ag-490 and Neoplasms

Topics: Animals; Antineoplastic Agents; Drug Resistance, Neoplasm; Humans; Neoplasms; Receptor, IGF Type 1; Signal Transduction

Stat3 is constitutively activated in many human cancers where it functions as a critical mediator of oncogenic signaling through transcriptional activation of genes encoding apoptosis inhibitors (e.g. Bcl-x(L), Mcl-1 and survivin), cell-cycle regulators (e.g. cyclin D1 and c-Myc) and inducers of angiogenesis (e.g. vascular endothelial growth factor). This article reviews several approaches that have been pursued for targeting Stat3 in cancer therapy including antisense strategies, tyrosine kinase inhibition, decoy phosphopeptides, decoy duplex oligonucleotides and G-quartet oligodeoxynucleotides (GQ-ODN). The GQ-ODN strategy is reviewed in somewhat greater detail than the others because it includes a novel system that effectively delivers drug into cells and tissues, addresses successfully the issue of specificity of targeting Stat3 versus Stat1, and has demonstrated efficacy in vivo.

Topics: Angiogenesis Inducing Agents; Animals; Anticarcinogenic Agents; Apoptosis; Cell Cycle Proteins; Cell Movement; Cell Proliferation; Humans; Inhibitor of Apoptosis Proteins; Ligands; Neoplasms; Oligonucleotides; Oligonucleotides, Antisense; Phosphopeptides; Plasmids; Protein Conformation; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Signal Transduction; src Homology Domains; STAT3 Transcription Factor; Transcriptional Activation; Triterpenes; Tyrphostins

Tumor permeability is a critical determinant of drug delivery and sensitivity, but systematic methods to identify factors that perform permeability barrier functions in the tumor microenvironment are not yet available. Multicellular tumor spheroids have become tractable in vitro models to study the impact of a three-dimensional (3D) environment on cellular behavior. In this study, we characterized the spheroid-forming potential of cancer cells and correlated the resulting spheroid morphologies with genetic information to identify conserved cellular processes associated with spheroid structure. Spheroids generated from 100 different cancer cell lines were classified into four distinct groups based on morphology. In particular, round and compact spheroids exhibited highly hypoxic inner cores and permeability barriers against anticancer drugs. Through systematic and correlative analysis, we reveal JAK-STAT signaling as one of the signature pathways activated in round spheroids. Accordingly, STAT3 inhibition in spheroids generated from the established cancer cells and primary glioblastoma patient-derived cells altered the rounded morphology and increased drug sensitivity. Furthermore, combined administration of the STAT3 inhibitor and 5-fluorouracil to a mouse xenograft model markedly reduced tumor growth compared with monotherapy. Collectively, our findings demonstrate the ability to integrate 3D culture and genetic profiling to determine the factors underlying the integrity of the permeability barrier in the tumor microenvironment, and may help to identify and exploit novel mechanisms of drug resistance.

Topics: Animals; Benzoquinones; Cell Line, Tumor; Cell Membrane Permeability; Drug Resistance, Neoplasm; Fluorouracil; Humans; Janus Kinases; Lactams, Macrocyclic; Mice; Neoplasms; Signal Transduction; Spheroids, Cellular; STAT3 Transcription Factor; Tumor Microenvironment; Tyrphostins

Activation of the immune system is a way for host tissue to defend itself against tumor growth. Hence, treatment strategies that are based on immunomodulation are on the rise. Conventional cytostatic drugs such as the anthracycline doxorubicin can also activate immune cell functions of macrophages and natural killer cells. In addition, cytotoxicity of doxorubicin can be enhanced by combining this drug with the cytokine interferon-γ (IFNγ). Although doxorubicin is one of the most applied cytostatics, the molecular mechanisms of its immunomodulation ability have not been investigated thoroughly. In microarray analyses of HeLa cells, a set of 19 genes related to interferon signaling was significantly over-represented among genes regulated by doxorubicin exposure, including signal transducer and activator of transcription (STAT) 1 and 2, interferon regulatory factor 9, N-myc and STAT interactor, and caspase 1. Regulation of these genes by doxorubicin was verified with real-time polymerase chain reaction and immunoblotting. An enhanced secretion of IFNγ was observed when HeLa cells were exposed to doxorubicin compared with untreated cells. IFNγ-neutralizing antibodies and inhibition of Janus tyrosine kinase (JAK)-STAT signaling [aurintricarboxylic acid (ATA), (E)-2-cyano-3-(3,4-dihydrophenyl)-N-(phenylmethyl)-2-propenamide (AG490), STAT1 small interfering RNA] significantly abolished doxorubicin-stimulated expression of interferon signaling-related genes. Furthermore, inhibition of JAK-STAT signaling significantly reduced doxorubicin-induced caspase 3 activation and desensitized HeLa cells to doxorubicin cytotoxicity. In conclusion, we demonstrate that doxorubicin induces interferon-responsive genes via IFNγ-JAK-STAT1 signaling and that this pathway is relevant for doxorubicin's cytotoxicity in HeLa cells. Immunomodulation is a promising strategy in anticancer treatment, so this novel mode of action of doxorubicin may help to further improve the use of this drug among different types of anticancer treatment strategies.

Topics: Antibiotics, Antineoplastic; Cell Line, Tumor; Doxorubicin; Gene Expression Profiling; Humans; Interferon-gamma; Janus Kinase 1; Killer Cells, Natural; Neoplasms; Signal Transduction; STAT1 Transcription Factor; Tyrphostins

Herpesvirus saimiri (HVS) is capable of infecting a range of human carcinoma cell types with high efficiency and the viral genome persists as high copy number, circular, non-integrated episomes which segregate to progeny upon cell division. This allows HVS-based vectors to stably transduce a dividing cell population and provide sustained transgene expression for an extended period of time both in vitro and in vivo. Moreover, the insertion of a bacterial artificial chromosome cassette into the HVS genome simplifies the incorporation of large amounts of heterologous DNA for gene delivery. Herein we have produced a recombinant HVS-based vector containing full-length human TRAIL under the control of the α-survivin promoter, and subsequently challenged a variety of cancer cell lines with this vector. The TRAIL transgene was expressed in infected colorectal SW480 cells, causing considerable apoptosis induction. Apoptosis was also observed when several other cancer cell lines derived from different tissues were infected. Moreover, co-treatment with Jak inhibitor AG490 led to the disruption of spheroid cultures grown from the melanoma Mel888 line. These data suggest that an HVS gene therapy vector expressing TRAIL could be an effective treatment against cancer.

Topics: Antineoplastic Agents; Apoptosis; Caspases; Cell Line, Tumor; Cloning, Molecular; Genetic Therapy; Genetic Vectors; HEK293 Cells; Herpesvirus 2, Saimiriine; Humans; Neoplasms; Recombinant Proteins; Sequence Deletion; Spheroids, Cellular; TNF-Related Apoptosis-Inducing Ligand; Transcription, Genetic; Tyrphostins

Constitutive activation of the Janus kinase (JAK)/signal transducer and activator of transcription (STAT) pathway occurs frequently in cancer cells and contributes to oncogenesis. Among the members of STAT family, STAT3 plays a pivotal role in the development and progression of human tumors. The STAT3-mediated signaling pathway has been recognized as a promising anticancer target. Here, we show that 17-Hydroxy-jolkinolide B (HJB), a diterpenoid from the Chinese medicinal herb Euphorbia fischeriana Steud, strongly inhibits interleukin (IL)-6-induced as well as constitutive STAT3 activation. Furthermore, we show that HJB directly targets the JAK family kinases, JAK1, JAK2, and TYK2, by inducing dimerization of the JAKs via cross-linking. Addition of DTT or glutathione prevents the JAK cross-linking and blocks the inhibitory effects of HJB on IL-6-induced STAT3 activation, suggesting that HJB may react with cystein residues of JAKs to form covalent bonds that inactivate JAKs. Liquid chromatography/mass spectrometry analysis confirmed that each HJB reacted with two thiols. The effect of HJB on the JAK/STAT3 pathway is specific as HJB has no effect on platelet-derived growth factor, epidermal growth factor, or insulin-like growth factor I signaling pathways. Finally, we show that HJB inhibits growth and induces apoptosis of tumor cells, particularly those tumor cells with constitutively activated STAT3. We propose that the natural compound HJB is a promising anticancer drug candidate as a potent STAT3 signaling inhibitor.

Topics: Apoptosis; Cell Line, Tumor; Diterpenes; Drugs, Chinese Herbal; Euphorbia; Humans; Interleukin-6; Janus Kinase 2; Janus Kinases; Neoplasms; Signal Transduction; STAT3 Transcription Factor; Tyrphostins

The identification of self-renewing and multipotent neural stem cells (NSCs) in the mammalian brain holds promise for the treatment of neurological diseases and has yielded new insight into brain cancer. However, the complete repertoire of signaling pathways that governs the proliferation and self-renewal of NSCs, which we refer to as the 'ground state', remains largely uncharacterized. Although the candidate gene approach has uncovered vital pathways in NSC biology, so far only a few highly studied pathways have been investigated. Based on the intimate relationship between NSC self-renewal and neurosphere proliferation, we undertook a chemical genetic screen for inhibitors of neurosphere proliferation in order to probe the operational circuitry of the NSC. The screen recovered small molecules known to affect neurotransmission pathways previously thought to operate primarily in the mature central nervous system; these compounds also had potent inhibitory effects on cultures enriched for brain cancer stem cells. These results suggest that clinically approved neuromodulators may remodel the mature central nervous system and find application in the treatment of brain cancer.

Topics: Animals; Cell Survival; Cells, Cultured; Mice; Molecular Structure; Neoplasms; Neurons; Pharmaceutical Preparations; Sensitivity and Specificity; Stem Cells

Constitutive activation of Janus kinases (JAKs) and signal transducers and activators of transcription (STAT) occurs at very high frequency in various hematopoietic malignancies and solid tumors. It has been demonstrated that the tyrosine kinase inhibitor, AG-490, selectively blocks JAK activity and completely eliminates leukemia cells in a severe combined immunodeficient (SCID) mouse model. Because many cytokines, including interleukin (IL)-12, have been shown to signal through JAK/STAT pathways, AG-490 may inhibit cytokine-based cancer therapy. In this study, we evaluated the effects of AG-490 on IL-12 functional signaling and IL-12-mediated antitumor response in vivo. Previous studies have established the critical roles of macrophages and IFN-gamma in mediating IL-12-induced antitumor effects. Our results show that in vivo administration of AG-490 causes tumor cell apoptosis but does not inhibit IL-12-mediated macrophage activation and IFN-gamma production by lymphocytes. Furthermore, our data indicate that combined therapy with AG-490 and IL-12-induces greater antitumor effects than either agent alone in a murine myeloma tumor model. These results suggest that JAK/STAT inhibitors deserve further investigation for use with IL-12 therapy in treating human cancers with elevated JAK/STAT activity.

Topics: Animals; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Nucleus; DNA-Binding Proteins; Female; Humans; Immunohistochemistry; In Situ Nick-End Labeling; Interferon-gamma; Interleukin-12; Macrophages; Macrophages, Peritoneal; Mice; Mice, Inbred BALB C; Mice, SCID; Neoplasms; Signal Transduction; Spleen; STAT3 Transcription Factor; Time Factors; Trans-Activators; Tumor Cells, Cultured; Tyrphostins