Anti-angiogenic gene therapy for hepatocellular carcinoma mediated by microbubble-enhanced ultrasound exposure: an in vivo experimental study

Synchronous Intravital Imaging and Cavitation Monitoring of Antivascular Focused Ultrasound in Tumor Microvasculature Using Monodisperse Low Boiling Point Nanodroplets

Focused ultrasound-stimulated microbubbles can induce blood flow shutdown and ischemic necrosis at higher pressures in an approach termed antivascular ultrasound. Combined with conventional therapies of chemotherapy, immunotherapy, and radiation therapy, this approach has demonstrated tumor growth inhibition and profound synergistic antitumor effects. However, the lower cavitation threshold of microbubbles can potentially yield off-target damage that the polydispersity of clinical agent may further exacerbate. Here we investigate the use of a monodisperse nanodroplet formulation for achieving antivascular effects in tumors. We first develop stable low boiling point monodisperse lipid nanodroplets and examine them as an alternative agent to mediate antivascular ultrasound. With synchronous intravital imaging and ultrasound monitoring of focused ultrasound-stimulated nanodroplets in tumor microvasculature, we show that nanodroplets can trigger blood flow shutdown and do so with a sharper pressure threshold and with fewer additional events than conventionally used microbubbles. We further leverage the smaller size and prolonged pharmacokinetic profile of nanodroplets to allow for potential passive accumulation in tumor tissue prior to antivascular ultrasound, which may be a means by which to promote selective tumor targeting. We find that vascular shutdown is accompanied by inertial cavitation and complex-order sub- and ultraharmonic acoustic signatures, presenting an opportunity for effective feedback control of antivascular ultrasound.

Suicide Gene Delivery System Mediated by Ultrasound-Targeted Microbubble Destruction: A Promising Strategy for Cancer Therapy

The treatment of malignant tumors has always been one of the challenges that have plagued researchers and clinicians. The ideal status in cancer treatment is to eliminate tumor cells while avoiding damage to normal tissues. Different approaches have been investigated to achieve such a goal, and suicide gene therapy has emerged as a novel mode of cancer treatment. This approach involves the delivery of genes encoding enzymes that activate non-toxic prodrugs into cytotoxic metabolites that cause the death of transfected cancer cells. Despite promising results obtained both in vitro and in vivo, this innovative approach has long been stalled in the clinic due to the lack of a suitable delivery system to introduce the suicide gene into cancer cells. Ultrasound-targeted microbubble destruction (UTMD) represents a valuable non-viral vector system for site-specific and noninvasive gene therapy. Ultrasound promotes intracellular uptake of therapeutic agents by increasing vascular and cell membrane permeability, especially in the presence of microbubbles. In this scenario, the true potential of suicide genes can be translated into clinically valuable treatments for patients. This review provides background information on suicide gene therapy and UTMD technology, summarizes the current state of knowledge about UTMD-mediated suicide gene delivery in cancer treatment, and presents an outlook on its future development.

Ultrasound-sensitive siRNA-loaded nanobubbles fabrication and antagonism in drug resistance for NSCLC

Due to the lack of safe, effective, and gene-targeted delivery technology. In this study, we have prepared nanobubbles loaded PDLIM5 siRNA (PDLIM5siRNA-NBs) to investigate the transfection efficiency and their antagonism in drug resistance in combination with ultrasound irradiation for non-small-cell lung cancer (NSCLC). Research results show that the PDLIM5 siRNA are effectively bound to the shell of NBs with a mean diameter of 191.6 ± 0.50 nm and a Zeta potential of 11.8 ± 0.68 mV. And the ultrasonic imaging indicated that the PDLIM5 siRNA NBs maintain the same signals as the microbubbles (SonoVue). Under the optimized conditions of 0.5 W/m² ultrasound intensity and 1 min irradiation duration, the highest transfection efficiency of PC9GR cells was 90.23 ± 1.45%, which resulted in the inhibition of PDLIM5 mRNA and protein expression. More importantly, the anti-tumor effect of fabricated PDLIM5siRNA-NBs with the help of ultrasound irradiation has been demonstrated to significantly inhibit tumor cell growth and promote apoptosis. Therefore, NBs carrying PDLIM5siRNA may have the potential to act as gene vectors combined with ultrasound irradiation to antagonize drug resistance for NSCLC.

Ultrasonic particles: An approach for targeted gene delivery

Gene therapy has been widely investigated for the treatment of genetic, acquired, and infectious diseases. Pioneering work utilized viral vectors; however, these are suspected of causing serious adverse events, resulting in the termination of several clinical trials. Non-viral vectors, such as lipid nanoparticles, have attracted significant interest, mainly due to their successful use in vaccines in the current COVID-19 pandemic. Although they allow safe delivery, they come with the disadvantage of off-target delivery. The application of ultrasound to ultrasound-sensitive particles allows for a direct, site-specific transfer of genetic materials into the organ/site of interest. This process, termed ultrasound-targeted gene delivery (UTGD), also increases cell membrane permeability and enhances gene uptake. This review focuses on the advances in ultrasound and the development of ultrasonic particles for UTGD across a range of diseases. Furthermore, we discuss the limitations and future perspectives of UTGD.

Ultrasound-enhanced fluorescence imaging and chemotherapy of multidrug-resistant tumors using multifunctional dendrimer/carbon dot nanohybrids

Development of innovative nanomedicine enabling enhanced theranostics of multidrug-resistant (MDR) tumors remains to be challenging. Herein, we report the development of a newly designed multifunctional yellow-fluorescent carbon dot (y-CD)/dendrimer nanohybrids as a platform for ultrasound (US)-enhanced fluorescence imaging and chemotherapy of MDR tumors. Generation 5 (G5) poly(amidoamine) dendrimers covalently modified with efflux inhibitor of d-α-tocopheryl polyethylene glycol 1000 succinate (G5-TPGS) were complexed with one-step hydrothermally synthesized y-CDs via electrostatic interaction. The formed G5-TPGS@y-CDs complexes were then physically loaded with anticancer drug doxorubicin (DOX) to generate (G5-TPGS@y-CDs)-DOX complexes. The developed nanohybrids display a high drug loading efficiency (40.7%), strong y-CD-induced fluorescence emission, and tumor microenvironment pH-preferred DOX release profile. Attributing to the DOX/TPGS dual drug design, the (G5-TPGS@y-CDs)-DOX complexes can overcome the multidrug resistance (MDR) of cancer cells and effectively inhibit the growth of cancer cells and tumors. Furthermore, the introduction of US-targeted microbubble destruction technology was proven to render the complexes with enhanced intracellular uptake and anticancer efficacy in vitro and improved chemotherapeutic efficacy and fluorescence imaging of tumors in vivo due to the produced sonoporation effect. The developed multifunctional dendrimer/CD nanohybrids may represent an advanced design of nanomedicine for US-enhanced theranostics of different types of MDR tumors.

Ultrasound and microbubble mediated therapeutic delivery: Underlying mechanisms and future outlook

Beyond the emerging field of oncological ultrasound molecular imaging, the recent significant advancements in ultrasound and contrast agent technology have paved the way for therapeutic ultrasound mediated microbubble oscillation and has shown that this approach is capable of increasing the permeability of microvessel walls while also initiating enhanced extravasation and drug delivery into target tissues. In addition, a large number of preclinical studies have demonstrated that ultrasound alone or combined with microbubbles can efficiently increase cell membrane permeability resulting in enhanced tissue distribution and intracellular drug delivery of molecules, nanoparticles, and other therapeutic agents. The mechanism behind the enhanced permeability is the temporary creation of pores in cell membranes through a phenomenon called sonoporation by high-intensity ultrasound and microbubbles or cavitation agents. At low ultrasound intensities (0.3-3 W/cm²), sonoporation may be caused by microbubbles oscillating in a stable motion, also known as stable cavitation. In contrast, at higher ultrasound intensities (greater than 3 W/cm²), sonoporation usually occurs through inertial cavitation that accompanies explosive growth and collapse of the microbubbles. Sonoporation has been shown to be a highly effective method to improve drug uptake through microbubble potentiated enhancement of microvascular permeability. In this review, the therapeutic strategy of using ultrasound for improved drug delivery are summarized with the special focus on cancer therapy. Additionally, we discuss the progress, challenges, and future of ultrasound-mediated drug delivery towards clinical translation.

EXPERIMENTAL COMPARISON OF MCF7 AND MCF10A RESPONSE TO LOW INTENSITY ULTRASOUND

The low-intensity ultrasound effects on MCF7 (human breast adenocarcinoma) and MCF10A (healthy breast cells) have been investigated at different sonication protocol to probe the effectiveness and the selectivity of the ultrasound (US) treatment and to understand the implications between cell mortality, biomechanical interactions and cell elastic modulus. Experiments performed at fixed and variable frequency demonstrated the effectiveness of some protocols in killing carcinogenic cells and the healthy cells insensitivity. Variation of elastic properties of MCF7 cells exposed to US under varying sonication conditions was examined. Sonication was carried out at fixed frequency (as it is usually done in therapy protocols), between 400[Formula: see text]kHz and 620[Formula: see text]kHz, following two protocols: (i) at fixed power output; (ii) at fixed voltage of the US generator. Evolution of cell stiffness during the US treatment was monitored via atomic force spectroscopy (AFS). It was found that cell mortality has a similar trend of variation with respect to sonication frequency regardless of the way specimens are exposed to US. Mechanical properties do not show a uniform trend with respect to frequency, but variations of Young’s modulus are more marked near the very low (400–480) kHz or very high frequencies (580–620) kHz. The observed variations may be related to mechanical interactions occurring in the cell culture, suggesting a primacy of the environment on other factors.

Penile prosthesis biofilm formation and emerging therapies against them

Infections are among the most feared and devastating complications of penile prosthesis infections, often requiring surgical exploration and explantation are prosthesis infections. While the rate of infections have decreased due to antibiotic prophylaxis, antiseptic device preparation, increased sterility in implantation techniques and device modifications, infections still occur at a rate of 1-3%. This article reviews the formation of biofilms on penile prostheses and novel, experimental methods to prevent and eradicate them.

Low‑frequency ultrasound and microbubbles combined with simvastatin promote the apoptosis of MCF‑7 cells by affecting the LATS1/YAP/RHAMM pathway

Ultrasound scanning has widespread used in clinical practice and also has therapeutic applications. Simvastatin is a statins that is able to competitively inhibit the activity of 3‑hydroxy‑3‑methylglutaryl‑coenzyme A reductase. The aim of the present study was to investigate the roles and mechanisms of low‑frequency ultrasound (LFU) and microbubbles combined with simvastatin on MCF‑7 cell growth and apoptosis. Cell viability, apoptosis and cell cycle were evaluated using an MTT assay and flow cytometry, respectively. The expression of related proteins was measured by western blot assay. The results revealed that simvastatin and LFU with microbubbles reduces the viability of MCF‑7 cells. The combination of LFU and microbubbles with simvastatin promoted the apoptosis of MCF‑7 cells. Furthermore, it was confirmed that LFU and microbubbles combined with simvastatin affected the large tumor suppressor 1 (LATS1)/yes‑associated protein (YAP)/receptor of the hyaluronan‑mediated motility (RHAMM) pathway in MCF‑7 cells. It was determined that LATS1 acts as a negative regulator in the LATS1/YAP/RHAMM pathway in MCF‑7 cells. In conclusion, the results of the present study indicate that LFU and microbubbles combined with simvastatin promotes the apoptosis of MCF‑7 cells via the LATS1/YAP/RHAMM pathway. The present study suggested a possible strategy for the treatment of breast cancer.

Sonodynamic therapy (SDT): a novel strategy for cancer nanotheranostics

Sonodynamic therapy (SDT) is a promising non-invasive therapeutic modality. Compared to photo-inspired therapy, SDT provides many opportunities and benefits, including deeper tissue penetration, high precision, less side effects, and good patient compliance. Thanks to the facile engineerable nature of nanotechnology, nanoparticles-based sonosensitizers exhibit predominant advantages, such as increased SDT efficacy, binding avidity, and targeting specificity. This review aims to summarize the possible mechanisms of SDT, which can be expected to provide the theoretical basis for SDT development in the future. We also extensively discuss nanoparticle-assisted sonosensitizers to enhance the outcome of SDT. Additionally, we focus on the potential strategy of combinational SDT with other therapeutic modalities and discuss the limitations and challenges of SDT toward clinical applications.

Ultrasound-guided drug delivery in cancer

Recent advancements in ultrasound and microbubble (USMB) mediated drug delivery technology has shown that this approach can improve spatially confined delivery of drugs and genes to target tissues while reducing systemic dose and toxicity. The mechanism behind enhanced delivery of therapeutics is sonoporation, the formation of openings in the vasculature, induced by ultrasound-triggered oscillations and destruction of microbubbles. In this review, progress and challenges of USMB mediated drug delivery are summarized, with special focus on cancer therapy.

Study of cellular response induced by low intensity ultrasound frequency sweep pattern on myelomonocytic lymphoma U937 cells

PURPOSE

This study will analyze the mechanical effects (immediate lysis) and biological effects (cell survival, apoptosis, cell cycle) on U937 cells subjected to different sonication conditions with increasing and decreasing frequencies and burst rate (number of burst of a repeating signal in a specific time unit), in order to determine the best conditions of sonication to produce high mortality, apoptosis and inhibition of hyperproliferation.

METHOD

Cells are been stressed by pulse wave ultrasounds with increasing and decreasing frequencies between 400 and 620 kHz, at burst rates of 0.5, 10, 50 Hz and 50 % duty cycle (percentage of one period in which a signal is active), ultrasound intensities (spatial average-temporal peak) 0.045 and 0.09 W/cm(2). The sonication durations were 90 and 180 s.

RESULTS

The decreasing mode was found to be better than the increasing mode for 10 and 50 Hz burst rates, while at 0.5 Hz the increasing mode gave better results for the time of 180 s. For 10 Hz burst rate, decreasing frequency, 180 s, 0.09 W/cm(2), 20 % survival rate was found; after 6-h incubation, cells showed 13 % of early apoptosis and 11 % of late apoptosis. For these conditions of sonication, the hyperproliferation of cells was inhibited.

CONCLUSION

Survival rate decreases for increasing intensity and duration with each burst rate. The best performance is decreasing mode in a range between 620 and 400 kHz, duty cycle 50 %, burst rate 10 Hz. In these conditions after 180 s duration, the average survival rate is 20 %, the survived cells manifest apoptosis after 6-h incubation and hyperproliferation is prevented. The results seem to lead toward a non-invasive and effective purging of leukemic cells.

Ultrasound-targeted microbubble destruction in gene therapy: A new tool to cure human diseases

Human gene therapy has made significant advances in less than two decades. Within this short period of time, gene therapy has proceeded from the conceptual stage to technology development and laboratory research, and finally to clinical trials for the treatment of a variety of deadly diseases. Cardiovascular disease, cancer, and stroke are leading causes of death worldwide. Despite advances in medical, interventional, radiation and surgical treatments, the mortality rate remains high, and the need for novel therapies is great. Gene therapy provides an efficient approach to disease treatment. Notable advances in gene therapy have been made for genetic disorders, including severe combined immune deficiency, chronic granulomatus disorder, hemophilia and blindness, as well as for acquired diseases, including cancer and neurodegenerative and cardiovascular diseases. However, lack of an efficient delivery system to target cells as well as the difficulty of sustained expression of transgenes has hindered advancements in gene therapy. Ultrasound targeted microbubble destruction (UTMD) is a promising approach for target-specific gene delivery, and it has been successfully investigated for the treatment of many diseases in the past decade. In this paper, we review UTMD-mediated gene delivery for the treatment of cardiovascular diseases, cancer and stroke.

Sonoporation: Applications for Cancer Therapy

Therapeutic efficacy of both traditional chemotherapy and gene therapy in cancer is highly dependent on the ability to deliver drugs across natural barriers, such as the vessel wall or tumor cell membranes. In this regard, sonoporation induced by ultrasound-guided microbubble (USMB) destruction has been widely investigated in the enhancement of therapeutic drug delivery given it can help overcome these natural barriers, thereby increasing drug delivery into cancer. In this chapter we discuss challenges in current cancer therapy and how some of these challenges could be overcome using USMB-mediated drug delivery. We particularly focus on recent advances in delivery approaches that have been developed to further improve therapeutic efficiency and specificity of various cancer treatments. An example of clinical translation of USMB-mediated drug delivery is also shown.

Combined effect of ultrasound/SonoVue microbubble on CD4(+)CD25(+) regulatory T cells viability and optimized parameters for its transfection

The purpose of this study was to investigate the combined effect of ultrasound and SonoVue microbubble on CD4(+)CD25(+) regulatory T cells (Tregs) viability and to explore the appropriate parameters for Tregs transfection. Tregs were separated from peripheral venous blood of patients with hepatocellular carcinoma and seeded in 96-well plates. The optimal ultrasound exposure time and optimal SonoVue microbubble concentration for Tregs were measured by mechanical index (MI) of 1.2 or 1.4, exposure time of 0, 30, 60, 90, 120, 150, 180s, and 0, 10, 20, 30, 40, 50μL/100μL microbubble per well, respectively. In addition, the combined effect of ultrasound and microbubble on Tregs viability was evaluated according to the following parameters: MI 1.2/1.4+exposure time of 120, 150, 180s+0, 10, 20, 30, 40, 50μL/100μL microbubble per well. Tregs viability investigations were performed in order to explore the optimal transfection condition. The efficiency of plasmid transfer was determined by detection of luciferase activity on the microscopic examinations. The proliferation of Tregs could be promoted by ultrasound exposures, while being decreased with the increasing concentration of microbubbles. Under the current experimental conditions, the optimal ultrasound parameters were MI=1.4 and exposure time=150/180s. The optimal microbubble concentration was 10μL/100μL. Compared with treatment with ultrasound or microbubbles alone, the transfection efficiency of Tregs improved 50% by combining ultrasound and microbubble. The results indicate that both ultrasound and microbubble could affect the Tregs proliferation and the optimal Treg transfection rate was obtained by treating with 10% microbubbles and ultrasound exposure for 150/180s under ultrasound MI of 1.4.

Using the Promise of Sonodynamic Therapy in the Clinical Setting against Disseminated Cancers

Sonodynamic therapy (SDT) is a form of ultrasound therapy in which specialized chemotherapeutic agents known as sonosensitizers are administered to increase the efficacy of ultrasound-mediated preferential damage of neoplastic cells. Multiple in vitro and in vivo studies have indicated that SDT has the ability to exhibit profound physical and chemical changes on cellular structure. As supportive as the data have been, assessment of this method at the clinical level has been limited to only solid tumors. Although SDT has shown efficacy against multiple adherent neoplastic cell lines, it has also shown particular promise with leukemia-derived cell lines. Potential procedures to administer SDT to leukemia patients are heating the appendages as ultrasound is applied to these areas (Heat and Treat), using an ultrasound probe to scan the body for malignant growths (Target and Destroy), and extracorporeal blood sonication (EBS) through dialysis. Each method offers a unique set of benefits and concerns that will need to be evaluated in preclinical mammalian models of malignancy before clinical examination can be considered.

A review of low-intensity ultrasound for cancer therapy

The literature describing the use of low-intensity ultrasound in four major areas of cancer therapy-sonodynamic therapy, ultrasound-mediated chemotherapy, ultrasound-mediated gene delivery and anti-vascular ultrasound therapy-was reviewed. Each technique consistently resulted in the death of cancer cells, and the bio-effects of ultrasound were attributed primarily to thermal actions and inertial cavitation. In each therapeutic modality, theranostic contrast agents composed of microbubbles played a role in both therapy and vascular imaging. The development of these agents is important as it establishes a therapeutic-diagnostic platform that can monitor the success of anti-cancer therapy. Little attention, however, has been given either to the direct assessment of the mechanisms underlying the observed bio-effects or to the viability of these therapies in naturally occurring cancers in larger mammals; if such investigations provided encouraging data, there could be prompt application of a therapy technique in the treatment of cancer patients.

Apoptosis induced by sonodynamic therapy in human osteosarcoma cells in vitro

The aim of the present study was to investigate the potential effect of hematoporphyrin monomethyl ether-sonodynamic therapy (HMME-SDT) on MG-63 osteosarcoma cells. The HMME concentration was kept constant at 20 µg/ml and the MG-63 osteosarcoma cell line was exposed to ultrasound with an intensity of 1.0 W/cm2 for 30 sec. Cell cytotoxicity was quantified using an MTT assay 6 h after HMME-SDT. The intracellular localization of HMME was imaged using inverted confocal laser scanning microscopy. Apoptosis was investigated using flow cytometry with Annexin V-fluorescein isothiocyanate and propidium iodine staining. The cytotoxicity of HMME-mediated sonodynamic action on MG-63 cells was significantly higher than that of other treatments, including ultrasound alone, HMME alone and sham treatment. Flow cytometry demonstrated that HMME‑SDT action markedly enhanced the apoptotic rate of MG-63 cells. The mechanisms of apoptosis were analyzed by measuring the protein expression of poly ADP-ribose polymerase (PARP), cleaved PARP, procaspase-3, cleaved caspase-3 and cleaved caspase-9. The data demonstrated that HMME-SDT action markedly induced the apoptosis of MG-63 cells.

Gene silencing of Rac1 with RNA interference mediated by ultrasound and microbubbles in human LoVo cells: evaluation of cell invasion inhibition and metastatic

OBJECTIVE

The objective of this study was to assess the change of cytoskeleton and cell cycle in LoVo (human colorectal cancer) cell via gene silencing of Rac1 with RNA interference mediated by microbubble (SonoVue) and ultrasound (US).

METHODS

The compound of plasmid Rac1-shRNA, LoVo cells, and SonoVue was exposed to US (1 MHz, 2 W/cm(2), 5 min). The expression of Rac1 mRNA and Rac1 protein was detected by RT-PCR and Western blot. Cytoskeleton was taken by confocal microscope in a random fashion. Cell invasion was assayed using modified Boyden chambers, and cell cycle and apoptosis were analyzed by flow cytometry in LoVo cells.

RESULTS

Rac1 gene is overexpressed in human colorectal cancer cells, gene silencing of Rac1 with RNA interference mediated by microbubble and US strongly inhibited lamellipodia formation, cell invasion, and delayed cell cycle, as well as enhanced cell apoptosis of LoVo cells in vitro.

CONCLUSION

Silencing Rac1 gene mediated by microbubble and US may become a new treatment option for the inhibition of the invasion and metastasis of colorectal cancer cells.

Design and development of a robotized system coupled to µCT imaging for intratumoral drug evaluation in a HCC mouse model

Hepatocellular carcinoma (HCC) is one of the most common cancer related deaths worldwide. One of the main challenges in cancer treatment is drug delivery to target cancer cells specifically. Preclinical evaluation of intratumoral drugs in orthotopic liver cancer mouse models is difficult, as percutaneous injection hardly can be precisely performed manually. In the present study we have characterized a hepatoma model developing a single tumor nodule by implantation of Hep55.1C cells in the liver of syngeneic C57BL/6J mice. Tumor evolution was followed up by µCT imaging, and at the histological and molecular levels. This orthotopic, poorly differentiated mouse HCC model expressing fibrosis, inflammation and cancer markers was used to assess the efficacy of drugs. We took advantage of the high precision of a previously developed robotized system for automated, image-guided intratumoral needle insertion, to administer every week in the tumor of the Hep55.1C mouse model. A significant tumor growth inhibition was observed using our robotized system, whereas manual intraperitoneal administration had no effect, by comparison to untreated control mice.

Ultrasound and microbubble-mediated gene delivery in cancer: progress and perspectives

Ultrasound-mediated gene delivery with microbubbles has emerged as an attractive nonviral vector system for site-specific and noninvasive gene therapy. Ultrasound promotes intracellular uptake of therapeutic agents, particularly in the presence of microbubbles, by increasing vascular and cell membrane permeability. Several preclinical studies have reported successful gene delivery into solid tumors with significant therapeutic effects using this novel approach. This review provides background information on gene therapy and ultrasound bioeffects and discusses the current progress and overall perspectives on the application of ultrasound and microbubble-mediated gene delivery in cancer.

Enhancement of adenovirus delivery after ultrasound-stimulated therapy in a cancer model

Improving the efficiency of adenovirus (Ad) delivery to target tissues has the potential to advance the translation of cancer gene therapy. Ultrasound (US)-stimulated therapy uses microbubbles (MBs) exposed to low-intensity US energy to improve localized delivery. We hypothesize that US-stimulated gene therapy can improve Ad infection in a primary prostate tumor through enhanced tumor uptake and retention of the Ad vector. In vitro studies were performed to analyze the degree of Ad infectivity after application of US-stimulated gene therapy. A luciferase-based Ad on a ubiquitous cytomegalovirus (CMV) promoter (Ad5/3-CMV-Luc) was used in an animal model of prostate cancer (bilateral tumor growth) to evaluate Ad transduction efficiency after US-stimulated therapy. Bioluminescence imaging was employed for in vivo analysis to quantify Ad infection within the tumor. In vitro studies revealed no difference in Ad transduction between groups receiving US-stimulated therapy using high, low or sham US intensity exposures at various multiplicities of infection (MOIs) (p = 0.80). In vivo results indicated that tumors receiving US-stimulated therapy after intra-tumoral injection of Ad5/3-CMV-Luc (1 × 10(6) plaque-forming units) exhibited a 95.1% enhancement in tumor delivery compared with control tumors receiving sham US (p = 0.03). US-stimulated therapy has significant potential to immediately affect Ad-based cancer gene therapy by improving virus bioavailability in target tissues.

Kidney-targeted transplantation of mesenchymal stem cells by ultrasound-targeted microbubble destruction promotes kidney repair in diabetic nephropathy rats

We test the hypothesis that ultrasound-targeted microbubble destruction (UTMD) technique increases the renoprotective effect of kidney-targeted transplantation of bone-marrow-derived mesenchymal stem cells (BM-MSCs) in diabetic nephropathy (DN) rats. Diabetes was induced by streptozotocin injection (60 mg/Kg, intraperitoneally) in Sprague-Dawley rats. MSCs were administered alone or in combination with UTMD to DN rats at 4 weeks after diabetes onset. Random blood glucose concentrations were measured at 1, 2, 4, and 8 weeks, and plasma insulin levels, urinary albumin excretion rate (UAER) values, the structures of pancreas and kidney, the expressions of TGF- β 1, synaptopodin, and IL-10 were assessed at 8 weeks after MSCs transplantation. MSCs transplantation decreased blood glucose concentrations and attenuated pancreatic islets/ β cells damage. The permeability of renal interstitial capillaries and VCAM-1 expression increased after UTMD, which enhanced homing and retention of MSCs to kidneys. MSCs transplantation together with UTMD prevented renal damage and decreased UAER values by inhibiting TGF- β 1 expression and upregulating synaptopodin and IL-10 expression. We conclude that MSCs transplantation reverts hyperglycemia; UTMD technique noninvasively increases the homing of MSCs to kidneys and promotes renal repair in DN rats. This noninvasive cell delivery method may be feasible and efficient as a novel approach for personal MSCs therapy to diabetic nephropathy.

Optimization of Ultrasound-mediated Anti-angiogenic Cancer Gene Therapy

Ultrasound-targeted microbubble destruction (UTMD) can be used to deliver silencing gene therapy to tumors. We hypothesized that UTMD would be effective in suppressing angiogenesis within tumors, and that modulation of the ultrasound pulsing intervals (PI) during UTMD would affect the magnitude of target knockdown. We performed UTMD of vascular endothelial growth factor receptor-2 (VEGFR2) short hairpin (sh)RNA plasmid in an heterotopic mammary adenocarcinoma model in rats, evaluating PIs of 2, 5, 10, and 20 seconds. We demonstrated that UTMD with a PI of 10 seconds resulted in the greatest knockdown of VEGFR2 by PCR, immunostaining, western blotting, smaller tumor volumes and perfused areas, and lower tumor microvascular blood volume (MBV) and flow by contrast-enhanced ultrasound (CEU) compared with UTMD-treated tumors at 2, 5, and 20 seconds, control tumors, tumors treated with intravenous shRNA plasmid and scrambled plasmid. CEU perfusion assessment using the therapeutic probe demonstrated that tumors were fully replenished with microbubbles within 10 seconds, but incompletely replenished at PI-2 and PI-5 seconds. In conclusion, for anti-VEGFR2 cancer gene therapy by UTMD, PI of 10 seconds results in higher target knockdown and a greater anti-angiogenic effect. Complete replenishment of tumor vasculature with silencing gene-bearing microbubbles in between destructive pulses of UTMD is required to maximize the efficacy of anti-angiogenic cancer gene therapy.Molecular Therapy - Nucleic Acids (2013) 2, e94; doi:10.1038/mtna.2013.20; published online 21 May 2013.

The induction of the apoptosis of cancer cell by sonodynamic therapy: a review

Ultrasound can be used not only in the examination, but also in the therapy, especially in the therapy of cancer, which has got effect in the treatment. Sonodynamic therapy is an experimental cancer therapy which uses ultrasound to enhance the cytotoxic effects of drugs known as sonosensitizers. It has been tested in vitro and in vivo. The ultrasound could penetrate the tissue and cell under some of conditions which directly changes the cell membranes permeability, thereby allowing the delivery of exogenous molecules into the cells in some degree. Ultrasound could inhibit the proliferation or induce the apoptosis of the cancer cell in vitro or in vivo. Recent research indicated low frequency and low intensity ultrasound could induce cells apoptosis, and which could be strengthened by sonodynamic sensitivities, microbubbles, chemotherapeutic drugs and so on. Most kinds of ultrasound suppressed the proliferation of cancer cell through inducing the apoptosis of cancer cell. The mechanism of apoptosis is not clear. In this review, we will focus on and discuss the mechanisms of the induction of the apoptosis of cancer cell by ultrasound.

Study of the UTMD-based delivery system to induce cervical cancer cell apoptosis and inhibit proliferation with shRNA targeting Survivin

Apoptosis induction by short hairpin RNA (shRNA) expression vectors could be an efficient and promising strategy for cancer gene therapy. Ultrasound-targeted microbubble destruction (UTMD) is an appealing technique. In this study, we investigated the apoptosis induction and suppression of cell proliferation in vivo transfected by the UTMD-based shRNA delivery system. Nude mice with transplanted tumors of cervical cancer were randomly arranged into three groups: control group, plasmid injection and ultrasound (P + US), P + UTMD group. Expressions of Survivin and proliferating cell nuclear antigen (PCNA), Bcl-2, Bax, Caspase-3, Ki-67, nucleostemin (NS) were investigated by immunohistochemistry. Furthermore, microvessel density (MVD) was detected by CD34 protein expressions and apoptotic index (AI) was measured by TUNEL. As compared with those in the control and P + US groups, protein expressions of PCNA, Ki-67, Bcl-2, Survivin and NS in P + UTMD groups were down-regulated markedly, while those of Bax, Caspase-3 were up-regulated significantly (p < 0.05). MVD decreased significantly, whereas AI increased remarkably (p < 0.05). We suggested that UTMD-based shRNA delivery system could induce apoptosis and inhibit proliferation significantly, without causing any apparently adverse effect, representing a new, promising technology that would be used in the future gene therapy and research.

Advances in ultrasound mediated gene therapy using microbubble contrast agents

Microbubble ultrasound contrast agents have the potential to dramatically improve gene therapy treatments by enhancing the delivery of therapeutic DNA to malignant tissue. The physical response of microbubbles in an ultrasound field can mechanically perturb blood vessel walls and cell membranes, enhancing drug permeability into malignant tissue. In this review, we discuss literature that provided evidence of specific mechanisms that enhance in vivo gene delivery utilizing microbubble contrast agents, namely their ability to 1) improving cell membrane permeability, 2) modulate vascular permeability, and 3) enhance endocytotic uptake in cells. Additionally, we review novel microbubble vectors that are being developed in order to exploit these mechanisms and deliver higher gene payloads with greater target specificity. Finally, we discuss some future considerations that should be addressed in the development of next-generation microbubbles in order to improve in vivo microbubble gene delivery. Overall, microbubbles are rapidly gaining popularity as efficient gene carriers, and combined with their functionality as imaging contrast agents, they represent powerful theranostic tools for image guided gene therapy applications.

Ultrasound-targeted microbubble destruction to deliver siRNA cancer therapy

Microbubble contrast agents can specifically deliver nucleic acids to target tissues when exposed to ultrasound treatment parameters that mediate microbubble destruction. In this study, we evaluated whether microbubbles and ultrasound-targeted microbubble destruction (UTMD) could be used to enhance delivery of EGF receptor (EGFR)-directed siRNA to murine squamous cell carcinomas. Custom-designed microbubbles efficiently bound siRNA and mediated RNAse protection. UTMD-mediated delivery of microbubbles loaded with EGFR-directed siRNA to murine squamous carcinoma cells in vitro reduced EGFR expression and EGF-dependent growth, relative to delivery of control siRNA. Similarly, serial UTMD-mediated delivery of EGFR siRNA to squamous cell carcinoma in vivo decreased EGFR expression and increased tumor doubling time, relative to controls receiving EGFR siRNA-loaded microbubbles but not ultrasound or control siRNA-loaded microbubbles and UTMD. Taken together, our results offer a preclinical proof-of-concept for customized microbubbles and UTMD to deliver gene-targeted siRNA for cancer therapy.

Era of diagnostic and interventional ultrasound

It is an era of diagnostic and interventional ultrasound (US). Various new techniques such as three-dimensional US (3D US), interventional US, and contrast-enhanced US (CEUS) have been introduced into clinical practice. Dr. Xu and his colleagues have taken advantage of these techniques and carried out a series of relevant studies. Their use of 3D US in the liver, gallbladder, liver tumor volumetry, guidance for ablation, and 3D CEUS has widened the application of 3D US in the clinic. They found that prognosis in patients with hepatocellular carcinoma (HCC) after thermal ablation with curative intent was determined by treatment response to ablation, pretreatment serum AFP, and liver function reserve. Tumor response to treatment was the most predictive factor for long-term survival. They compared the use of percutaneous microwave ablation and radiofrequency ablation for the treatment of HCC and found that both are effective methods in treating HCCs. The local tumor control, complications related to treatment, and long-term survival were equivalent for the two modalities. They first compared the enhancement patterns of HCC and intrahepatic cholangiocarcinoma (ICC) and proposed the diagnostic clues for ICC, liver angiomyolipoma (AML), gallbladder cancer, renal carcinoma, and renal AML, which have greatly enhanced the role of CEUS in the clinic. They also evaluated the diagnostic performance of CEUS in characterizing complex cystic focal liver lesions and the agreement between two investigators with different experience levels; and found that CEUS is especially useful for the young investigator. They assessed the effect of anti-angiogenic gene therapy for HCC treated by microbubble-enhanced US exposure and concluded that gene therapy mediated by US exposure enhanced by a microbubble contrast agent may become a new treatment option for HCC.

Therapeutic ultrasonic microbubbles carrying paclitaxel and LyP-1 peptide: preparation, characterization and application to ultrasound-assisted chemotherapy in breast cancer cells

The aim of this work was to develop a novel targeted drug-loaded microbubble (MB) and to investigate its chemotherapy effect in vitro. Paclitaxel (PTX)-loaded lipid MBs were prepared by a mechanical vibration technique. The LyP-1, a breast tumor homing peptide, was coated onto the surface of PTX-loaded MBs through biotin-avidin linkage. The resulting targeted drug-loaded MBs were characterized and applied to ultrasound-assisted chemotherapy in breast cancer cells. Our results showed the ultrasonic MBs were able to achieve 43%-63% of drug encapsulation efficiency, depending on drug loading amount. The binding affinity assay indicated the attachment of targeted MBs to human MDA-MB-231 breast cancer cells was highly efficient and stable even with ultrasonic irradiation on. The cellular uptake efficiency of payload in targeted MBs was 3.71-, 4.95-, 7.43- and 7.66-fold higher than that of non-targeted MBs at the applied ultrasound time of 30, 60, 90 and 120 s, respectively. In addition, the cell proliferation inhibition assay showed the cell viability of targeted PTX-loaded MBs was significantly lower than that of non-targeted PTX-loaded MBs and non-targeted unloaded MBs when ultrasound was utilized. In conclusion, the study indicated the LyP-1-coated PTX-loaded MBs significantly increased the antitumor efficacy and can be used as a potential chemotherapy approach for ultrasound-assisted breast cancer treatment.

Gene therapy of carcinoma using ultrasound-targeted microbubble destruction

When microbubble contrast agents are loaded with genes and systemically injected, ultrasound-targeted microbubble destruction (UTMD) facilitates focused delivery of genes to target tissues. A mouse model of squamous cell carcinoma was used to test the hypothesis that UTMD would specifically transduce tumor tissue and slow tumor growth when treated with herpes simplex virus thymidine kinase (TK) and ganciclovir. UTMD-mediated delivery of reporter genes resulted in tumor expression of luciferase and green fluorescent protein (GFP) in perivascular areas and individual tumor cells that exceeded expression in control tumors (p=0.02). The doubling time of TK-treated tumors was longer than GFP-treated tumors (p=0.02), and TK-treated tumors displayed increased apoptosis (p=0.04) and more areas of cellular drop-out (p=0.03). These data indicate that UTMD gene therapy can transduce solid tumors and mediate a therapeutic effect. UTMD is a promising nonviral method for targeting gene therapy that may be useful in a spectrum of tumors.

Targeted renal therapies through microbubbles and ultrasound

Microbubbles and ultrasound enhance the cellular uptake of drugs (including gene constructs) into the kidney. Microbubble induced modifications to the size selectivity of the filtration capacity of the kidney may enable drugs to enter previously inaccessible compartments of the kidney. So far, negative renal side-effects such as capillary bleeding have been reported only in rats, with no apparent damage in larger models such as pigs and rabbits. Although local delivery is accomplished by applying ultrasound only to the target area, efficient delivery using conventional microbubbles has depended on the combined injection of both drugs and microbubbles directly into the renal artery. Conjugation of antibodies to the shell of microbubbles allows for the specific accumulation of microbubbles in the target tissue after intravenous injection. This exciting approach opens new possibilities for both drug delivery and diagnostic ultrasound imaging in the kidney.

Ultrasound-mediated gene delivery

IMPORTANCE OF THE FIELD

The use of ultrasound with microbubbles raises the possibility of an efficient and safe gene delivery.

AREAS COVERED IN THIS REVIEW

This review summarizes the current state of the art of gene delivery by sonoporation under the following topics. First, the basic ultrasound parameters and the characteristics of microbubble in biological systems are discussed. Second, the extensions of sonoporation to other fields of gene delivery such as viral and non-viral vector are briefly reviewed. Finally, recent applications in an animal model for various diseases are introduced.

WHAT THE READER WILL GAIN

Information and comments on gene delivery by sonoporation or enhanced cell membrane permeability by means of ultrasound.

TAKE HOME MESSAGE

Ultrasound-mediated gene delivery combined with microbubble agents provides significant safety advantages over other methods of local gene delivery.

Sonoporation, drug delivery, and gene therapy

Ultrasound is a very effective modality for drug delivery and gene therapy because energy that is non-invasively transmitted through the skin can be focused deeply into the human body in a specific location and employed to release drugs at that site. Ultrasound cavitation, enhanced by injected microbubbles, perturbs cell membrane structures to cause sonoporation and increases the permeability to bioactive materials. Cavitation events also increase the rate of drug transport in general by augmenting the slow diffusion process with convective transport processes. Drugs and genes can be incorporated into microbubbles, which in turn can target a specific disease site using ligands such as the antibody. Drugs can be released ultrasonically from microbubbles that are sufficiently robust to circulate in the blood and retain their cargo of drugs until they enter an insonated volume of tissue. Local drug delivery ensures sufficient drug concentration at the diseased region while limiting toxicity for healthy tissues. Ultrasound-mediated gene delivery has been applied to heart, blood vessel, lung, kidney, muscle, brain, and tumour with enhanced gene transfection efficiency, which depends on the ultrasonic parameters such as acoustic pressure, pulse length, duty cycle, repetition rate, and exposure duration, as well as microbubble properties such as size, gas species, shell material, interfacial tension, and surface rigidity. Microbubble-augmented sonothrombolysis can be enhanced further by using targeting microbubbles.

Contrast-enhanced ultrasound: The evolving applications

Contrast-enhanced ultrasound (CEUS) is a major breakthrough for ultrasound imaging in recent years. By using a microbubble contrast agent and contrast-specific imaging software, CEUS is able to depict the micro- and macro-circulation of the targeted organ, which in turn leads to improved performance in diagnosis. Due to the special dual blood supply system in the liver, CEUS is particularly suitable for liver imaging. It is evident that CEUS facilitates improvement for characterization of focal liver lesions (FLLs), detection of liver malignancy, guidance for interventional procedures, and evaluation of treatment response after local therapies. CEUS has been demonstrated to be equal to contrast-enhanced computed tomography or magnetic resonance imaging for the characterization of FLLs. In addition, the applicability of CEUS has expanded to non-liver structures such as gallbladder, bile duct, pancreas, kidney, spleen, breast, thyroid, and prostate. The usefulness of CEUS in these applications is confirmed by extensive literature production. Novel applications include detecting bleeding sites and hematomas in patients with abdominal trauma, guiding percutaneous injection therapy and therefore achieving the goal of using interventional ultrasonography in managing splenic trauma, assessing the activity of Crohn’s disease, and detecting suspected endoleaks after endovascular abdominal aneurysm repair. Contrast-enhanced intraoperative ultrasound (US) and intracavitary use of CEUS have been developed and clinically studied. The potential use of CEUS involves sentinel lymph node detection, drug or gene delivery, and molecular imaging. In conclusion, the advent of CEUS has greatly enhanced the usefulness of US and even changed the status of US in clinical practice. The application of CEUS in the clinic is continuously evolving and it is expected that its use will be expanded further in the future.

Electroporation and ultrasound enhanced non-viral gene delivery in vitro and in vivo

Non-viral vectors are less efficient than the use of viral vectors for delivery of genetic material to cells in vitro and especially in vivo. However, viral vectors involve the use of foreign proteins that can stimulate both the innate and acquired immune response. In contrast, plasmid DNA can be delivered without carrier proteins and is non-immunogenic. Plasmid gene delivery can be enhanced by the use of physical methods that aid the passage of the plasmid through the cell membrane. Electroporation and microbubble-enhanced ultrasound are two of the most effective physical delivery methods and these can be applied to a range of different cell types in vitro and a broad range of tissues in vivo. Both techniques also have the advantage that, unlike viral vectors, they can be used to target specific tissues with systemic delivery. Although electroporation is often the more efficient of the two, microbubble-enhanced ultrasound causes less damage and is less invasive. This review provides an introduction to the methodology and summarises the range of cells and tissues that have been genetically modified using these techniques.

Optimising ultrasound-mediated gene transfer (sonoporation) in vitro and prolonged expression of a transgene in vivo: potential applications for gene therapy of cancer

Therapeutic approaches using gene-based medicines promise alternatives or adjuncts to conventional cancer treatment. Because of its non-invasive nature, ultrasound, as a membrane-permeabilising stimulus has the potential to be highly competitive with viral gene delivery and existing non-viral alternatives. In optimising ultrasound-mediated, microbubble-assisted (MB101) gene tranfection in vitro, we demonstrate efficiencies of up to 18% using ultrasound at 1 MHz at a duty cycle of 25% at intensities ranging from 1 to 4 W cm(-2). Using ultrasound-mediated transfection together with an episomal plasmid-based gene expression system, we demonstrate prolonged functional gene expression of luciferase in mouse hind leg muscle and in tumours in vivo.