Vascular disrupting agents (VDAs) represent a novel approach to the treatment of cancer, resulting in the collapse of tumor vasculature and tumor death. 5,6-dimethylxanthenone-4-acetic acid (DMXAA) is a VDA currently in advanced phase II clinical trials, yet its precise mechanism of action is unknown despite extensive preclinical and clinical investigations. Our data demonstrate that DMXAA is a novel and specific activator of the TANK-binding kinase 1 (TBK1)–interferon (IFN) regulatory factor 3 (IRF-3) signaling pathway. DMXAA treatment of primary mouse macrophages resulted in robust IRF-3 activation and ∼750-fold increase in IFN-β mRNA, and in contrast to the potent Toll-like receptor 4 (TLR4) agonist lipopolysaccharide (LPS), signaling was independent of mitogen-activated protein kinase (MAPK) activation and elicited minimal nuclear factor κB–dependent gene expression. DMXAA-induced signaling was critically dependent on the IRF-3 kinase, TBK1, and IRF-3 but was myeloid differentiation factor 88–, Toll–interleukin 1 receptor domain–containing adaptor inducing IFN-β–, IFN promoter-stimulator 1–, and inhibitor of κB kinase–independent, thus excluding all known TLRs and cytosolic helicase receptors. DMXAA pretreatment of mouse macrophages induced a state of tolerance to LPS and vice versa. In contrast to LPS stimulation, DMXAA-induced IRF-3 dimerization and IFN-β expression were inhibited by salicylic acid. These findings detail a novel pathway for TBK1-mediated IRF-3 activation and provide new insights into the mechanism of this new class of chemotherapeutic drugs.
Vascular disrupting agents (VDAs) such as DMXAA (5,6-dimethylxanthenone-4-acetic acid) represent a novel approach for cancer treatment. DMXAA has potent anti-tumor activity in mice and, despite significant pre-clinical promise, failed human clinical trials. The anti-tumor activity of DMXAA has been linked to its ability to induce type I interferons in macrophages although the molecular mechanisms involved are poorly understood. Here we identify STING as a direct receptor for DMXAA leading to TBK1 and IRF3 signaling. Remarkably, the ability to sense DMXAA was restricted to murine STING. Human STING failed to bind to or signal in response to DMXAA. Human STING also failed to signal in response to cyclic-dinucleotides, conserved bacterial second messengers known to bind and activate murine STING signaling. Collectively, these findings detail an unexpected species-specific role for STING as a receptor for an anti-cancer drug and uncover important insights that may explain the failure of DMXAA in clinical trials for human cancer.
5,6-Dimethylxanthenone-4-acetic acid (DMXAA) acts through tumor vascular disruption and cytokine production and is the first of its class to enter phase 3 trials. We characterized leukocytes and cytokines in murine Colon 38 tumors before and after DMXAA treatment. Tumor mass declined 50% 24 hours after DMXAA administration, but the leukocyte count per gram of tumor increased threefold owing to a large influx of Ly6G+CD11b+F4/80- cells with the morphology of neutrophils. However, B and T lymphocytes, natural killer cells, and macrophages in the tumor all decreased in numbers. Seven chemokines were substantially induced in the tumor, spleen, and serum 4 hours after DMXAA administration. Using cultured spleen cell subpopulations, CD11b+ cells (largely monocytes and macrophages) were shown to be the primary producers of tumor necrosis factor α, interleukin 6 (IL-6), and macrophage inflammatory 1α (MIP-1α). CD49b+ natural killer cells produced IP-10, whereas CD45R+ B lymphocytes produced regulated upon activation normal T cell express sequence. T lymphocytes were not major producers of cytokines in the response to DMXAA. Murine peripheral blood leukocytes (PBLs) produced a similar panel of cytokines in culture to that detected in mouse serum after DMXAA treatment. Cytokines in human PBL cultures were subsequently measured with the aim of identifying potential serum markers of the human response to DMXAA. IP-10 (P < .001), monocyte chemoattractant protein 1 (P < .001), and sCD40L (P < .01) were decreased, whereas IL-8 (P < .001) and MIP-1α (P = .03) were increased in DMXAA-treated compared with untreated PBL cultures from a group of 12 donors.
AIM: To explore the possibility that nucleotide oligomerization domain 1 (NOD1) pathway involved in refractoriness of interferon-β signaling in mouse respiratory epithelial cells induced by the anticancer xanthone compound, 5,6-dimethylxanthenone-4-acetic acid (DMXAA).
METHODS: C10 mouse bronchial epithelial cells were grown in Dulbecco’s modified Eagle’s medium supplemented with 10% fetal bovine serum, 2 mmol/L glutamine, 100 units/mL penicillin, 100 g/mL streptomycin. Pathogen-free female BALB/c mice were used to explore the mechanisms of refractoriness of interferon-signaling. Mouse thioglycollate-elicited peritoneal macrophages, bone marrow derived macrophages and bone marrow derived dendritic cells were collected and cultured. The amount of interferon (IFN)-inducible protein-10 (IP10/CXCL10), macrophage chemotactic protein (MCP1/CCL2) and interleukin (IL)-6 secreted by cells activated by DMXAA was quantified using enzyme-linked immunosorbent assay kits according to the instructions of the manufacturers. Total RNA was isolated from cells or nasal epithelium with RNeasy Plus Mini Kit, and cDNA was synthesized. Gene expression was checked using Applied Biosystems StepOne Real-Time Polymerase Chain Reaction System. Transfection of small interfering RNA (siRNA) control, NOD1 duplexed RNA oligonucleotides, and high-mobility group box 1/2/3 (HMGB1/2/3) siRNA was performed using siRNA transfection reagent.
RESULTS: DMXAA activates IFN-β pathway with high level of IFN-β dependent antiviral genes including 2’, 5’-oligoadenylate synthetase 1 and myxovirus resistance 1 in mouse thioglycollate-elicited peritoneal macrophages, bone marrow derived macrophages and bone marrow derived dendritic cells. Activation of IFN-β by DMXAA involved in NOD1, but not HMGB1/2/3 signal pathway demonstrated by siRNA. NOD1 pathway plays an important role in refractoriness of IFN-β signaling induced by DMXAA in mouse C10 respiratory epithelial cells and BALB/c mice nasal epithelia. These data indicate that DMXAA is not well adapted to the intrinsic properties of IFN-β signaling. Approaches to restore sensitivity of IFN-β signaling by find other xanthone compounds may function similarly, could enhance the efficacy of protection from influenza pneumonia and potentially in other respiratory viral infections.
CONCLUSION: NOD1 pathway may play an important role in refractoriness of IFN-β signaling in mouse respiratory epithelial cells induced by DMXAA.
Innate immunity; Interferon; Refractoriness; Xanthone; Bronchial epithelium
Vascular disrupting agents (VDAs), anti-cancer drugs that target established tumor blood vessels, fall into two main classes: microtubule targeting drugs, exemplified by combretastatin A4 (CA4), and flavonoids, exemplified by 5,6-dimethylxanthenone-4-acetic acid (DMXAA). Both classes increase permeability of tumor vasculature in mouse models, and DMXAA in particular can cause massive tumor necrosis. The molecular target of CA4 is clearly microtubules. The molecular target(s) of DMXAA remains unclear. It is thought to promote inflammatory signaling in leukocytes, and has been assumed to not target microtubules, though it is not clear from the literature how carefully this assumption has been tested. An earlier flavone analog, flavone acetic acid, was reported to promote mitotic arrest suggesting flavones might possess anti-microtubule activity, and endothelial cells are sensitive to even mild disruption of microtubules. We carefully investigated whether DMXAA directly affects the microtubule or actin cytoskeletons of endothelial cells by comparing effects of CA4 and DMXAA on human umbilical vein endothelial cells (HUVEC) using time-lapse imaging and assays for cytoskeleton integrity. CA4 caused retraction of the cell margin, mitotic arrest and microtubule depolymerization, while DMXAA, up to 500 µM, showed none of these effects. DMXAA also had no effect on pure tubulin nucleation and polymerization, unlike CA4. We conclude that DMXAA exhibits no direct anti-microtubule action and thus cleanly differs from CA4 in its mechanism of action at the molecular level.
Successful immunotherapy will require alteration of the tumour microenvironment and/or decreased immune suppression. Tumour-associated macrophages (TAMs) are one major factor affecting tumour microenvironment. We hypothesised that altering TAM phenotype would augment the efficacy of immunotherapy.
We and others have reported that 5,6-Dimethylxanthenone-4-acetic-acid (DMXAA, Vadimezan) has the ability to change TAM phenotypes, inducing a tumour microenvironment conducive to antitumour immune responses. We therefore combined DMXAA with active immunotherapies, and evaluated anti-tumour efficacy, immune cell phenotypes (flow cytometry), and tumour microenvironment (RT–PCR).
In several different murine models of immunotherapy for lung cancer, DMXAA-induced macrophage activation significantly augmented the therapeutic effects of immunotherapy. By increasing influx of neutrophils and anti-tumour (M1) macrophages to the tumour, DMXAA altered myeloid cell phenotypes, thus changing the intratumoural M2/non-M2 TAM immunoinhibitory ratio. It also altered the tumour microenvironment to be more pro-inflammatory. Modulating macrophages during immunotherapy resulted in increased numbers, activity, and antigen-specificity of intratumoural CD8+ T cells. Macrophage depletion reduced the effect of combining immunotherapy with macrophage activation, supporting the importance of TAMs in the combined effect.
Modulating intratumoural macrophages dramatically augmented the effect of immunotherapy. Our observations suggest that addition of agents that activate TAMs to immunotherapy should be considered in future trials.
tumour immunology; immunotherapy; tumour-associated macrophages; lung cancer
Antigen-specific immunotherapy and vascular disrupting agents, such as 5,6-dimethylxanthenone-4-acetic acid (DMXAA), have emerged as attractive approaches for the treatment of cancers. In the current study, we tested the combination of DMXAA treatment with therapeutic human papillomavirus type 16 (HPV-16) E7 peptide-based vaccination for their ability to generate E7-specific CD8+ T-cell immune responses, as well as their ability to control E7-expressing tumors in a subcutaneous and a cervicovaginal tumor model. We found that the combination of DMXAA treatment with E7 long peptide (amino acids 43–62) vaccination mixed with polyriboinosinic:polyribocytidylic generated significantly stronger E7-specific CD8+ T-cell immune responses and antitumor effects compared with treatment with DMXAA alone or HPV peptide vaccination alone in the subcutaneous model. Additionally, we found that the DMXAA-mediated enhancement of E7-specific CD8+ T-cell immune responses generated by the therapeutic HPV peptide-based vaccine was dependent on the timing of administration of DMXAA. Treatment with DMXAA in tumor-bearing mice was also shown to lead to increased dendritic cell maturation and increased production of inflammatory cytokines in the tumor. Furthermore, we observed that the combination of DMXAA with HPV-16 E7 peptide vaccination generated a significant enhancement in the antitumor effects in the cervicovaginal TC-1 tumor growth model, which closely resembles the tumor microenvironment of cervical cancer. Taken together, our data demonstrated that administration of the vascular disrupting agent, DMXAA, enhances therapeutic HPV vaccine-induced cytotoxic T-lymphocyte responses and antitumor effects against E7-expressing tumors in two different locations. Our study has significant implications for future clinical translation.
Vascular disrupting agents such as 5,6-dimethylxanthenone-4-acetic acid (DMXAA) have emerged as a new class of potential anticancer drugs that selectively destroy the established tumor vasculature and shut down blood supply to solid tumors. In this study, Zeng and colleagues test the combination of DMXAA treatment with E7 long peptide vaccination mixed with poly(I:C) to enhance cellular immunity against E7-expressing tumors in mice.
In this report, we examined the antitumor activity of photodynamic therapy (PDT) in combination with 5,6-dimethylxanthenone- 4-acetic acid (DMXAA), a vascular disrupting agent currently undergoing clinical evaluation. BALB/c mice bearing subcutaneous CT-26 colon carcinomas were treated with PDT using the second-generation chlorin-based sensitizer, 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (Photochlor) with or without DMXAA. Long-term (60-days) treatment outcome, induction of tumor necrosis factor-alpha (TNF-α) and interleukin- 6 (IL-6), vascular damage (microvessel density, MVD) were evaluated as endpoints. In addition, treatment selectivity was evaluated using magnetic resonance imaging (MRI) and the foot response assay. A highly synergistic interaction was observed with the combination of low-dose DMXAA and PDT (48 J cm−2 at 112 mW cm−2) resulting in ~60% long-term cures. The duration of the PDT session for this combination therapy protocol was only 7 min, while the duration of a monotherapy PDT session, selected to yield the equivalent cure rate, was 152 min. MRI showed markedly less peritumoral edema after DMXAA + short-duration PDT compared with long-duration PDT monotherapy. Similarly, DMXAA + PDT caused significantly less phototoxicity to normal mouse foot tissue than PDT alone. Increased induction of cytokines TNF-α and IL-6 (P < 0.001) was observed at 4 h followed by extensive vascular damage, demonstrated by a significant reduction in MVD at 24 h after combination treatment. In conclusion, Photochlorsensitized PDT in combination with DMXAA exhibits superior efficacy and improved selectivity with clinically feasible illumination schemes. Clinical evaluation of this novel combination strategy is currently being planned.
The investigative anti-tumour agent 5,6-dimethylxanthenonone-4-acetic acid (DMXAA, NSC 640488), developed in this laboratory as an improved analogue of flavone acetic acid (FAA, NSC 347512), is currently in clinical trial. The ability of DMXAA to up-regulate tumour necrosis factor (TNF) mRNA and protein synthesis in cultured human peripheral blood leucocytes (HPBLs) has been investigated and compared with that of flavone acetic acid (FAA) and of bacterial lipopolysaccharide (LPS). Human peripheral blood leucocytes were isolated from buffy coats obtained from a blood transfusion centre and also from blood samples from laboratory volunteers. At a concentration of 400 microg ml(-1) and an incubation time of 2 h, DMXAA up-regulated mRNA synthesis in six of eight individuals tested, as measured by Northern blotting. The degree of up-regulation varied in different individuals from one to nine times that of control levels. In contrast, FAA caused no induction above that of control levels and in some cases suppressed expression relative to controls, extending previous data that DMXAA but not FAA up-regulates TNF mRNA in the human HL-60 tumour cell line. At the same concentration but with longer incubation times (6-12 h), DMXAA induced increases in TNF protein in 11 of 15 samples of HPBLs from buffy coats and also in 11 of 15 samples of HPBLs from volunteers, as measured by cytotoxicity assays with L929 cells. FAA caused no increase in TNF protein, while LPS induced TNF to approximately 20-fold higher levels than did DMXAA. Considerable heterogeneity of response was observed with both sources of HPBLs, and there was little or no correlation between the extent of TNF induction by DMXAA and LPS in individual samples. In vitro analysis of the response of human peripheral blood leucocytes to DMXAA may be a useful test in clinical trials of agents such as DMXAA.
To investigate the early effects of a vascular disrupting agent (VDA) in ectopic and orthotopic tumors using macromolecular contrast media-enhanced magnetic resonance imaging (MMCM-MRI).
Methods and Materials
MMCM-MRI of ectopic and orthotopic MCA205 murine fibrosarcomas was performed using the intravascular contrast agent, albumin-(Gd-DTPA)35. Change in longitudinal relaxation rate (ΔR1) was measured 24 hours after treatment with 5,6-dimethylxanthenone-4-acetic acid (DMXAA; 30 mg/kg) and used to compute tumor vascular volume and permeability. Correlative histology and immunohistochemistry was carried out along with measurement of tumor necrosis factor-alpha (TNF-α) and vascular endothelial growth factor (VEGF) levels in whole tumor extracts using the enzyme-linked immunosorbent assay (ELISA).
Orthotopic tumors exhibited higher vascular volume (P<0.05) than ectopic tumors prior to treatment. Twenty-four hours after DMXAA treatment, a significant (P<0.0001) but differential reduction in ΔR1 (70% in ectopic and 50% in orthotopic tumors) was observed compared to baseline estimates. Consistent with this observation, higher levels of TNF-α, an important mediator of the antivascular activity of DMXAA were measured in ectopic tumors three hours post treatment compared to orthotopic tumors (P<0.05). Immunohistochemical (CD31) and histological (H&E) sections of ectopic and orthotopic tumors showed a highly tumor selective vascular damage following treatment with the presence of viable surrounding normal tissue.
MMCM-MRI provided early quantitative estimates of change in tumor perfusion following VDA treatment that showed good correlation with cytokine induction. Differences in the response of ectopic and orthotopic tumors highlight the influence of host microenvironment in modulating the activity of VDAs.
VDA; DMXAA; ASA404; MMCM-MRI
5,6-Dimethylxanthenone-4-acetic acid (DMXAA), a potent type I interferon (IFN) inducer, was evaluated as a chemotherapeutic agent in mouse cancer models and proved to be well tolerated in human cancer clinical trials. Despite its multiple biological functions, DMXAA has not been fully characterized for the potential application as a vaccine adjuvant. In this report, we show that DMXAA does act as an adjuvant due to its unique property as a soluble innate immune activator. Using OVA as a model antigen, DMXAA was demonstrated to improve on the antigen specific immune responses and induce a preferential Th2 (Type-2) response. The adjuvant effect was directly dependent on the IRF3-mediated production of type-I-interferon, but not IL-33. DMXAA could also enhance the immunogenicity of influenza split vaccine which led to significant increase in protective responses against live influenza virus challenge in mice compared to split vaccine alone. We propose that DMXAA can be used as an adjuvant that targets a specific innate immune signaling pathway via IRF3 for potential applications including vaccines against influenza which requires a high safety profile.
The tumor-vascular disrupting agent (VDA) vadimezan (5,6-dimethylxanthenone-4-acetic acid, DMXAA) has been shown to potentiate the antitumor activity of photodynamic therapy (PDT) using systemically administered photosensitizers. Here, we characterized the response of subcutaneous syngeneic Colon26 murine colon adenocarcinoma tumors to PDT using the locally applied photosensitizer precursor aminolevulinic acid (ALA) in combination with a topical formulation of vadimezan. Diffuse correlation spectroscopy (DCS), a non-invasive method for monitoring blood flow, was utilized to determine tumor vascular response to treatment. Additionally, correlative CD31-immunohistochemistry to visualize endothelial damage, ELISA assays to measure induction of tumor necrosis factor-alpha (TNF-α) and tumor weight measurements were also examined in separate animals. In our previous work, DCS revealed a selective decrease in tumor blood flow over time following topical vadimezan. ALA-PDT treatment also induced a decrease in tumor blood flow. The onset of blood flow reduction was rapid in tumors treated with both ALA-PDT and vadimezan. CD31-immunostaining of tumor sections confirmed vascular damage following topical application of vadimezan. Tumor weight measurements revealed enhanced tumor growth inhibition with combination treatment compared to ALA-PDT or vadimezan treatment alone. In conclusion, vadimezan as a topical agent enhances treatment efficacy when combined with ALA-PDT. This combination could be useful in clinical applications.
The macrophage proinflammatory response to Francisella tularensis (Ft) LVS was shown previously to be TLR2-dependent. The observation that intracellular Ft LVS co-localizes with TLR2 and MyD88 inside macrophages suggested that Ft LVS might signal from within the phagosome. Macrophages infected with LVSΔiglC, a Ft LVS mutant that fails to escape from the phagosome, displayed greatly increased expression of a subset of TLR2-dependent, proinflammatory genes (e.g., Tnf) but decreased expression of others (e.g., Ifnb1). This latter subset was similarly mitigated in IFN-β−/− macrophages indicating that while Ft LVS-induced TLR2 signaling is necessary, cytosolic sensing of Ft to induce IFN-β is required for full induction of the macrophage proinflammatory response. While LVSΔiglC greatly increased IL-1β mRNA in wild-type macrophages, protein secretion was not observed. IL-1β secretion was also diminished in Ft LVS-infected IFN-β−/− macrophages. rIFN-β failed to restore IL-1β secretion in LVSΔiglC-infected macrophages, suggesting that signals in addition to IFN-β are required for assembly of the inflammasome and activation of caspase-1. IFN-β plays a central role in controlling the macrophage bacterial burden: bacterial recovery was greater in IFN-β−/− than in wild-type macrophages and treatment of Ft LVS-infected macrophages with rIFN-β or 5,6-dimethylxanthenone-4-acetic acid (DMXAA), a potent IFN-β inducer, greatly decreased the intracellular Ft LVS burden. In toto, these observations support the hypothesis that the host inflammatory response to Ft LVS is complex and requires engagement of multiple signaling pathways downstream of TLR2 including production of IFN-β via an unknown cytosolic sensor and activation of the inflammasome.
ERK1 and ERK2 mitogen-activated protein kinases (MAPK) play a critical role in regulation of cell proliferation and differentiation in response to mitogens and other extracellular stimuli. Mitogens and cytokines that activate MAPK in T cells have been shown to activate human immunodeficiency virus type 1 (HIV-1) replication. Little is known about the signal transduction pathways that activate HIV-1 replication in T cells upon activation by extracellular stimulation. Here, we report that activation of MAPK through the Ras/Raf/MEK signaling pathway enhances the infectivity of HIV-1 virions. Virus infectivity was enhanced by treatment of cells with MAPK stimulators, such as serum and phorbol myristate acetate, as well as by coexpression of constitutively activated Ras, Raf, or MEK (MAPK kinase) in the absence of extracellular stimulation. Treatment of cells with PD 098059, a specific inhibitor of MAPK activation, or with a MAPK antisense oligonucleotide reduced the infectivity of HIV-1 virions without significantly affecting virus production or the levels of virion-associated Gag and Env proteins. MAPK has been shown to regulate HIV-1 infectivity by phosphorylating Vif (X. Yang and D. Gabuzda, J. Biol. Chem. 273:29879–29887, 1998). However, MAPK activation enhanced virus infectivity in some cells lines that do not require Vif function. The HIV-1 Rev, Tat, p17Gag, and Nef proteins were directly phosphorylated by MAPK in vitro, suggesting that other HIV-1 proteins are potential substrates for MAPK phosphorylation. These results suggest that activation of the ERK MAPK pathway plays a role in HIV-1 replication by enhancing the infectivity of HIV-1 virions through Vif-dependent as well as Vif-independent mechanisms. MAPK activation in producer cells may contribute to the activation of HIV-1 replication when T cells are activated by mitogens and other extracellular stimuli.
Hemagglutinin B (HagB) is a nonfimbrial adhesin expressed on the surface of Porphyromonas gingivalis and has been implicated as a potential virulence factor involved in mediating the attachment of the bacteria to host cells. However, the molecular mechanisms underlying host responses to HagB and their roles in pathogenesis have yet to be elucidated. Mitogen-activated protein kinases (MAPKs) are activated following engagement of a variety of cell surface receptors via dual tyrosine and threonine phosphorylation and are thought to be involved in various cellular responses. The purpose of this study was to determine the role of intracellular signaling pathways including the MAPKs and NF-κB in regulating the production of proinflammatory and anti-inflammatory cytokines following stimulation of murine macrophages with recombinant HagB (rHagB). Stimulation of peritoneal macrophages with rHagB resulted in the production of the proinflammatory cytokines interleukin-12p40 (IL-12p40), gamma interferon (IFN-γ), and tumor necrosis factor alpha, as well as the anti-inflammatory cytokine IL-10. We also demonstrated the activation of extracellular signal-related kinase (ERK), c-Jun NH2-terminal protein kinase (JNK), and p38 MAPKs by rHagB-stimulated macrophages. Furthermore, blocking of the ERK and p38 signaling pathways by using specific inhibitors revealed differential regulatory roles in the rHagB-mediated production of proinflammatory and anti-inflammatory cytokines. ERK and p38 were important in down-regulation of IL-12p40 and IFN-γ production and up-regulation of IL-10 production. The enhanced levels of IL-12p40 in rHagB-stimulated macrophages by inhibition of ERK or p38 activity were partially attributable to the inhibition of IL-10 production. Moreover, NF-κB was found to be critical for up-regulation of IL-12p40 and down-regulation of IL-10 production in rHagB-stimulated macrophages. Taken together, our results demonstrate a role for the p38 and ERK pathways and the transcription factor NF-κB in modulating key immunoregulatory cytokines involved in the development of immune responses to P. gingivalis HagB.
The acute effects of the vascular-disrupting agent 5,6-dimethylxanthenone-4-acetic acid (DMXAA) were investigated in vivo using intravital microscopy (IVM) and magnetic resonance imaging (MRI). Changes in vascular permeability and blood flow of syngeneic CT-26 murine colon adenocarcinomas were assessed at 4 and 24 hours after DMXAA treatment (30 mg/kg, i.p.) and correlated with induction of tumor necrosis factor-α (TNF-α), endothelial damage [CD31/terminal deoxynucleotidyl transferase (TdT)], and treatment outcome. Intravital imaging revealed a marked increase in vascular permeability 4 hours after treatment, consistent with increases in intratumoral mRNA and protein levels of TNF-α. Parallel contrast-enhanced MRI studies showed a ∼ 4-fold increase in longitudinal relaxation rates (ΔR1), indicative of increased contrast agent accumulation within the tumor. Dual immunostained tumor sections (CD31/TdT) revealed evidence of endothelial apoptosis at this time point. Twenty-four hours after treatment, extensive hemorrhage and complete disruption of vascular architecture were observed with IVM, along with a significant reduction in ΔR1; and virtual absence of CD31 immunostaining. DMXAA-induced tumor vascular damage resulted in significant long-term (60-day) cures compared to untreated controls. Multimodality imaging approaches are useful in visualizing the effects of antivascular therapy in vivo. Such approaches allow cross validation and correlation of findings with underlying molecular changes contributing to treatment outcome.
Vascular-disrupting agents; DMXAA; multimodality imaging; tumor vasculature; tumor necrosis factor-α
The adverse effects of lipopolysaccharide (LPS) are mediated primarily by tumor necrosis factor alpha (TNF-alpha). TNF-alpha production by LPS-stimulated macrophages is regulated at the levels of both transcription and translation. It has previously been shown that several mitogen-activated protein kinases (MAPKs) are activated in response to LPS. We set out to determine which MAPK signaling pathways are activated in our system and which MAPK pathways are required for TNF-alpha gene transcription or TNF-alpha mRNA translation. We confirm activation of the MAPK family members extracellular-signal-regulated kinases 1 and 2 (ERK1 and ERK2), p38, and Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), as well as activation of the immediate upstream MAPK activators MAPK/ERK kinases 1 and 4 (MEK1 and MEK4). We demonstrate that LPS also activates MEK2, MEK3, and MEK6. Furthermore, we demonstrate that dexamethasone, which inhibits the production of cytokines, including TNF-alpha, significantly inhibits LPS induction of JNK/SAPK activity but not that of p38, ERK1 and ERK2, or MEK3, MEK4, or MEK6. Dexamethasone also blocks the sorbitol but not anisomycin stimulation of JNK/SAPK activity. A kinase-defective mutant of SAPKbeta, SAPKbeta K-A, blocked translation of TNF-alpha, as determined by using a TNF-alpha translational reporting system. Finally, overexpression of wild-type SAPKbeta was able to overcome the dexamethasone-induced block of TNF-alpha translation. These data confirm that three MAPK family members and their upstream activators are stimulated by LPS and demonstrate that JNK/SAPK is required for LPS-induced translation of TNF-alpha mRNA. A novel mechanism by which dexamethasone inhibits translation of TNF-alpha is also revealed.
The sustenance of most solid tumors including head and neck cancers (HNCs) is strongly dependent on the presence of a functioning vascular network. In this study, we examined the acute effects of a tumor vascular disrupting agent (VDA), 5,6-dimethylxanthenone-4-acetic acid (DMXAA; ASA404), in an orthotopic model of human HNC. Noninvasive magnetic resonance imaging (MRI) was used to monitor the vascular response of orthotopic FaDu xenografts to VDA therapy. Untreated tumors showed a marked but heterogeneous pattern of enhancement after contrast agent injection on serial T1-weighted (T1W) MR images. After VDA treatment, T2W and T1W MRI revealed evidence of hemorrhaging and lack of functioning vessels (enhancement) within the tumor. Quantitative estimates of relative vascular volume also showed a significant (P < .01) reduction in DMXAA-treated tumors 24 hours after therapy compared with untreated controls. Histology and immunostaining of untreated orthotopic FaDu tumors revealed poorly differentiated squamous cell carcinoma histology with distinctly visible CD31+ endothelial cells. In sharp contrast, minimal CD31 staining with irregular endothelial fragments and faint outlines of blood vessels were seen in DMXAA-treated tumor sections. CD31 immunostaining and histology also highlighted the selectivity of vascular damage and tissue necrosis after VDA therapy with no evidence of toxicity observed in normal salivary gland, heart, liver, and skeletal muscle tissues. Together, our results demonstrate a potent and selective vascular disruptive activity of DMXAA in an orthotopic HNC model. Further evaluation into its antitumor effects alone and in combination with other agents is warranted.
Head and neck squamous cell carcinomas (HNSCC) constitute a majority of the tumors of the upper aerodigestive tract and continue to present a significant therapeutic challenge. To explore the potential of vascular-targeted therapy in HNSCC, we investigated the antivascular, antitumor activity of the potent vascular-disrupting agent (VDA) 5,6-dimethylxanthenone-4-acetic acid (DMXAA) against two HNSCC xenografts with markedly different morphologic and vascular characteristics. Athymic nude mice bearing subcutaneous FaDu (human pharyngeal squamous cell carcinoma) and A253 (human submaxillary gland epidermoid carcinoma) tumors were administered a single dose of DMXAA (30 mg/kg, i.p). Changes in vascular function were evaluated 24 hours after treatment using contrast-enhanced magnetic resonance imaging (MRI) and immunohistochemistry (CD31). Signal enhancement (E) and change in longitudinal relaxation rates (ΔR1) were calculated to measure alterations in vascular perfusion. MRI showed a 78% and 49% reduction in vascular perfusion in FaDu and A253 xenografts, respectively. CD31-immunostaining of tumor sections revealed three-fold (FaDu) and two-fold (A253) reductions in microvessel density (MVD) 24 hours after treatment. DMXAA was equally effective against both xenografts, with significant tumor growth inhibition observed 30 days after treatment. These results indicate that DMXAA may be beneficial in the management of HNSCC, alone or in combination with other treatments.
Head and neck cancers; DMXAA; tumor vasculature; MRI; antivascular therapies
Macrophages represent an essential part of innate immunity, and the viral infection of macrophages results in the release of multiple proinflammatory mediators, such as nitric oxide (NO), cytokines, and chemokines. This study was undertaken to define the molecular mechanism of macrophage activation in response to rabies virus (RV) infection. In RAW264 murine macrophage cells, a well-characterized macrophage model, RV replication was strictly restricted, whereas cell proliferation was significantly enhanced upon RV inoculation. Transcriptional analyses for the expression of inducible forms of NO synthase (iNOS), cytokines, and chemokines revealed that RV virions potentiate the gene expression of iNOS and CXC chemokine ligand 10 (CXCL10), a major chemoattractant of T helper cell type 1. However, RV stimulation had little or no effect on the expression profiles of proinflammatory cytokines and other types of chemokines. In macrophages stimulated with UV-inactivated RV virions, as well as infectious viruses, the phosphorylation of extracellular signal-regulated kinase (ERK) 1 and 2, members of the mitogen-activated protein kinase family, was significantly induced. Specific inhibitors of MAPK/ERK kinase reduced the RV-induced production of NO and CXCL10. Furthermore, the RV-induced activation of the ERK1/2 pathway was severely impaired by the neutralization of the endosomal and lysosomal pH environment with lysosomotropic agents, indicating that endocytosis is a key step leading to the activation of ERK1/2 signaling. Taken together, these results suggest that the ERK1/2-mediated signaling pathway plays a cardinal role in the selective activation of macrophages in response to RV virions, thereby regulating cellular functions during virus infection.
Activated microglia elicits a robust amount of pro-inflammatory cytokines, which are implicated in the pathogenesis of tuberculosis in the central nervous system (CNS). However, little is known about the intracellular signaling mechanisms governing these inflammatory responses in microglia in response to Mycobacterium tuberculosis (Mtb).
Murine microglial BV-2 cells and primary mixed glial cells were stimulated with sonicated Mtb (s-Mtb). Intracellular ROS levels were measured by staining with oxidative fluorescent dyes [2',7'-Dichlorodihydrofluorescein diacetate (H2DCFDA) and dihydroethidium (DHE)]. NADPH oxidase activities were measured by lucigenin chemiluminescence assay. S-Mtb-induced MAPK activation and pro-inflammatory cytokine release in microglial cells were measured using by Western blot analysis and enzyme-linked immunosorbent assay, respectively.
We demonstrate that s-Mtb promotes the up-regulation of reactive oxygen species (ROS) and the rapid activation of mitogen-activated protein kinases (MAPKs), including p38 and extracellular signal-regulated kinase (ERK) 1/2, as well as the secretion of tumor necrosis factor (TNF)-α, interleukin (IL)-6, and IL-12p40 in murine microglial BV-2 cells and primary mixed glial cells. Both NADPH oxidase and mitochondrial electron transfer chain subunit I play an indispensable role in s-Mtb-induced MAPK activation and pro-inflammatory cytokine production in BV-2 cells and mixed glial cells. Furthermore, the activation of cytosolic NADPH oxidase p47phox and MAPKs (p38 and ERK1/2) is mutually dependent on s-Mtb-induced inflammatory signaling in murine microglia. Neither TLR2 nor dectin-1 was involved in s-Mtb-induced inflammatory responses in murine microglia.
These data collectively demonstrate that s-Mtb actively induces the pro-inflammatory response in microglia through NADPH oxidase-dependent ROS generation, although the specific pattern-recognition receptors involved in these responses remain to be identified.
It was recently suggested that heat shock protein (HSP)70, an intracellular protein, is a potential mediator of inflammatory disease when it is released into the extracellular compartment. Although elevated HSP70 levels have been identified in rheumatoid arthritis (RA) synovial tissues and RA synovial fluid compared with patients with osteoarthritis and healthy individuals, it remains unclear what role extracellular HSP70 plays in the pathogenesis of RA. This study was conducted to investigate the effects of extracellular HSP70 on the production of RA-associated cytokines in fibroblast-like synoviocytes from patients with RA and to elucidate the mechanisms involved.
IL-6, IL-8 and monocyte chemoattractant protein (MCP)-1 levels in culture supernatants were measured using enzyme-linked immunosorbent assays. Activation of mitogen-activated protein kinases (MAPKs), such as extracellular signal-regulated protein kinases (ERKs), c-Jun amino-terminal kinase (JNK) and p38 MAPK, was detected using Western blotting. Nuclear translocation of nuclear factor-κB (NF-κB) and degradation of the inhibitory protein IκBα were examined using immunohistochemistry and Western blotting.
Human HSP70 downregulated IL-6, IL-8 and MCP-1 production in RA fibroblast-like synoviocytes induced by tumour necrosis factor (TNF)-α in a concentration dependent manner. HSP70 inhibited the activation of ERK, JNK and p38 MAPK in fibroblast-like synoviocytes stimulated by TNF-α. Furthermore, HSP70 also significantly inhibited nuclear translocation of nuclear factor-κB and degradation of IκBα induced by TNF-α.
Extracellular HSP70 has an anti-inflammatory effect on RA by downregulating production of IL-6, IL-8 and MCP-1 in fibroblast-like synoviocytes, which is mediated through inhibited activation of the MAPKs and NF-κB signal pathways.
The potential of noninvasive laser Doppler flowmetry (LDF) and near infrared spectroscopy (NIRS) to detect acute effects of different vascular-modifying agents on perfusion and blood volume in tumors was evaluated. C3H mouse mammary carcinomas (∼200 mm3) in the rear foot of CDF1 mice were treated with flavone acetic acid (FAA, 150 mg/kg), 5,6-dimethylxanthenone-4-acetic acid (DMXAA, 20 mg/kg), combretastatin A-4 disodium phosphate (CA4DP, 250 mg/kg), hydralazine (HDZ, 5 mg/kg), or nicotinamide (NTA, 500 mg/kg). Tumor perfusion before and after treatment was evaluated by noninvasive LDF, using a 41°C heated custom-built LDF probe with four integrated laser/receiver units, and tumor blood volume was estimated by NIRS, using light guide coupled reflectance measurements at 800±10 nm. FAA, DMXAA, CA4DP, and HDZ significantly decreased tumor perfusion by 50%, 47%, 73%, and 78%, respectively. In addition, FAA, DMXAA, and HDZ significantly reduced the blood volume within the tumor, indicating that these compounds to some degree shunted blood from the tumor to adjacent tissue, HDZ being most potent. CA4DP caused no change in the tumor blood volume, indicating that the mechanism of action of CA4DP was vascular shut down with the blood pool trapped in the tumor. NTA caused no change in either tumor perfusion or tumor blood volume. We conclude that noninvasive LDF and NIRS can determine acute effects of vascular modifying agents on tumor perfusion and blood volume.
laser Doppler flow (LDF); near infrared spectroscopy (NIRS); combretastatin A4 disodium phosphate; hydralazine; C3H mouse mammary carcinoma
Ionizing radiation, like a variety of other cellular stress factors, can activate or down-regulate multiple signaling pathways, leading to either increased cell death or increased cell proliferation. Modulation of the signaling process, however, depends on the cell type, radiation dose, and culture conditions. The mitogen-activated protein kinase (MAPK) pathway transduces signals from the cell membrane to the nucleus in response to a variety of different stimuli and participates in various intracellular signaling pathways that control a wide spectrum of cellular processes, including growth, differentiation, and stress responses, and is known to have a key role in cancer progression. Multiple signal transduction pathways stimulated by ionizing radiation are mediated by the MAPK superfamily including the extracellular signal–regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. The ERK pathway, activated by mitogenic stimuli such as growth factors, cytokines, and phorbol esters, plays a major role in regulating cell growth, survival, and differentiation. In contrast, JNK and p38 MAPK are weakly activated by growth factors but respond strongly to stress signals including tumor necrosis factor (TNF), interleukin-1, ionizing and ultraviolet radiation, hyperosmotic stress, and chemotherapeutic drugs. Activation of JNK and p38 MAPK by stress stimuli is strongly associated with apoptotic cell death. MAPK signaling is also known to potentially influence tumor cell radiosensitivity because of their activity associated with radiation-induced DNA damage response. This review will discuss the MAPK signaling pathways and their roles in cellular radiation responses.
MAP kinases; radiation; signaling pathways
Influenza viruses of avian origin continue to pose pandemic threats to human health. Some of the H5N1 and H9N2 virus subtypes induce markedly elevated cytokine levels when compared with the seasonal H1N1 virus. We previously showed that H5N1/97 hyperinduces tumor necrosis factor (TNF)-alpha through p38 mitogen activated protein kinase (MAPK). However, the detailed mechanisms of p38MAPK activation and TNF-alpha hyperinduction following influenza virus infections are not known. Negative feedback regulations of cytokine expression play important roles in avoiding overwhelming production of proinflammatory cytokines. Here we hypothesize that protein phosphatases are involved in the regulation of cytokine expressions during influenza virus infection. We investigated the roles of protein phosphatases including MAPK phosphatase-1 (MKP-1) and protein phosphatase type 2A (PP2A) in modulating p38MAPK activation and downstream TNF-alpha expressions in primary human monocyte-derived macrophages (PBMac) infected with H9N2/G1 or H1N1 influenza virus. We demonstrate that H9N2/G1 virus activated p38MAPK and hyperinduced TNF-alpha production in PBMac when compared with H1N1 virus. H9N2/G1 induced PP2A activity in PBMac and, with the treatment of a PP2A inhibitor, p38MAPK phosphorylation and TNF-alpha production were further increased in the virus-infected macrophages. However, H9N2/G1 did not induce the expression of PP2A indicating that the activation of PP2A is not mediated by p38MAPK in virus-infected PBMac. On the other hand, PP2A may not be the targets of H9N2/G1 in the upstream of p38MAPK signaling pathways since H1N1 also induced PP2A activation in primary macrophages. Our results may provide new insights into the control of cytokine dysregulation.
protein phosphatase 2A; tumor necrosis factor-alpha; p38 mitogen activated protein kinase; influenza virus