC cells. The combination treatment of KRGE and sorafenib more clearly suppressed cyclic adenosine monophosphate response element-binding protein and c-Jun phosphorylation and induced phosphorylation of p53 than did the individual treatment regimen. Our results clearly demonstrate that KRGE can enhance the anticancer activity of sorafenib and may have a substantial potential in the treatment of RCC. Copyright © 2017 John Wiley & Sons, Ltd.

Isorhynchophylline, a Potent Plant Alkaloid, Induces Apoptotic and Anti-Metastatic Effects in Human Hepatocellular Carcinoma Cells through the Modulation of Diverse Cell Signaling Cascades.

Isorhynchophylline (Rhy) is an active pharmacological component of Uncaria rhynchophylla that has been reported previously to exert significant antihypertensive and neuroprotective effects. However, very little is known about its potential anti-cancer activities. This study was carried out to evaluate the anticancer effects of Rhy against various human carcinoma cell lines. We found that Rhy exhibited substantial cytotoxic effect against human hepatocellular carcinoma HepG2 cells when compared with other human carcinoma cell lines including those of lung, pancreas, prostate, head and neck, breast, multiple myeloma, brain and renal cell carcinoma. Rhy induced apoptosis as characterized by accumulation of cells in sub G1 phase; positive Annexin V binding; activation of caspase-8, -9, and -3; and cleavage of PARP (poly-ADP ribose polymerase). This effect of Rhy correlated with the down-regulation of various proteins that mediated cell proliferation, cell survival, metastasis, and angiogenesis. Moreover, cell proliferation, migration, and constitutive CXCR4 (C-X-C chemokine receptor type 4), MMP-9 (Matrix metallopeptidase-9), and MMP-2 expression were inhibited upon Rhy treatment. We further investigated the effect of Rhy on the oncogenic cell signaling cascades through phospho-kinase array profiling assay. Rhy was found to abrogate phospho-p38, ERK, JNK, CREB, c-Jun, Akt, and STAT3 signals, but interestingly enhanced phospho-p53 signal. Overall, our results indicate, for the first time, that Rhy could exert anticancer and anti-metastatic effects through regulation of multiple signaling cascades in hepatocellular carcinoma cells.

Ginkgolic Acid C 17:1, Derived from Ginkgo biloba Leaves, Suppresses Constitutive and Inducible STAT3 Activation through Induction of PTEN and SHP-1 Tyrosine Phosphatase.

Ginkgolic acid C 17:1 (GAC 17:1) extracted from Ginkgo biloba leaves, has been previously reported to exhibit diverse antitumor effect(s) through modulation of several molecular targets in tumor cells, however the detailed mechanism(s) of its actions still remains to be elucidated. Signal transducer and activator of transcription 3 (STAT3) is an oncogenic transcription factor that regulates various critical functions involved in progression of diverse hematological malignancies, including multiple myeloma, therefore attenuating STAT3 activation may have a potential in cancer therapy. We determined the anti-tumor mechanism of GAC 17:1 with respect to its effect on STAT3 signaling pathway in multiple myeloma cell lines. We found that GAC 17:1 can inhibit constitutive activation of STAT3 through the abrogation of upstream JAK2, Src but not of JAK1 kinases in U266 cells and also found that GAC can suppress IL-6-induced STAT3 phosphorylation in MM.1S cells. Treatment of protein tyrosine phosphatase (PTP) inhibitor blocked suppression of STAT3 phosphorylation by GAC 17:1, thereby indicating a critical role for a PTP. We also demonstrate that GAC 17:1 can induce the substantial expression of PTEN and SHP-1 at both protein and mRNA level. Further, deletion of PTEN and SHP-1 genes by siRNA can repress the induction of PTEN and SHP-1, as well as abolished the inhibitory effect of drug on STAT3 phosphorylation. GAC 17:1 down-regulated the expression of STAT3 regulated gene products and induced apoptosis of tumor cells. Overall, GAC 17:1 was found to abrogate STAT3 signaling pathway and thus exert its anticancer effects against multiple myeloma cells.

Supercritical Fluid Extraction of Citrus iyo Hort. ex Tanaka Pericarp Inhibits Growth and Induces Apoptosis Through Abrogation of STAT3 Regulated Gene Products in Human Prostate Cancer Xenograft Mouse Model.

Activation of signal transducer and activator of transcription 3 (STAT3) is well known to play a major role in the cell growth, survival, proliferation, metastasis, and angiogenesis of various cancer cells. Most of the citrus species offer large quantities of phytochemicals that have beneficial effects attributed to their chemical components. Our study was carried out to evaluate the anticancer effects of the pericarp of Iyokan ( Citrus iyo Hort. ex Tanaka), locally known as yeagam in Korea, through modulation of the STAT3 signaling pathway in both tumor cells and a nude mice model. The effect of supercritical extracts of yeagam peel (SEYG) on STAT3 activation, associated protein kinases, STAT3-regulated gene products, cellular proliferation, and apoptosis was examined. The in vivo effect of SEYG on the growth of DU145 human prostate xenograft tumors in athymic nu/nu male mice was also investigated. We found SEYG exerted substantial inhibitory effect on STAT3 activation in human prostate cancer DU145 cells as compared to other tumor cells analyzed. SEYG inhibited proliferation and downregulated the expression of various STAT3-regulated gene products such as bcl-2, bcl-xL, survivin, IAP-1/2, cyclin D1, cyclin E, COX-2, VEGF, and MMP-9. This correlated with an increase in apoptosis as indicated by an increase in the expression of p53 and p21 proteins, the sub-G1 arrest, and caspase-3-induced PARP cleavage. When administered intraperitoneally, SEYG reduced the growth of DU145 human prostate xenograft tumors through downmodulation of STAT3 activation in athymic nu/nu male mice. Overall, these results suggest that SEYG extract has the potential source of STAT3 inhibitors that may have a potential in chemoprevention of human prostate cancer cells.

Capsazepine inhibits JAK/STAT3 signaling, tumor growth, and cell survival in prostate cancer.

Persistent STAT3 activation is seen in many tumor cells and promotes malignant transformation. Here, we investigated whether capsazepine (Capz), a synthetic analogue of capsaicin, exerts anticancer effects by inhibiting STAT3 activation in prostate cancer cells. Capz inhibited both constitutive and induced STAT3 activation in human prostate carcinoma cells. Capz also inhibited activation of the upstream kinases JAK1/2 and c-Src. The phosphatase inhibitor pervanadate reversed Capz-induced STAT3 inhibition, indicating that the effect of Capz depends on a protein tyrosine phosphatase. Capz treatment increased PTPε protein and mRNA levels. Moreover, siRNA-mediated knockdown of PTPε reversed the Capz-induced induction of PTPε and inhibition of STAT3 activation, indicating that PTPε is crucial for Capz-dependent STAT3 dephosphorylation. Capz also decreased levels of the protein products of various oncogenes, which in turn inhibited proliferation and invasion and induced apoptosis. Finally, intraperitoneal Capz administration decreased tumor growth in a xenograft mouse prostate cancer model and reduced p-STAT3 and Ki-67 expression. These data suggest that Capz is a novel pharmacological inhibitor of STAT3 activation with several anticancer effects in prostate cancer cells.