Targeting Multiple Signaling Pathways Research Articles

Honokiol: A Novel Natural Agent for Cancer Prevention and Therapy

Honokiol (3',5-di-(2-propenyl)-1,1'-biphenyl-2,4'-diol) is a bioactive natural product derived from Magnolia spp. Recent studies have demonstrated anti-inflammatory, anti-angiogenic, anti-oxidative and anticancer properties of honokiol in vitro and in preclinical models. Honokiol targets multiple signaling pathways including nuclear factor kappa B (NF-κB), signal transducers and activator of transcription 3 (STAT3), epidermal growth factor receptor (EGFR) and mammalian target of rapamycin (m-TOR), which have great relevance during cancer initiation and progression. Furthermore, pharmacokinetic profile of honokiol has revealed a desirable spectrum of bioavailability after intravenous administration in animal models, thus making it a suitable agent for clinical trials. In this review, we discuss recent data describing the molecular targets of honokiol and its anti-cancer activities against various malignancies in pre-clinical models. Evaluation of honokiol in clinical trials will be the next step towards its possible human applications.

Continuous daily sunitinib for recurrent glioblastoma

Bevacizumab ((BEV) has become a mainstay of treating recurrent glioblastoma, but eventual tumor resistance is expected. Targeting multiple growth-associated signaling pathways may result in more effective treatment than targeting VEGF alone. Patients with recurrent glioblastoma were stratified by prior BEV exposure and treated with sunitinib 37.5mg daily in this phase II study. Response evaluations were performed at baseline and at the end of every 4week cycle. Six-month progression-free survival (PFS6) was the primary endpoint for both arms of the study. Secondary endpoints included health related quality of life measures and FDG-PET correlatives with patient outcomes. Sixty-three patients were accrued to this study; thirty-two were BEV-naïve, 31 were BEV-resistant. PFS6 was 10.4% [95% CI 3.2-33.8] in the BEV-naïve cohort and 0% in the BEV-resistant cohort. Median overall survival was 9.4months [95% CI 6.15-21.90] in the BEV-naïve cohort and 4.37months [95% CI 3.02-6.21] in the BEV-resistant cohort. 3/29 patients (10%) of the BEV-naïve, and 0/27 BEV-resistant patients achieved radiographic response. Thrombocytopenia, leukopenia, and neutropenia were the most common drug-associated adverse events and occurred with higher frequency than expected. Sunitinib treatment in BEV-naïve patients did not appear to affect outcomes with subsequent BEV therapy. Continuous daily sunitinib did not prolong progression-free survival in BEV-naïve nor BEV-resistant patients with recurrent glioblastoma.

Ursolic Acid Inhibits Growth and Metastasis of Human Colorectal Cancer in an Orthotopic Nude Mouse Model by Targeting Multiple Cell Signaling Pathways: Chemosensitization with Capecitabine

Development of chemoresistance, poor prognosis, and metastasis often renders the current treatments for colorectal cancer (CRC) ineffective. Whether ursolic acid, a component of numerous medicinal plants, either alone or in combination with capecitabine, can inhibit the growth and metastasis of human CRC was investigated. The effect of ursolic acid on proliferation of CRC cell lines was examined by mitochondrial dye uptake assay, apoptosis by esterase staining, NF-κB activation by DNA-binding assay, and protein expression by Western blot. The effect of ursolic acid on the growth and chemosensitization was also examined in orthotopically implanted CRC in nude mice. We found that ursolic acid inhibited the proliferation of different colon cancer cell lines. This is correlated with inhibition of constitutive NF-κB activation and downregulation of cell survival (Bcl-xL, Bcl-2, cFLIP, and survivin), proliferative (cyclin D1), and metastatic (MMP-9, VEGF, and ICAM-1) proteins. When examined in an orthotopic nude mouse model, ursolic acid significantly inhibited tumor volume, ascites formation, and distant organ metastasis, and this effect was enhanced with capecitabine. Immunohistochemistry of tumor tissue indicated that ursolic acid downregulated biomarkers of proliferation (Ki-67) and microvessel density (CD31). This effect was accompanied by suppression of NF-κB, STAT3, and β-catenin. In addition, ursolic acid suppressed EGF receptor (EGFR) and induced p53 and p21 expression. We also observed bioavailability of ursolic acid in the serum and tissue of animals. Overall, our results show that ursolic acid can inhibit the growth and metastasis of CRC and further enhance the therapeutic effects of capecitabine through the suppression of multiple biomarkers linked to inflammation, proliferation, invasion, angiogenesis, and metastasis.

Niclosamide, an old antihelminthic agent, demonstrates antitumor activity by blocking multiple signaling pathways of cancer stem cells

Niclosamide, an oral antihelminthic drug, has been used to treat tapeworm infection for about 50 years. Niclosamide is also used as a molluscicide for water treatment in schistosomiasis control programs. Recently, several groups have independently discovered that niclosamide is also active against cancer cells, but its precise mechanism of antitumor action is not fully understood. Evidence supports that niclosamide targets multiple signaling pathways (NF-κB, Wnt/β-catenin, Notch, ROS, mTORC1, and Stat3), most of which are closely involved with cancer stem cells. The exciting advances in elucidating the antitumor activity and the molecular targets of this drug will be discussed. A method for synthesizing a phosphate pro-drug of niclosamide is provided. Given its potential antitumor activity, clinical trials for niclosamide and its derivatives are warranted for cancer treatment.

MiR-125b, a Target of CDX2, Regulates Cell Differentiation through Repression of the Core Binding Factor in Hematopoietic Malignancies

MicroRNA-125b (miR-125b), a small noncoding RNA molecule, has been found to be deregulated and functions as an oncogene in many cancers including hematopoietic malignancies. However, the mechanisms accounting for miR-125b dysregulation remain to be elucidated. The present study aims to identify the factors that might contribute to up-regulation of miR-125b in human hematopoietic malignancies and its downstream targets for lineage-specific differentiation. We at first reported that CDX2, a homeobox transcription factor, binds to promoter regions of the miR-125b gene and activates transcriptional regulation of miR-125b in malignant myeloid cells. We further revealed that increasing levels of CDX2 in malignant myeloid cells activate miR-125b expression, which in turn inhibits core binding factor β (CBFβ) translation, thereby counteracting myeloid cell differentiation, at least for granulocytic lineage, and promoting leukemogenesis. Interestingly, we found that this novel pathway including CDX2, miR-125b, and CBFβ was mediated by undergoing all-trans-retinoic acid induction. Once differentiation ensues with all-trans-retinoic acid treatment, CDX2 activity decreases, leading to a reduction in miR-125b transcription and up-regulation of CBFβ in myeloid cells and in patients. The study provides a new mechanism that contributes to hematopoietic malignancies, which could involve deregulation of miR-125b and its up- and downstream factors. As altered expression of miRNAs has been reported in a wide range of malignancies, delineating the underlying molecular mechanisms of aberrant miRNA expression and characterizing the upstream and downstream factors will help to understand important steps in the pathogenesis of these afflictions.

Dysfunctional Immune-Mediated Inflammation in Rheumatoid Arthritis Dictates that Development of Anti-Rheumatic Disease Drugs Target Multiple Intracellular Signaling Pathways

A skewed repertoire of pro-inflammatory cytokines produced by the Th1 subset, one of the hallmarks of rheumatoid arthritis (RA), is characterized by an overabundance of pro-inflammatory cytokines. Tumor necrosis factor-α, interleukin- 1 (IL-1), IL-6, IL-7, IL-8, IL-21, IL-12/IL-23, IL-15, IL-17, IL-18, IL-32, and interferon-γ are primarily responsible for immune-mediated inflammation of RA by activating Janus kinases (JAK) -1, -2, -3, p38 kinase, C-Jun-Nterminal kinase, extracellular signal-regulated kinase 1/2 and the phosphatidylinosotide-3-kinase/Akt/mTor pathways. Activation of these signaling pathways results in up-regulation of pro-inflammatory cytokines, cyclooxygenase-2, matrix metalloproteinases, pro-angiogenesis proteins and anti-apoptosis proteins, the latter resulting in abnormal survival of activated T- and B-cells. Further, IL-17 also regulates the differentiation of CD4+ T-helper cells by inducing a Th17 T-cell subset, and a subpopulation of T-regulatory (Treg) cells. Although Treg cells are sufficiently abundant in RA synovial fluid, they fail to induce immune tolerance suggesting a functional deficiency likely coupled to putative protein kinase signaling abnormalities. The results of in vitro and studies in animal models of arthritis have indicated that inhibiting individual signaling pathways can blunt the synthesis of several of the pro-inflammatory biomarkers characteristic of human RA pathology. However, RA clinical trials indicated that small molecule inhibitors of JAK-1, -2-, 3 and/or p38 kinase while exhibiting acceptable safety and tolerability profiles have only marginal and transient clinical effectiveness. These results suggested that future RA clinical studies using these or other kinase inhibitors will have to consider strategies designed to simultaneously inhibit multiple kinase pathways.

Dysfunctional Immune-Mediated Inflammation in Rheumatoid Arthritis Dictates that Development of Anti-Rheumatic Disease Drugs Target Multiple Intracellular Signaling Pathways

Dysfunctional Immune-Mediated Inflammation in Rheumatoid Arthritis Dictates that Development of Anti-Rheumatic Disease Drugs Target Multiple Intracellular Signaling Pathways

5-Deoxykaempferol Plays a Potential Therapeutic Role by Targeting Multiple Signaling Pathways in Skin Cancer

Nontoxic small molecules with multitargeting effects are believed to have potential in cancer prevention. Dietary phytochemicals were shown to exhibit cancer-preventive effects attributed to their antioxidant capacities. In this report, we show that the natural compound 5-deoxykaempferol (5-DK) exerts a chemopreventive effect on UVB-induced skin carcinogenesis by targeting multiple signaling molecules. 5-DK suppressed the UVB-induced expression of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor in mouse skin epidermal JB6 P+ cells. Moreover, 5-DK inhibited phosphorylation of MKK3/6, MKK4, and Akt, but had no effect on phosphorylation of Src, extracellular signal-regulated kinases, or ribosomal S6 kinase (RSK). However, 5-DK affected multiple targets by reducing Src, phosphoinositide 3-kinase (PI3K), and RSK2 activities. In particular, pull-down assays revealed that 5-DK specifically bound to and competed with ATP for binding with Src, PI3K, and RSK2. Exposure to 5-DK significantly suppressed UVB-induced tumorigenesis in mouse skin in a dose-dependent manner, and it inhibited the UVB-induced expression of COX-2, proliferating cell nuclear antigen, vascular endothelial growth factor, and matrix metalloproteinase-9. Our data suggest that 5-DK docks at the ATP-binding site of Src, PI3K, and RSK2. For RSK2, the ATP-binding site is located between the N- and C-lobes of the kinase domain. Taken together, our results indicate that 5-DK holds promise for the treatment of UVB-induced skin cancer by targeting Src, PI3K, and RSK2 signaling.

S2034 CEA Increases Metastatic Potential of CRC Cells By Targeting Multiple Signaling Pathways

BCL6 and nuclear translocation of HB-EGF-CTF in gastric cancers. Method: We examined BCL6 and cyclinD2 expression level under the 12-0-tetradecanoylphorbor-13-acetate (TPA) stimulation. KB-R7785 was used to suppress HB-EGF-CTF nuclear translocation. We also investigated the interaction and translocation of BCL6 with HB-EGF-CTF by using immunofluorescence microscopy and immunoprecipitation. Furthermore, we immunohistochemically studied 100 surgical specimens of advanced gastric cancers to analyze the expression of HB-EGF, BCL6, and cyclin D2. Results: TPA treatment resulted in BCL6 degradation and cyclin D2 up-regulation. This phenomenon was inhibited by the suppression of the nuclear translocation of HB-EGF-CTF. The HB-EGF-CTF nuclear translocation lead to the interaction of BCL6 with HB-EGF-CTF and the nuclear export of BCL6, and the ubiquitin/proteasome pathway mediated the BCL6 degradation. siRNA targeting BCL6 revealed that the upregulation of cyclin D2 depends on BCL6 degradation. BCL6 interacts with nuclear translocated HB-EGF-CTF and the nuclear export and degradation of BCL6 (caused by this interaction and the ubiquitin/proteasome pathway) induces cyclin D2 up-regulation. In human gastric cancer tissues, BCL6 expression is associated with differentiated gastric cancers. The inverse correlation between BCL6 and cyclin D2 was also found in HB-EGF-positive human gastric cancers. BCL6 degradation caused by the HB-EGF-CTF also induced cyclin D2 expression In Vivo (human cancer tissues). Conclusion: Inhibition of HB-EGF-CTF nuclear translocation and the resulting maintenance of BCL6 function are important for the regulation of gastric cancer progression.

Vaccinia virus blocks Stat1-dependent and Stat1-independent gene expression induced by type I and type II interferons.

Blocking the function of Stat (signal transducer and activator of transcription) proteins, which are critical for antiviral responses, has evolved as a common mechanism for pathogen immune evasion. The poxvirus-encoded phosphatase H1 is critical for viral replication, and may play an additional role in the evasion of host defense by dephosphorylating Stat1 and blocking interferon (IFN)-stimulated innate immune responses. Vaccinia virus (VACV) H1 can inhibit the phosphorylation of the transcription factor Stat1 after IFN-gamma stimulation of epithelial cells, greatly attenuating IFN-induced biological functions. In this study, we demonstrate that VACV infection is capable of inhibiting the phosphorylation of Stat1 and Stat2 after stimulation of fibroblasts or bone marrow-derived macrophages with either type I or type II IFNs, but did not inhibit the activation of Stat3 or Stat5 in either cell type. By using recombinant proteins for in vitro assays, we observe that variola virus H1 is more active than VACV H1, although it has similar selectivity for Stat targets. Differential effects of VACV infection were observed on the induction of IFN-stimulated genes, with complete inhibition of some genes by VACV infection, while others were less affected. Despite the IFN-gamma-induced expression of some genes in VACV-infected cells, IFN-gamma was unable to rescue the VACV-mediated inhibition of MHC class II antigen presentation. Moreover, VACV infection can affect the IFN-induced expression of Stat1-dependent and Stat1-independent genes, suggesting that the virus may target additional IFN-activated pathways. Thus, VACV targets multiple signaling pathways in the evasion of antiviral immune responses.

Carnosol, a Dietary Diterpene, Displays Growth Inhibitory Effects in Human Prostate Cancer PC3 Cells Leading to G2-Phase Cell Cycle Arrest and Targets the 5′-AMP-Activated Protein Kinase (AMPK) Pathway

This study examines the anti-cancer effect of carnosol in human prostate cancer PC3 cells and its role in modulating multiple signaling pathways associated with carcinogenesis. PC3 cells were treated with carnosol and were evaluated using a flow cytometry, a protein array and Western blot analysis to identify signaling pathways targeted by carnosol. Using an MTT assay we found that carnosol (10-70 microM) decreases cell viability in a time and dose-dependent manner. Further analysis using flow cytometry as well as biochemical analysis identified G2-phase cell cycle arrest. To establish a more precise mechanism, we performed a protein array that evaluated 638 proteins involved in cell signaling pathways. The protein array identified 5'-AMP-activated protein kinase (AMPK), a serine/threonine protein kinase involved in the regulation of cellular energy balance as a potential target. Further downstream effects consistent with cancer inhibition included the modulation of the mTOR/HSP70S6k/4E-BP1 pathway. Additionally, we found that carnosol targeted the PI3K/Akt pathway in a dose dependent manner. These results suggest that carnosol targets multiple signaling pathways that include the AMPK pathway. The ability of carnosol to inhibit prostate cancer in vitro suggests carnosol may be a novel agent for the management of PCa.

New Paradigms in Anticancer Therapy: Targeting Multiple Signaling Pathways With Kinase Inhibitors

Signal transduction in cancer cells is a sophisticated process that involves receptor tyrosine kinases (RTKs) that eventually trigger multiple cytoplasmic kinases, which are often serine/threonine kinases. A number of tumor models have identified several key cellular signaling pathways that work independently, in parallel, and/or through interconnections to promote cancer development. Three major signaling pathways that have been identified as playing important roles in cancer include the phosphatidyl inositol-3-kinase (PI3K)/AKT, protein kinase C (PKC) family, and mitogen-activated protein kinase (MAPK)/Ras signaling cascades. In clinical trials, highly selective or specific blocking of only one of the kinases involved in these signaling pathways has been associated with limited or sporadic responses. Improved understanding of the complexity of signal transduction processes and their roles in cancer has suggested that simultaneous inhibition of several key kinases at the level of receptors and/or downstream serine/threonine kinases may help to optimize the overall therapeutic benefit associated with molecularly targeted anticancer agents. Using targeted agents to inhibit multiple signaling pathways has emerged as a new paradigm for anticancer treatment based on preclinical and clinical data showing potent anti-tumor activity of single drugs inhibiting multiple molecular targets or combination therapies involving multiple drugs with selective or narrow target specificity. Preclinical and clinical studies point to molecules on vascular endothelial cells and pericytes as being important targets for anticancer therapies, as well as molecules on or within tumor cells themselves. This suggests that optimal therapeutic approaches to cancer may involve targeting multiple molecules found in both the tumor and supportive tissues. In this review, we will use the most recent preclinical and clinical data to describe this emerging paradigm for anticancer therapy involving targeting multiple signaling pathways with tyrosine or serine/threonine kinase inhibitors.

Targeting Multiple Signaling Pathways by Green Tea Polyphenol (−)-Epigallocatechin-3-Gallate

Cell signaling pathways, responsible for maintaining a balance between cell proliferation and death, have emerged as rational targets for the management of cancer. Emerging data amassed from various laboratories around the world suggests that green tea, particularly its major polyphenolic constituent (-)-epigallocatechin-3-gallate (EGCG), possesses remarkable cancer chemopreventive and therapeutic potential against various cancer sites in animal tumor bioassay systems and in some human epidemiologic studies. EGCG has been shown to modulate multiple signal transduction pathways in a fashion that controls the unwanted proliferation of cells, thereby imparting strong cancer chemopreventive as well as therapeutic effects. This review discusses the modulations of important signaling events by EGCG and their implications in cancer management.

Targeting Multiple Signaling Pathways as a Strategy for Managing Prostate Cancer: Multifocal Signal Modulation Therapy

The aberrant behavior of cancer reflects upregulation of certain oncogenic signaling pathways that promote proliferation, inhibit apoptosis, and enable the cancer to spread and evoke angiogenesis. Theoretically, it should be feasible to decrease the activity of these pathways-or increase the activity of pathways that oppose them-with noncytotoxic agents. Since multiple pathways are dysfunctional in most cancers, and cancers accumulate new oncogenic mutations as they progress, the greatest and most durable therapeutic benefit will likely be achieved with combination regimens that address several targets. Thus, a multifocal signal modulation therapy (MSMT) of cancer is proposed. This concept has already been documented by researchers who have shown that certain combinations of signal modulators-of limited utility when administered individually-can achieve dramatic suppression of tumor growth in rodent xenograft models. The present essay attempts to guide development of MSMTs for prostate cancer. Androgen ablation is a signal-modulating measure already in standard use in the management of delocalized prostate cancer. The additional molecular targets considered here include the type 1 insulin-like growth factor receptor, the epidermal growth factor receptor, mammalian target of rapamycin, NF-kappaB, hypoxia-inducible factor-1alpha, hsp90, cyclooxygenase-2, protein kinase A type I, vascular endothelial growth factor, 5-lipoxygenase, 12-lipoxygenase, angiotensin II receptor type 1, bradykinin receptor type 1, c-Src, interleukin-6, ras, MDM2, bcl-2/bclxL, vitamin D receptor, estrogen receptor-beta, and PPAR-. Various nutrients and phytochemicals suspected to have potential utility in prostate cancer prevention and therapy, but whose key molecular targets are still unknown, might reasonably be incorporated into MSMTs for prostate cancer; these include lycopene, selenium, green tea polyphenols, genistein, and silibinin. MSMTs can be developed systematically by testing various combinations of signal-modulating agents, in concentrations that can feasibly be achieved and maintained clinically, on human prostate cancer cell lines; combinations that appear promising can then be tested in xenograft models and, ultimately, in the clinic. Some signal modulators can increase response to cytotoxic drugs by upregulating effectors of apoptosis. When MSMTs fail to raise the spontaneous apoptosis rate sufficiently to achieve tumor stasis or regression, incorporation of appropriate cytotoxic agents into the regimen may improve the clinical outcome.