Disruption Of Tumor Vasculature Research Articles

A nanocapsular combinatorial sequential drug delivery system for antiangiogenesis and anticancer activities

We reported a precise engineered nanocapsule encapsulating a neovasculature disruption agent, combretastatin A4 (CA4) in a matrix that was made up of paclitaxel (PTX) conjugated amphiphilic polyester. The nanocapsule was able to release CA4 and PTX sequentially for temporal antiangiogenesis and anticancer activities. The nanocapsule has a small particle size at 68 nm with narrow size distribution (∼0.15). Cellular uptake of the nanocapsule was efficient, and detectable at as early as 20 min, and drugs sequestered in the nanocapsule could exert effective therapeutic effects on tumor neovasculature and cancer cells, respectively. Biodistribution experiments demonstrated the long circulation of nanocapsule in body fluid and the preferential accumulation of nanocapsule in tumor. Both in vivo artificial pro-angiogenesis and tumor xenograft assays demonstrated the promising therapeutic effect of the nanocapsule on tumor vasculature disruption, tumor cell proliferation inhibition and tumor cell apoptosis induction. The intrasplenic liver metastasis experiment also confirmed the liver metastatic prevention capacity of this nanocapsule. In summary, the findings indicated that this dual drug loaded nanocapsule with sequential drug delivery capacity is a promising candidate in combinatorial therapy in fighting against cancer, and may open an avenue for cancer therapy and diagnosis.

BNC105: A Novel Tubulin Polymerization Inhibitor That Selectively Disrupts Tumor Vasculature and Displays Single-Agent Antitumor Efficacy

Vascular disruption agents (VDA) cause occlusion of tumor vasculature, resulting in hypoxia-driven tumor cell necrosis. Tumor vascular disruption is a therapeutic strategy of great potential; however, VDAs currently under development display a narrow therapeutic margin, with cardiovascular toxicity posing a dose-limiting obstacle. Discovery of new VDAs, which display a wider therapeutic margin, may allow attainment of improved clinical outcomes. To identify such compounds, we used an in vitro selectivity screening approach that exploits the fact that tumor endothelial cells are in a constant state of activation and angiogenesis and do not undergo senescence. Our effort yielded the compound BNC105. This compound acts as a tubulin polymerization inhibitor and displays 80-fold higher potency against endothelial cells that are actively proliferating or are engaged in the formation of in vitro capillaries compared with nonproliferating endothelial cells or endothelium found in stable capillaries. This selectivity was not observed with CA4, a VDA currently under evaluation in phase III clinical trials. BNC105 is more potent and offers a wider therapeutic window. CA4 produces 90% vascular disruption at its no observed adverse event level (NOAEL), whereas BNC105 causes 95% vascular disruption at 1/8th of its NOAEL. Tissue distribution analysis of BNC105 in tumor-bearing mice showed that while the drug is cleared from all tissues 24 hours after administration, it is still present at high concentrations within the solid tumor mass. Furthermore, BNC105 treatment causes tumor regressions with complete tumor clearance in 20% of treated animals.

Plasma biomarker analysis of a phase I trial of ASA404 (vadimezan) in combination with paclitaxel and carboplatin in Japanese patients with non-small cell lung cancer (NSCLC).

e18035 Background: ASA404 (vadimezan, DMXAA) is a flavonoid, non-tubulin-binding tumor-vascular disrupting agent (Tumor- VDA) that causes irreversible tumor vasculature disruption and extensive hemorrhagic necrosis of the tumor core. In combination with paclitaxel and carboplatin (P/C), ASA404 increased the median overall survival of previously untreated NSCLC patients from 8.8 to 14.0 months in a phase II clinical trial. Methods: A phase I trial assessed the safety profile and tolerability of three dose levels of ASA404 (600, 1,200, and 1,800 mg/m2) administered in combination with P/C (P, 200 mg/m2; C, AUC 6) every 3 weeks in Japanese patients with NSCLC. A panel of plasma biomarkers of angiogenesis and cytokines were evaluated to investigate the pharmacodynamic effect and mechanism of action (MOA) of ASA404. Plasma VEGF and basic FGF (bFGF) were measured by multiplex assays using the Meso-Scale Discovery platform. Plasma IL-8 and macrophage chemotactic protein (MCP)1 were analyzed by Luminex beads platform. Plasma 5-hydroxyindole-3-acetic acid (5HIAA), a by-product of platelet activation and putative biomarker for ASA404's vascular disruption activity, was analyzed by tandem mass spectrometry. Results: Four-hours after ASA404 infusion at Cycle 1 Day 1, plasma 5HIAA levels increased in a dose-dependent manner by 15%, 111%, or 137% compared with pre-ASA404 treatment level in the 600 (n = 3), 1,200 (n = 6) or 1,800 (n = 6) mg/m2 groups, respectively. Plasma VEGF levels decreased by 5 to 50% after 4 h and 24 h of ASA404 infusion. Plasma bFGF levels decreased by 55 to 88% after 24 h ASA404 infusion in the three ASA404 dose groups. Furthermore, over 50% induction of plasma IL-8 and MCP-1 were observed after 24 h infusion of ASA404. Conclusions: ASA404 caused dose-dependent induction of plasma 5HIAA levels. Unlike anti-angiogenic compounds such as sunitinib, sorafenib or bevacizumab which upregulate systemic VEGF, ASA404 did not appear to cause a systemic VEGF elevation. Induction of plasma inflammatory cytokines (IL-8, MCP-1) after ASA404 treatment may represent ASA404 MOA and amplify the direct antivascular effect of ASA404. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration Novartis Novartis

Abstract 4425: Oral efficacy and preclinical ADME evaluation of CKD-516, a novel tubulin polymerization inhibitor

Abstract CKD-516 is a potent anticancer agent that inhibits microtubule assembly and disrupts tumor vasculature (VDA). CKD-516 is an amino acid prodrug of S516 releasing S516 in vivo. Previously we reported the discovery and its antitumor efficacy of CKD-516 as well as various in vitro studies (Abstract 5561, 2009 AACR). As a continuation of the investigation, a detailed ADME evaluation of CKD-516 in both rats and dogs and its potential as an oral agent is described in this report. Following intravenous administration to rats and dogs, CKD-516 rapidly became the active metabolite S516 in plasma and the half-lives of S516 were 1.5 hrs in rats, and 8 hrs in dogs. Protein binding was high with an unbound fraction less than or equal to 20% in all species tested. In distribution studies in rats dosed intravenously, S516 was mainly distributed in thymus, lung and stomach and had a short half-life less than 2 hrs in all tissues tested. In rats, the excretion of CKD-516 in urine, bile and feces amounted to 0.22%, 8.22% and 4.92%, respectively. S516 was found to have comparable metabolic stabilities both in dog and human liver microsomes where there was no difference between male and female microsomes. However, the rate of metabolism in rats from male and female liver microsomes were markedly different. In general, S516 is expected to have low drug-drug interaction with IC50 values of >10 μM against most CYP450 enzymes but had a moderate inhibition against CYP450 1A2 and 2C8. The intestinal absorption of CKD-516 was predicted to be moderate to high as the apparent permeabilities (×106 cm/sec) of CKD-516 and its active metabolite S516 in Caco-2 permeability assay were 15.1 and 35.4, respectively. Thus, CKD-516 was found to have an acceptable oral bioavailability in rats, supporting its potential efficacy as an oral agent. In vivo antitumor experiments were performed in the HCT116 human tumor xenograft model. When the established tumor reached the size of 150 mm3, CKD-516 was administered to mice orally. Groups of animals were received CKD-516 with doses of 10 mg/kg or 20 mg/kg (Q4d × 5). The treated group showed a tumor growth suppression (IR = 50∼60%). Drug related toxicity and body weight decrease were not detected at doses tested. In summary, a complete ADME characterization of CKD-516, a novel tubulin polymerization inhibitor and VDA, both in vitro and in vivo was described. Moreover, CKD-516 was found to have a good potential as an oral agent. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4425.

Targeting mutant p53 protein and the tumor vasculature: an effective combination therapy for advanced breast tumors

Breast cancer progression depends upon the elaboration of a vasculature sufficient for the nourishment of the developing tumor. Breast tumor cells frequently contain a mutant form of p53 (mtp53), a protein which promotes their survival. The aim of this study was to determine whether combination therapy targeting mtp53 and anionic phospholipids (AP) on tumor blood vessels might be an effective therapeutic strategy for suppressing advanced breast cancer. We examined the therapeutic effects, singly, or in combination, of p53 reactivation and induction of massive apoptosis (PRIMA-1), which reactivates mtp53 and induces tumor cell apoptosis, and 2aG4, a monoclonal antibody that disrupts tumor vasculature by targeting AP on the surface of tumor endothelial cells and causes antibody-dependent destruction of tumor blood vessels, leading to ischemia and tumor cell death. Xenografts from two tumor cell lines containing mtp53, BT-474 and HCC-1428, were grown in nude mice to provide models of advanced breast tumors. After treatment with PRIMA-1 and/or 2aG4, regressing tumors were analyzed for vascular endothelial growth factor (VEGF) expression, blood vessel loss, and apoptotic markers. Individual drug treatment led to partial suppression of breast cancer progression. In contrast, combined treatment with PRIMA-1 and 2aG4 was extremely effective in suppressing tumor growth in both models and completely eradicated approximately 30% of tumors in the BT-474 model. Importantly, no toxic effects were observed in any treatment group. Mechanistic studies determined that PRIMA-1 reactivated mtp53 and also exposed AP on the surface of tumor cells as determined by enhanced 2aG4 binding. Combination treatment led to significant induction of tumor cell apoptosis, loss of VEGF expression, as well as destruction of tumor blood vessels. Furthermore, combination treatment severely disrupted tumor blood vessel perfusion in both tumor models. The observed in vitro PRIMA-1-induced exposure of tumor epithelial cell AP might provide a target for 2aG4 and contribute to the increased effectiveness of such combination therapy in vivo. We conclude that the combined targeting of mtp53 and the tumor vasculature is a novel effective strategy for combating advanced breast tumors.

Preparation and Characterization of Heparin-Retinoic Acid-Folic Acid Conjugates for Targeted Cancer Therapy

To make significant progress in the fight against cancer, treatment should target cells more specifically, produce fewer side effects, be easy to administer and deter tumor viability on multiple levels. We have attained dramatic in vivo tumor shrinkage and tumor vasculature disruption using a ternary biomolecular nanoparticle comprised of polymeric carrier polysaccharide heparin, anticancer drug retinoid and targeting ligand folic acid. The conjugation of retinoid and folic acid to heparin enhanced the water solubility of the drug, enabled selective targeting, and enhanced the role of heparin as anti-cancer drug carrier by eluding the coagulation cascade. This approach for targeting tumor holds great promise for treatment of various types of cancer. The folic acid linked heparin-retinoid conjugates (HFR) reactions was conjugated with ester and amide bonding which was confirmed by fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1H-NMR). The ratio of HFR conjugates was measured with Ultra-Violet spectrometry (UV-spectrometry). The particle size of HFR nanoparticles was measured by dynamic light scattering (DLS), and transmission electron microscopy (TEM). HFR conjugates were spherical and showed a diameter range of 200-300 nm in size. The nanoparticles maintained their stability in serum condition for 48hrs and have the high potential for applications in biomedical field.

The Fibroblast Growth Factor Receptor Inhibitor PD173074 Blocks Small Cell Lung Cancer Growth In vitro and In vivo

Lung cancer is the commonest cancer killer. Small cell lung cancer (SCLC) is initially chemosensitive, but rapidly relapses in a chemoresistant form with an overall survival of <5%. Consequently, novel therapies are urgently required and will likely arise from an improved understanding of the disease biology. Our previous work showed that fibroblast growth factor-2 induces proliferation and chemoresistance in SCLC cells. Here, we show that the selective fibroblast growth factor receptor (FGFR) inhibitor PD173074 blocks H-510 and H-69 SCLC proliferation and clonogenic growth in a dose-dependent fashion and prevents FGF-2-induced chemoresistance. These effects correlate with the inhibition of both FGFR1 and FGFR2 transphosphorylation. We then determined the efficacy of daily oral administration of PD173074 for 28 days in two human SCLC models. In the H-510 xenograft, tumor growth was impaired similar to that seen with single-agent cisplatin administration, increasing median survival compared with control sham-treated animals. Crucially, the effect of cisplatin was significantly potentiated by coadministration of PD173074. More dramatically, in H-69 xenografts, PD173074 induced complete responses lasting >6 months in 50% of mice. These effects were not a consequence of disrupted tumor vasculature but instead correlated with increased apoptosis (caspase 3 and cytokeratin 18 cleavage) in excised tumors. Moreover, in vivo imaging with 3'-deoxy-3'-[(18)F]fluorothymidine-positron emission tomography ([(18)F]FLT-PET) showed decreased intratumoral proliferation in live animals treated with the compound at 7 to 14 days. Our results suggest that clinical trials of FGFR inhibitors should be undertaken in patients with SCLC and that [(18)F]FLT-PET imaging could provide early in vivo evidence of response.

ABT-751, a novel tubulin-binding agent, decreases tumor perfusion and disrupts tumor vasculature

ABT-751 is an orally bioavailable tubulin-binding agent that is currently under clinical development for cancer treatment. In preclinical studies, ABT-751 showed antitumor activity against a broad spectrum of tumor lines including those resistant to conventional chemotherapies. In this study, we investigated the antivascular properties of ABT-751 in a rat subcutaneous tumor model using dynamic contrast-enhanced magnetic resonance imaging. A single dose of ABT-751 (30 mg/kg, intravenously) induced a rapid, transient reduction in tumor perfusion. After 1 h, tumor perfusion decreased by 57% before recovering to near pretreatment levels within 6 h. In contrast, ABT-751 produced little change in muscle perfusion at either time point. To further elucidate mechanisms of drug action at the cellular level, we examined the effects of ABT-751 on endothelial cells using an in-vitro assay. ABT-751, at concentrations corresponding to plasma levels achieved in vivo, caused endothelial cell retraction and significant loss of microtubules within 1 h. The severity of these morphological changes was dose-dependent but reversible within 6 h after the discontinuation of the drug. Taken together, these results show that ABT-751 is a tubulin-binding agent with antivascular properties. Microtubule disruption and morphological changes in vascular endothelial cells may be responsible, at least in part, for the dysfunction of tumor blood vessels after ABT-751 treatment.

Targeting Tumor Endothelial Marker 8 in the Tumor Vasculature of Colorectal Carcinomas in Mice

Abstract Tumor endothelial marker 8 (TEM8) is a recently described protein that is preferentially expressed within tumor endothelium. We have developed a fusion protein that targets TEM8 and disrupts tumor vasculature by promoting localized thrombosis. Fusion protein specificity and function were evaluated using Western blot analysis, ELISA, and enzymatic assays. A xenograft model of colorectal carcinoma was used to test the efficacy of targeted and control fusion proteins. Mice treated with the gene encoding anti-TEM8/truncated tissue factor exhibited a 53% reduction in tumor volume when compared with the untreated animals (P &amp;lt; 0.0001; n = 10) and achieved a 49% increase in tumor growth delay by Kaplan-Meier analysis (P = 0.0367; n = 6). Immunohistochemistry confirmed tumor endothelial expression of TEM8, fusion protein homing to tumor vasculature, decrease in vessel density, and localized areas of thrombosis. These data support the hypothesis that targeting TEM8 can be an effective approach to influence tumor development by disrupting tumor vasculature. [Cancer Res 2009;69(12):5126–32]

Targeting Tumor Endothelial Marker 8 in the Tumor Vasculature of Colorectal Carcinomas in Mice

Tumor endothelial marker 8 (TEM8) is a recently described protein that is preferentially expressed within tumor endothelium. We have developed a fusion protein that targets TEM8 and disrupts tumor vasculature by promoting localized thrombosis. Fusion protein specificity and function were evaluated using Western blot analysis, ELISA, and enzymatic assays. A xenograft model of colorectal carcinoma was used to test the efficacy of targeted and control fusion proteins. Mice treated with the gene encoding anti-TEM8/truncated tissue factor exhibited a 53% reduction in tumor volume when compared with the untreated animals (P < 0.0001; n = 10) and achieved a 49% increase in tumor growth delay by Kaplan-Meier analysis (P = 0.0367; n = 6). Immunohistochemistry confirmed tumor endothelial expression of TEM8, fusion protein homing to tumor vasculature, decrease in vessel density, and localized areas of thrombosis. These data support the hypothesis that targeting TEM8 can be an effective approach to influence tumor development by disrupting tumor vasculature.

The Targeted Oncolytic Poxvirus JX-594 Demonstrates Antitumoral, Antivascular, and Anti-HBV Activities in Patients With Hepatocellular Carcinoma

JX-594 is a targeted oncolytic poxvirus that is designed to eradicate cancer cells having cell-cycle defects, through replication, cell lysis, and spread within tumors; oncolysis-induced tumor vascular shutdown and immunostimulation are augmented by granulocyte monocyte-colony-stimulating factor (GM-CSF) transgene expression. We have previously shown, in animal models of hepatocellular carcinoma (HCC), that JX-594 is a promising anticancer agent. We tested JX-594 in three patients with advanced refractory hepatitis B virus (HBV)-associated HCC through intratumoral administration. JX-594 treatment was well-tolerated and resulted in antitumoral efficacy in all three patients, despite the presence of high levels of neutralizing antibodies. JX-594 replication, its release into the circulation, distant tumor targeting were demonstrated. JX-594 administration resulted in the induction of antivascular cytokines, and was associated with tumor vascular shutdown. We also showed, for the first time, that oncolytic virotherapy can suppress underlying HBV replication in HCC patients, and that tumor tissue could be the primary source of acute HBV replication and acute post-treatment HBV release. JX-594 treatment in HBV-associated HCC warrants further clinical testing; a Phase II trial is underway.

Systemic Vesicular Stomatitis Virus Selectively Destroys Multifocal Glioma and Metastatic Carcinoma in Brain

Metastatic tumors and malignant gliomas make up the majority of cancers in the brain. They are invariably fatal and there is currently no cure. From in vitro comparisons of a number of viruses, we selected one that appeared the best in selectively killing glioblastoma cells. This replication-competent virus, the glioma-adapted vesicular stomatis virus strain VSVrp30a, was used for in vivo tests with the underlying view that infection of tumor cells will lead to an increase in the number of viruses subsequently released to kill additional tumor cells. Intravenous injection of VSVrp30a expressing a green fluorescent protein reporter, rapidly targeted and destroyed multiple types of human and mouse tumors implanted in the mouse brain, including glioblastoma and mammary tumors. When tumors were implanted both in the brain and peripherally, emulating systemic cancer metastasis, tumors inside and outside the brain were simultaneously infected. Intranasal inoculation, leading to olfactory nerve transport of the virus into the brain, selectively infected and killed olfactory bulb tumors. Neither control cortical wounds nor transplanted normal mouse or human cells were targeted, indicating viral tumor selectivity. Control viruses, including pseudorabies, adeno-associated, or replication-deficient VSV, did not infect the brain tumor. Confocal laser time-lapse imaging through a cranial window showed that intravenous VSV infects the tumor at multiple sites and kills migrating tumor cells. Disrupted tumor vasculature, suggested by dye leakage, may be the port of entry for intravenously delivered VSV. Quantitative PCR analysis of how VSVrp30a selectively infected tumor cells suggested multiple mechanisms, including cell surface binding and internalization.

Inhibition of MAPK Kinase Signaling Pathways Suppressed Renal Cell Carcinoma Growth and Angiogenesis In vivo

The mitogen-activated protein kinase (MAPK) signaling pathways play essential roles in cell proliferation and differentiation. Recent studies also show the activation of MAPK signaling pathways in tumorigenesis, metastasis, and angiogenesis of multiple human malignancies, including renal cell carcinoma (RCC). To assess the role of this pathway in regulating the proliferation and survival of RCC cells, we first examined the expression of MAPK kinase (MKK) and MAPK in clear cell RCC and confirmed the overexpression of MKK1 and extracellular signal-regulated kinase 2 (ERK2) in these tumors. We then tested the effects of pharmacologic inhibition of MKK on human RCC cell lines, both in vitro and in vivo, using anthrax lethal toxin (LeTx), which cleaves and inactivates several MKKs. Western blotting showed that the phosphorylation levels of ERK, c-Jun-NH(2) kinase, and p38 MAPK decreased after 72 h of LeTx treatment. Exposure to LeTx for 72 h reduced cell proliferation by 20% without significant effects on cell cycle distribution and apoptosis. Anchorage-independent growth of RCC cells was dramatically inhibited by LeTx. In vivo studies showed that tumor growth of RCC xenografts could be suppressed by LeTx. Extensive necrosis and decreased tumor neovascularization were observed after LeTx treatment. LeTx also showed direct inhibition of proliferation of endothelial cells in vitro. Our results suggest that suppression of one or more MAPK signaling pathways may inhibit RCC growth through the disruption of tumor vasculature.

Randomized phase II study of docetaxel with or without DMXAA (AS1404) in hormone-refractory metastatic prostate cancer (HRMPC)

5115 Background: DMXAA (AS1404) is a small-molecule agent that disrupts tumor vasculature. Combination of DMXAA with taxanes produces synergistic inhibition of tumor growth in animal models. A randomized phase II study in non-small cell lung cancer reported a substantial survival benefit when DMXAA was added to paclitaxel-based chemotherapy. This randomized phase II study examined the effect of adding DMXAA to docetaxel in HRMPC. Methods: Patients had progressive metastatic, androgen-independent, histologically confirmed prostate adenocarcinoma previously untreated with cytotoxics. Patients were randomized 1:1 to receive docetaxel (75 mg/m2) ± DMXAA (1,200 mg/m2) every 21 days for up to 10 cycles. Efficacy endpoints were prostate-specific antigen (PSA) response rate, objective response rate, time to tumor progression, duration of response and disease stabilization, time to PSA progression, and median and 1-year survival. Results: 74 patients were randomized: 34 to DMXAA plus docetaxel (DMXAA arm) and 40 to docetaxel alone (control arm). Median baseline PSA values were 83 ng/ml (range 6–3574 ng/ml) in the DMXAA arm and 87 ng/ml (range 1–570 ng/ml) in the control arm. PSA response data are available from 64 patients (see table ). Latest safety data show a similar number of serious adverse events reported across the treatment groups with 15 and 19 in the DMXAA and control arms, respectively. Conclusions: Addition of DMXAA to standard-dose docetaxel was well tolerated and the combination produced a substantially higher PSA response rate than docetaxel alone. DMXAA demonstrates promising activity in this patient population. [Table: see text] [Table: see text]

The Potential of New Tumor Endothelium-Specific Markers for the Development of Antivascular Therapy

Angiogenesis is a hallmark of solid tumors, and disruption of tumor vasculature is an active anticancer therapy in some cases. Several proteins expressed on the surface of tumor endothelium have been identified during the last decade. However, due to the expression in both physiological and tumor angiogenesis, only a few targets have been developed for clinical therapeutics. By thorough SAGE analysis of mouse endothelial cells isolated from various normal resting tissues, regenerating liver, and liver-metastasized tumor, Seaman and colleagues in this issue of Cancer Cell have demonstrated organ-specific endothelial markers, physiological angiogenesis endothelial markers, and tumor endothelial markers and revealed striking differences between physiological and pathological angiogenesis.

New multitargeted treatments with antiangiogenic and antitumor activity: focus on sunitinib

Tumor growth and survival requires both proliferative and angiogenic signals, involving many molecular pathways. There is increasing preclinical and clinical evidence that agents targeting more than one pathway or receptor may be more efficacious in inducing tumor regression and disrupting tumor vasculature than those directed at a single target. This review considers several multitargeted agents recently approved or currently in clinical development for various solid tumors. These include sunitinib malate, an oral multitargeted receptor tyrosine kinase inhibitor conditionally approved in the EU in July 2006 for the treatment of patients with advanced renal cell carcinoma (RCC) after failure of cytokine-based therapy and patients with gastrointestinal stromal tumors (GIST) whose disease has progressed or who are unable to tolerate imatinib mesylate. Also reviewed are the multitargeted inhibitors sorafenib (also recently approved for the treatment of advanced RCC after failure of cytokine-based therapy); lapatinib (in clinical development for several solid tumors, with promising activity in advanced breast cancer); and dasatinib (preliminary indications of activity in GIST and other solid tumors). These agents have demonstrated activity against a range of tumor types and show promise in settings for which few (if any) alternative treatments are available. The present challenge is to optimize the way in which these drugs are used in the clinic. This will require further evaluation of dosing schedules, combination regimens (with chemotherapy and/or other targeted agents), and patient populations likely to derive greatest clinical benefit.

Antivascular effects of TZT‐1027 (Soblidotin) on murine Colon26 adenocarcinoma

We investigated the ability of TZT-1027 (Soblidotin), a novel antimicrotubule agent, to induce antivascular effects, because most vascular targeting agents that selectively disrupt tumor vasculature also inhibit tubulin polymerization. Treatment with 10(-7) g/mL TZT-1027 rapidly disrupted the microtubule cytoskeleton in human umbilical vascular endothelial cells (HUVEC), and significantly enhanced vascular permeability in HUVEC monolayers. In addition, single intravenous administration of 2 mg/kg TZT-1027 to mice bearing Colon26 tumors significantly reduced tumor perfusion and caused extravascular leakage of erythrocytes 1 h after administration. Subsequently, thrombus formation with deposition of fibrin and tumor necrosis was observed 3 and 24 h after administration, respectively. These results strongly suggest that TZT-1027 possesses antivascular effects. TZT-1027 induced apoptosis not only in HUVEC but also in C26 cancer cells (cell line of Colon26 solid tumor) in vitro, suggesting it exerts direct cytotoxicity against tumor cells in addition to its antivascular effects. A single intravenous administration of 1, 2 and 4 mg/kg TZT-1027 significantly prolonged the survival of mice with advanced-stage Colon26 tumors in a dose-dependent manner. Furthermore, TZT-1027 itself less markedly enhanced the permeability of normal vessels, but was additive with vascular endothelial growth factor, indicating the possibility that TZT-1027 selectively exerts its activity on tumor vessels. In summary, these results suggest that TZT-1027 exerts both an indirect antivascular effect and a direct cytotoxic effect, resulting in strong antitumor activity against advanced-stage tumors, and that TZT-1027 may be useful clinically for treating solid tumors.

Effects of the Vascular Disrupting Agent ZD6126 on Interstitial Fluid Pressure and Cell Survival in Tumors

Interstitial fluid pressure (IFP) is elevated in tumors due to abnormal vasculature, lack of lymphatic drainage, and alterations in the tumor interstitium. ZD6126 is a tubulin-binding agent that selectively disrupts tumor vasculature resulting in tumor necrosis. This study examined the effect of ZD6126 on tumor IFP and the response of tumors with different IFP levels to ZD6126. Pretreatment IFP was measured using the wick-in-needle method in tumors (murine KHT-C and human CaSki) growing i.m. in the hind legs of mice. Mice were treated i.p. with a single dose of ZD6126 (100 or 200 mg/kg) and posttreatment IFP measurements were made. Blood flow imaging was conducted using Doppler optical coherence tomography, whereas oxygen partial pressure was measured using a fiber optic probe. Clonogenic assays were done to determine tumor cell survival. In KHT-C tumors, IFP dropped significantly at 1 hour posttreatment, returned to pretreatment values at 3 hours, and then declined to approximately 25% of the pretreatment values by 72 hours. In CaSki tumors, the IFP decreased progressively, beginning at 1 hour, to approximately 30% of pretreatment values by 72 hours. Clonogenic cell survival data indicated that ZD6126 was less effective in tumors with high IFP values (>25 mm Hg). Vascular disrupting agents, such as ZD6126, can affect IFP levels and initial IFP levels may predict tumor response to these agents. The higher cell survival in high IFP tumors may reflect greater microregional blood flow limitations in these tumors and reduced access of the drug to the target endothelial cells.

Oncolytic HSV Exerts Direct Antiangiogenic Activity in Ovarian Carcinoma

In the present study, we investigated the ability of replication-restricted herpes simplex virus (HSV) 1716 lacking ICP34.5 to infect endothelium and disrupt tumor vasculature. HSV-1716 efficiently infected and killed mouse endothelial cell lines H5V and MS1 cells, as well as human umbilical vein endothelial cells in vitro. Capillary tube formation by endothelial cells was inhibited by HSV-1716 in vitro and in vivo. Following intratumoral administration of oncolytic HSV-1716, HSV-glycoproteins could be detected in CD31-positive tumor vascular endothelium by immunostaining. Viral DNA was recovered from highly purified microdissected tumor vascular endothelium. Furthermore, endothelium of tumors treated with HSV-1716 exhibited expression of tissue factor, a marker of endothelial damage. Importantly, HSV antigen and DNA were also detected in endothelium distant from foci of active tumor infection. After intravascular inoculation of HSV-1716, viral glycoproteins were detected in association to tumor endothelium, but not vascular endothelium of different organs. Purified tumor endothelial cells showed high proliferative capability and were susceptible to HSV-1716 infection and killing ex vivo while endothelium from normal organs was not. We conclude that oncolytic HSV-1716 exerts direct antiangiogenic effects, which may contribute to the overall therapeutic efficacy of the virus.

Antivascular and antitumor evaluation of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes, a novel series of anticancer agents

Abstract A novel series of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes was identified as potent apoptosis inducers through a cell-based high throughput screening assay. Six compounds from this series, MX-58151, MX-58276, MX-76747, MX-116214, MX-116407, and MX-126303, were further profiled and shown to have potent in vitro cytotoxic activity toward proliferating cells only and to interact with tubulin at the colchicine-binding site, thereby inhibiting tubulin polymerization and leading to cell cycle arrest and apoptosis. Furthermore, these compounds were shown to disrupt newly formed capillary tubes in vitro at low nanomolar concentrations. These data suggested that the compounds might have vascular targeting activity. In this study, we have evaluated the ability of these compounds to disrupt tumor vasculature and to induce tumor necrosis. We investigated the pharmacokinetic and toxicity profiles of all six compounds and examined their ability to induce tumor necrosis. We next examined the antitumor efficacy of a subset of compounds in three different human solid tumor xenografts. In the human lung tumor xenograft (Calu-6), MX-116407 was highly active, producing tumor regressions in all 10 animals. Moreover, MX-116407 significantly enhanced the antitumor activity of cisplatin, resulting in 40% tumor-free animals at time of sacrifice. Our results identify MX-116407 as the lead candidate and strongly support its continued development as a novel anticancer agent for human use.