Kinin-generating cascade in advanced cancer patients and in vitro study

Diagnostic and prognostic role of circulating neutrophil extracellular trap markers and prekallikrein in patients with high-grade serous ovarian cancer

Objective

Tumor-promoting inflammation is among the hallmarks of cancer. Prekallikrein is among the acute-phase reactants in the inflammatory response; moreover, neutrophils release nuclear contents into the extracellular space to create neutrophil extracellular traps (NET). We aimed to investigate the diagnostic and prognostic utilities of circulating plasma NET markers and prekallikrein for high-grade serous ovarian cancer (HGSOC).

Methods

Circulating levels of three NET markers (histone-DNA complex, cell-free DNA, and neutrophil elastase) and prekallikrein were measured in 75 patients with HGSOC and 23 healthy controls. We used an area under the receiver operating characteristic curve (AUC) analysis to investigate their diagnostic and prognostic utilities for HGSOC.

Results

Compared with healthy controls, patients with HGSOC showed significantly higher levels of the three NET markers and prekallikrein. Patients with advanced-stage HGSOC showed significantly higher levels of the cell-free DNA (87.4 vs. 79.5 ng/ml; P = 0.013), compared with those with early-stage HGSOC. Further, the levels of histone-DNA complex, neutrophil elastase, and prekallikrein did not significantly differ according to the cancer stage. All markers showed significant diagnostic utility. Notably, a logistic regression-based model that comprised all four markers showed the strongest diagnostic power (AUC, 0.966; 95% confidence interval [CI], 0.933-1.000). Specifically, neutrophil elastase was identified as an independent poor prognostic factor for overall survival (adjusted hazard ratio [aHR], 10.17; 95% CI, 1.09-94.97; P = 0.042) and progression-free survival (aHR, 14.47; 95% CI, 1.52-137.35; P = 0.020) in patients with HGSOC.

Conclusions

The levels of the three NET markers and prekallikrein might be novel diagnostic and prognostic markers for HGSOC.

Enhanced Permeability and Retention Effect as a Ubiquitous and Epoch-Making Phenomenon for the Selective Drug Targeting of Solid Tumors

In 1979, development of the first polymer drug SMANCS [styrene-co-maleic acid (SMA) copolymer conjugated to neocarzinostatin (NCS)] by Maeda and colleagues was a breakthrough in the cancer field. When SMANCS was administered to mice, drug accumulation in tumors was markedly increased compared with accumulation of the parental drug NCS. This momentous result led to discovery of the enhanced permeability and retention effect (EPR effect) in 1986. Later, the EPR effect became known worldwide, especially in nanomedicine, and is still believed to be a universal mechanism for tumor-selective accumulation of nanomedicines. Some research groups recently characterized the EPR effect as a controversial concept and stated that it has not been fully demonstrated in clinical settings, but this erroneous belief is due to non-standard drug design and use of inappropriate tumor models in investigations. Many research groups recently provided solid evidence of the EPR effect in human cancers (e.g., renal and breast), with significant diversity and heterogeneity in various patients. In this review, we focus on the dynamics of the EPR effect and restoring tumor blood flow by using EPR effect enhancers. We also discuss new applications of EPR-based nanomedicine in boron neutron capture therapy and photodynamic therapy for solid tumors.

Exploration of Site-Specific Drug Targeting-A Review on EPR-, Stimuli-, Chemical-, and Receptor-Based Approaches as Potential Drug Targeting Methods in Cancer Treatment

Cancer has been one of the most dominant causes of mortality globally over the last few decades. In cancer treatment, the selective targeting of tumor cells is indispensable, making it a better replacement for conventional chemotherapies by diminishing their adverse side effects. While designing a drug to be delivered selectively in the target organ, the drug development scientists should focus on various factors such as the type of cancer they are dealing with according to which drug, targeting moieties, and pharmaceutical carriers should be targeted. All published articles have been collected regarding cancer and drug-targeting approaches from well reputed databases including MEDLINE, Embase, Cochrane Library, CENTRAL and ClinicalTrials.gov, Science Direct, PubMed, Scopus, Wiley, and Springer. The articles published between January 2010 and December 2020 were considered. Due to the existence of various mechanisms, it is challenging to choose which one is appropriate for a specific case. Moreover, a combination of more than one approach is often utilized to achieve optimal drug effects. In this review, we have summarized and highlighted central mechanisms of how the targeted drug delivery system works in the specific diseased microenvironment, along with the strategies to make an approach more effective. We have also included some pictorial illustrations to have a precise idea about different types of drug targeting. The core contribution of this work includes providing a cancer drug development scientist with a broad preliminary idea to choose the appropriate approach among the various targeted drug delivery mechanisms. Also, the study will contribute to improving anticancer treatment approaches by providing a pathway for lesser side effects observed in conventional chemotherapeutic techniques.

The versatile role of the contact system in cardiovascular disease, inflammation, sepsis and cancer

The human contact system consists of plasma proteins, which - after contact to foreign surfaces - are bound to them, thereby activating the zymogens of the system into enzymes. This activation mechanism gave the system its name - contact system. It is considered as a procoagulant and proinflammatory response mechanism, as activation finally leads to the generation of fibrin and bradykinin. To date, no physiological processes have been described that are mediated by contact activation. However, contact system factors play a pathophysiological role in numerous diseases, such as cardiovascular diseases, arthritis, colitis, sepsis, and cancer. Contact system factors are therefore an interesting target for new therapeutic options in different clinical conditions.

Development of a Selective Tumor-Targeted Drug Delivery System: Hydroxypropyl-Acrylamide Polymer-Conjugated Pirarubicin (P-THP) for Pediatric Solid Tumors

Simple Summary

Hydroxypropyl acrylamide polymer-conjugated pirarubicin (P-THP), an innovative polymer-conjugated anticancer agent, theoretically has highly tumor-specific distribution via the enhanced permeability and retention (EPR) effect. While anthracyclines are extremely important in the treatment of most pediatric solid tumors, P-THP may serve as a less toxic and more effective substitute for conventional anthracyclines in both newly diagnosed and refractory/recurrent pediatric cancers.

Abstract

Most pediatric cancers are highly chemo-sensitive, and cytotoxic chemotherapy has always been the mainstay of treatment. Anthracyclines are highly effective against most types of childhood cancer, such as neuroblastoma, hepatoblastoma, nephroblastoma, rhabdomyosarcoma, Ewing sarcoma, and so forth. However, acute and chronic cardiotoxicity, one of the major disadvantages of anthracycline use, limits their utility and effectiveness. Hydroxypropyl acrylamide polymer-conjugated pirarubicin (P-THP), which targets tumor tissue highly selectively via the enhanced permeability and retention (EPR) effect, and secondarily releases active pirarubicin molecules quickly into the acidic environment surrounding the tumor. Although, the latter rarely occurs in the non-acidic environment surrounding normal tissue. This mechanism has the potential to minimize acute and chronic toxicities, including cardiotoxicity, as well as maximize the efficacy of chemotherapy through synergy with tumor-targeting accumulation of the active molecules and possible dose-escalation. Simply replacing doxorubicin with P-THP in a given regimen can improve outcomes in anthracycline-sensitive pediatric cancers with little risk of adverse effects, such as cardiotoxicity. As cancer is a dynamic disease showing intra-tumoral heterogeneity during its course, continued parallel development of cytotoxic agents and molecular targeting agents is necessary to find potentially more effective treatments.

The contact system in liver injury

Coagulation is controlled by a delicate balance of prothrombotic and antithrombotic mechanisms, to prevent both excessive blood loss from injured vessels and pathologic thrombosis. The liver plays a pivotal role in hemostasis through the synthesis of plasma coagulation factors and their inhibitors that, in addition to thrombosis and hemostasis, orchestrates an array of inflammatory responses. As a result, impaired liver function has been linked with both hypercoagulability and bleeding disorders due to a pathologic balance of pro- and anticoagulant plasma factors. At sites of vascular injury, thrombus propagation that finally may occlude the blood vessel depends on negatively charged biopolymers, such as polyphosphates and extracellular DNA, that provide a physiological surface for contact activation of coagulation factor XII (FXII). FXII initiates the contact system that drives both the intrinsic pathway of coagulation, and formation of the inflammatory mediator bradykinin by the kallikrein–kinin system. Moreover, FXII facilitates receptor-mediated signalling, thereby promoting mitogenic activities, angiogenesis, and neutrophil stimulation with implications for liver diseases. Here, we summarize current knowledge on the FXII-driven contact system in liver diseases and review therapeutic approaches to target its activities during impaired liver function.

The 35th Anniversary of the Discovery of EPR Effect: A New Wave of Nanomedicines for Tumor-Targeted Drug Delivery-Personal Remarks and Future Prospects

This Special Issue on the enhanced permeability and retention (EPR) effect commemorates the 35th anniversary of its discovery, the original 1986 Matsumura and Maeda finding being published in Cancer Research as a new concept in cancer chemotherapy. My review here describes the history and heterogeneity of the EPR effect, which involves defective tumor blood vessels and blood flow. We reported that restoring obstructed tumor blood flow overcomes impaired drug delivery, leading to improved EPR effects. I also discuss gaps between small animal cancers used in experimental models and large clinical cancers in humans, which usually involve heterogeneous EPR effects, vascular abnormalities in multiple necrotic foci, and tumor emboli. Here, I emphasize arterial infusion of oily formulations of nanodrugs into tumor-feeding arteries, which is the most tumor-selective drug delivery method, with tumor/blood ratios of 100-fold. This method is literally the most personalized medicine because arterial infusions differ for each patient, and drug doses infused depend on tumor size and anatomy in each patient. Future developments in EPR effect-based treatment will range from chemotherapy to photodynamic therapy, boron neutron capture therapy, and therapies for free radical diseases. This review focuses on our own work, which stimulated numerous scientists to perform research in nanotechnology and drug delivery systems, thereby spawning a new cancer treatment era.

Nanodrug Delivery Systems Modulate Tumor Vessels to Increase the Enhanced Permeability and Retention Effect

The use of nanomedicine for antitumor therapy has been extensively investigated for a long time. Enhanced permeability and retention (EPR) effect-mediated drug delivery is currently regarded as an effective way to bring drugs to tumors, especially macromolecular drugs and drug-loaded pharmaceutical nanocarriers. However, a disordered vessel network, and occluded or embolized tumor blood vessels seriously limit the EPR effect. To augment the EPR effect and improve curative effects, in this review, we focused on the perspective of tumor blood vessels, and analyzed the relationship among abnormal angiogenesis, abnormal vascular structure, irregular blood flow, extensive permeability of tumor vessels, and the EPR effect. In this commentary, nanoparticles including liposomes, micelles, and polymers extravasate through the tumor vasculature, which are based on modulating tumor vessels, to increase the EPR effect, thereby increasing their therapeutic effect.

Polymer Capsules with Hydrophobic Liquid Cores as Functional Nanocarriers

Recent developments in the fabrication of core-shell polymer nanocapsules, as well as their current and future applications, are reported here. Special attention is paid to the newly introduced surfactant-free fabrication method of aqueous dispersions of nanocapsules with hydrophobic liquid cores stabilized by amphiphilic copolymers. Various approaches to the efficient stabilization of such vehicles, tailoring their cores and shells for the fabrication of multifunctional, navigable nanocarriers and/or nanoreactors useful in various fields, are discussed. The emphasis is placed on biomedical applications of polymer nanocapsules, including the delivery of poorly soluble active compounds and contrast agents, as well as their use as theranostic platforms. Other methods of fabrication of polymer-based nanocapsules are briefly presented and compared in the context of their biomedical applications.

Exploiting the dynamics of the EPR effect and strategies to improve the therapeutic effects of nanomedicines by using EPR effect enhancers

The enhanced permeability and retention (EPR) effect is a unique phenomenon of solid tumors that is related to their particular anatomical and pathophysiological characteristics, e.g. defective vascular architecture; large gaps between endothelial cells in blood vessels; abundant vascular mediators such as bradykinin, nitric oxide, carbon monoxide, and vascular endothelial growth factor; and impaired lymphatic recovery. These features lead to tumor tissues showing considerable extravasation of plasma components and nanomedicines. These data comprise the basic theory underlying the development of macromolecular agents or nanomedicines. The EPR effect is not necessarily valid for all solid tumors, because tumor blood flow and vascular permeability vary greatly. Tumor blood flow is frequently obstructed as tumor size increases, as often seen clinically; early stage, small tumors show a more uniform EPR effect, whereas advanced large tumor show heterogeneity in EPR effect. Accordingly, it would be very important to apply enhancers of EPR effect in clinical setting to make EPR effect more uniform. In this review, we discuss the EPR effect: its history, factors involved, and dynamics and heterogeneity. Strategies to overcome the EPR effect's heterogeneity may guarantee better therapeutic outcomes of drug delivery to advanced cancers.

Coagulation and fibrinolysis in gastric cancer

Coagulation is a highly conserved process occurring after an injury to a blood vessel and resulting in hemostasis. In the thrombus microenvironment, finely orchestrated events restore vessel integrity through platelet activation, adhesion, and aggregation (primary hemostasis), followed by the coagulation cascades, thrombin generation, and fibrin clot deposition (secondary hemostasis). Several studies on cancer have provided insight into dramatic changes to coagulation-related events (i.e., fibrin clot deposition, fibrinolysis) during tumor pathogenesis, progression, and metastasis, in addition to a tumor-driven systemic activation of hemostasis and thrombosis (Trousseau's syndrome). Diverse molecular and cellular effectors participate in the cross talk between hemostasis and tumors. Here, we focus on some aspects of the interconnection between cancer biology and hemostatic components, with particular attention to some key coagulation-related proteins (e.g., tissue factor, thrombin, fibrinogen, and D-dimers) in the particular case of gastric cancer (GC). Recent advances in deciphering the complex molecular link between GC and the coagulation system are described, showing their important roles in better management of patients affected by GC.

Bradykinin Promotes Cell Proliferation, Migration, Invasion, and Tumor Growth of Gastric Cancer Through ERK Signaling Pathway

Bradykinin (BK) has been reported to be involved in the progression of diverse types of cancer. In the present study, we investigated the possible role of BK in cell proliferation, migration, invasion, and tumor growth of gastric cancer (GC). Cell proliferation was evaluated by MTT assays. Cell migration and invasion were assessed by Transwell assays. Tumor growth of nude mice was detected by establishing subcutaneous xenograft tumor model. Silencing of bradykinin B1 receptor (B1R) and the bradykinin B2 receptor (B2R) was performed by transfecting cells with si-B1R and si-B2R, respectively. The protein expression levels of phospho-ERK1/2 (p-ERK1/2), matrix metalloproteinase (MMP)-2, MMP-9, and E-Cadherin were examined by Western blot. Data revealed that BK promoted cell proliferation, migration, invasion, and the in vivo tumor growth of GC cells SGC-7901 and HGC-27. Furthermore, BK elevated the protein levels of p-ERK1/2, MMP-2, and MMP-9, but reduced E-Cadherin. In addition, by repressing B2R using si-B2R or inhibiting ERK signaling pathway using PD98059, BK-mediated promotion of cell proliferation, migration, and invasion and upregulation of p-ERK1/2, MMP-2/9, as well as downregulation of E-Cadherin were attenuated. Taken together, the present study demonstrated that BK promoted cell proliferation, migration, invasion, and tumor growth by binding to B2R via ERK signaling pathway. Our findings may provide promising options for the further treatment of GC. J. Cell. Biochem. 118: 4444-4453, 2017. © 2017 Wiley Periodicals, Inc.

Conjugation of Succinylated Gelatin to Soybean Trypsin Inhibitor

Kunitz-type soybean trypsin inhibitor (SBTI) and succinylated gelatin fragment (Suc-gel) were conjugated by using water-soluble carbodiimide, and physicochemical and biopharmaceutical properties of the conjugate (Suc-gel-SBTI) were characterized. The conjugate contains about 2.5 mol of Suc-gel with a mean molecular weight of 32,000 per mole of SBTI, based on the content of hydroxyproline. After iv injection of the radiolabeled conjugate or native SBTI into mice, it was found that native SBTI showed rapid elimination from plasma ( t½α = 2 min), whereas Suc-gel-SBTI was slowly ( t½α = 2 min) eliminated. Organ distribution of the two agents at 30 min after iv injection was different: Suc-gel-SBTI accumulated to a large extent in both the liver and the spleen, about 23.4 and 6.9%, respectively which was more than the native SBTI. Native SBTI was taken up more rapidly by the kidney (~ 45%) and excreted into the urine (~34%) before it accumulated in other organs and tissues. In addition, we evaluated the pharmacological effects of these agents in an animal model. Suc-gel-SBTI was more effective than native SBTI against trypsin-induced lethal shock in mice. This polymer-conjugated SBTI seems to exhibit better pharmacological and therapeutic properties than its native counterpart.

The role of kinin receptors in cancer and therapeutic opportunities

Kinins are generated within inflammatory tissue microenvironments, where they exert diverse functions, including cell proliferation, leukocyte activation, cell migration, endothelial cell activation and nociception. These pleiotropic functions depend on signaling through two cross talking receptors, the constitutively expressed kinin receptor 2 (B2R) and the inducible kinin receptor 1 (B1R). We have reviewed evidence, which supports the concept that kinin receptors, especially kinin receptor 1, are promising targets for cancer therapy, since (1) many tumor cells express aberrantly high levels of these receptors; (2) some cancers produce kinins and use them as autocrine factors to stimulate their growth; (3) activation of kinin receptors leads to activation of macrophages, dendritic cells and other cells from the tumor microenvironment; (4) kinins have pro-angiogenic properties; (5) kinin receptors have been implicated in cancer migration, invasion and metastasis; and (6) selective antagonists for either B1R or B2R have shown anti-proliferative, anti-inflammatory, anti-angiogenic and anti-migratory properties. The multiple cross talks between kinin receptors and renin-angiotensin system (RAS) as well as its implications for targeting KKS or RAS for the treatment of malignancies are also discussed. It is expected that B1R antagonists would interfere less with housekeeping functions and therefore would be attractive compounds to treat selected types of cancer. Reliable clinical studies are needed to establish the translatability of these data to human settings and the usefulness of kinin receptor antagonists.

The link between infection and cancer: tumor vasculature, free radicals, and drug delivery to tumors via the EPR effect

This review focuses primarily on my own research, including pathogenic mechanisms of microbial infection, vascular permeability in infection and tumors, and effects of nitric oxide (NO), superoxide anion radical (O₂⁻), and 8-nitroguanosine in the enhanced permeability and retention (EPR) effect for the tumor-selective delivery of macromolecular agents (nanomedicines). Infection-induced vascular permeability is mediated by activation of the kinin-generating protease cascade (kallikrein-kinin) triggered by exogenous microbial proteases. A similar mechanism operates in cancer tissues and in carcinomatosis of the pleural and peritoneal cavities. Infection also stimulates O₂⁻ generation via activation of xanthine oxidase while generating NO by inducing NO synthase. These chemicals function in mutation and carcinogenesis and promote inflammation, in which peroxynitrite (a product of O₂⁻ and NO) activates MMP, damages DNA and RNA, and regenerates 8-nitroguanosine and 8-oxoguanosine. We showed vascular permeability by using macromolecular drugs, which are not simply extravasated through the vascular wall into the tumor interstitium but remain there for prolonged periods. We thus discovered the EPR effect, which led to the rational development of tumor-selective delivery of polymer conjugates, micellar and liposomal drugs, and genes. Our styrene-maleic acid copolymer conjugated with neocarzinostatin was the first agent of its kind used to treat hepatoma. The EPR effect occurs not only because of defective vascular architecture but also through the generation of various vascular mediators such as kinin, NO, and vascular endothelial growth factor. Although most solid tumors, including human tumors, show the EPR effect, heterogeneity of tumor tissue may impede drug delivery. This review describes the barriers and countermeasures for improved drug delivery to tumors by using nanomedicines.

The EPR effect for macromolecular drug delivery to solid tumors: Improvement of tumor uptake, lowering of systemic toxicity, and distinct tumor imaging in vivo

The EPR effect results from the extravasation of macromolecules or nanoparticles through tumor blood vessels. We here provide a historical review of the EPR effect, including its features, vascular mediators found in both cancer and inflamed tissue. In addition, architectural and physiological differences of tumor blood vessels vs that of normal tissue are commented. Furthermore, methods of augmentation of the EPR effect are described, that result in better tumor delivery and improved therapeutic effect, where nitroglycerin, angiotensin I-converting enzyme (ACE) inhibitor, or angiotensin II-induced hypertension are employed. Consequently, better therapeutic effect and reduced systemic toxicity are generally observed. Obviously, the EPR effect based delivery of nanoprobes are also useful for tumor-selective imaging agents with using fluorescent or radio nuclei in nanoprobes. We also commented a key difference between passive tumor targeting and the EPR effect in tumors, particularly as related to drug retention in tumors: passive targeting of low-molecular-weight X-ray contrast agents involves a retention period of less than a few minutes, whereas the EPR effect of nanoparticles involves a prolonged retention time-days to weeks.

Humoral innate immune response and disease

The humoral innate immune response consists of multiple components, including the naturally occurring antibodies (NAb), pentraxins and the complement and contact cascades. As soluble, plasma components, these innate proteins provide key elements in the prevention and control of disease. However, pathogens and cells with altered self proteins utilize multiple humoral components to evade destruction and promote pathogy. Many studies have examined the relationship between humoral immunity and autoimmune disorders. This review focuses on the interactions between the humoral components and their role in promoting the pathogenesis of bacterial and viral infections and chronic diseases such as atherosclerosis and cancer. Understanding the beneficial and detrimental aspects of the individual components and the interactions between proteins which regulate the innate and adaptive response will provide therapeutic targets for subsequent studies.

Vascular permeability in cancer and infection as related to macromolecular drug delivery, with emphasis on the EPR effect for tumor-selective drug targeting

Tumor and inflammation have many common features. One hallmark of both is enhanced vascular permeability, which is mediated by various factors including bradykinin, nitric oxide (NO), peroxynitrite, prostaglandins etc. A unique characteristic of tumors, however, is defective vascular anatomy. The enhanced vascular permeability in tumors is also distinctive in that extravasated macromolecules are not readily cleared. We utilized the enhanced permeability and retention (EPR) effect of tumors for tumor selective delivery of macromolecular drugs. Consequently, such drugs, nanoparticles or lipid particles, when injected intravenously, selectively accumulate in tumor tissues and remain there for long periods. The EPR effect of tumor tissue is frequently inhomogeneous and the heterogeneity of the EPR effect may reduce the tumor delivery of macromolecular drugs. Therefore, we developed methods to augment the EPR effect without inducing adverse effects for instance raising the systemic blood pressure by infusing angiotensin II during arterial injection of SMANCS/Lipiodol. This method was validated in clinical setting. Further, benefits of utilization of NO-releasing agent such as nitroglycerin or angiotensin-converting enzyme (ACE) inhibitors were demonstrated. The EPR effect is thus now widely accepted as the most basic mechanism for tumor-selective targeting of macromolecular drugs, or so-called nanomedicine.

Preclinical and clinical studies of NK012, an SN-38-incorporating polymeric micelles, which is designed based on EPR effect

Polymeric micelles are ideally suited to exploit the EPR effect, and they have been used for the delivery of a range of anticancer drugs in preclinical and clinical studies. NK012 is an SN-38-loaded polymeric micelle constructed in an aqueous milieu by the self-assembly of an amphiphilic block copolymer, PEG-PGlu(SN-38). The antitumor activity was evaluated in several orthotopic tumor models including glioma, renal cancer, stomach cancer, and pancreatic cancer. Two independent phase I clinical trials were conducted in Japan and the USA. In the preclinical studies, it was demonstrated that NK012 exerted significantly more potent antitumor activity with no intestinal toxicity against various orthotopic human tumor xenografts than CPT-11. In clinical trials, predominant toxicity was neutropenia. Non-hematologic toxicity, especially diarrhea, was mostly Grade 1 or 2 during study treatments. Total 8 partial responses were obtained. According to data of preclinical studies, NK012 showing enhanced distribution with prolonged SN-38 release may be ideal for cancer treatment because the antitumor activity of SN-38 is time dependent. Clinical studies showed that NK012 was well tolerated and had antitumor activity including partial responses and several occurrences of prolonged stable disease across a variety of advanced refractory cancers. Phase II studies are ongoing in patients with colorectal cancer in Japan and in patients with triple negative breast cancer and small cell lung cancer in the USA.

The EPR effect: Unique features of tumor blood vessels for drug delivery, factors involved, and limitations and augmentation of the effect

The enhanced permeability and retention (EPR) effect is a unique phenomenon of solid tumors related to their anatomical and pathophysiological differences from normal tissues. For example, angiogenesis leads to high vascular density in solid tumors, large gaps exist between endothelial cells in tumor blood vessels, and tumor tissues show selective extravasation and retention of macromolecular drugs. This EPR effect served as a basis for development of macromolecular anticancer therapy. We demonstrated methods to enhance this effect artificially in clinical settings. Of great importance was increasing systolic blood pressure via slow angiotensin II infusion. Another strategy involved utilization of NO-releasing agents such as topical nitroglycerin, which releases nitrite. Nitrite is converted to NO more selectively in the tumor tissues, which leads to a significantly increased EPR effect and enhanced antitumor drug effects as well. This review discusses molecular mechanisms of factors related to the EPR effect, the unique anatomy of tumor vessels, limitations and techniques to avoid such limitations, augmenting tumor drug delivery, and experimental and clinical findings.

Strong cytotoxic effect of the bradykinin antagonist BKM-570 in ovarian cancer cells--analysis of the molecular mechanisms of its antiproliferative action

The standard chemotherapy for epithelial ovarian cancer (EOC) patients is currently a combination of taxane and platinum. However, most EOC patients still suffer relapses, and there is an immediate need for the development of novel and more effective therapeutic modalities against this deadly disease. Recently, the nonpeptide bradykinin (BK) antagonist 2,3,4,5,6-pentafluorocinnamoyl-(o-2,6-dichlorobenzyl)-l-tyrosine-N-(4-amino-2,2,6,6-tetramethyl-piperidyl) amide (BKM-570) was shown to cause impressive growth inhibition of lung and prostate tumors, displaying superior in vivo inhibitory effects than convential chemotherapeutic drugs. Here, we investigated BKM-570 cytotoxic effects in two EOC cell lines, derived from different EOC histopathologies: a clear cell carcinoma (TOV-21), and an endometrioid carcinoma (TOV-112). We showed that BKM-570 effectively inhibited the growth of ovarian cancer cells, as its cytotoxic effects were comparable to those of cisplatin, and were independent of the functional status of BK receptors. Moreover, BKM-570 synergized with cisplatin in inhibiting EOC cell growth. To better understand the molecular mechanisms of the antiproliferative action of this BK antagonist in EOC cells, we performed gene expression profiling in TOV-21 and TOV-112 cells following treatment with 10 μM BKM-570 for 24 h. BKM-570 displayed similar cytotoxic effects in the two cell lines analyzed, as genes with previously shown involvement in apoptosis/antiapoptosis and cell adhesion were proportionally upregulated and downregulated in both cell lines, whereas genes involved in basic cellular mechanisms, including cell growth and maintenance, metabolism, cell cycle control, inflammatory and immune response, signal transduction, protein biosynthesis, transcription regulation, and transport, were predominantly downregulated upon treatment. Our data are indicative of the therapeutic potential of BKM-570 and related compounds in EOC management.

Tumor-selective delivery of macromolecular drugs via the EPR effect: background and future prospects

This paper briefly documents the history of the discovery of the EPR (enhanced permeability and retention) effect and elucidates an analogy between bacterial infection involving proteases that trigger kinin generation and cancer. The EPR effect of macromolecules in cancer tissues is defined, and the distinction between the EPR effect (with reference to clearance of macromolecules from the interstitial space of tumor tissues) and the simple passive targeting of drugs to tumors is described. Additional points of discussion include the uniqueness of tumor vessels, the influence of kinin and other vascular mediators such as nitric oxide (NO) and prostaglandins, and the heterogeneity of the EPR effect. Two different strategies to augment the EPR effect that were discovered are elevating blood pressure artificially via slow infusion of angiotensin II and applying nitroglycerin or other NO donors. Use of the nitroagent increased not only the blood flow of the tumor, but also the delivery of drug to the tumor and the drug's therapeutic effect. This finding shows an intriguing analogy to hypoxic cardiac infarct tissue, in that both are improved by NO. These two methods were applied to treatment of rodents and human cancers, in combination with other anticancer agents, with successful results achieved in rodents as well as humans. These data suggest very appealing prospects for utilization of the EPR effect in future development of cancer therapeutics.

Elevating blood pressure as a strategy to increase tumor-targeted delivery of macromolecular drug SMANCS: cases of advanced solid tumors

The purpose of this study is to evaluate the improved method of arterial infusion therapy of SMANCS (SX) with lipiodol under the angiotensin-induced hypertensive state for various difficult-to-treat solid tumors. Most patients were unresectable with no other therapeutic options, recurrence after resection, or patients do not respond to common treatments. The new method utilizes angiotensin II (AT) to induce hypertension (e.g. approximately 15-30 mmHg above norm) for 15-20 min. This method was successfully applied to metastatic liver cancer, cholangiocarcinoma, massive renal cell carcinoma, pancreatic and other abdominal solid cancers. This AT-induced hypertension resulted in remarkably enhanced tumor delivery accompanied by improved therapeutic response, and a shorter time to achieve 50% regression of tumor size with least toxicity. We demonstrated clinically herein improved therapy for various advanced solid tumors with SX by elevating the tumor blood flow selectively. This is the first clinical proof that modulations of vascular pathophysiology can uniquely accomplish enhanced tumor selective delivery of polymeric drugs and thus yielded better clinical outcome.

Potent antitumor effect of SN-38-incorporating polymeric micelle, NK012, against malignant glioma

Recent published reports on clinical trials of CPT-11 indicate the effectiveness of this compound, a prodrug of SN-38, against malignant glioma in combination with anti-vascular endothelial growth factor antibody. Here, we determined if NK012, and SN-38 incorporating micelle, can be an appropriate formulation for glioblastoma treatment compared with CPT-11. In vitro cytotoxicity was evaluated against several glioma lines with NK012, CPT-11, SN-38, ACNU, CDDP and etoposide. For the in vivo test, a human glioma line (U87MG) transfected with the luciferase gene was inoculated into nude mice brain for pharmacokinetic analysis by fluorescence microscopy and high-performance liquid chromatography after intravenous injection of NK012 and CPT-11. In vivo antitumor activity of NK012 and CPT-11 was evaluated by bioluminescence image and Kaplan-Meier analyses. The growth-inhibitory effects of NK012 were 34- to 444-fold more potent than those of CPT-11. Markedly enhanced and prolonged distribution of free SN-38 in the xenografts was observed after NK012 injection compared with CPT-11. NK012 showed significantly potent antitumor activity against an orthotopic glioblastoma multiforme xenograft and significantly longer survival rate than CPT-11 (p = 0.0014). This implies that NK012 can pass through the blood brain tumor barrier effectively. NK012, which combines enhanced distribution with prolonged sustained release, may be ideal for glioma treatment. Currently, a phase I study of NK012 is almost complete in Japan and the US. The present translational study warrants the clinical phase II study of NK012 in patients with malignant glioma.

Stimulation of the bradykinin B(1) receptor induces the proliferation of estrogen-sensitive breast cancer cells and activates the ERK1/2 signaling pathway

Kinin peptides exert multiple biological effects by binding to two types of G protein-coupled receptors known as B(1) (B(1)R) and B(2) receptors. Expression of the B(1)R in human breast cancer was recently reported, but up to now the consequences of its stimulation are unknown. Our aims were (1) to investigate the capacity of B(1)R to trigger cell proliferation in breast cancer cells, (2) to explore some of the downstream events occurring after B(1)R stimulation that may be linked to cell proliferation, and (3) to determine whether human breast tumors express potentially active B(1)R assessed by the binding of a radiolabeled agonist. Breast cancer cells expressed both the mRNA and the immunoreactive protein of B(1)R that once stimulated triggered cell proliferation at nanomolar concentrations of the ligand. Inhibitor studies suggested that the proliferative effects depend on the activity of epidermal growth factor receptor and subsequent ERK1/2 mitogen-activated protein kinases phosphorylation. B(1)R binding sites, were detected in 3/4 fibroadenomas, in 4/4 ductal carcinomas in situ and in 11/13 invasive ductal carcinomas. The B(1)R-epidermal growth factor receptor crosstalk may be a key interaction that maintains tumor growth, and antagonism of B(1)R may be a valuable alternative for the treatment of breast cancer.

Antitumor effect of SN-38-releasing polymeric micelles, NK012, on spontaneous peritoneal metastases from orthotopic gastric cancer in mice compared with irinotecan

7-Ethyl-10-hydroxy-camptothecin (SN-38), an active metabolite of irinotecan hydrochloride (CPT-11), has potent antitumor activity. Moreover, we have reported the strong antitumor activity of NK012 (i.e., SN-38-releasing polymeric micelles) against human cancer xenografts compared with CPT-11. Here, we investigated the advantages of NK012 over CPT-11 treatment in mouse models of gastric cancer with peritoneal dissemination. NK012 or CPT-11 was i.v. administered thrice every 4 days at their respective maximum tolerable doses (NK012, 30 mg/kg/day; CPT-11, 67 mg/kg/day) to mice receiving orthotopic transplants of gastric cancer cell lines (44As3Luc and 58As1mLuc) transfected with the luciferase gene (n = 5). Antitumor effect was evaluated using the photon counting technique. SN-38 concentration in gastric tumors and peritoneal nodules was examined by high-performance liquid chromatography (HPLC) 1, 24, and 72 hours after each drug injection. NK012 or CPT-11 distribution in these tumors was evaluated using a fluorescence microscope on the same schedule. In both models, the antitumor activity of NK012 was superior to that of CPT-11. High concentrations of SN-38 released from NK012 were detected in gastric tumors and peritoneal nodules up to 72 hours by HPLC. Only a slight conversion from CPT-11 to SN-38 was observed from 1 to 24 hours. Fluorescence originating from NK012 was detected up to 72 hours, whereas that from CPT-11 disappeared until 24 hours. NK012 also showed antitumor activity against peritoneal nodules. Thus, NK012 showing enhanced distribution with prolonged SN-38 release may be ideal for cancer treatment because the antitumor activity of SN-38 is time dependent.

Polymeric micelles for drug targeting

Polymeric micelles are nano-delivery systems formed through self-assembly of amphiphilic block copolymers in an aqueous environment. The nanoscopic dimension, stealth properties induced by the hydrophilic polymeric brush on the micellar surface, capacity for stabilized encapsulation of hydrophobic drugs offered by the hydrophobic and rigid micellar core, and finally a possibility for the chemical manipulation of the core/shell structure have made polymeric micelles one of the most promising carriers for drug targeting. To date, three generations of polymeric micellar delivery systems, i.e. polymeric micelles for passive, active and multifunctional drug targeting, have arisen from research efforts, with each subsequent generation displaying greater specificity for the diseased tissue and/or targeting efficiency. The present manuscript aims to review the research efforts made for the development of each generation and provide an assessment on the overall success of polymeric micellar delivery system in drug targeting. The emphasis is placed on the design and development of ligand modified, stimuli responsive and multifunctional polymeric micelles for drug targeting.

Degradation of PCL-MPEG diblock copolymer in rat plasma

The poly(epsilon-caprolactone)-co-poly(ethylene glycol) (PCL-MPEG) amphiphilic diblock copolymer with molar ratio of epsilon-CL to MPEG 81:1 is synthesized via a ring-opening polymerization without a catalyst. The M(w) and M(n) molecular weights and the polydispersities are 18,000, 11,000 g/mole and 1.55, respectively. The pegylated amphiphilic copolymer forms micelles with a low critical micelle concentration 6.71 x 10(-8) mole/L, and the average particle size of copolymeric micelles is 62.3 +/- 12.9 nm. The degradation behavior of diblock copolymer was studied in rat plasma at 37 degrees C for 90 days. The changes of mass, composition, morphology, molecular weight, and thermal property of PCL-MPEG copolymer were investigated. The decrease of copolymer mass shows two phases with rate constants of 1.91 x 10(-1) day(-1) in the first-phase (1-24 h) and 1.77 x 10(-3) day(-1) in the second-phase (1-90 days). The degradation of labile ester linkage between PCL block and MPEG block accounts for continuous decrease of copolymer mass in plasma. The decrease of EG molar ratio from 1.30 to 0.67 and prominent reduction of enthalpy of fusion of remained copolymer from 116.5 to 85.2 J/g provide evidences of PCL-MPEG chain scission. On the other hand, the presence of partially degraded copolymers in the residuals results in its polydispersity increased from 1.55 to 2.24 at the end of 90 days. Nevertheless, the surface erosion of copolymer makes the molecular weight not quite different from its original value.

Enhanced permeability and retention of macromolecular drugs in solid tumors: a royal gate for targeted anticancer nanomedicines

Over the past two decades cancer has ascended the causes of human death to be number one or two in many nations world wide. A major limitation inherent to most conventional anticancer chemotherapeutic agents is their lack of tumor selectivity. One way to achieve selective drug targeting to solid tumors is to exploit abnormalities of tumor vasculature, namely, hypervascularisation; aberrant vascular architecture; extensive production of vascular permeability factors stimulating extravasation within tumor tissues; and lack of lymphatic drainage. Maeda and his colleagues have extensively studied tumor vascular abnormalities in terms of active and selective delivery of anticancer drugs to tumor tissues, notably defining the enhanced permeability and retention effect (EPR effect) of macromolecular drugs in solid tumors. Due to their large molecular size, nanosized macromolecular anticancer drugs administered intravenously (i.v.) escape renal clearance. Often they can not penetrate the tight endothelial junctions of normal blood vessels, but they can extravasate in tumour vasculature and become trapped in the tumor vicinity. With time the tumor concentration will build up reaching several folds higher than that of the plasma due to lack of efficient lymphatic drainage in solid tumor; an ideal application for EPR-based selective anticancer drug delivery. Establishing this principle hastened development of various polymer conjugates and polymeric micelles as well as multifunctional nanoparticles for targeted cancer chemotherapy. Indeed this selective high local concentration of nanosized anticancer drugs in tumor tissues has proven superior in therapeutic effect with minimal side effects in both preclinical and clinical settings. In this review the mechanisms and factors involved in the EPR effect, as well as the uniqueness of nanoscale drugs for tumor targeting through EPR effect, will be discussed in detail.

Characterization of thimet oligopeptidase and neurolysin activities in B16F10-Nex2 tumor cells and their involvement in angiogenesis and tumor growth

Background

Angiogenesis is a fundamental process that allows tumor growth by providing nutrients and oxygen to the tumor cells. Beyond the oxygen diffusion limit from a capillary blood vessel, tumor cells become apoptotic. Angiogenesis results from a balance of pro- and anti-angiogenic stimuli. Endogenous inhibitors regulate enzyme activities that promote angiogenesis. Tumor cells may express pro-angiogenic factors and hydrolytic enzymes but also kinin-degrading oligopeptidases which have been investigated.

Results

Angiogenesis induced by B16F10-Nex2 melanoma cells was studied in a co-culture with HUVEC on Matrigel. A stimulating effect on angiogenesis was observed in the presence of B16F10-Nex2 lysate and plasma membrane. In contrast, the B16F10-Nex2 culture supernatant inhibited angiogenesis in a dose-dependent manner. This effect was abolished by the endo-oligopeptidase inhibitor, JA-2. Thimet oligopeptidase (TOP) and neurolysin activities were then investigated in B16F10-Nex2 melanoma cells aiming at gene sequencing, enzyme distribution and activity, influence on tumor development, substrate specificity, hydrolytic products and susceptibility to inhibitors. Fluorescence resonance energy transfer (FRET) peptides as well as neurotensin and bradykinin were used as substrates. The hydrolytic activities in B16F10-Nex2 culture supernatant were totally inhibited by o-phenanthrolin, JA-2 and partially by Pro-Ile. Leupeptin, PMSF, E-64, Z-Pro-Prolinal and captopril failed to inhibit these hydrolytic activities. Genes encoding M3A enzymes in melanoma cells were cloned and sequenced being highly similar to mouse genes. A decreased proliferation of B16F10-Nex2 cells was observed in vitro with specific inhibitors of these oligopeptidases. Active rTOP but not the inactive protein inhibited melanoma cell development in vivo increasing significantly the survival of mice challenged with the tumor cells. On Matrigel, rTOP inhibited the bradykinin – induced angiogenesis. A possible regulation of the homologous tumor enzyme in the perivascular microenvironment is suggested based on the observed rTOP inhibition by an S-nitrosothiol NO donor.

Conclusion

Data show that melanoma cells secrete endo-oligopeptidases which have an important role in tumor proliferation in vitro and in vivo. rTOP inhibited growth of subcutaneously injected B16F10-Nex2 cells in mice. TOP from tumor cells and bradykinin in endothelial cells are two antagonist factors that may control angiogenesis essential for melanoma growth. A regulatory role of NO or S-nitrosothiols is suggested.

Exploiting the enhanced permeability and retention effect for tumor targeting

Of the tumor targeting strategies, the enhanced permeability and retention (EPR) effect of macromolecules is a key mechanism for solid tumor targeting, and considered a gold standard for novel drug design. In this review, we discuss various endogenous factors that can positively impact the EPR effect in tumor tissues. Further, we discuss ways to augment the EPR effect by use of exogenous agents, as well as practical methods available in the clinical setting. Some innovative examples developed by researchers to combat cancer by the EPR mechanism are also discussed.

Novel SN-38-incorporating polymeric micelles, NK012, eradicate vascular endothelial growth factor-secreting bulky tumors

7-Ethyl-10-hydroxy-camptothecin (SN-38), a biological active metabolite of irinotecan hydrochloride (CPT-11), has potent antitumor activity but has not been used clinically because it is a water-insoluble drug. For delivery by i.v. injection, we have successfully developed NK012, a SN-38-releasing nanodevice. The purpose of this study is to investigate the pharmacologic character of NK012 as an anticancer agent, especially in a vascular endothelial growth factor (VEGF)-secreting tumor model. The particle size of NK012 was approximately 20 nm with a narrow size distribution. NK012 exhibited a much higher cytotoxic effect against lung and colon cancer cell lines as compared with CPT-11. NK012 showed significantly potent antitumor activity against a human colorectal cancer HT-29 xenograft as compared with CPT-11. Enhanced and prolonged distribution of free SN-38 in the tumor was observed after the injection of NK012. NK012 also had significant antitumor activity against bulky SBC-3/Neo (1,533.1 +/- 1,204.7 mm(3)) and SBC-3/VEGF tumors (1,620.7 +/- 834.0 mm(3)) compared with CPT-11. Furthermore, NK012 eradicated bulky SBC-3/VEGF tumors in all mice but did not eradicate SBC-3/Neo tumors. In the drug distribution analysis, an increased accumulation of SN-38 in SBC-3/VEGF tumors was observed as compared with that in SBC-3/Neo tumors. NK012 markedly enhanced the antitumor activity of SN-38, especially in highly VEGF-secreting tumors, and could be a promising SN-38-based formulation.

Characterization of pegylated copolymeric micelles and in vivo pharmacokinetics and biodistribution studies

The aim of this study was to evaluate the influence of pegylated copolymeric micelle carrier on the biodistribution of drug in rats. The copolymers were synthesized via a modified ring-opening copolymerization of lactone monomers (epsilon-caprolactone, delta-valerolactone, L-lactide) and poly(ethylene glycol) (PEG(10,000) and PEG(4000)). The molecular weights and the polydispersities of synthesized copolymers were in the range of 15,000-31,000 g/mol and 1.7-2.7, respectively. All of the pegylated amphiphilic copolymers were micelles formed with low CMC values in the range of 10(-7)-10(-8)M. The drug-loaded micelles were prepared via a dialysis method. The average particle size of micelles was around 150-200 nm. The cytotoxicity in terms of cell viability after treated with PCL-PEG, PVL-PEG, and PLA-PEG micelles was insignificant. PCL-PEG and PVL-PEG micelles without branch side chain in structures had higher drug loading than PLA-PEG micelles. In vitro release profiles indicated the release of indomethacin from these micelles exhibited a sustained release behavior. The similar phenomenon was also observed in vivo in rats. The pegylated copolymeric micelles not only decreased drug uptake by the liver and kidney, but also prolonged drug retention in the blood.

Activation of the kallikrein-kinin system and release of new kinins through alternative cleavage of kininogens by microbial and human cell proteinases

Kinins are released from kininogens through the activation of the Hageman factor-prekallikrein system or by tissue kallikrein. These peptides exert various biological activities, such as vascular permeability increase, smooth muscle contraction, pain sensation and induction of hypotension. In many instances kinins are thought to be involved in the pathophysiology of various diseases. Recent studies have revealed that microbial and human cell proteinases activate Hageman factor and/or prekallikrein, or directly release kinin from kininogens. This review discusses the activation of the kinin-release system by mast-cell tryptase and microbial proteinases, including gingipains, which are cysteine proteinases from Porphyromonas gingivalis , the major pathogen of periodontal disease. Each enzyme is evaluated in the context of its association to allergy and infectious diseases, respectively. Furthermore, a novel system of kinin generation directly from kininogens by the concerted action of two proteinases is described. An interesting example of this system with implications to bacterial pathogenicity is the release of kinins from kininogens by neutrophil elastase and a synergistic action of cysteine proteinases from Staphylococcus aureus . This alternative production of kinins by proteinases present in diseased sites indicates a significant contribution of proteinases other than kallikreins in kinin generation. Therefore kinin receptor antagonists and proteinase inhibitors may be useful as therapeutic agents.

International union of pharmacology. XLV. Classification of the kinin receptor family: from molecular mechanisms to pathophysiological consequences

Kinins are proinflammatory peptides that mediate numerous vascular and pain responses to tissue injury. Two pharmacologically distinct kinin receptor subtypes have been identified and characterized for these peptides, which are named B1 and B2 and belong to the rhodopsin family of G protein-coupled receptors. The B2 receptor mediates the action of bradykinin (BK) and lysyl-bradykinin (Lys-BK), the first set of bioactive kinins formed in response to injury from kininogen precursors through the actions of plasma and tissue kallikreins, whereas the B(1) receptor mediates the action of des-Arg9-BK and Lys-des-Arg9-BK, the second set of bioactive kinins formed through the actions of carboxypeptidases on BK and Lys-BK, respectively. The B2 receptor is ubiquitous and constitutively expressed, whereas the B1 receptor is expressed at a very low level in healthy tissues but induced following injury by various proinflammatory cytokines such as interleukin-1beta. Both receptors act through G alpha(q) to stimulate phospholipase C beta followed by phosphoinositide hydrolysis and intracellular free Ca2+ mobilization and through G alpha(i) to inhibit adenylate cyclase and stimulate the mitogen-activated protein kinase pathways. The use of mice lacking each receptor gene and various specific peptidic and nonpeptidic antagonists have implicated both B1 and B2 receptors as potential therapeutic targets in several pathophysiological events related to inflammation such as pain, sepsis, allergic asthma, rhinitis, and edema, as well as diabetes and cancer. This review is a comprehensive presentation of our current understanding of these receptors in terms of molecular and cell biology, physiology, pharmacology, and involvement in human disease and drug development.

Host stromal bradykinin B2 receptor signaling facilitates tumor-associated angiogenesis and tumor growth

We evaluated the significance of the host kallikrein-kinin system in tumor angiogenesis and tumor growth using two rodent models genetically deficient in a kallikrein-kinin system. Inoculation of Walker 256 carcinoma cells into the s.c. tissues of the back of normal Brown Norway Kitasato rats (BN-Ki rats) resulted in the rapid development of solid tumors with marked angiogenesis. By contrast, in kininogen-deficient Brown Norway Katholiek rats (BN-Ka rats), which cannot generate intrinsic bradykinin (BK), the weights of the tumors and the extent of angiogenesis were significantly less than those in BN-Ki rats. Daily administration of B(2) receptor antagonists significantly reduced angiogenesis and tumor weights in BN-Ki rats to levels similar to those in BN-Ka rats but did not do so in BN-Ka rats. Angiogenesis and tumor growth were significantly suppressed in B(2) receptor knockout mice bearing sarcoma 180 compared with their wild-type counterparts. Immunoreactive vascular endothelial growth factor (VEGF) was localized in Walker tumor stroma more extensively in BN-Ki rats than in BN-Ka rats, although immunoreactive B(2) receptor also was detected in the stroma to the same extent in both types of rats. Cultured stromal fibroblasts isolated from BN-Ki rats and BN-Ka rats produced VEGF in response to BK (10(-8)-10(-6) m), and this stimulatory effect of BK was abolished with a B(2) receptor antagonist, Hoe140 (10(-5) m). These results suggest that BK generated from kininogens supplied from the host may facilitate tumor-associated angiogenesis and tumor growth by stimulating stromal B(2) signaling to up-regulate VEGF production mainly in fibroblasts.