Targeting the tumor vascular compartment to improve conventional cancer therapy

Targeting M2 Macrophages with a Novel NADPH Oxidase Inhibitor

ROS in cancer cells play a key role in pathways regulating cell death, stemness maintenance, and metabolic reprogramming, all of which have been implicated in resistance to chemo/ immunotherapy. Adjusting ROS levels to reverse the resistance of cancer cells without impairing normal cell functions is a new therapeutic avenue. In this paper, we describe new inhibitors of NADPH oxidase (NOX), a key enzyme in many cells of the tumor microenvironment. The first inhibitor, called Nanoshutter-1, NS1, decreased the level of tumor-promoting "M2" macrophages differentiated from human blood monocytes. NS1 disrupted the active NADPH oxidase-2 (NOX2) complex at the membrane and in the mitochondria of the macrophages, as shown by confocal microscopy. As one of the characteristics of tumor invasion is hypoxia, we tested whether NS1 would affect vascular reactivity by reducing ROS or NO levels in wire and pressure myograph experiments on isolated blood vessels. The results show that NS1 vasodilated blood vessels and would likely reduce hypoxia. Finally, as both NOX2 and NOX4 are key proteins in tumors and their microenvironment, we investigated whether NS1 would probe these proteins differently. Models of NOX2 and NOX4 were generated by homology modeling, showing structural differences at their C-terminal NADPH site, in particular in their last Phe. Thus, the NADPH site presents an unexploited chemical space for addressing ligand specificity, which we exploited to design a novel NOX2-specific inhibitor targeting variable NOX2 residues. With the proper smart vehicle to target specific cells of the microenvironment as TAMs, NOX2-specific inhibitors could open the way to new precision therapies.

Design, synthesis, and antitumor evaluation of trimethoxyflavonoid with arylurea structure against hepatocellular carcinoma

Simultaneous targeting of tumor vasculature and inhibitors of tumor cell glycolysis may be a promising antitumor strategy. Here, we reported the total synthesis and biological evaluation of A-ring arylurea flavonoid derivatives with B-ring trimethoxy group, which exhibited potent antitumor activity against a variety of tumor cells in vitro. Most of the derivatives showed in vitro antitumor activity on HepG-2, HGC-27, MDA-MB-231, and A549 cells. Among them, compounds 8e, 8f, 8g, 8h, 8j, and 8l also exhibited significant anti-proliferation effects on liver tumor cell subtypes BEL-7402 and SMMC-7721. Compound 8l had the lowest IC₅₀ value (5.61 ± 0.39 μM) on HepG-2 cells, and showed the effects of inhibiting colony formation, arresting the cell cycle in G₀ /G₁ phase, and inducing apoptosis in a concentration-dependent manner. In addition, the toxicity of compound 8l on human normal cells LO2 and GES-1 was lower than that of sorafenib. The inhibitory effects of compound 8l on the expression of glycolytic rate-limiting enzymes HKII, PFK-1, PKM2 and vascular endothelial growth factor were further evaluated. Corresponding reduction in intracellular lactate was also detected after compound 8 treatment. Our results support an antitumor strategy targeting tumor vasculature and glycolysis to discover and develop a new generation of antitumor drugs.

Tackling TAMs for Cancer Immunotherapy: It's Nano Time

The tumor microenvironment (TME) is a highly complex environment that surrounds tumors. Interactions between cancer cells/non-cancerous cells and cells/non-cell components in the TME support tumor initiation, development, and metastasis. Of the cell types in the TME, tumor-associated macrophages (TAMs) have gained attention owing to their crucial roles in supporting tumors and conferring therapy resistance. Recent developments in nanotechnology raise opportunities for the application of nano targeted drug-delivery systems (Nano-TDDS) in cancer therapy. We focus our discussion on current knowledge of TAMs, and describe recent examples of Nano-TDDS-based TAM modulation, highlighting strategies to overcome in vivo delivery barriers associated with the TME and their potential for clinical translation.

Inhibition of fibronectin accumulation suppresses tumor growth

Understanding how the extracellular matrix affects cancer development constitutes an emerging research field. Fibronectin and collagen are two intriguing matrix components found in cancer. Large concentrations of fibronectin or collagen type I have been implicated in poor prognosis in patients. In a mouse model, we had shown that genetically decreasing circulating fibronectin resulted in smaller tumors. We therefore aimed to manipulate fibronectin pharmacologically and determine how cancer development is affected. Deletion of fibronectin in human breast cancer cells (MDA-MB-231) using shRNA (knockdown: Kd) improved survival and diminished tumor burden in a model of metastatic lesions and in a model of local growth. Based on these findings, it seemed reasonable to attempt to prevent fibronectin accumulation using a bacterial derived peptide called pUR4. Treatment with this peptide for 10 days in the breast cancer local growth model or for 5 days in a melanoma skin cancer model (B16) was associated with a significant suppression of cancer growth. Treatment aimed at inhibiting collagen type I accumulation without interfering with fibronectin could not affect any changes in vivo. In the absence of fibronectin, diminished cancer progression was due to inhibition of proliferation, even though changes in blood vessels were also detected. Decreased proliferation could be attributed to decreased ERK phosphorylation and diminished YAP expression. In summary, manipulating fibronectin diminishes cancer progression, mostly by suppressing cell proliferation. This suggests that matrix modulation could be used as an adjuvant to conventional therapy as long as a decrease in fibronectin is obtained.

CaCO3 nanoparticles pH-sensitively induce blood coagulation as a potential strategy for starving tumor therapy

Based on the concept of starving tumor therapy, in this study we put forward a new idea that the pH-sensitive Ca²⁺ delivery of calcium carbonate nanoparticles (CaCO₃ NPs) induced blood coagulation of tumor vessels, and first explored the effect of CaCO₃ NPs on the in vitro and in vivo blood coagulation by acid stimulus. CaCO₃ NPs with a size of about 100 nm and a porous structure of several nanometers were synthesized in an emulsion system, which showed a high loading capacity (49%) of doxorubicin hydrochloride (DOX) with an encapsulation efficiency of 98% and a pH-sensitive drug delivery. The hemolysis test showed that CaCO₃ NPs were blood compatible. The in vitro Ca²⁺ delivery and blood clotting tests indicated that CaCO₃ NPs pH-sensitively released Ca²⁺, and caused rapid blood coagulation at pH 5.0 but no thrombus at pH 7.4. Confocal laser scanning microscopy showed that after uptake by MCF-7 or MDA-MB-231 breast cancer cells, CaCO₃ NPs mainly distributed in endosomes/lysosomes within the initial 2 h and then decomposed by acid stimulus, leading to the intracellular delivery of Ca²⁺ that subsequently migrated outside the cells. CaCO₃ NPs were nontoxic to NIH3T3 mouse fibroblasts, but highly toxic to both MCF-7 and MDA-MB-231 cells after loading DOX. After topical administration into the breast tumors of mice, CaCO₃ NPs evoked significant thrombosis and hemorrhage of tumor vasculature by hematoxylin-eosin and Masson's trichrome staining. These results indicated that CaCO₃ NPs could induce blood coagulation via acid stimulus, showing potential applications in blocking tumor vessels for starving tumor therapy.

BRACHYTHERAPY ALONE OR WITH NEOADJUVANT PHOTODYNAMIC THERAPY FOR AMELANOTIC CHOROIDAL MELANOMA: Functional Outcomes and Local Tumor Control

PURPOSE

To compare visual outcomes and local tumor control between two groups of patients with amelanotic choroidal melanoma treated with brachytherapy alone, or neoadjuvant photodynamic therapy before brachytherapy.

METHODS

Patients diagnosed with amelanotic choroidal melanoma were recruited for the study and divided into two groups: brachytherapy alone (Group A) and photodynamic therapy preceding brachytherapy (Group B). Patients of both groups were selected to be comparable.

RESULTS

Twenty-six patients with amelanotic choroidal melanoma were enrolled in the study. Within Group B, 1 month after photodynamic therapy, ultrasonography showed reduction of tumor height in 11 patients (73.4%). The mean doses of irradiation to macula and optic nerve, at baseline were 74.37 and 52.07 Gy, whereas after photodynamic therapy there was a decrease of 17.26% (P = 0.008) and 21.22% (P = 0.025), respectively. In terms of visual acuity, a mean decrease of 14 ETDRS letters and 5 ETDRS letters was observed at 24 months follow-up, in Groups A and B, respectively (P = 0.001).

CONCLUSION

Photodynamic therapy as neoadjuvant therapy before brachytherapy reduces tumor thickness in 73.4% of cases. As a result, a decrease of radiation toxic effects on visual function could be obtained, without compromising disease control.

Synthesis of 2-anilinopyridyl-triazole conjugates as antimitotic agents

A series of 2-anilinopyridyl–triazole conjugates (6a–t) were prepared and evaluated for their cytotoxic activity against a panel of three human cancer cell lines. Among them compounds 6q, 6r and 6s showed significant cytotoxic activity with IC50 values ranging from 0.1 to 4.1 μM. Structure–activity relationships were elucidated with various substitutions on these conjugates. Flow cytometric analysis revealed that these compounds arrest the cell cycle at the G2/M phase and induce cell death by apoptosis. The tubulin polymerization assay and immunofluorescence analysis showed that these compounds (6q, 6r and 6s) effectively inhibited the microtubule assembly in human prostate cancer cells (DU-145). The docking studies showed that 6s interacts and binds efficiently with the tubulin protein at the colchicine binding site. This was further confirmed by the colchicine competitive binding assay. Moreover, compounds 6q, 6r and 6s possess anti-tubulin activity both in vitro and within cells as demonstrated by the ratio of soluble versus polymerized tubulin. Further the apoptotic effects of compounds were confirmed by Hoechst staining, caspase 3 activation, annexin-V FITC, mitochondrial membrane potential and DNA fragmentation analysis. Interestingly, these compounds did not affect the normal human embryonic kidney cells, HEK-293.

Magnetic resonance elastography (MRE) in cancer: Technique, analysis, and applications

Tissue mechanical properties are significantly altered with the development of cancer. Magnetic resonance elastography (MRE) is a noninvasive technique capable of quantifying tissue mechanical properties in vivo. This review describes the basic principles of MRE and introduces some of the many promising MRE methods that have been developed for the detection and characterization of cancer, evaluation of response to therapy, and investigation of the underlying mechanical mechanisms associated with malignancy.

Delivery of platinum(IV) drug to subcutaneous tumor and lung metastasis using bradykinin-potentiating peptide-decorated chitosan nanoparticles

Selectively activating tumor vessels to increase drug delivery and reduce interstitial fluid pressure of tumors is actively pursued. Here we developed a vasoactive peptide-decorated chitosan nanoparticles for enhancing drug accumulation and penetration in subcutaneous tumor and lung metastasis. The vasoactive peptide used here is bradykinin-potentiating peptide (BPP) containing 9 amino acid residues and the drug is bioreductively sensitive platinum(IV) compound which becomes cisplatin in intracellular reductive environments. Both peptide and drug are covalently linked with chitosan nanoparticles with a diameter of 120 nm. We demonstrate that BPP-decorated chitosan nanoparticles increase the tumorous vascular permeability and reduce the interstitial fluid pressure of tumor simultaneously, both of which improve the penetration of nanoparticles in tumor tissues. The in vivo biodistribution and tumor inhibition examinations demonstrate that the BPP-decorated nanoparticle formulation has more superior efficacy in enhancing drug accumulation in tumor, restraining tumor growth and prolonging the lifetime of tumor-bearing mice than free drug and non-decorated nanoparticle formulation. Meanwhile, the drug accumulation in the lung with metastasis reaches 17% and 20% injected dose per gram of lung for the chitosan nanoparticles without and with BPP decoration, respectively, which is 10-fold larger than that of free cisplatin. The examination of lung metastasis inhibition further indicates that BPP-decorated chitosan nanoparticle formulations can more effectively inhibit lung metastasis.

Tumour hypoxia determines the potential of combining mTOR and autophagy inhibitors to treat mammary tumours

BACKGROUND

Hypoxia can activate autophagy, a self-digest adaptive process that maintains cell turnover. Mammalian target of rapamycin (mTOR) inhibitors are used to treat cancer but also stimulate autophagy.

METHODS

Human mammary cancer cells and derived xenografts were used to examine whether hypoxia could exacerbate autophagy-mediated resistance to the mTOR inhibitor rapamycin.

RESULTS

Rapamycin exerted potent antitumour effects in MCF-7 and MDA-MB-231 mammary tumours through a marked inhibition of angiogenesis, but the autophagy inhibitor chloroquine (CQ) failed to further sensitise tumours to mTOR inhibition. Rapamycin treatment actually led to tumour reoxygenation, thereby preventing the development of autophagy. Chloroquine alone, however, blocked the growth of MCF-7 tumours and in vitro blunted the hypoxia-induced component of autophagy in these cells. Finally, when initiating CQ treatment in large, hypoxic tumours, a robust antitumour effect could be observed, which also further increased the antiproliferative effects of rapamycin.

CONCLUSION

The mTOR inhibitor rapamycin significantly contributes to tumour growth inhibition and normalisation of the tumour vasculature through potent antiangiogenic effects. The resulting reduction in hypoxia accounts for a lack of sensitisation by the autophagy inhibitor CQ, except if the tumours are already at an advanced stage, and thus largely hypoxic at the initiation of the combination of rapamycin and CQ treatment.

Tumor-penetrating peptides

Tumor-homing peptides can be used to deliver drugs into tumors. Phage library screening in live mice has recently identified homing peptides that specifically recognize the endothelium of tumor vessels, extravasate, and penetrate deep into the extravascular tumor tissue. The prototypic peptide of this class, iRGD (CRGDKGPDC), contains the integrin-binding RGD motif. RGD mediates tumor-homing through binding to αv integrins, which are selectively expressed on various cells in tumors, including tumor endothelial cells. The tumor-penetrating properties of iRGD are mediated by a second sequence motif, R/KXXR/K. This C-end Rule (or CendR) motif is active only when the second basic residue is exposed at the C-terminus of the peptide. Proteolytic processing of iRGD in tumors activates the cryptic CendR motif, which then binds to neuropilin-1 activating an endocytic bulk transport pathway through tumor tissue. Phage screening has also yielded tumor-penetrating peptides that function like iRGD in activating the CendR pathway, but bind to a different primary receptor. Moreover, novel tumor-homing peptides can be constructed from tumor-homing motifs, CendR elements and protease cleavage sites. Pathologies other than tumors can be targeted with tissue-penetrating peptides, and the primary receptor can also be a vascular "zip code" of a normal tissue. The CendR technology provides a solution to a major problem in tumor therapy, poor penetration of drugs into tumors. The tumor-penetrating peptides are capable of taking a payload deep into tumor tissue in mice, and they also penetrate into human tumors ex vivo. Targeting with these peptides specifically increases the accumulation in tumors of a variety of drugs and contrast agents, such as doxorubicin, antibodies, and nanoparticle-based compounds. Remarkably the drug to be targeted does not have to be coupled to the peptide; the bulk transport system activated by the peptide sweeps along any compound that is present in the blood.

Microbubble and ultrasound radioenhancement of bladder cancer

BACKGROUND

Tumour vasculature is an important component of tumour growth and survival. Recent evidence indicates tumour vasculature also has an important role in tumour radiation response. In this study, we investigated ultrasound and microbubbles to enhance the effects of radiation.

METHODS

Human bladder cancer HT-1376 xenografts in severe combined immuno-deficient mice were used. Treatments consisted of no, low and high concentrations of microbubbles and radiation doses of 0, 2 and 8 Gy in short-term and longitudinal studies. Acute response was assessed 24 h after treatment and longitudinal studies monitored tumour response weekly up to 28 days using power Doppler ultrasound imaging for a total of 9 conditions (n=90 animals).

RESULTS

Quantitative analysis of ultrasound data revealed reduced blood flow with ultrasound-microbubble treatments alone and further when combined with radiation. Tumours treated with microbubbles and radiation revealed enhanced cell death, vascular normalisation and areas of fibrosis. Longitudinal data demonstrated a reduced normalised vascular index and increased tumour cell death in both low and high microbubble concentrations with radiation.

CONCLUSION

Our study demonstrated that ultrasound-mediated microbubble exposure can enhance radiation effects in tumours, and can lead to enhanced tumour cell death.

CD31 angiogenesis and combined expression of HIF-1α and HIF-2α are prognostic in primary clear-cell renal cell carcinoma (CC-RCC), but HIFα transcriptional products are not: implications for antiangiogenic trials and HIFα biomarker studies in primary CC-RCC

Hypoxia-inducible factors, HIF-1α and HIF-2α, are expressed in the majority of clear-cell renal cell carcinoma (CC-RCC). In vitro, HIFα isoforms regulate a differential set of genes, and their effects in vivo within CC-RCC tumours may affect outcome. The role of angiogenesis and HIFα transcriptional products, including those involved in cell metabolism and morphological dedifferentiation have not been extensively investigated and might have relevance to the development of antiangiogenic or anti-HIFα trials in primary CC-RCC, either before or after radical nephrectomy. We analysed 168 consecutive clear-cell renal tumours from 1983 to 1999 within tissue microarrays and assessed expression of HIF-1α and HIF-2α together with the protein expression of seven of their target genes (BNIP3, CA9, Cyclin D1, GLUT-1, LDH5, Oct-4 and VEGF). The expression of these factors was compared with patient overall survival and CD31 angiogenesis. We found that HIFα antigenicity deteriorated with the age of the paraffin block (P < 0.0001) and in tumours from 1983 to 1992 was deemed not to be reliable. Similar findings were found in aged archival osteosarcoma samples. This might have important implications for retrospective biomarker studies that rely on archival tissue material. HIF-1α(HIGH)/HIF-2α(LOW) tumours had a worse overall survival compared with HIF-1α(LOW)/HIF-2α(LOW) tumours (P = 0.04). Surprisingly, on multivariate analysis, high levels of CD31(+) angiogenesis was shown to be an independent prognostic marker of increased overall survival (P = 0.003). We propose that better differentiation of vascular endothelium may be a reflection of a greater production of vessel stabilization factors versus pro-angiogenic factors, and therefore a less aggressive phenotype.

Colon tumor growth and antivascular treatment in mice: complementary assessment with MR elastography and diffusion-weighted MR imaging

PURPOSE

To investigate the potential value of magnetic resonance (MR) elastography and diffusion-weighted (DW) MR imaging in the detection of microstructural changes of murine colon tumors during growth and antivascular treatment.

MATERIALS AND METHODS

The study was approved by the regional ethics committee for animal care. Sixty Balb-C mice, bearing ectopic and orthotopic colon tumors, were monitored for 3 weeks with high-resolution T2-weighted MR imaging, three-dimensional steady-state MR elastography, and DW MR imaging at 7 T. The same imaging protocol was performed 24 hours after injection of combretastatin A4 phosphate (CA4P) in 12 mice. The absolute value of the complex shear modulus (|G*|) and the apparent diffusion coefficient (ADC) were measured in the viable zones of tumors and compared with microvessel density (MVD), cellularity, and micronecrosis by using the Pearson correlation coefficient.

RESULTS

During tumor growth, |G*| increase was correlated with MVD (r = 0.70 [P = .08] and r = 0.78 [P = .002], for both the ectopic and orthotopic models, respectively). Moreover, the ectopic tumors displayed decreased ADC, which correlated with increased cellularity (r = 0.77, P = .04), whereas no changes in ADC and cellularity were observed in orthotopic tumors. After CA4P administration, |G*| decreased in the ectopic model (P < .0001), similar to the MVD evolution (P = .03), whereas no significant changes in |G*| (P = .7) and MVD (P = .6) were observed in the orthotopic model. ADC increased in both models (P = .047 and P = .01 for the ectopic and the orthotopic models, respectively) in relation to increased micronecrosis.

CONCLUSION

Imaging of mechanical properties and diffusivity provide complementary information during tumor growth and regression that are respectively linked to vascularity and tumor cell alterations, including cellularity and micronecrosis.

Targeting tumor perfusion and oxygenation to improve the outcome of anticancer therapy

Radiotherapy and chemotherapy are widespread clinical modalities for cancer treatment. Among other biological influences, hypoxia is a main factor limiting the efficacy of radiotherapy, primarily because oxygen is involved in the stabilization of the DNA damage caused by ionizing radiations. Radiobiological hypoxia is found in regions of rodent and human tumors with a tissue oxygenation level below 10 mmHg at which tumor cells become increasingly resistant to radiation damage. Since hypoxic tumor cells remain clonogenic, their resistance to the treatment strongly influences the therapeutic outcome of radiotherapy. There is therefore an urgent need to identify adjuvant treatment modalities aimed to increase tumor pO(2) at the time of radiotherapy. Since tumor hypoxia fundamentally results from an imbalance between oxygen delivery by poorly efficient blood vessels and oxygen consumption by tumor cells with high metabolic activities, two promising approaches are those targeting vascular reactivity and tumor cell respiration. This review summarizes the current knowledge about the development and use of tumor-selective vasodilators, inhibitors of tumor cell respiration, and drugs and treatments combining both activities in the context of tumor sensitization to X-ray radiotherapy. Tumor-selective vasodilation may also be used to improve the delivery of circulating anticancer agents to tumors. Imaging tumor perfusion and oxygenation is of importance not only for the development and validation of such combination treatments, but also to determine which patients could benefit from the therapy. Numerous techniques have been developed in the preclinical setting. Hence, this review also briefly describes both magnetic resonance and non-magnetic resonance in vivo methods and compares them in terms of sensitivity, quantitative or semi-quantitative properties, temporal, and spatial resolutions, as well as translational aspects.

Targeted and intracellular triggered delivery of therapeutics to cancer cells and the tumor microenvironment: impact on the treatment of breast cancer

Limiting tumor invasion to the surrounding healthy tissues has proven to be clinically relevant for anticancer treatment options. We have demonstrated that, within a solid tumor, it is possible to achieve such a goal with the same nanoparticle by intracellular and triggered targeted drug delivery to more than one cell population. We have identified the nucleolin receptor in endothelial and cancer cells in tissue samples from breast cancer patients, which enabled the design of a F3-peptide-targeted sterically stabilized pH-sensitive liposome. The clinical potential of such strategy was demonstrated by the successful specific cellular association by breast cancer cells harvested from tumors of patients submitted to mastectomy. In vitro, the nanoparticle targeted the nucleolin receptor on a cell and ligand-specific manner and improved cytotoxicity of doxorubicin (used as a model drug) towards breast cancer and endothelial cells by 177- and 162-fold, respectively, relative to the commercially available non-targeted non-pH-sensitive liposomes. Moreover, active accumulation of F3-targeted pH-sensitive liposomes into human orthotopic tumors, implanted in the mammary fat pad of nude mice, was registered for a time point as short as 4 h, reaching 48% of the injected dose/g of tissue. Twenty-four hours post-injection the accumulation of the dual-targeted pH-sensitive nanoparticle in the tumor tissue was 33-fold higher than the non-targeted non-pH-sensitive counterpart. In mice treated with the developed targeted nanoparticle significant decrease of the tumor viable rim area and microvascular density, as well as limited invasion to surrounding healthy tissues were observed (as opposed to other tested controls), which may increase the probability of tumors falling in the category of "negative margins" with reduced risk of relapse.

Delivery of soluble VEGF receptor 1 (sFlt1) by gene electrotransfer as a new antiangiogenic cancer therapy

Since tumor growth is highly dependent on the formation of new blood vessels, angiogenesis inhibitors have become important players in anticancer treatments. Although less cytotoxic than conventional chemotherapy, most of the available antiangiogenic agents may provoke severe adverse effects which can limit their use. The design of new antiangiogenic strategies therefore requires integrating an early evaluation of possible interference with quiescent endothelial cells and nontumor angiogenesis. Here, we describe such a novel antiangiogenic approach based on the in vivo delivery by gene electrotransfer of a negative regulator of angiogenesis, namely, sFlt1. We found that this soluble variant of the vascular endothelial growth factor receptor 1 (Flt1, also known as VEGFR1), which acts as a VEGF trap, differentially influences tumor and postischemic hind limb angiogenesis in mice. sFlt1 gene electrotransfer in tibial cranial muscle leads to high sFlt1 protein expression and secretion, leading to a significant delay in the growth of syngeneic tumors but not altering the revascularization of ischemic peripheral tissue. The higher sensitivity of tumor-bearing animals toward sFlt1 trapping effects (vs ischemia-recovering animals) might be explained by a distinct pattern of VEGF release, as shown by VEGF measurements in plasma and tissue. In conclusion, our data support sFlt1 gene electrotransfer as a novel and safe modality to target VEGF-driven tumor angiogenesis and to maintain unaltered the recovery potential of ischemic tissues.

MT-MMPS as Regulators of Vessel Stability Associated with Angiogenesis

The development of vascular system depends on the coordinated activity of a number of distinct families of molecules including growth factors and their receptors, cell adhesion molecules, extracellular matrix (ECM) molecules, and proteolytic enzymes. Matrix metalloproteases (MMPs) are a family of ECM degrading enzymes required for both physiological and pathological angiogenesis. Increasing evidence, point to a direct role of membrane type-MMPs (MT-MMPs) in vascular system stabilization, maturation, and leakage. Our understanding of the nature of MT-MMP interaction with extracellular and cell surface molecules and their multiple roles in vessel walls and perivascular stroma may provide new insights into mechanisms underlying vascular cell–ECM interactions and cell fate decisions in pathological conditions. Regulation of vascular leakage by MT-MMP interactions with the ECM could also lead to novel targeting opportunities for drug delivery in tumor. This review will shed lights on the emerging roles of MT1-MMP and MT4-MMP in vascular system alterations associated with cancer progression.

Blood vessel maturation, vascular phenotype and angiogenic potential in malignant melanoma: one step forward for overcoming anti-angiogenic drug resistance?

Angiogenesis is a pivotal process for growth, invasion and spread of the majority of solid tumors including melanoma. Anti-angiogenic agents have not been systematically tested in patients with advanced melanoma. Clinical efficacy of angiogenesis inhibitors targeting endothelial cells has not been as affirmative as initially hoped and improved clinical outcomes have been observed in combination with chemotherapy or additional drugs for many types of human cancer. However, angiogenesis is not only dependent on endothelial cell invasion and proliferation, it also requires pericyte coverage of vascular sprouts for stabilization and maturation of vascular walls. Recent data suggest that pericytes might be able to confer resistance to anti-vascular endothelial growth factor (VEGF) therapy. This review will focus on the significance of the vascular phenotype but also on the impact of pericyte-mediated vessel maturation for the susceptibility to anti-angiogenic therapy, including malignant melanoma, which we identified as crucial factor regarding therapeutic efficacy.

Tumor-penetrating peptides: a shift from magic bullets to magic guns

The targeted delivery of drugs and imaging agents to tumor vessels is an attractive strategy to enhance anticancer therapy and tumor detection, but such targeting does not mean efficient distribution into the tumor. Two consecutive papers, one in Cancer Cell and one in Science, report that a single peptide has the potential to selectively deliver a large variety of therapeutic agents and diagnostics to a tumor site and then to ensure their distribution deep in the tumor parenchyma. This peptide has the capacity to bind specific alpha(V) integrins through an arginine-glycine-aspartate motif and, after local proteolysis reveals a cryptic arginine/lysine-X-X-arginine/lysine motif, to bind the neuropilin-1 receptor and thereby increase tumor vascular permeability. Remarkably, this penetrating peptide works not only when it is conjugated to the payload, but also when it is coadministered with small molecules, nanoparticles, or monoclonal antibodies.

Angiogenesis in cutaneous malignant melanoma and potential therapeutic strategies

Metastatic melanoma (MM) carries a dismal prognosis, as it is largely resistant to conventional cytotoxic chemotherapy, biochemotherapy and immunotherapy. There is, therefore, a pressing need to identify new, effective treatments to improve outcomes from MM. Innovative approaches in oncology drug development include anti-angiogenic strategies, in the form of monoclonal antibodies and small-molecule kinase inhibitors. In this review we aim to present current concepts and controversies surrounding the role of angiogenesis and anti-angiogenic therapies in MM, alluding to other tumor types in which increasing knowledge may supply avenues for future directions in melanoma research and management. An overview of angiogenesis and its importance in melanoma progression is presented, highlighting the key molecules that represent potential therapeutic targets. The results of using anti-angiogenic strategies in preclinical and clinical trials are discussed and future perspectives for anti-angiogenic therapies in MM are considered.

Use of Xanthinol Nicotinate as a co-treatment for radio- and chemo-therapy in experimental tumors

The tumor micro-environment plays a key role in the tumor resistance to cytotoxic treatments. It has been demonstrated that it is possible to modulate the tumor microenvironment to potentiate anti-cancer therapy. Here, we made the hypothesis that the vasoactive agent xanthinol nicotinate (XN) could be an important modulator of the tumor perfusion and oxygenation. Using functional non invasive techniques (in vivo EPR oximetry and dynamic contrast enhanced MRI), we were able to define a time window in which tumor oxygenation, flow and permeability were significantly increased in the TLT tumor model implanted in muscles of mice. As a consequence of the alleviation of tumor hypoxia, we found out that XN was able to radiosensitize the tumors when applying 10 Gy of X-Rays during the reoxygenation of the tumors (enhancement in radiation response of 1.4). Moreover, the administration of cyclosphosphamide (50 mg/kg) used as a chemotherapeutic agent was more efficient when applying the treatment after XN administration (enhancement in response to chemotherapy of 2.7). These results show the importance of the dynamic evolution of the tumor microenvironment on the response to treatments, and that XN is an efficient modulator of the tumor hemodynamics that may potentiate cytotoxic treatments.

Potential role of vascular targeted therapy to combat against tumor

Tumors, like other tissues, have a fundamental requirement for access to the nutrients, oxygen and waste removal functions of the circulatory system. Vascular targeted therapy exploits this basic need, along with molecular heterogeneity observed between normal and tumor blood vessels, to develop efficient and selective chemotherapies that essentially starve tumors by destroying their vasculature. As the basic principle on which this therapy is based differs from agents that directly target cancerous cells, combining it with traditional therapies such as radiation, surgery and existing chemotherapies has the potential to create powerful new anticancer strategies. As the requirement for vascularization is universal to solid tumors, vascular targeted therapies have the potential for broad applicability. Vascular targeted therapies include both angiogenesis inhibitors, which inhibit neovascularization, and vascular disrupting agents, which destroy existing vasculature. Applications of this model include finding peptides that bind specifically to cell surface markers on tumor vessel endothelial cells and might deliver chemotherapeutic agents. Expression profiling with microarrays, serial analysis of gene expression, and in vitro and in vivo screening of phage display libraries have identified candidate peptides for targeted delivery to the tumor endothelium.

Efficacy of weekly docetaxel and bevacizumab in mesenchymal chondrosarcoma: a new theranostic method combining xenografted biopsies with a mathematical model

The paucity of clinical treatment data on rare tumors, such as mesenchymal chondrosarcoma (MCS), emphasizes the need in theranostic tools for these diseases. We put forward and validated a new theranostic method, combining tumor xenografts and mathematical models, and used it to suggest an improved treatment schedule for a particular MCS patient. Growth curves and gene expression analysis of xenografts, derived from a patient's lung metastasis, served for creating a mathematical model of MCS progression and adapting it to the xenograft setting. The pharmacokinetics and pharmacodynamics of six drugs were modeled, with model variables being adjusted by patient-specific chemosensitivity tests. The xenografted animals were treated by various monotherapy and combination schedules, and the MCS xenograft model was computer simulated under the same treatment scenario. The mathematical model for xenograft growth was then up-scaled to retrieve the MCS patient's tumor progression under different treatment schedules. An average accuracy of 87.1% was obtained when comparing model predictions with the observed tumor growth inhibition in the xenografted animals. Simulation results suggested that a regimen containing bevacizumab applied i.v. in combination with once-weekly docetaxel would be more efficacious in the MCS patient than all other simulated schedules. Weekly docetaxel in the patient resulted in stable metastatic disease and relief of pancytopenia due to tumor infiltration. We suggest that the advantage of weekly docetaxel on the triweekly regimen is directly related to the angiogenesis rate of the tumor. Further validation of this conclusion, and the theranostic method we provide, may facilitate personalization of solid cancer pharmacotherapy.

Nanovehicular intracellular delivery systems

This article provides an overview of principles and barriers relevant to intracellular drug and gene transport, accumulation and retention (collectively called as drug delivery) by means of nanovehicles (NV). The aim is to deliver a cargo to a particular intracellular site, if possible, to exert a local action. Some of the principles discussed in this article apply to noncolloidal drugs that are not permeable to the plasma membrane or to the blood-brain barrier. NV are defined as a wide range of nanosized particles leading to colloidal objects which are capable of entering cells and tissues and delivering a cargo intracelullarly. Different localization and targeting means are discussed. Limited discussion on pharmacokinetics and pharmacodynamics is also presented. NVs are contrasted to micro-delivery and current nanotechnologies which are already in commercial use. Newer developments in NV technologies are outlined and future applications are stressed. We also briefly review the existing modeling tools and approaches to quantitatively describe the behavior of targeted NV within the vascular and tumor compartments, an area of particular importance. While we list "elementary" phenomena related to different level of complexity of delivery to cancer, we also stress importance of multi-scale modeling and bottom-up systems biology approach.

Transport and peripheral bioactivities of nitrogen oxides carried by red blood cell hemoglobin: role in oxygen delivery

The biology of NO (nitric oxide) is poorly explained by the activity of the free radical NO ((.)NO) itself. Although (.)NO acts in an autocrine and paracrine manner, it is also in chemical equilibrium with other NO species that constitute stable stores of NO bioactivity. Among these species, S-nitrosylated hemoglobin (S-nitrosohemoglobin; SNO-Hb) is an evolved transducer of NO bioactivity that acts in a responsive and exquisitely regulated manner to control cardiopulmonary and vascular homeostasis. In SNO-Hb, O(2) sensing is dynamically coupled to formation and release of vasodilating SNOs, endowing the red blood cell (RBC) with the capacity to regulate its own principal function, O(2) delivery, via regulation of blood flow. Analogous, physiological actions of RBC SNO-Hb also contribute to central nervous responses to blood hypoxia, the uptake of O(2) from the lung to blood, and baroreceptor-mediated control of the systemic flow of blood. Dysregulation of the formation, export, or actions of RBC-derived SNOs has been implicated in human diseases including sepsis, sickle cell anemia, pulmonary arterial hypertension, and diabetes mellitus. Delivery of SNOs by the RBC can be harnessed for therapeutic gain, and early results support the logic of this approach in the treatment of diseases as varied as cancer and neonatal pulmonary hypertension.

Targeting tumor stroma and exploiting mature tumor vasculature to improve anti-cancer drug delivery

The identification of a critical role of tumour stroma in the regulation of tumour interstitial fluid pressure and the simultaneous discovery of the impact of anti-angiogenic drugs on tumour hemodynamics have provided new potential for improving tumour delivery of anti-cancer drugs. Here, we review the most recent studies investigating how tumour-associated fibroblasts and macrophages as well as the extracellular matrix itself may be targeted to facilitate delivery of both low-molecular weight drugs and macromolecules. In addition, we summarize the current understanding of the use of vasoactive compounds, radiotherapy and vascular-disrupting agents as potential adjuvants to maximize tumour delivery of anti-cancer drugs. The impact of these strategies on the diffusive and convective modes of drug transport is discussed in the light of Fick's and Starling's laws. Finally, we discuss how transcytosis through caveolae may also be exploited to optimize the selective delivery of conventional chemotherapy to the subendothelial tumour cell compartment.

High-grade clear cell renal cell carcinoma has a higher angiogenic activity than low-grade renal cell carcinoma based on histomorphological quantification and qRT-PCR mRNA expression profile

Clear cell renal cell carcinoma (CC-RCC) is a highly vascularised tumour and is therefore an attractive disease to study angiogenesis and to test novel angiogenesis inhibitors in early clinical development. Endothelial cell proliferation plays a pivotal role in the process of angiogenesis. The aim of this study was to compare angiogenesis parameters in low nuclear grade (n=87) vs high nuclear grade CC-RCC (n=63). A panel of antibodies was used for immunohistochemistry: CD34/Ki-67, carbonic anhydrase IX, hypoxia-inducible factor-1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF). Vessel density (MVD - microvessel density), endothelial cell proliferation fraction (ECP%) and tumour cell proliferation fraction (TCP%) were assessed. mRNA expression levels of angiogenesis stimulators and inhibitors were determined by quantitative RT-PCR. High-grade CC-RCC showed a higher ECP% (P=0.049), a higher TCP% (P=0.009), a higher VEGF protein expression (P<0.001), a lower MVD (P< 0.001) and a lower HIF-1alpha protein expression (P=0.002) than low-grade CC-RCC. Growth factor mRNA expression analyses revealed a higher expression of angiopoietin 2 in low-grade CC-RCC. Microvessel density and ECP% were inversely correlated (Rho=-0.26, P=0.001). Because of the imperfect association of nuclear grade and ECP% or MVD, CC-RCC was also grouped based on low/high MVD and ECP%. This analysis revealed a higher expression of vessel maturation and stabilisation factors (placental growth factor, PDGFB1, angiopoietin 1) in CC-RCC with high MVD, a group of CC-RCC highly enriched in low nuclear grade CC-RCC, with low ECP%. Our results suggest heterogeneity in angiogenic activity and vessel maturation of CC-RCC, to a large extent linked to nuclear grade, and, with probable therapeutic implications.

IRL-1620, a tumor selective vasodilator, augments the uptake and efficacy of chemotherapeutic agents in prostate tumor rats

BACKGROUND

IRL-1620, a potent endothelin B receptor agonist, enhanced the efficacy of paclitaxel in a breast tumor model, but its effect in prostate cancer is not known. The present study was conducted to evaluate the effect of IRL-1620 on tumor perfusion, uptake of [(14)C]-doxorubicin in the tumor and efficacy of doxorubicin (DOX), and 5-flurouracil (5-FU) in a rat prostate tumor model.

METHODS

JHU-4 (Mat-Lu) cells inoculated prostate tumor model in Copenhagen rats was used for the study.

RESULTS

Administration of IRL-1620 (3 nmol/kg, i.v) significantly increased (102.8%) prostate tumor perfusion and tumor uptake of [(14)C]-doxorubicin (115%) compared to vehicle treated rats. Results of the efficacy study demonstrate that IRL-1620 administration 15 min prior to DOX (5 mg/kg) or 5-FU (50 mg/kg) on every third day for a total of four doses significantly reduced tumor volume compared to vehicle treated rats.

CONCLUSIONS

IRL-1620 significantly enhanced the uptake and efficacy of anticancer agents in prostate cancer.

Two distinct types of blood vessels in clear cell renal cell carcinoma have contrasting prognostic implications

PURPOSE

Intratumoral microvascular density (MVD) has been controversial as an indicator of prognosis in clear cell renal cell carcinoma (CCRCC). Classification of the intratumoral blood vessels based on differential expressions of blood vessel markers has not been correlated with patient prognosis in CCRCC. In this study, we aimed to evaluate the association of different categories of blood vessels with the patients' outcomes.

EXPERIMENTAL DESIGN

Seventy-eight CCRCC patients who underwent nephrectomy alone were enrolled. Paraffin-embedded CCRCC tissues, together with 16 nonmalignant kidney cortex tissues, were used in tissue microarray analyses and conventional section analyses. The characteristics of intratumoral blood vessels were identified by multiple blood vessel markers and pericyte markers. A computerized image analysis program was used to quantitatively calculate the vascular density.

RESULTS

Two distinct types of microvessels were identified in CCRCC: undifferentiated (CD31(+)/CD34(-)) and differentiated (CD34(+)) vessels. A higher undifferentiated MVD significantly correlated with higher tumor grades and shorter patient survival. In contrast, a higher differentiated MVD significantly correlated with lower tumor grade and longer survival. Multivariate analyses showed that undifferentiated MVD was an independent prognostic factor for patient survival. An inverse correlation between undifferentiated MVD and differentiated MVD was also identified in CCRCC.

CONCLUSIONS

This is the first report showing distinct types of vasculature in CCRCC correlated with contrasting prognoses. A refined classification of CCRCC based on vasculature is therefore important for evaluating prognosis, and it may also have therapeutic implications.

Preconditioning of the Tumor Vasculature and Tumor Cells by Intermittent Hypoxia: Implications for Anticancer Therapies

Hypoxia is a common feature in tumors associated with an increased resistance of tumor cells to therapies. In addition to O(2) diffusion-limited hypoxia, another form of tumor hypoxia characterized by fluctuating changes in pO(2) within the disorganized tumor vascular network is described. Here, we postulated that this form of intermittent hypoxia promotes endothelial cell survival, thereby extending the concept of hypoxia-driven resistance to the tumor vasculature. We found that endothelial cell exposure to cycles of hypoxia reoxygenation not only rendered them resistant to proapoptotic stresses, including serum deprivation and radiotherapy, but also increased their capacity to migrate and organize in tubes. By contrast, prolonged hypoxia failed to exert protective effects and even seemed deleterious when combined with radiotherapy. The use of hypoxia-inducible factor-1alpha (HIF-1alpha)-targeting small interfering RNA led us to document that the accumulation of HIF-1alpha during intermittent hypoxia accounted for the higher resistance of endothelial cells. We also used an in vivo approach to enforce intermittent hypoxia in tumor-bearing mice and found that it was associated with less radiation-induced apoptosis within both the vascular and the tumor cell compartments (versus normoxia or prolonged hypoxia). Radioresistance was further ascertained by an increased rate of tumor regrowth in irradiated mice preexposed to intermittent hypoxia and confirmed in vitro using distinctly radiosensitive tumor cell lines. In conclusion, we have documented that intermittent hypoxia may condition endothelial cells and tumor cells in such a way that they are more resistant to apoptosis and more prone to participate in tumor progression. Our observations also underscore the potential of drugs targeting HIF-1alpha to resensitize the tumor vasculature to anticancer treatments.

Synthesis and Biological Evaluation of 2-(3‘,4‘,5‘-Trimethoxybenzoyl)-3-Amino 5-Aryl Thiophenes as a New Class of Tubulin Inhibitors

2-(3',4',5'-Trimethoxybenzoyl)-3-amino-5-aryl/heteroaryl thiophene derivatives were synthesized and evaluated for antiproliferative activity, inhibition of tubulin polymerization, and cell cycle effects. SARs were elucidated with various substitutions on the aryl moiety 5-position of the thienyl ring. Substituents at the para-position of the 5-phenyl group showed antiproliferative activity in the order of F=CH(3) > OCH(3)=Br=NO(2) > CF(3)=I > OEt. Several of these compounds led to arrest of HL-60 cells in the G2/M phase of the cell cycle and induction of apoptosis.

Reversal of temporal and spatial heterogeneities in tumor perfusion identifies the tumor vascular tone as a tunable variable to improve drug delivery

Maturation of tumor vasculature involves the recruitment of pericytes that protect the endothelial tubes from a variety of stresses, including antiangiogenic drugs. Mural cells also provide mature tumor blood vessels with the ability to either relax or contract in response to substances present in the tumor microenvironment. The observed cyclic alterations in tumor blood flow and the associated deficit in chemotherapeutic drug delivery could in part arise from this vasomodulatory influence. To test this hypothesis, we focused on endothelin-1 (ET-1), which, besides its autocrine effects on tumor cell growth, is a powerful vasoconstrictor. We first document that an ET(A) receptor antagonist induced relaxation of microdissected tumor arterioles and selectively and quantitatively increased tumor blood flow in experimental tumor models. We then combined dye staining of functional vessels, fluorescent microsphere-based mapping, and magnetic resonance imaging to identify heterogeneities in tumor blood flow and to examine the reversibility of such phenomena. Data from all these techniques concurred to show that administration of an ET(A) receptor antagonist could reduce the extent of underperfused tumor areas, proving the key role of vessel tone variations in tumor blood flow heterogeneity. We also provide evidence that ET(A) antagonist administration could, despite an increase in tumor interstitial fluid pressure, improve access of cyclophosphamide to the tumor compartment and significantly influence tumor growth. In conclusion, tumor endogenous ET-1 production participates largely in the temporal and spatial variations in tumor blood flow. ET(A) antagonist administration may wipe out such heterogeneities, thus representing an adjuvant strategy that could improve the delivery of conventional chemotherapy to tumors.

Novel Combretastatin Analogues Endowed with Antitumor Activity

We studied the anticancer activity of a series of new combretastatin derivatives with B-ring modifications. The structure-activity relationship (SAR) information confirmed the importance of cis-stereochemistry and of a phenolic moiety in B-ring. We selected the benzo[b]thiophene and benzofuran combretastatin analogues 11 (ST2151) and 13 (ST2179) and their phosphate prodrugs (29 and 30) for their high antitumor activity in in vitro and in vivo models. Cell exposure to IC50 of 11, 13, and CA-4 led to the arrest of various cell types in the G2/M phase of the cell cycle and induction of apoptosis. Mainly, 11 and 13 induced the formation of multinucleated cells with abnormal chromatin distribution, with only a minimal effect on the microtubule organization, with respect to CA-4. Interestingly, both the pharmacokinetic profile of 29 and its in vivo antitumor effect and those of 30, active even after oral administration, suggest additional pharmacological differences between these compounds and CA-4P.

Mechanisms of pericyte recruitment in tumour angiogenesis: a new role for metalloproteinases

Pericytes occur in tumour blood vessels and are critical for the development of a functional vascular network. Targeting tumour pericytes is a promising anti-angiogenic therapy but requires identifying the mechanisms of their recruitment in tumour and addressing whether these mechanisms can be selectively harnessed. Among the pathways involved in pericyte recruitment during embryonic development, the contribution of platelet-derived growth factor B and sphingosine 1-phosphate is confirmed in tumour angiogenesis. The effect of angiopoietin 1 depends on the tumour model. Transforming growth factor-beta1 enhances tumour vascularization and microvessel maturation. Recent reports suggest a participation of matrix metalloproteinases (MMP) in tumour pericyte recruitment that is consistent with the effect of certain MMPs in the development of microvasculature in embryonic development and in in vitro models of vascular remodelling. Here, we discuss the possibility for MMPs to contribute to pericyte recruitment at six levels: (1) direct promotion of pericyte invasion by extracellular matrix degradation; (2) stimulation of pericyte proliferation and protection against apoptosis by modification of the ECM; (3) activation of pericytes through the release of growth factor bound to the ECM; (4) transactivation of angiogenic cell surface receptor; (5) propagation of angiogenic signalling as cofactor; and (6) recruitment of bone marrow-derived stem cells.