Applications of Ultrasound to Stimulate Therapeutic Revascularization.

Many pathological conditions are characterized or caused by the presence of an insufficient or aberrant local vasculature. Thus, therapeutic approaches aimed at modulating the caliber and/or density of the vasculature by controlling angiogenesis and arteriogenesis have been under development for many years. As our understanding of the underlying cellular and molecular mechanisms of these vascular growth processes continues to grow, so too do the available targets for therapeutic intervention. Nonetheless, the tools needed to implement such therapies have often had inherent weaknesses (i.e., invasiveness, expense, poor targeting, and control) that preclude successful outcomes. Approximately 20 years ago, the potential for using ultrasound as a new tool for therapeutically manipulating angiogenesis and arteriogenesis began to emerge. Indeed, the ability of ultrasound, especially when used in combination with contrast agent microbubbles, to mechanically manipulate the microvasculature has opened several doors for exploration. In turn, multiple studies on the influence of ultrasound-mediated bioeffects on vascular growth and the use of ultrasound for the targeted stimulation of blood vessel growth via drug and gene delivery have been performed and published over the years. In this review article, we first discuss the basic principles of therapeutic ultrasound for stimulating angiogenesis and arteriogenesis. We then follow this with a comprehensive cataloging of studies that have used ultrasound for stimulating revascularization to date. Finally, we offer a brief perspective on the future of such approaches, in the context of both further research development and possible clinical translation.

Deformable Discoidal Polymeric Nanoconstructs for the Precise Delivery of Therapeutic and Imaging Agents.

Over the last 15 years, a plethora of materials and different formulations have been proposed for the realization of nanomedicines. Yet drug-loading efficiency, sequestration by phagocytic cells, and tumor accumulation are sub-optimal. This would imply that radically new design approaches are needed to propel the clinical integration of nanomedicines, overcoming well-accepted clichés. This work briefly reviews the use of deformable discoidal nanoconstructs as a novel delivery strategy for therapeutic and imaging agents. Inspired by blood cell behavior, these nanoconstructs are designed to efficiently navigate the circulatory system, minimize sequestration by phagocytic cells, and recognize the tortuous angiogenic microvasculature of neoplastic masses. This article discusses the notion of nanoparticle margination and vascular adhesion, as well as advantages associated with deformable particles. Finally, details on the synthesis, physico-chemical properties, and in vivo characterization of discoidal polymeric nanoconstructs are provided, with particular emphasis on their ability to independently control size, shape, surface properties, and mechanical stiffness. These nanoconstructs could help in gaining a deeper understanding of the mechanisms regulating the behavior of nanomedicines and identifying optimal delivery strategies for patient-specific therapeutic interventions.

Near-infrared light-activated IR780-loaded liposomes for anti-tumor angiogenesis and Photothermal therapy.

Tumor angiogenesis is a key step in the process of tumor development, and antitumor angiogenesis has a profound influence on tumor growth. Herein we report a dual-function drug delivery system comprising a Near-infrared (NIR) dye and an anti-angiogenic drug within liposomes (Lip-IR780-Sunitinib) for enhanced antitumor therapy. The hydrophobic NIR dye IR780 was loaded into the liposome phospholipid bilayer, and the bilayer would be disrupted by laser irradiation so that anti-angiogenic drug sunitinib release would be activated remotely at the tumor site. The released hydrophilic sunitinib could potentially target multiple VEGF receptors on the tumor endothelial cell surface to inhibit angiogenesis. Meanwhile, IR780-loaded liposomes kill the cancer cells by photothermal therapy. Lip-IR780-Sunitinib exhibited enhanced anti-tumor and anti-angiogenic effects in vitro and in vivo. This system facilitates easy and controlled release of cargos to achieve anti-tumor angiogenesis and photothermal therapy.

No beneficial effect of Polidocanol treatment in Achilles tendinopathy: a randomised controlled trial.

PURPOSE: Polidocanol injections have been used to treat chronic Achilles tendinopathy in clinical settings, but the few studies published show inconsistent results. The aim of this study was to evaluate the mid-term effect of Polidocanol in patients with chronic Achilles tendinopathy. It was hypothesised that patients treated with Polidocanol would have significant improvements in the outcome measures investigated compared to patients treated with a placebo treatment at mid-term follow-up. METHODS: This randomised controlled trial included forty-eight patients aged 32-77 years with a history of Achilles tendinopathy for at least 3 months and with neovascularisation demonstrated by ultrasonography was included. A minimum of 3 months of eccentric exercise treatment was required before participating. The patients were allocated to a maximum of two injection of either Polidocanol or Lidocaine (placebo). The primary outcome measure was pain during walking reported on a visual analogue scale. Secondary outcome measures were Foot and Ankle Outcome Score (FAOS), patient satisfaction with treatment and, shortly after inclusion, the Victorian Institute of Sports Assessment-Achilles questionnaire (VISA-A) was also included. Follow-up examinations were performed after 3 and 6 months. RESULTS: Pain during walking decreased during the 6-month follow-up period, but no significant differences were seen between the two groups. The same tendency was seen for FAOS and VISA-A in which both groups showed an improvement at 3- and 6-month follow-up, but no mid-term differences between the groups were seen. An equal number of patients in the two groups were satisfied with the treatment at follow-up. CONCLUSIONS: The results indicate that Polidocanol is a safe treatment, but the mid-term effects are the same as a placebo treatment. This further questions the use of Polidocanol in the treatment of chronic Achilles tendinopathy. LEVEL OF EVIDENCE: I.

Ultrasensitive pH Triggered Charge/Size Dual-Rebound Gene Delivery System.

A facile strategy is developed to construct an ultrasensitive pH triggered charge/size dual-rebound gene delivery system for efficient tumor treatment. The therapeutic gene is complexed by polyethylenimine (PEI) and poly-l-glutamate (PLG), further in situ tightened by aldehyde modified polyethylene glycol (PEG) via Schiff base reaction. The generated Schiff base bonds are stable in neutral pH but cleavable in tumor extracellular pH. This gene delivery system possesses following favorable properties: (1) the tunable gene delivery system is constructed by chemical bench-free "green" and fast process which is favored by clinician, (2) PEG cross-linking shields the surface positive charges and tightens the complex particles, leading to decreased cytotoxicity, improved stability, and prolonged circulation, (3) PEG shielding can be rapidly peeled off by acidic pH as soon as arriving tumors, (4) dual charge/size ultrasensitively rebounding to higher positive potential and bigger size enhances tumor cell uptake efficiency. A series of experiments both in vitro and in vivo are carried out to investigate this gene delivery system in detail. An antiangiogenesis therapeutic gene is carried for the treatment of CT26 tumors in mice, achieving superior antitumor efficacy which is well proved by sufficient biological evidence. The system has great potentials for cancer therapy in the future.

Nanotherapy silencing the interleukin-8 gene produces regression of prostate cancer by inhibition of angiogenesis.

Interleukin-8 (IL-8) is a pro-angiogenic cytokine associated with aggressive prostate cancer (CaP). We detected high levels of IL-8 in sera from patients with CaP compared with healthy controls and patients with benign prostatic hypertrophy. This study examines the role of IL-8 in the pathogenesis of metastatic prostate cancer. We developed a biocompatible, cationic polylactide (CPLA) nanocarrier to complex with and efficiently deliver IL-8 small interfering RNA (siRNA) to CaP cells in vitro and in vivo. CPLA IL-8 siRNA nanocomplexes (nanoplexes) protect siRNA from rapid degradation, are non-toxic, have a prolonged lifetime in circulation, and their net positive charge facilitates penetration of cell membranes and subsequent intracellular trafficking. Administration of CPLA IL-8 siRNA nanoplexes to immunodeficient mice bearing human CaP tumours produced significant antitumour activities with no adverse effects. Systemic (intravenous) or local intra-tumour administration of IL-8 siRNA nanoplexes resulted in significant inhibition of CaP growth. Magnetic resonance imaging and ultrasonography of experimental animals demonstrated reduction of tumour perfusion in vivo following nanoplex treatment. Staining of tumour sections for CD31 confirmed significant damage to tumour neovasculature after nanoplex therapy. These studies demonstrate the efficacy of IL-8 siRNA nanotherapy for advanced, treatment-resistant human CaP.

Hypervascular cervical spine metastases: embolization by direct injection of Onyx-18.

PURPOSE: Spinal metastases are common in patients with cancer. Following lung and liver, spine is the most common site for cancers to metastasize. Many of them are hypervascularized. These cases are a particular challenge for the surgeon and represent a significant danger of massive blood loss during surgery. Hypervascularized metastases of the cervical spine also include the risk of postoperative bleeding with severe neurological impairment. We report a case of a 67-year-old women with breast cancer (BC) metastasis within the vertebral bodies of C3 and C4 with nearly complete bony destruction of the ventral column and intraspinal tumor masses compressing the spinal cord at level C3 and C4. The hypervascularized tumor was supplied by multiple minor vessels from both vertebral arteries, too small to be coiled individually. Due to an allergy to aspirin, intravascular stenting of the vertebral arteries was not an option. We decided to perform a preoperative direct injection of onyx-18 for embolization of the tumor. CONCLUSION: Presurgical direct injection of Onyx-18 for treating hypervascular spinal metastases of breast cancer seems to be an effective and safe technique and reduces intraoperative bleeding to a minimum.

Cycloamylose-nanogel drug delivery system-mediated intratumor silencing of the vascular endothelial growth factor regulates neovascularization in tumor microenvironment.

RNAi enables potent and specific gene silencing, potentially offering useful means for treatment of cancers. However, safe and efficient drug delivery systems (DDS) that are appropriate for intra-tumor delivery of siRNA or shRNA have rarely been established, hindering clinical application of RNAi technology to cancer therapy. We have devised hydrogel polymer nanoparticles, or nanogel, and shown its validity as a novel DDS for various molecules. Here we examined the potential of self-assembled nanogel of cholesterol-bearing cycloamylose with spermine group (CH-CA-Spe) to deliver vascular endothelial growth factor (VEGF)-specific short interfering RNA (siVEGF) into tumor cells. The siVEGF/nanogel complex was engulfed by renal cell carcinoma (RCC) cells through the endocytotic pathway, resulting in efficient knockdown of VEGF. Intra-tumor injections of the complex significantly suppressed neovascularization and growth of RCC in mice. The treatment also inhibited induction of myeloid-derived suppressor cells, while it decreased interleukin-17A production. Therefore, the CH-CA-Spe nanogel may be a feasible DDS for intra-tumor delivery of therapeutic siRNA. The results also suggest that local suppression of VEGF may have a positive impact on systemic immune responses against malignancies.

Development of a miR-92a delivery system for anti-angiogenesis-based cancer therapy.

BACKGROUND: RNA interference has received much attention as a novel therapeutic strategy. MicroRNA (miRNA) appears to be promising as a novel nucleic-acid medicine because it is able to suppress a series of protein expression that relates to a specific event such as angiogenesis. In the present study, we used dicetyl phosphate-tetraethylenepentamine-based polycation liposomes (TEPA-PCL) as a delivery system for miR-92a, one of the miRNAs regulating angiogenesis, and attempted to deliver miR-92a to angiogenic endothelial cells for the development of cancer therapy by anti-angiogenesis. METHODS: Cholesterol-grafted miR-92a (miR-92a-C) was bound to TEPA-PCL, and the ratio of nitrogen of TEPA-PCL to phosphorus of miR-92a-C (N/P ratio) was optimized. This complex was transfected into human umbilical vein endothelial cells (HUVECs), and the intracellular localization of miR-92a-C was observed under a confocal laser-scanning microscope by the use of fluorescein isothiocyanate-labeled miR-92a-C. After transfection of HUVECs with miR-92a-C/TEPA-PCL, the expression of miR-92a-target proteins (e.g. integrin α5, mitogen-activated protein kinase kinase 4, sphingosine-1-phosphate receptor 1) was examined by western blotting, and a tube formation assay was performed. RESULTS: The complex of miR-92a-C with TEPA-PCL was formed and miR-92a-C remained stable with TEPA-PCL at the N/P ratio of 10. After transfection of HUVECs with miR-92a-C complex, miR-92a-C spread into the whole cytoplasm of the cells without any change of cellular morphology, and the expression of several proteins encoded by miR-92a-target genes was suppressed. Furthermore, the capability of forming capillary tubes was impaired in complex-treated HUVECs. CONCLUSIONS: We have developed a miR-92a delivery system into angiogenic endothelial cells by the use of TEPA-PCL. These results suggest that miR-92a-C/TEPA-PCL is promising for the treatment of tumors via the suppression of angiogenesis.

A comparison of particulate and Onyx embolization in preoperative devascularization of carotid body tumors.

INTRODUCTION: Preoperative embolization of a carotid body tumor (CBT) is a useful adjunct prior to surgical excision because it decreases operative blood loss and improves surgical outcomes. Traditionally, this is performed by transarterial particulate embolization (TAPE). More recently, direct percutaneous embolization (DPE) with Onyx is recognized as a promising technique for preoperative embolization. We compared these two techniques in patients treated for CBTs at our institution. METHODS: We retrospectively reviewed cases of preoperative devascularization of CBT from 1 January 1995 through 1 September 2012. Patient cases were placed into two groups: TAPE and DPE. Operative blood loss, operative length, angiographic devascularization, embolization procedure complications, operative transfusion requirements, postoperative hospital stay, intensive care unit (ICU) stay, and procedure-related mortalities were compared. RESULTS: A total of 17 patients underwent preoperative devascularization of their CBT with TAPE technique and ten patients using the DPE technique with Onyx. Average operative blood loss was significantly higher in the TAPE group (Mann-Whitney U test, p = 0.04). Operative time was also higher, although this difference was not significant. Two patients required intraoperative blood transfusions in the TAPE group while none required transfusions in the DPE group. There was no significant difference in ICU stay or length of hospitalization. One serious embolization procedure complication occurred in the TAPE group and none in the DPE group. CONCLUSION: Operative blood loss in the DPE group was significantly less than the TAPE group. Blood transfusion requirement, operative time, and complications were less in the DPE group, although they did not reach statistical significance.

A comparison of particulate and onyx embolization in preoperative devascularization of juvenile nasopharyngeal angiofibromas.

INTRODUCTION: Juvenile nasopharyngeal angiofibromas (JNAs) are hypervascular tumors that may benefit from preoperative devascularization to reduce intraoperative blood loss (IBL). The purpose of this study was to compare transarterial particulate embolization (TAPE) with the direct percutaneous embolization (DPE) technique using ethylene vinyl alcohol (Onyx, ev3, Irvine, CA) for the preoperative devascularization of a JNA. METHODS: We retrospectively reviewed 50 consecutive JNA resections since 1995 for which preoperative embolization was either transarterial with particulate material (n = 39) or DPE (n = 11) using only Onyx. The IBL, transfusion requirements, operative time, and length of hospital admission were compared between the two groups. RESULTS: The mean IBL was 1,348.7 ± 932.2 mL particulate group, 569.1 ± 700.7 mL Onyx group (one-tailed Student's t test p = 0.003). The mean unit of packed red blood cells was 1.56 ± 2.01 units particulate group, 0.45 ± 1.04 units Onyx group (p = 0.009). The relationship between embolization type and IBL remained significant or strongly correlated when accounting for the Fisch stage of the tumor (p = 0.010 and p = 0.056, respectively, by a multivariate least squares fit; alternately p = 0.0003 and p = 0.023, respectively, in the subset of patients with Fisch stage III tumors only). We also found that the proportion of resections for which an endoscopic approach could be used was significantly higher in the Onyx group than the particulate group (81.8 and 18.2 %; Pearson p = 0.0002), and this was also significant both in our multivariate nominal logistic fit (p < 0.001) and in the subset of patients with Fisch stage III tumors (p = 0.018). CONCLUSION: Pre-operative DPE with Onyx of a JNA when compared to TAPE significantly decreased IBL and RBC transfusion requirement during surgical resection. The proportion of surgical resections performed from an endoscopic approach was higher in the DPE Onyx group, which may have affected the results.

Improving the efficacy of antibody-based cancer therapies.

A quarter of a century after their advent, monoclonal antibodies have become the most rapidly expanding class of pharmaceuticals for treating a wide variety of human diseases, including cancer. Although antibodies have yet to achieve the ultimate goal of curing cancer, many innovative approaches stand poised to improve the efficacy of antibody-based therapies.

Paramagnetic and fluorescent liposomes for target-specific imaging and therapy of tumor angiogenesis.

Angiogenesis is essential for tumor growth and metastatic potential and for that reason considered an important target for tumor treatment. Noninvasive imaging technologies, capable of visualizing tumor angiogenesis and evaluating the efficacy of angiostatic therapies, are therefore becoming increasingly important. Among the various imaging modalities, magnetic resonance imaging (MRI) is characterized by a superb spatial resolution and anatomical soft-tissue contrast. Revolutionary advances in contrast agent chemistry have delivered versatile angiogenesis-specific molecular MRI contrast agents. In this paper, we review recent advances in the preclinical application of paramagnetic and fluorescent liposomes for noninvasive visualization of the molecular processes involved in tumor angiogenesis. This liposomal contrast agent platform can be prepared with a high payload of contrast generating material, thereby facilitating its detection, and is equipped with one or more types of targeting ligands for binding to specific molecules expressed at the angiogenic site. Multimodal liposomes endowed with contrast material for complementary imaging technologies, e.g., MRI and optical, can be exploited to gain important preclinical insights into the mechanisms of binding and accumulation at angiogenic vascular endothelium and to corroborate the in vivo findings. Interestingly, liposomes can be designed to contain angiostatic therapeutics, allowing for image-supervised drug delivery and subsequent monitoring of therapeutic efficacy.

Preoperative transcatheter arterial embolization of hypervascular metastatic tumors of long bones.

BACKGROUND: Complete resection of hypervascular metastatic tumors is often complicated by massive intraoperative blood loss. PURPOSE: To assess the technical success and clinical effectiveness of transcatheter arterial embolization (TAE) of hypervascular metastatic tumors of long bones to reduce blood loss during orthopedic surgery. MATERIAL AND METHODS: From January 2000 to September 2009, 25 patients (M:F=13:12; mean age 58.3 years) were treated with TAE of metastatic bone tumors before elective, orthopedic surgery. In all cases, the indication for TAE was preoperative devascularization. Technical success, defined as obliteration of tumor staining to 70% or more, requirement for red blood cell transfusion within 24 h following surgery, and hematologic parameters, i.e. the hemoglobin, hematocrit, and erythrocyte counts before and after surgery, were obtained. RESULTS: The technical success rate was 96% (24/25 patients). Gelatin sponge particles (n=21) or polyvinyl alcohol particles (n=4) were used as embolic materials. The mean amount of red blood cell transfusion within the 24 h following surgery was 1.91 units (range 0-6) in the 23 patients with technically successful TAE and who underwent surgery within 3 days after TAE. In 22 patients with technically successful TAE and available hematologic data, the mean gaps in the hemoglobin, hematocrit, and erythrocyte counts before and after operation were 1.22 g/dl, 4.07%, and 0.45 x 10(6)/mm(3), respectively. CONCLUSION: Preoperative TAE is technically successful and clinically effective to minimize intraoperative and postoperative bleeding in patients with hypervascular metastasis to long bones.

Pre-operative direct puncture embolization of head and neck hypervascular tumors using SQUID 12.

OBJECTIVE: The authors have evaluated their experience in pre-operative direct puncture embolization of hypervascular tumors of the head and neck using SQUID 12, an embolic liquid agent. METHODS: Between July 2016 and March 2019, the authors retrospectively reviewed clinical, embolization and surgical data of 11 consecutive patients with 12 hypervascular head and neck tumors who had undergone pre-operative embolization using SQUID 12. Percutaneous embolizations were performed by inserting a 19-22 Gauge needle directly into the tumor under ultrasound, fluoroscopic and/or endoscopic guidance. The hub of the needle was connected to a 15-cm DMSO-compatible extension tube, and the SQUID 12 was injected. RESULTS: Total or near-total devascularization was achieved in 11 over 12 cases. Complete en-bloc tumor removal by surgery was achieved in all cases. Only one patient required blood transfusion. No major periprocedural adverse events were recorded. CONCLUSIONS: Direct puncture embolization of hypervascular tumors of the head and neck using SQUID 12 seems to be safe and effective. It may offer almost complete devascularization due to homogenous, deep penetration in the tumor, with optimal visibility of the agent throughout the percutaneous procedure. It may reduce intraoperative blood loss and the need for transfusion, thus facilitating complete surgical resection.

Targeting tumor cells and neovascularization using RGD-functionalized magnetoliposomes.

PURPOSE: Magnetoliposomes (MLs) have shown great potential as magnetic resonance imaging contrast agents and as delivery vehicles for cancer therapy. Targeting the MLs towards the tumor cells or neovascularization could ensure delivery of drugs at the tumor site. In this study, we evaluated the potential of MLs targeting the αvß3 integrin overexpressed on tumor neovascularization and different tumor cell types, including glioma and ovarian cancer. METHODS: MLs functionalized with a Texas Red fluorophore (anionic MLs), and with the fluorophore and the cyclic Arginine-Glycine-Aspartate (cRGD; cRGD-MLs) targeting the αvß3 integrin, were produced in-house. Swiss nude mice were subcutaneously injected with 107 human ovarian cancer SKOV-3 cells. Tumors were allowed to grow for 3 weeks before injection of anionic or cRGD-MLs. Biodistribution of MLs was followed up with a 7T preclinical magnetic resonance imaging (MRI) scanner and fluorescence imaging (FLI) right after injection, 2h, 4h, 24h and 48h post injection. Ex vivo intratumoral ML uptake was confirmed using FLI, electron paramagnetic resonance spectroscopy (EPR) and histology at different time points post injection. RESULTS: In vivo, we visualized a higher uptake of cRGD-MLs in SKOV-3 xenografts compared to control, anionic MLs with both MRI and FLI. Highest ML uptake was seen after 4h using MRI, but only after 24h using FLI indicating the lower sensitivity of this technique. Furthermore, ex vivo EPR and FLI confirmed the highest tumoral ML uptake at 4 h. Last, a Perl's stain supported the presence of our iron-based particles in SKOV-3 xenografts. CONCLUSION: Uptake of cRGD-MLs can be visualized using both MRI and FLI, even though the latter was less sensitive due to lower depth penetration. Furthermore, our results indicate that cRGD-MLs can be used to target SKOV-3 xenograft in Swiss nude mice. Therefore, the further development of this particles into theranostics would be of interest.

A ternary-complex of a suicide gene, a RAGE-binding peptide, and polyethylenimine as a gene delivery system with anti-tumor and anti-angiogenic dual effects in glioblastoma.

The receptor for advanced glycation end-products (RAGE) is involved in tumor angiogenesis. Inhibition of RAGE might be an effective anti-angiogenic therapy for cancer. In this study, a cationic RAGE-binding peptide (RBP) was produced as an antagonist of RAGE, and a ternary-complex consisting of RBP, polyethylenimine (2 kDa, PEI2k), and a suicide gene (pHSVtk) was developed as a gene delivery system with dual functions: the anti-tumor effect of pHSVtk and anti-angiogenic effect of RBP. As an antagonist of RAGE, RBP decreased the secretion of vascular-endothelial growth factor (VEGF) in activated macrophages and reduced the tube-formation of endothelial cells in vitro. In in vitro transfection assays, the RBP/PEI2k/plasmid DNA (pDNA) ternary-complex had higher transfection efficiency than the PEI2k/pDNA binary-complex. In an intracranial glioblastoma animal model, the RBP/PEI2k/pHSVtk ternary-complex reduced α-smooth muscle actin expression, suggesting that the complex has an anti-angiogenic effect. In addition, the ternary-complex had higher pHSVtk delivery efficiency than the PEI2k/pHSVtk and PEI25k/pHSVtk binary-complexes in an animal model. As a result, the ternary-complex induced apoptosis and reduced tumor volume more effectively than the PEI2k/pHSVtk and PEI25k/pHSVtk binary-complexes. In conclusion, due to its dual anti-tumor and anti-angiogenesis effects, the RBP/PEI2k/pHSVtk ternary-complex might be an efficient gene delivery system for the treatment of glioblastoma.

Delivery of small interfering RNA against Nogo-B receptor via tumor-acidity responsive nanoparticles for tumor vessel normalization and metastasis suppression.

Nogo-B receptor (NgBR) plays fundamental roles in regulating angiogenesis, vascular development, and the epithelial-mesenchymal transition (EMT) of cancer cells. However, the therapeutic effect of NgBR blockade on tumor vasculature and malignancy is unknown, investigations on which requires an adequate delivery system for small interfering RNA against NgBR (NgBR siRNA). Here a surface charge switchable polymeric nanoparticle that was sensitive to the slightly acidic tumor microenvironment was developed for steady delivery of NgBR siRNA to tumor tissues. The nanoformulation was constructed by conjugating 2, 3-dimethylmaleic anhydride (DMMA) molecules to the surface amines of micelles formed by cationic co-polymer poly(lactic-co-glycolic acid)2-poly(ethylenimine) and subsequent absorption of NgBR siRNAs. The nanoparticles remained negatively charged in physiological condition and smartly converted to positive surface charge due to tumor-acidity-activated shedding of DMMA. The charge conversion facilitated cellular uptake of siRNAs and in turn efficiently depleted the expression of NgBR in tumor-bearing tissues. Silencing of NgBR suppressed endothelial cell migration and tubule formation, and reverted the EMT process of breast cancer cells. Delivery of the nanoformulation to mice bearing orthotopic breast carcinoma showed no effect on tumor growth, but led to remarkable decrease of distant metastasis by normalizing tumor vessels and suppressing the EMT of breast cancer cells. This study demonstrated that NgBR is a promising therapeutic target in abnormal tumor vasculature and aggressive cancer cells, and the tumor-responsive nanoparticle with the feature of charge transformation offers great potential for tumor-specific delivery of gene therapeutics.