Ultrasound-mediated augmented exosome release from astrocytes alleviates amyloid-ß-induced neurotoxicity.

Background: Extracellular vesicles, including exosomes, are secreted by a variety of cell types in the central nervous system. Exosomes play a role in removing intracellular materials from the endosomal system. Alzheimer's disease (AD) is caused by an overproduction or reduced amyloid-beta (Aß) peptide clearance. Increased Aß levels in the brain may impair the exosome-mediated Aß clearance pathway. Therapeutic ultrasound stimulation demonstrated its potential for promoting Aß degradation efficiency in clinical trials. However, the underlying mechanism of ultrasound stimulation is still unclear. Methods: In this study, astrocytes, the most abundant glial cells in the brain, were used for exosome production. Post insonation, exosomes from ultrasound-stimulated HA cells (US-HA-Exo) were collected, nanoparticle tracking analysis and protein analysis were used to measure and characterize exosomes. Neuroprotective effect of US-HA-Exo in oligomeric Aß42 toxicated SH-SY5Y cells was tested. Cellular uptake and distribution of exosomes were observed by flow cytometry and confocal laser scanning microscopy. Focused ultrasound (FUS) with microbubbles was employed for blood-brain-barrier opening to achieve brain-targeted exosome delivery. After US-HA-Exo/FUS treatment, amyloid-ß plaque in APP/PS1 mice were evaluated by Aß immunostaining and thioflavin-S staining. Results: We showed that ultrasound resulted in an almost 5-fold increase in the exosome release from human astrocytes. Exosomes were rapidly internalized in SH-SY5Y cells, and colocalized with FITC-Aß42, causing a decreased uptake of FITC-Aß42. CCk-8 test results showed that US-HA-Exo could mitigate Aß toxicity to neurons in vitro. The therapeutic potential of US-HA-Exo/FUS delivery was demonstrated by a decrease in thioflavin-S-positive amyloid plaques and Aß immuno-staining, a therapeutic target for AD in APP/PS1 transgenic mice. The iTRAQ-based proteomic quantification was performed to gain mechanistic insight into the ultrasound effect on astrocyte-derived exosomes and their ability to alleviate Aß neurotoxicity. Conclusion: Our results imply that US-HA-Exo have the potential to provide neuroprotective effects to reverse oligomeric amyloid-ß-induced cytotoxicity in vitro and, when combined with FUS-induced BBB opening, enable the clearance of amyloid-ß plaques in vivo.

Real-Time Imaging Tracking of Mesenchymal Stem Cells Labeled with Lipid-Poly(lactic-co-glycolic acid) Nanobubbles.

Stem-cell-based therapy has attracted considerable attention due to the significant benefits to patients experiencing a wide range of diseases and injuries. However, their underlying mechanism of action is not completely understood. One main reason is the lack of imaging tools for real-time tracking of deep-seated transplanted stem cells. For the present study, we exploited a lipid poly(lactic-co-glycolic acid) nanobubble (LPN) probe with nanoscale size, good compatibility, and strong contrast-enhanced ultrasound signals. Due to the nanoscale particle size, cellular labeling of mesenchymal stem cells can be achieved via incubation with LPNs. Significantly enhanced ultrasound images of these labeled stem cells were obtained in vitro and in vivo. More importantly, the labeled stem cells could be tracked by ultrasound imaging for up to 5 days. Additional evaluation found that the in vivo detection limit achieved 2,000 labeled stem cells in the subcutaneous tissues of living mice. Our study presents a strategy to achieve real-time ultrasound imaging tracking, paving the way for an investigation on the underlying mechanism and future clinical application of stem cell therapy.

Ultrasound-Induced Blood-Brain-Barrier Opening Enhances Anticancer Efficacy in the Treatment of Glioblastoma: Current Status and Future Prospects.

Glioblastoma multiforme (GBM) diffusely infiltrates normal brain tissue. The presence of the blood-brain barrier (BBB) poses difficulties for targeted delivery of currently available antitumor drugs. Novel brain drug delivery strategies are far from satisfactory for glioma treatment. Recently, focused ultrasound (FUS) combined with microbubbles presents a transient, reversible, and noninvasive approach for local induction of BBB opening. This strategy demonstrated its potential to increase local concentrations of both diagnostic and therapeutic agents in glioma therapy. Current status and related physic mechanisms of this drug delivery technique are discussed in this review. Delivery efficiency enhancement in many preclinical glioma models was obtained by FUS-BBB opening combined with various nanoparticles. And, the clinical translational status of FUS-BBB will be discussed.

Biosynthetic nanobubbles for targeted gene delivery by focused ultrasound.

Ultrasound-targeted microbubble destruction (UTMD) has recently drawn considerable attention in biomedicine applications due to its great potential to locally enhance gene delivery. However, conventional microbubbles have a microscale particle size and polydisperse particle size distribution, which makes it difficult for them to directly come into contact with tumor cells and to efficiently deliver therapeutic genes via ultrasound cavitation effects. In the current study, we developed a kind of novel cationic biosynthetic nanobubble (CBNB) as an ultrasonic gene delivery carrier through coating PEI on the surface of these biosynthetic nanobubbles (BNBs). The BNBs, produced from an extremely halophilic archaeon (Halobacterium NRC-1), possess a nanoscale size and can produce stable contrast signals both in vitro and in vivo. Surface modification with PEI polymer greatly increased the DNA loading capability of BNBs, leading to significantly improved gene transfection efficiency when combining with ultrasound. To our knowledge, this is the first report to apply biosynthetic bubbles as non-viral gene carriers which can effectively deliver genes into tumor cells with the aid of ultrasound cavitation. Our study provides a powerful tool for image-guided and efficient gene delivery using biosynthetic nanoscale contrast agents.

MR imaging tracking of inflammation-activatable engineered neutrophils for targeted therapy of surgically treated glioma.

Cell-based drug delivery systems have shown promising capability for tumor-targeted therapy owing to the intrinsic tumor-homing and drug-carrying property of some living cells. However, imaging tracking of their migration and bio-effects is urgently needed for clinical application, especially for glioma. Here, we report the inflammation-activatable engineered neutrophils by internalizing doxorubicin-loaded magnetic mesoporous silica nanoparticles (ND-MMSNs) which can provide the potential for magnetic resonance (MR) imaging tracking of the drug-loaded cells to actively target inflamed brain tumor after surgical resection of primary tumor. The phagocytized D-MMSNs possess high drug loading efficiency and do not affect the host neutrophils' viability, thus remarkably improving intratumoral drug concentration and delaying relapse of surgically treated glioma. Our study offers a new strategy in targeted cancer theranostics through combining the merits of living cells and nanoparticle carriers.

Noninvasive and Local Delivery of Adenoviral-Mediated Herpes Simplex Virus Thymidine Kinase to Treat Glioma Through Focused Ultrasound-Induced Blood-Brain Barrier Opening in Rats.

Adenoviral-mediated gene therapy has been shown great prospects for tumor treatment. However, it is still a great challenge for its application in the glioma. A main cause is the blood-brain barrier (BBB) limits the delivery of adenoviral vectors, greatly compromising their efficacy. Here, we used focused ultrasound (FUS) induced microbubble cavitation to locally and reversibly open BBB for enhancing gene delivery. In this study, Ad-CMV-TK-IRES-EGFP (Ad-HSV-TK-EGFP) carrying the herpes simplex virus thymidine kinase (HSV-TK) and EGFP transgenes was chose as gendicine and Ad-CMV-IRES-EGFP (Ad-EGFP) as the control. The in vitro experiments showed that Ad-HSV-TK-EGFP had a high infection efficiency for C6 glioma cells, producing good tumor cell killing effects when these cells were exposed to more than 10 µg/ml ganciclovir (GCV). Taking advantage of FUS-induced BBB opening, Ad-HSV-TK-EGFP could be effectively delivered into the brain tumors, getting the overexpression of HSV-TK gene in the tumor cells. After exposure to GCV, the significantly stronger anti-tumor efficacy and longer survival time were observed in tumor-bearing mice treated with Ad-HSV-TK-EGFP + FUS than those treated with Ad-EGFP + FUS or only Ad-HSV-TK-EGFP. Histological examination indicated that the reduced expression level of Ki67 proteins and the increased apoptotic tumor cells in tumor xenografts, causing the inhibition of tumor growth. In conclusion, our study provided a new strategy to efficiently and locally deliver recombinant adenoviral vector-mediated HSV-TK gene into the brain to treat glioma.

Ultrasound-Triggered Drug Delivery for Breast Tumor Therapy Through iRGD-Targeted Paclitaxel-Loaded Liposome-Microbubble Complexes.

Liposome-microbubble complexes (LMC) have become a promising therapeutic carrier for ultrasound-triggered local drug release. However, it is still desirable for the released drugs to be delivered to tumors as effectively as possible. Here, we fabricated iRGD-targeted paclitaxel-loaded liposome-microbubble complexes (iRGD-PTX-LMC) and investigated the feasibility of enhancing the local drug delivery to breast tumors by using these complexes along with ultrasound irradiation. Our results showed that iRGD-modified PTX-loaded liposomes (iRGD-PTX-PL) were successfully conjugated to the surface of microbubbles (MBs) through biotin-avidin linkage. The resulting iRGD-PTX-LMC retained the ultrasound imaging capability and showed effective ultrasound-triggered drug release. High cell affinity and enhanced drug delivery into tumor cells was confirmed for iRGD-PTX-LMC upon ultrasound exposure. Additionally, our data revealed that iRGD-PTX-LMC with ultrasound had a significantly better tumor growth inhibition effect than iRGD-PTX-PL or nontargeted PTX-LMC in not only in vitro but also in vivo studies. Histological examination indicated that the inhibition of tumor growth was caused by the increases in the drug concentration and the number of apoptotic tumor cells in tumor xenografts. In conclusion, our study revealed the great potential of iRGD-PTX-LMC as a new tool to enhance local drug delivery and significantly improve antitumor efficacy.

Focused Ultrasound-Augmented Delivery of Biodegradable Multifunctional Nanoplatforms for Imaging-Guided Brain Tumor Treatment.

The blood brain barrier is the main obstacle to delivering diagnostic and therapeutic agents to the diseased sites of brain. It is still of great challenge for the combined use of focused ultrasound (FUS) and theranostic nanotechnology to achieve noninvasive and localized delivery of chemotherapeutic drugs into orthotopic brain tumor. In this work, a unique theranostic nanoplatform for highly efficient photoacoustic imaging-guided chemotherapy of brain tumor both in vitro and in vivo, which is based on the utilization of hollow mesoporous organosilica nanoparticles (HMONs) to integrate ultrasmall Cu2-x Se particles on the surface and doxorubicin inside the hollow interior, is synthesized. The developed multifunctional theranostic nanosystems exhibit tumor-triggered programmed destruction due to the reducing microenvironment-responsive cleavage of disulfide bonds that are incorporated into the framework of HMONs and linked between HMONs and Cu2-x Se, resulting in tumor-specific biodegradation and on-demand drug-releasing behavior. Such tumor microenvironment-responsive biodegradable and biocompatible theranostic nanosystems in combination with FUS provide a promising delivery nanoplatform with high performance for orthotopic brain tumor imaging and therapy.

Tumor-penetrating Peptide-integrated Thermally Sensitive Liposomal Doxorubicin Enhances Efficacy of Radiofrequency Ablation in Liver Tumors.

Purpose To investigate the role of a tumor-penetrating peptide (internalizing CRGDRGPDC [iRGD])-integrated thermally sensitive liposomal (TSL) doxorubicin (DOX) in combination with radiofrequency (RF) ablation of liver tumors in an animal model. Materials and Methods Approval from the institutional animal care and use committee was obtained. Characterization of iRGD-TSL-DOX was performed in vitro. Next, H22 liver adenocarcinomas were implanted in 138 mice in vivo. The DOX accumulation and cell apoptosis of iRGD-TSL-DOX and TSL-DOX with or without RF were evaluated (n = 5) at different time points after treatment with quantitative analysis or pathologic staining. Mice bearing tumors were randomized into the following six groups (each group, eight mice): no treatment, iRGD-TSL-DOX, TSL-DOX, RF alone, RF ablation followed by TSL-DOX at 30 minutes (TSL-DOX combined with RF), and RF ablation followed by iRGD-TSL-DOX (iRGD-TSL-DOX combined with RF). Kaplan-Meier method was used to estimate the survival curves and log-rank test was used for comparison with statistical software. Results DOX encapsulation efficiency in iRGD-TSL-DOX was 97.5% ± 1.3 (standard deviation) with temperature-dependent drug release capability confirmed in vitro. In vivo, the iRGD-TSL-DOX group had overall higher DOX concentration in the tumor and had maximal difference at 24 hours compared with TSL-DOX group (2.7-fold). RF caused more intense cell apoptosis at 24 hours (median, 65% vs 21%, respectively; P < .001). For end-point survival, the iRGD-TSL-DOX combined with RF group had better survival (median, 32 days) than TSL-DOX combined with RF (median, 27 days; P = .035) or RF alone (median, 21 days; P < .001). Conclusion Conjugation to iRGD helped to improve intratumoral DOX accumulation and further enhanced the activity of TSL-DOX in RF ablation of liver tumors. © RSNA, 2017 Online supplemental material is available for this article.

Hyperthermia-triggered drug delivery from iRGD-modified temperature-sensitive liposomes enhances the anti-tumor efficacy using high intensity focused ultrasound.

An important limitation to successful cancer treatment with chemotherapeutics is the inability to achieve therapeutically effective drug concentrations while avoiding healthy tissue damage. In this work, a new tumor-targeting peptide iRGD (CCRGDKGPDC) was used to modify drug-loaded low temperature-sensitive liposomes (iRGD-LTSL-DOX) to explore the anti-tumor effects in combination with high intensity focused ultrasound (HIFU) in vitro and in vivo. iRGD-LTSL-DOX can specifically target to ανß3-positive cells and locally release the encapsulated doxorubicin (DOX) in a hyperthermia-triggered manner. In vivo results showed that DOX from iRGD-LTSL-DOX was intravascularly released and rapidly penetrated into tumor interstitial space after HIFU-triggered heat treatment, thereby overcoming the limited tumor penetration of anticancer drugs. Significantly stronger anti-tumor efficacy further supported the effective combination of iRGD-LTSL-DOX with HIFU-induced hyperthermia. Our study provided a novel tumor-targeting LTSL-DOX and demonstrated its usefulness in HIFU-induced hyperthermia-triggered drug delivery.

IR-780 Dye as a Sonosensitizer for Sonodynamic Therapy of Breast Tumor.

Sonodynamic therapy (SDT) has become a new modality for cancer therapy through activating certain chemical sensitizers by ultrasound (US). Discovery and development of novel sonosensitizers are attracting extensive attentions. Here, we introduce IR-780 iodide, a lipophilic heptamethine dye with a peak optical absorption of 780 nm wavelength, which can function as SDT agents for breast cancer treatment. The in vitro cellular uptake, cell viability, and the generation levels of reactive oxygen species (ROS) were examined by using 4T1 breast cancer cells incubated with various concentrations of IR-780 followed by US irradiation. Our results showed a dose- and time-dependent cellular uptake of IR-780 iodide in 4T1 cancer cells. Significant lower viabilities and more necrotic/apoptotic cells were found when these cancer cells were treated with IR-780 iodide with US irradiation. Further analyzing the generation of ROS demonstrated significant increase of (1)O2 level and H2O2, but not ⋅OH in the SDT-treated cells. The in vivo anti-tumor efficacy of SDT with IR-780 revealed significant tumor growth inhibition of xenografts of 4T1 cancer cells; it was further confirmed by histological analysis and TUNEL staining. Our results strongly suggest that SDT combined with IR-780 may provide a promising strategy for tumor treatment with minimal side effects.

Molecular imaging-guided photothermal/photodynamic therapy against tumor by iRGD-modified indocyanine green nanoparticles.

Multifunctional near-infrared (NIR) nanoparticles demonstrate great potential in tumor theranostic applications. To achieve the sensitive detection and effective phototherapy in the early stage of tumor genesis, it is highly desirable to improve the targeting of NIR theranostic agents to biomarkers and to enhance their accumulation in tumor. Here we report a novel targeted multifunctional theranostic nanoparticle, internalized RGD (iRGD)-modified indocyanine green (ICG) liposomes (iRGD-ICG-LPs), for molecular imaging-guided photothermal therapy (PTT) and photodynamic therapy (PDT) therapy against breast tumor. The iRGD peptides with high affinity to αvß3 integrin and effective tumor-internalized property were firstly used to synthesize iRGD-PEG2000-DSPE lipopeptides, which were further utilized to fabricate the targeted ICG liposomes. The results indicated that iRGD-ICG-LPs exhibited excellent stability and could provide an accurate and sensitive detection of breast tumor through NIR fluorescence molecular imaging. We further employed this nanoparticle for tumor theranostic application, demonstrating significantly higher tumor accumulation and tumor inhibition efficacy through PTT/PDT effects. Histological analysis further revealed much more apoptotic cells, confirming the advantageous anti-tumor effect of iRGD-ICG-LPs over non-targeted ICG-LPs. Notably, the targeting therapy mediated by iRGD provides almost equivalent anti-tumor efficacy at a 12.5-fold lower drug dose than that by monoclonal antibody, and no tumor recurrence and obvious treatment-induced toxicity were observed in our study. Our study provides a promising strategy to realize the sensitive detection and effective treatment of tumors by integrating molecular imaging into PTT/PDT therapy.

A Disposable Microfluidic Device for Controlled Drug Release from Thermal-Sensitive Liposomes by High Intensity Focused Ultrasound.

The drug release triggered thermally by high intensity focused ultrasound (HIFU) has been considered a promising drug delivery strategy due to its localized energy and non-invasive characters. However, the mechanism underlying the HIFU-mediated drug delivery remains unclear due to its complexity at the cellular level. In this paper, micro-HIFU (MHIFU) generated by a microfluidic device is introduced which is able to control the drug release from temperature-sensitive liposomes (TSL) and evaluate the thermal and mechanical effects of ultrasound on the cellular drug uptake and apoptosis. By simply adjusting the input electrical signal to the device, the temperature of sample can be maintained at 37 °C, 42 °C and 50 °C with the deviation of ± 0.3 °C as desired. The flow cytometry results show that the drug delivery under MHIFU sonication leads to a significant increase in apoptosis compared to the drug release by incubation alone at elevated temperature of 42 °C. Furthermore, increased squamous and protruding structures on the surface membrane of cells were detected by atomic force microscopy (AFM) after MHIFU irradiation of TSL. We demonstrate that compared to the routine HIFU treatment, MHIFU enables monitoring of in situ interactions between the ultrasound and cell in real time. Furthermore, it can quantitatively analyze and characterize the alterations of the cell membrane as a function of the treatment time.

A Lipopeptide-Based αvß3 Integrin-Targeted Ultrasound Contrast Agent for Molecular Imaging of Tumor Angiogenesis.

The design and fabrication of targeted ultrasound contrast agents are key factors in the success of ultrasound molecular imaging applications. Here, we introduce a transformable αvß3 integrin-targeted microbubble (MB) by incorporation of iRGD-lipopeptides into the MB membrane for non-invasive ultrasound imaging of tumor angiogenesis. First, the iRGD-lipopeptides were synthesized by conjugating iRGD peptides to distearoylphosphatidylethanolamine-polyethylene glycol 2000-maleimide. The resulting iRGD-lipopeptides were used for fabrication of the iRGD-carrying αvß3 integrin-targeted MBs (iRGD-MBs). The binding specificity of iRGD-MBs for endothelial cells was found to be significantly stronger than that of control MBs (p < 0.01) under in vitro static and dynamic conditions. The binding of iRGD-MBs on the endothelial cells was competed off by pre-incubation with the anti-αv or anti-ß3 antibody (p < 0.01). Ultrasound images taken of mice bearing 4T1 breast tumors after intravenous injections of iRGD-MBs or control MBs revealed strong contrast enhancement within the tumors from iRGD-MBs but not from the control MBs; the mean acoustic signal intensity was 10.71 ± 2.75 intensity units for iRGD-MBs versus 1.13 ± 0.18 intensity units for the control MBs (p < 0.01). The presence of αvß3 integrin was confirmed by immunofluorescence staining. These data indicate that iRGD-MBs can be used as an ultrasound imaging probe for the non-invasive molecular imaging of tumor angiogenesis, and may have further implications for ultrasound image-guided tumor targeting drug delivery.

Reversal of multidrug resistance phenotype in human breast cancer cells using doxorubicin-liposome-microbubble complexes assisted by ultrasound.

The circumvention of multidrug resistance (MDR) plays a critically important role in the success of chemotherapy. The aim of this work is to investigate the effectiveness and possible mechanisms of the reversal of MDR phenotype in human breast cancer cells by using doxorubicin-liposome-microbubble complexes (DLMC) assisted by ultrasound (US). DLMC is fabricated through conjugating doxorubicin (DOX)-liposome (DL) to the surface of microbubbles (MBs) via the biotin-avidin linkage. The resulting drug-loaded complexes are then characterized and incubated with MCF-7/ADR human breast cancer cells and followed by US exposure. Our results show the more rapid cellular uptake, evident enhancement of nuclear accumulation and less drug efflux in the resistant cells treated by DLMC+US than those treated by DL, DL+verapamil under the same US treatment or DLMC without US. The enhanced drug delivery and cellular uptake also associated with the increase of cytotoxicity against MCF-7/ADR cells, lower MCF-7/ADR cell viability and higher apoptotic cells. Mechanism investigations further disclose a significant increase of reactive oxygen species (ROS) level, enhanced DNA damage and obvious reduction of P-glycoprotein expression in the resistant cells treated with DLMC+US compared with the control cases of cells treated by DLMC, DL+US or DL+verapamil+US. In conclusion, our study demonstrates that DLMC in combination with US may provide an effective delivery of drug to sensitize cells to circumvent MDR and to enhance the therapeutic index of the chemotherapy.

A novel cationic microbubble coated with stearic acid-modified polyethylenimine to enhance DNA loading and gene delivery by ultrasound.

A novel cationic microbubble (MB) for improvement of the DNA loading capacity and the ultrasound-mediated gene delivery efficiency has been developed; it has been prepared with commercial lipids and a stearic acid modified polyethylenimine 600 (Stearic-PEI600) polymer synthesized via acylation reaction of branched PEI600 and stearic acid mediated by N, N'-carbonyldiimidazole (CDI). The MBs' concentration, size distribution, stability and zeta potential (ζ-potential) were measured and the DNA loading capacity was examined as a function of the amount of Stearic-PEI600. The gene transfection efficiency and cytotoxicity were also examined using breast cancer MCF-7 cells via the reporter plasmid pCMV-Luc, encoding the firefly luciferase gene. The results showed that the Stearic-PEI600 polymer caused a significant increase in magnitude of ζ-potential of MBs. The addition of DNA into cationic MBs can shift ζ-potentials from positive to negative values. The DNA loading capacity of the MBs grew linearly from (5±0.2) ×10⁻³ pg/µm² to (20±1.8) ×10⁻³ pg/µm² when Stearic-PEI600 was increased from 5 mol% to 30 mol%. Transfection of MCF-7 cells using 5% PEI600 MBs plus ultrasound exposure yielded 5.76±2.58×10³ p/s/cm²/sr average radiance intensity, was 8.97- and 7.53-fold higher than those treated with plain MBs plus ultrasound (6.41±5.82) ×10² p/s/cm²/sr, (P<0.01) and PEI600 MBs without ultrasound (7.65±6.18) ×10² p/s/cm²/sr, (P<0.01), respectively. However, the PEI600 MBs showed slightly higher cytotoxicity than plain MBs. The cells treated with PEI600-MBs and plain MBs plus ultrasound showed 59.5±6.1% and 71.4±7.1% cell viability, respectively. In conclusion, our study demonstrated that the novel cationic MBs were able to increase DNA loading capacity and gene transfection efficiency and could be potentially applied in targeted gene delivery and therapy.

Paclitaxel-liposome-microbubble complexes as ultrasound-triggered therapeutic drug delivery carriers.

Liposome-microbubble complexes (LMC) have become a promising therapeutic carrier for ultrasound-triggered drug delivery to treat malignant tumors. However, the efficacy for ultrasound-assisted chemotherapy in vivo and the underlying mechanisms remain to be elucidated. Here, we investigated the feasibility of using paclitaxel-liposome-microbubble complexes (PLMC) as possible ultrasound (US)-triggered targeted chemotherapy against breast cancer. PTX-liposomes (PL) were conjugated to the microbubble (MB) surface through biotin-avidin linkage, increasing the drug-loading efficiency of MBs. The significant increased release of payloads from liposome-microbubble complexes was achieved upon US exposure. We used fluorescent quantum dots (QDs) as a model drug to show that released QDs were taken up by 4T1 breast cancer cells treated with QD-liposome-microbubble complexes (QLMC) and US, and uptake depended on the exposure time and intensity of insonication. We found that PLMC plus US inhibited tumor growth more effectively than PL plus US or PLMC without US, not only in vitro, but also in vivo. Histologically, the inhibition of tumor growth appeared to result from increased apoptosis and reduced angiogenesis in tumor xenografts. In addition, a significant increase of drug concentration in tumors was observed in comparison to treatment with non-conjugated PL or PLMC without US. The significant increase in an antitumor efficacy of PLMC plus US suggests their potential use as a new targeted US chemotherapeutic approach to inhibit breast cancer growth.

Effects of the novel vascular targeting agent MDS-11P on tumor vascularity and its antitumor activity.

Vascular disrupting agents show selective effects on tumor established vasculature, and achieve encouraging results in both pre-clinical and clinical experiments. In the present study, we investigated the effects of a new CA4 derivative MDS-11 and its prodrug MDS-11P on vascular disrupting activity in vitro and in vivo. Surface plasmon resonance (SPR) and tubulin polymerization assay showed that MDS-11 interacted with tubulin directly and inhibited tubulin polymerization in a cell free system, and western blot assay further confirmed the action in the cellular level. MDS-11 was found to significantly disrupt the microtubulin skeleton in proliferating HUVECs than quiescent ones determined by confocal microscopy. Furthermore, MDS-11 was found to damage the HUVEC-formed tube quickly, but did not influence structures of microvessels from aortic ring possessing pericytes and smooth muscle cells until 3 h treatment. In A549 xenograft mice, immunohistochemistry staining of tumor sections revealed that a single dose of MDS-11P led to large areas of necrosis within tumor and reduced the number of tumor vessels, which was consolidated by perfused vascular volume assay. Pharmacokinetic studies of MDS-11P indicated that MDS-11P rapidly converted to the active form, MDS-11, and exhibited a much faster elimination in mice. The antitumor analysis using H22 and A549 mice xenograft models revealed that the growth inhibition rates of MDS-11P at 50 mg/kg (twice a day for three weeks) reached 59.4%, 60.5% respectively without obvious weight loss. Taken together, these results suggest that MDS-11 is a potential vascular disrupting agent for further development of antitumor drug.