Antivascular Activity Research Articles

Coadministration of nanosystems of short silencing RNAs targeting oestrogen receptor α and anti-oestrogen synergistically induces tumour growth inhibition in human breast cancer xenografts

The suppression of oestrogen receptor alpha (ERalpha) functions by silencing RNAs in association with or not with anti-oestrogens (AEs) both in vitro and in breast cancer cell xenografts was assessed. In vitro, a prolonged decrease in ERalpha protein expression and an enhanced AE-induced inhibition of ERalpha-mediated transcription, together with antiproliferative activity, were observed. Incorporation of ERalpha-siRNAs in pegylated nanocapsules (NC) was achieved; and their intravenous injections in MCF-7 xenografts, in contrast to scramble siRNA containing NCs, lead to decrease in ERalpha protein content and Ki67 labelling in tumour cells. The pure AE RU58668 (RU) both free and entrapped in stealth nanospheres (NS) at very low concentration (8 microg/kg/week) had no effect on tumour growth evolution. However, coinjection of the two nanocarriers potentiated the decrease in ERalpha protein, concomitantly with decreasing tumour vasculature and glucose transporter-1. These data support that the targeted delivery of ERalpha-siRNA in breast tumours potentiates the inhibition of E(2)-induced proliferative activity by encapsulated AE through enhanced anti-vascular activity. In the hormone-independent MDA-MB-231 xenograft model, RU-NS at 4 mg/kg/week induce also a strong tumour vascular normalisation. Together, these findings suggest that the anti-oestrogen activity of RU as well as that of targeted ERalpha-siRNA leads to anti-angiogenic activity. Their delivery in stealth nanocarriers may constitute a new anti-cancer therapeutic strategy in solid tumours.

Interference with endothelial cell function by JG-03-14, an agent that binds to the colchicine site on microtubules

JG-03-14, a novel tetrasubstituted pyrrole with microtubule-depolymerizing and anti-proliferative activities, was tested for its effect on endothelial cell (EC) functions in vitro. JG-03-14 was a potent inhibitor of EC vessel-like tube formation on extracellular matrix (IC 50 of 40 nM) and caused the involution of established vessels, potential anti-angiogenic and vascular-disrupting activities, respectively. These actions were not due to the inhibition of EC proliferation or to the induction of apoptosis by JG-03-14. While similar effects were observed with the microtubule-depolymerizing and vascular-disrupting drug combretastatin-A4 (CoA4), JG-03-14 had a more selective effect on tube formation, relative to its cytotoxic actions, than did CoA4. Potential molecular mechanisms for JG-03-14's anti-vascular actions were explored. In contrast to the taxanes, which also have anti-vascular actions, JG-03-14 did not disrupt focal adhesion formation or block VEGF-induced phosphorylation of focal adhesion kinase. It did, however, inhibit VEGF-induced phosphorylation of VE-cadherin and reduce the association of β-catenin with VE-cadherin. It caused cell retraction, intercellular gaps, and abnormally elongated adherens junctions at low concentrations, and prominent, but reversible, plasma membrane blebbing at higher concentrations. These results suggest that JG-03-14 may affect vascular morphogenesis by disrupting the interaction of adjacent endothelial cells, possibly as a consequence of effects on VE-cadherin, β-catenin, and/or actin. They also provide the first report of anti-vascular activity for this class of compounds.

Phase II study of NGR-hTNF, a selective vascular targeting agent (VTA), in previously treated patients with malignant pleural mesothelioma (MPM)

7582 Background: NGR-hTNF is a VTA exploiting a tumor-homing peptide (NGR) that selectively binds to an aminopeptidase N (CD13) overexpressed on tumor blood vessels. In preclinical models, NGR-hTNF has shown potent anti-vascular and antitumor activity, both at low and at high doses. Methods: Patients with advanced MPM were treated with a low-dose of NGR-hTNF given intravenously at 0.8 μg/m2 as 1-hour infusion every 3 weeks (q3w). This phase II trial had a 2-stage design with 16 and a total of 27 patients to be enrolled after first and second stage, respectively. Primary endpoint was progression-free survival (PFS) with restaging performed q6w according to MPM-modified RECIST criteria. Results: From May 2007 to January 2008, forty-three patients with radiologically-documented progressive disease after a pemetrexed-based regimen were evaluated over 167 cycles (range, 1 to 17). Patient characteristics were: median age 64 years (range, 54 to 80); male/female 27/16; epithelial/non-epithelial histology 34/9; PS 0/1/2 24/10/9; EORTC score good/poor 34/9. Main grade 1–2 toxicity was chills (71%), transiently occurring after the first infusions. Only one grade 3 treatment-related toxicity was observed. One patient (2%) had a partial response lasting 7.1+ months and 17 patients (40%) maintained stable disease for a median duration of 4.4 months (range, 1.3 to 12.4+ months). The median and 3-month PFS were 2.8 months and 43%, respectively, whereas the median and 1-year overall survival were 11.6 months and 48%, respectively. In an additional 14 patients treated at same dose with a weekly schedule, there was any suggestion of toxicity exacerbation. In this cohort, the PFS rate at 6 months was 36%, with 7 patients (50%) experiencing stable disease for a median duration of 6.9 months (range, 2.4 to 9.3+ months). Conclusions: NGR-hTNF 0.8 μg/m2 weekly is well tolerated, showing prolonged disease control in previously treated MPM patients, and will be further developed in this setting. [Table: see text]

Phase II study of NGR-hTNF, a selective vascular targeting agent (VTA), in previously treated patients with hepatocellular carcinoma (HCC)

e15500 Background: NGR-hTNF is a VTA exploiting a tumor-homing peptide (NGR) that selectively binds to aminopeptidase N (CD13) overexpressed on tumor blood vessels. In preclinical models, NGR-hTNF has shown potent anti-vascular and antitumor activity, both at low and at high doses. Methods: Patients with recurrent or metastatic HCC were treated with NGR-hTNF given intravenously at 0.8 μg/m2 as 1-hour infusion every 3 weeks (q3w). This phase II trial had a 2-stage design with 16 and a total of 27 patients to be enrolled after first and second stage, respectively. Progression-free survival (PFS) was the primary endpoint with reassessment performed q6w according to WHO criteria. Results: 27 patients with progressive disease following prior loco- regional treatment (59%), systemic therapy (56%), or both (33%) were evaluated over 86 cycles (range, 1 to 14). Patient characteristics were: median age 67 years (range, 53 to 79); M/F 21/6; PS 0/1 18/9; Child-Pugh class A/B: 21/6. No grade 3–4 treatment-related adverse events were observed. Main grade 1–2 toxicities were short-lasting infusion-related constitutional symptoms, including chills (55%). Median PFS was 2.3 months (95% CI, 1.7–2.9 months). One complete response (4%) lasting 9.0+ months was observed in a sorafenib-refractory patient and one partial response (4%) was reported in a Child-Pugh class B patient. Additionally, a 28% tumor shrinkage was detected in one out of six patients (22%) experiencing stable disease. The median PFS duration in stable or responder patients was 4.3 months (95% CI, 2.7–5.8 months). With a median follow-up of 7.6 months, the overall survival rates at 3 and 6 months were 82% and 60%, respectively. Conclusions: NGR-hTNF given at 0.8 μg/m2 every 3 weeks is well tolerated and appears to have promising antitumor activity in previously treated patients with advanced HCC. The drug will be further developed in this setting and, currently, an additional cohort of 12 patients has been enrolled and treated at same dose with a weekly schedule. [Table: see text]

Antivascular Actions of Microtubule-Binding Drugs

Microtubule-binding drugs (MBD) are widely used in cancer chemotherapy and also have clinically relevant antiangiogenic and vascular-disrupting properties. These antivascular actions are due in part to direct effects on endothelial cells, and all MBDs (both microtubule-stabilizing and microtubule-destabilizing) inhibit endothelial cell proliferation, migration, and tube formation in vitro, actions that are thought to correspond to therapeutic antiangiogenic actions. In addition, the microtubule-destabilizing agents cause prominent changes in endothelial cell morphology, an action associated with rapid vascular collapse in vivo. The effects on endothelial cells occur in vitro at low drug concentrations, which do not affect microtubule gross morphology, do not cause microtubule bundling or microtubule loss and do not induce cell cycle arrest, apoptosis, or cell death. Rather, it has been hypothesized that, at low concentrations, MBDs produce more subtle effects on microtubule dynamics, block critical cell signaling pathways, and prevent the microtubules from properly interacting with transient subcellular assemblies (focal adhesions and adherens junctions) whose subsequent stabilization and/or maturation are required for cell motility and cell-cell interactions. This review will focus on recent studies to define the molecular mechanisms for the antivascular actions of the MBDs, information that could be useful in the identification or design of agents whose actions more selectively target the tumor vasculature.

Antimitotic Chalcones and Related Compounds as Inhibitors of Tubulin Assembly

The development of chalcones as antimitotic agents has led to the design of other analogues able to interact with tubulin and inhibit its assembly into microtubules. This activity has also been associated with their anti-vascular activity. This review focuses on the development of chalcones and related analogues as antimitotic agents.

Effect of Benincasa hispida Cogniaux on high glucose-induced vascular inflammation of human umbilical vein endothelial cells

Vascular inflammation is an important factor which can promote diabetic complications. Preliminary investigations of several crude plant extracts including aqueous extract of Benincasa hispida Cogniaux exhibit anti-inflammatory properties. This study investigates the mechanism of anti-vascular inflammatory activity of an aqueous extract of B. hispida Cogniaux (ABH) in human umbilical vein endothelial cells (HUVECs). The study was performed on HUVECs that were pretreated with various concentrations (1–20 µg/ml) of ABH before exposure with high glucose (25 mM) for 48 h. Cell ELISA and Western blot analysis showed that ABH inhibited high glucose-induced cell adhesion molecules (CAMs) surface and protein expression, resulting in reduced adhesion of U937 monocytes. ABH also inhibited the mRNA expression level of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8). High glucose-induced ROS production was inhibited by treatment of ABH. We observed that pretreatment with HUVECs with ABH blocks NF-κB activation via blocking phosphorylation and degradation of its inhibitory protein, IκB-α. ABH also reduced NF-kB promoter activity. These results suggest that ABH reduces high glucose-induced CAMs activation by inhibiting monocyte adhesion, ROS, and NF-κB in HUVECs.

Assessment of the Early Effects of 5,6-Dimethylxanthenone-4-Acetic Acid Using Macromolecular Contrast Media–Enhanced Magnetic Resonance Imaging: Ectopic Versus Orthotopic Tumors

To investigate the early effects of a vascular disrupting agent (VDA) in ectopic and orthotopic tumors by using macromolecular contrast media (MMCM)-enhanced magnetic resonance imaging (MMCM-MRI). The MMCM-MRI of ectopic and orthotopic MCA205 murine fibrosarcomas was performed using the intravascular contrast agent albumin-(gadopentetate dimeglumine)(35). Change in longitudinal relaxation rate (DeltaR1) 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 histologic and immunohistochemical evaluation was carried out, along with measurement of tumor necrosis factor alpha and vascular endothelial growth factor levels in whole tumor extracts using the enzyme-linked immunosorbent assay. Orthotopic tumors showed higher vascular volume (p < 0.05) than ectopic tumors before treatment. Twenty-four hours after DMXAA treatment, a significant (p < 0.0001), but differential, decrease in DeltaR1 (70% in ectopic and 50% in orthotopic tumors) was observed compared with baseline estimates. Consistent with this observation, greater levels of tumor necrosis factor alpha, an important mediator of the antivascular activity of DMXAA, were measured in ectopic tumors 3 hours posttreatment compared with orthotopic tumors (p < 0.05). Immunohistochemical (CD31) and histologic (hematoxylin and eosin) sections of ectopic and orthotopic tumors showed highly tumor-selective vascular damage after treatment with the presence of viable surrounding normal tissue. The MMCM-MRI provided early quantitative estimates of change in tumor perfusion after VDA treatment that showed good correlation with cytokine induction. Differences in the response of ectopic and orthotopic tumors highlight the influence of the host microenvironment in modulating the activity of VDAs.

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.

The Disruption of Murine Tumor Neovasculature by Low-intensity Ultrasound—Comparison Between 1- and 3-MHz Sonication Frequencies

The goal was to determine whether the tumor vascular disrupting actions of low-intensity ultrasound were frequency dependent. The effect of the frequency (1 MHz at 2.2 W/cm2 or 3 MHz at 2.4 W/cm2) of low-intensity ultrasound as a neovascular disrupting modality was investigated in 15 murine melanomas (K1735(22)) insonated for 3 minutes after the intravenous injection of a microbubble contrast agent (Definity). In contrast-enhanced power Doppler observations of each tumor (before and after treatment), measurements were made of the size of the area of the tumor that was perfused with blood containing the ultrasound contrast agent (percentage area of flow [PAF]), and the volume of contrast agent flowing through the unit volume of the tumor (color-weighted fractional area [CWFA]). During insonation of the tumor, the temperature was measured with a fine wire thermocouple in an additional eight mice. The antivascular action of low-intensity ultrasound was significantly enhanced (PAF by 64%; CWFA by 106%) when the tumor was treated with 3-MHz ultrasound rather than 1 MHz (analysis of variance: PAF, P=.02; CWFA, P=.04). The average rate of tumor temperature increase was 2.6+/-1.3 degrees C/min for 1 MHz and 5.0+/-1.7 degrees C/min for 3 MHz; these increases were significantly different (P=.04). Insonation of the tumor at a higher frequency amplified the heating of the neoplasm and led to greater disruption of the tumor vasculature; 3-MHz ultrasound was more efficacious than 1 MHz for antivascular cancer therapy.

Combretastatin anlogues: synthesis and biological evaluation of new disubstituted analogues of 6-methoxy-3-(3',4',5'-trimethoxy-benzoyl)-1H-indole (BPR0L075), as potential antivascular agents

6-Methoxy-3-(3',4',5'-trimethoxy-benzoyl)-1H-indole (BPR0L075) (1) is a potent inhibitor of tubulin polymerization which exhibits both in vitro and in vivo activities against a broad spectrum of solid tumours. This compound was originally designed as a heterocyclic analogue of combretastatin A4 (CA-4), a natural stilbene derivative that disrupts the tumour vasculature and causes tumour regression [1,2]. We describe here the design and synthesis of two disubstituted analogues of 1 (i.e. 15 and 8), presenting the B-ring substitution pattern of CA-4, along with their biological evaluation as potential antivascular agents. New compound 15, bearing a hydroxyl group at the 7-position of the indole nucleus that mimics the hydroxyl group at the 3-position of the B-ring of CA-4, was identified as a potent inhibitor of tubulin polymerization and also as a cytotoxic agent at nanomolar levels. In addition, compound 15 displayed marked morphological activity (rounding up) at nanomolar concentrations on endothelial cells, which is indicative of potential antivascular activity. The SAR are discussed here.

Synthesis and biological evaluation of new disubstituted analogues of 6-methoxy-3-(3′,4′,5′-trimethoxybenzoyl)-1 H-indole (BPR0L075), as potential antivascular agents

6-Methoxy-3-(3′,4′,5′-trimethoxybenzoyl)-1 H-indole (BPR0L075) ( 1) is a potent inhibitor of tubulin polymerization which exhibits both in vitro and in vivo activities against a broad spectrum of solid tumors. This compound was designed as a heterocyclic analogue of combretastatin A4 (CA-4), a natural stilbene derivative that disrupts the tumor vasculature and causes tumor regression. In the present work, we describe the design and synthesis of several new disubstituted analogues of 1, along with their biological evaluation as potential antivascular agents. Compound 13, bearing a hydroxyl group at the 7-position of the indole nucleus that mimics the hydroxyl group at the 3-position of the B-ring of CA-4, was identified as a potent inhibitor of tubulin polymerization and also as a cytotoxic agent against B16 melanoma cells at sub-micromolar concentration. In addition, compound 13 displayed marked morphological activity (rounding up) at nanomolar concentrations on endothelial cells (EA.hy 926 cells), which is indicative of potential antivascular activity. Interestingly, the corresponding 7- O-mesylate derivative 28 (an intermediate in the synthesis of 13), was also found active in cellular assays, although it was moderately active in the tubulin polymerization inhibition test. Finally, in order to better understand the SAR of disubstituted analogues of 1, two other position isomers ( 10 and 14), were synthesized and evaluated for their biological activities. It was noted that the 7-hydroxysubstituted analogue 13 was more potent than the 5-hydroxysubstituted analogue 10. In conclusion, this work has allowed the identification of biologically potent CA-4 analogues ( 13 and 28) and also contributes to a better understanding of the SAR of 1.

Antitumor Activity of Vinflunine: Effector Pathways and Potential for Synergies

Vinflunine is an innovative microtubule inhibitor of the vinca alkaloid class with distinct tubulin-binding properties. Preclinical evaluation of this novel microtubule inhibitor has shown superior antitumor activity against a broad spectrum of tumor types in vitro and in vivo, in comparison with other vinca alkaloids. The antitumor effect of vinflunine is largely attributable to its modulation of microtubule dynamics, and is mediated by its ability to induce apoptosis in target cells. At non-cytotoxic concentrations, vinflunine also exerts antiangiogenic and antivascular activity. The favorable preclinical profile of vinflunine, in addition to its synergism with a variety of other therapeutic modalities, justifies further clinical development of this compound.

Validation of the selected dose of aflibercept (VEGF Trap) plus irinotecan, 5-fluorouracil, and leucovorin (I-LV5FU2) in a phase I clinical trial of patients (pts) with advanced solid tumors (STs): Preliminary results

14540 Background: Aflibercept (AF), a potent angiogenesis inhibitor fusion protein, is comprised of human VEGF receptor VEGFR1 (Flt-1) and VEGFR2 (Flk-1) extracellular domains fused to the Fc portion of human IgG1. A phase I dose escalation study established the AF 4.0 mg/kg + I-LV5FU2 (standard dose) every 2 weeks (q2w) as the recommended dose to be confirmed in a feasibility study. Methods: This was a randomized, double blind feasibility study of AF (4.0 mg/kg) or placebo + I-LV5FU2 at cycle 1, followed in subsequent cy by AF (4.0 mg/kg) + I-LV5FU2 q2w in pts with solid tumors. Study endpoints were to confirm the AF dose, explore the safety, preliminary efficacy and antivascular activity (DCE MRI) of AF. DCE MRI was performed at cycle 1 and 2, all imagings were centrally reviewed. Results: 27 pts were treated in both arms (15 male/12 female), median age 54 [39–75], ECOG PS 0/1/2: 12/11/4, with 70% of colorectal cancers. All pts received prior chemotherapy (CT): median 3 [1–6], 21 pts were previously tre...

Tumor Blood Vessel Dynamics During and After Angiogenesis Inhibition

Inhibitors of VEGF signaling cause robust and rapid changes in blood vessels of tumors. The inhibitors block angiogenesis, have potent antivascular actions resulting in regression of tumor vessels, and reduce the abnormality of tumor vessels that survive. Within hours, endothelial fenestrations and vascular sprouts disappear, and patency is lost and blood flow ceases in a population of tumor vessels. By the end of the first week, as many as 80% of tumor vessels regress. Surviving tumor vessels acquire more normal structural and functional features, in a process called normalization. Pericytes of tumor vessels are not as severely impacted by VEGF inhibitors as endothelial cells. Empty sleeves of vascular basement membrane persist after tumor vessels regress, providing a historical record of degenerated tumor vessels and a scaffold for vascular regrowth. Withdrawal of treatment leads to regrowth of endothelial sprouts into empty sleeves of basement membrane. Regrowth begins within a day after withdrawal of inhibitors that are rapidly cleared. Within a week, tumors may be fully revascularized with functional blood vessels. These results raise the possibility that empty sleeves of vascular basement membrane and accompanying pericytes provide a scaffold for rapid revascularization of tumors after removal of anti‐VEGF therapy and highlight their importance as potential targets in cancer therapy.

The ability of coumarin-, flavanon- and flavonol-analogues of flavone acetic acid to stimulate human monocytes

Flavone acetic acid (FAA) is a semi-synthetic flavonoid characterised by potent immune-modulatory and antivascular activity on mice but not in humans. Previously, the synthesis and cytotoxic activity on a human adenocarcinoma cell line of coumarin-, flavanon- and flavonol-derivatives of FAA were described. These analogues were able to induce the reduction of lysosomal neutral red uptake at 5 x 10(-5) M concentration and some of them were more effective than FAA. Some of these derivatives were selected to investigate their ability to exert immune-modulation on a human model, by using the most potent analogue that has emerged thus far, 5,6-dimethylxanthenone-4-acetic acid (DMXAA), as a reference compound. We investigated the cytotoxicity of the selected derivatives on two human ovarian adenocarcinoma cell lines and their ability to activate the immune system by inducing lytic properties, TNF-alpha and nitric oxide in human monocytes. The immune-modulating activity was assessed by treating a cell line of human monocytes (Mono Mac 6, MM6) with FAA-derivatives alone or in association with lipopolysaccharide (LPS). None of the tested molecules showed any significant ability to directly affect tumor cell proliferation, whereas they were able to induce the lytic properties of MM6 cells. In particular, two coumarin derivatives, a and d, and the flavonol acetic acid, l, showed comparable results to DMXAA. The combination with LPS did not lead to synergistic interactions in the induction of the lytic properties of MM6, but it significantly increased the release of TNF-alpha, especially after 4 h of treatment. Instead, the maximum release of nitric oxide (NO) was detected after 24 h of treatment and after exposure to the FAA derivatives alone. Derivative a combined with LPS and analogue d alone were able to induce a higher TNF-alpha and NO release, respectively, whereas flavonol acetic acid was characterised by a strictly similar activity to DMXAA.

Comparison of the antivascular and cytotoxic activities of TZT-1027 (Soblidotin) with those of other anticancer agents

TZT-1027 (Soblidotin), a microtubule-depolymerizing agent exerts both a direct cytotoxic activity against cancer cells and an indirect antivascular activity against tumor vascular endothelial cells. We compared both activities of TZT-1027 with those of various anticancer agents having different mechanisms of action, including vinca alkaloids, a vascular targeting agent, a taxane and nonmicrotubule-binding agents. In the MTT assay, TZT-1027 most potently inhibited the growth of both murine colon C26 cancer cells and human umbilical vein endothelial cells, implying its potent antivascular activity against tumor vasculature in addition to its cytotoxic activity against cancer cells. Treatment with 0.1 microg/ml TZT-1027 significantly enhanced vascular permeability in human umbilical vein endothelial cell monolayers and a single intravenous administration of 2 mg/kg TZT-1027 significantly reduced the perfusion of Colon26 tumors implanted into mice, with efficacies superior to vinca alkaloids and comparable to a known vascular targeting agent. These results strongly suggest that TZT-1027 exerts marked antivascular activity. Next, to clarify the mechanism of the antivascular activity, we have taken a novel approach, and analyzed the relationships among human umbilical vein endothelial cells cytotoxicity, vascular permeability and tumor perfusion, on the basis of efficacies of each agent. Analyses revealed strong and significant correlations, and indicated that the vascular endothelial cell damage leads to endothelial barrier dysfunction and, thereby, tumor vascular shutdown. In summary, TZT-1027 was verified to have not only an excellent cytotoxic activity, but also an attractive antivascular activity through the induction of damage to vascular endothelial cells. We believe that these dual activities may make TZT-1027 useful for treating solid tumors.

The Antivascular Action of Physiotherapy Ultrasound on A Murine Tumor: Role of A Microbubble Contrast Agent

This study investigated whether a microbubble-containing ultrasound contrast agent had a role in the antivascular action of physiotherapy ultrasound on tumor neovasculature. Ultrasound images (B-mode and contrast-enhanced power Doppler [0.02 mL Definity]) were made of 22 murine melanomas (K1735 22). The tumor was insonated (I SATA = 1.7 W cm –2, 1 MHz, continuous output) for 3 min and the power Doppler observations of the pre- and postinsonation tumor vascularities were analyzed. Significant reductions ( p = 0.005 for analyses of color-weighted fractional area) in vascularity occurred when a contrast-enhanced power Doppler study occurred before insonation. Vascularity was unchanged in tumors without a pretherapy Doppler study. Histologic studies revealed tissue structural changes that correlated with the ultrasound findings. The underlying etiology of the interaction between the physiotherapy ultrasound beam, the microbubble-containing contrast agent and the tumor neovasculature is unknown. It was concluded that contrast agents play an important role in the antivascular effects induced by physiotherapy ultrasound. (E-mail: sehgalc@uphs.upenn.edu)

Imaging of angiogenesis in inflammation and cancer: lessons for novel treatment of allergic rhinitis

SummaryAngiogenesis is a feature of inflammatory and neoplastic disease. Imaging studies are revealing the distribution and accessibility of molecular targets at sites of angiogenesis and how abnormalities of angiogenic blood vessels can be exploited in diagnosis and treatment. Blood vessels at sites of angiogenesis have multiple abnormalities that provide targets for diagnostics and therapeutics. These abnormalities involve all components of the vessel wall, including endothelial cells, pericytes (mural cells), and the vascular basement membrane. Endothelial cells of angiogenic blood vessels in tumours may express abnormal proteins, sprout, proliferate, have a defective barrier function, and be dependent on vascular endothelial growth factor (VEGF) for survival. Endothelial cells of capillaries at sites of inflammation acquire a venule‐like phenotype, become leaky, and express adhesion molecules that support leucocyte influx. Inhibitors of VEGF signalling can stop angiogenesis, have a potent antivascular action, and reduce the abnormality of surviving vessels. Studies of VEGF inhibitors in mouse tumour models have shown robust and rapid changes in endothelial cells, pericytes, and the vascular basement membrane of angiogenic blood vessels. After treatment, endothelial fenestrations disappear, vascular sprouting is suppressed, and patency and blood flow cease in some vessels within 24 h. By 7 days, many tumour vessels regress. Surviving tumour vessels acquire more normal structural characteristics. Pericytes do not degenerate to the same extent as endothelial cells. The vascular basement membrane also persists after endothelial cells degenerate, providing a record of regressing vessels, sites for growth factor binding, and a scaffold for blood vessel regrowth after the cessation of therapy. The actions of angiogenesis inhibitors on blood vessels in tumours highlight the potential of exploiting the molecular and cellular abnormalities of angiogenic blood vessels in inflammatory conditions, including allergic rhinitis.

A novel class of tubulin inhibitors that exhibit potent antiproliferation and in vitro vessel-disrupting activity

Since anticancer agents that interfere with microtubule function are in widespread use and have a broad spectrum of activity against both hematological malignancies and solid tumors, there is an urgent need to develop novel tubulin inhibitors with broader activities and avoiding drug resistance. In this study, we describe the characterization of select lead compounds from a novel class of indazole-based tubulin inhibitors. Three lead compounds, TH-337, TH-482 and TH-494, exhibit potent antiproliferative activity against cell lines derived from human pancreatic carcinoma, human breast adenocarcinoma and human colorectal adenocarcinoma cells. The three compounds were also tested for cytotoxicity against a panel of clinically relevant drug resistant cancer cell lines that either overexpress the drug resistance pumps MDR-1, MRP-1 and BCRP-1 or have altered Topoisomerase II activity. TH-482 and -494 retained cytotoxic activities against all of the resistant cell lines tested; however, TH-337 exhibited decreased cytotoxicity in the cell line overexpressing BCRP-1, indicating that TH-337 is a substrate of that pump. We show that TH-482's antiproliferative activity is due to cell cycle arrest at the G(2)/M phase. We demonstrate that TH-482 binds specifically to the colchicine site of tubulin and that it inhibits tubulin polymerization in vitro in a concentration-dependent manner. The in vitro anti-vascular activities of TH-482 were assessed using the HUVEC-C cell line. TH-482 inhibits in vitro neovessel formation and disrupts pre-established vessels using HUVEC-C cells. TH-482 also increases permeability of vascular endothelial cells in a concentration- and time-dependent manner. TH-482 demonstrates potent in vitro efficacy as a novel tubulin-targeted anti-proliferative and anti-vascular agent and notably is more potent in antiproliferative assays than the benchmark compound combretastatin A-4. These results identify TH-482 as a potent tubulin inhibitor, and support the investigation of its in vivo efficacy and pharmacokinetic properties as the prototype of a new class of anti-tubulin agents.