Pulsed high intensity focused ultrasound increases penetration and therapeutic efficacy of monoclonal antibodies in murine xenograft tumors

Perspectives for Improving the Tumor Targeting of Nanomedicine via the EPR Effect in Clinical Tumors

Over the past few decades, the enhanced permeability and retention (EPR) effect of nanomedicine has been a crucial phenomenon in targeted cancer therapy. Specifically, understanding the EPR effect has been a significant aspect of delivering anticancer agents efficiently to targeted tumors. Although the therapeutic effect has been demonstrated in experimental models using mouse xenografts, the clinical translation of the EPR effect of nanomedicine faces several challenges due to dense extracellular matrix (ECM), high interstitial fluid pressure (IFP) levels, and other factors that arise from tumor heterogeneity and complexity. Therefore, understanding the mechanism of the EPR effect of nanomedicine in clinics is essential to overcome the hurdles of the clinical translation of nanomedicine. This paper introduces the basic mechanism of the EPR effect of nanomedicine, the recently discussed challenges of the EPR effect of nanomedicine, and various strategies of recent nanomedicine to overcome the limitations expected from the patients' tumor microenvironments.

Use of stimulatory responsive soft nanoparticles for intracellular drug delivery

Drug delivery has made tremendous advances in the last decade. Targeted therapies are increasingly common, with intracellular delivery highly impactful and sought after. Intracellular drug delivery systems have limitations due to imprecise and non-targeted release profiles. One way this can be addressed is through using stimuli-responsive soft nanoparticles, which contain materials with an organic backbone such as lipids and polymers. The choice of biomaterial is essential for soft nanoparticles to be responsive to internal or external stimuli. The nanoparticle must retain its integrity and payload in non-targeted physiological conditions while responding to particular intracellular environments where payload release is desired. Multiple internal and external factors could stimulate the intracellular release of drugs from nanoparticles. Internal stimuli include pH, oxidation, and enzymes, while external stimuli include ultrasound, light, electricity, and magnetic fields. Stimulatory responsive soft nanoparticulate systems specifically utilized to modulate intracellular delivery of drugs are explored in this review.

Advances in nanomaterial-based targeted drug delivery systems

Nanomaterial-based drug delivery systems (NBDDS) are widely used to improve the safety and therapeutic efficacy of encapsulated drugs due to their unique physicochemical and biological properties. By combining therapeutic drugs with nanoparticles using rational targeting pathways, nano-targeted delivery systems were created to overcome the main drawbacks of conventional drug treatment, including insufficient stability and solubility, lack of transmembrane transport, short circulation time, and undesirable toxic effects. Herein, we reviewed the recent developments in different targeting design strategies and therapeutic approaches employing various nanomaterial-based systems. We also discussed the challenges and perspectives of smart systems in precisely targeting different intravascular and extravascular diseases.

Efficacy and Safety of Dual Anti-HER2 Blockade and Docetaxel With or Without Carboplatin as Neoadjuvant Regimen for Treatment of HER2-Positive Breast Cancer

Introduction: This study aimed to compare the efficacy and safety of docetaxel + trastuzumab + pertuzumab and docetaxel + carboplatin + trastuzumab + pertuzumab for treating HER2-positive breast cancer. Method: HER2-positive breast cancer from patients diagnosed between January 2020 and September 2022 were included in this retrospective study. Docetaxel + trastuzumab + pertuzumab or docetaxel + carboplatin + trastuzumab + pertuzumab was selected as the neoadjuvant regimen. The primary endpoint was a complete pathological remission rate. Secondary endpoints were toxicity during neoadjuvant treatment, adjustment of the neoadjuvant therapy scheme, and adjuvant medication. Result: A total of 81 patients were included in this study (38 in the docetaxel + carboplatin + trastuzumab + pertuzumab treatment group and 43 in the docetaxel + trastuzumab + pertuzumab group). The complete pathological remission rates in the docetaxel + carboplatin + trastuzumab + pertuzumab and docetaxel + trastuzumab + pertuzumab groups were 44.7% (95% confidence interval: 30.2%-60.3%) and 51.2% (95% confidence interval: 36.8%-65.4%), respectively. The incidence of grade 3 or higher toxicity in the docetaxel + carboplatin + trastuzumab + pertuzumab group was significantly higher than that in the docetaxel + trastuzumab + pertuzumab group (68.4% vs 39.5%, P = .009). Neutropenia and asthenia were the most common grade 3 or higher toxicities. The incidence of neoadjuvant scheme adjustment was significantly higher in the docetaxel + carboplatin + trastuzumab + pertuzumab group than in the docetaxel + trastuzumab + pertuzumab group (26.3% vs 7.0%, P = .039). The proportion of patients who received <6 cycles of neoadjuvant therapy was significantly higher in the docetaxel + carboplatin + trastuzumab + pertuzumab group than in the docetaxel + trastuzumab + pertuzumab group (31.6% vs 4.7%, P = .004). Patients in the docetaxel + carboplatin + trastuzumab + pertuzumab group received higher doses of granulocyte-macrophage colony-stimulating factor. Conclusion: In the neoadjuvant treatment of HER2-positive breast cancer, the docetaxel + trastuzumab + pertuzumab regimen might be more tolerated than the docetaxel + carboplatin + trastuzumab + pertuzumab regimen and did not show a lower complete pathological remission rate. However, our findings require further validation through prospective studies.

High-Intensity Focused Ultrasound Enhanced Anti-Tumor Activities of Paclitaxel in Breast Cancer in vitro and in vivo

Background

Paclitaxel (PTX) is an important oncologic chemotherapeutic agent against breast cancer, but breast cancer patients develop significant resistance to PTX during chemotherapy. Alterations in tubulin and associated proteins have been implicated in resistance to PTX. High-intensity focused ultrasound (HIFU) induces deep tumor penetration of anti-tumor agents in solid tumors.

Methods

We investigated the influence of HIFU on the anti-tumor activities of PTX in breast cancer. Both in vivo and in vitro experiments were performed in this research: mice were treated with 2 mg/Kg PTX through tail vein injection, while breast cancer cells were treated with 400 nM PTX. Cell viability was analyzed through Cell Counting Kit-8. Cell apoptosis was evaluated through Annexin-V/PI Apoptosis Analysis Kit. The activities of catalase (CAT) and superoxide dismutase (SOD) and the concentration of malondialdehyde (MDA) were evaluated by relative commercial kits.

Results

HIFU enhanced PTX-inhibited breast cancer cell viability and PTX-induced cell apoptosis. Simultaneous treatment of HIFU and PTX decreased the activities of CAT and SOD and increased the concentration of MDA. In mice bearing MDA-MB-231 tumors, the treatment of HIFU and PTX significantly decreased tumor size, increased body weight and elevated animal survival. HIFU enhanced the distribution of PTX in tumor tissues.

Conclusion

The performance of HIFU promoted the distribution of PTX and enhanced its anti-tumor activities in breast cancer.

Mechanistic Insights and Therapeutic Delivery through Micro/Nanobubble-Assisted Ultrasound

Ultrasound with low frequency (20–100 kHz) assisted drug delivery has been widely investigated as a non-invasive method to enhance the permeability and retention effect of drugs. The functional micro/nanobubble loaded with drugs could provide an unprecedented opportunity for targeted delivery. Then, ultrasound with higher intensity would locally burst bubbles and release agents, thus avoiding side effects associated with systemic administration. Furthermore, ultrasound-mediated destruction of micro/nanobubbles can effectively increase the permeability of vascular membranes and cell membranes, thereby not only increasing the distribution concentration of drugs in the interstitial space of target tissues but also promoting the penetration of drugs through cell membranes into the cytoplasm. These advancements have transformed ultrasound from a purely diagnostic utility into a promising theragnostic tool. In this review, we first discuss the structure and generation of micro/nanobubbles. Second, ultrasound parameters and mechanisms of therapeutic delivery are discussed. Third, potential biomedical applications of micro/nanobubble-assisted ultrasound are summarized. Finally, we discuss the challenges and future directions of ultrasound combined with micro/nanobubbles.

Diacerein, an inhibitor of IL-1β downstream mediated apoptosis, improves radioimmunotherapy in a mouse model of Burkitt's lymphoma

Lymphoma has the characteristics of a solid tumor. Penetration of monoclonal antibodies is limited in solid tumors during radioimmunotherapy (RIT). Here, we first investigated the use of diacerein (DIA) as a combination drug to improve the penetration and therapeutic efficacy of ¹³¹I-rituximab (RTX) using the Burkitt's lymphoma mouse model. We selected DIA through computational drug repurposing and focused on rheumatoid arthritis (RA) drug interaction genes to minimize side effects. Then, the cytotoxicity of DIA was assessed in vitro using three different lymphoma cell lines. DIA-induced apoptosis was confirmed by Western blotting. After confirming apoptosis, we confirmed the enhanced uptake of ¹³¹I-RTX in Burkitt's lymphoma mouse model using SPECT/CT. Autoradiography of ¹³¹I-RTX confirmed the therapeutic effect of DIA. Finally, the tumor size and survival rate were assessed to measure the enhanced therapeutic efficacy when DIA was used. In addition, we assessed the dose-dependency of DIA in terms of the accumulation of ¹³¹I-RTX in tumor tissue, the tumor size, and the survival rate. The in vitro cytotoxicity was 10.9%. We showed that DIA induced apoptosis which was related to downstream IL-1β signaling by Western blotting. We found increased Annexin V positive apoptosis after DIA administration. Immuno SPECT/CT images demonstrated a higher uptake of ¹³¹I-RTX in tumors in the DIA-administered group than that in the PBS-alone group. However, there were no statistical differences of dose-dependency between 20 mg/kg and 40 mg/kg of DIA. Tumor growth was significantly inhibited in the group treated with the combination of DIA plus ¹³¹I-RTX at 7 days after injection. Our suggested combination of DIA and ¹³¹I-RTX strategies could enhance the efficacy of ¹³¹I-RTX treatment.

Overcoming physical stromal barriers to cancer immunotherapy

Immunotherapy has emerged as an unprecedented hope for the treatment of notoriously refractory cancers. Numerous investigational drugs and immunotherapy-including combination regimens are under preclinical and clinical investigation. However, only a small patient subpopulation across different types of cancer responds to the therapy due to the presence of several mechanisms of resistance. There have been extensive efforts to overcome this limitation and to expand the patient population that could be benefited by this state-of-the-art therapeutic modality. Among various causes of the resistance, we here focus on physical stromal barriers that impede the access of immunotherapeutic drug molecules and/or native and engineered immune cells to cancer tissues and cells. Two primary stromal barriers that contribute to the resistance include aberrant tumor vasculatures and excessive extracellular matrix build-ups that restrict extravasation and infiltration, respectively, of molecular and cellular immunotherapeutic agents into tumor tissues. Here, we review the features of these barriers that limit the efficacy of immunotherapy and discuss recent advances that could potentially help immunotherapy overcome the barriers and improve therapeutic outcomes.

The Role of Ultrasound in Modulating Interstitial Fluid Pressure in Solid Tumors for Improved Drug Delivery

The unique microenvironment of solid tumors, including desmoplasia within the extracellular matrix, enhanced vascular permeability, and poor lymphatic drainage, leads to an elevated interstitial fluid pressure which is a major barrier to drug delivery. Reducing tumor interstitial fluid pressure is one proposed method of increasing drug delivery to the tumor. The goal of this topical review is to describe recent work using focused ultrasound with or without microbubbles to modulate tumor interstitial fluid pressure, through either thermal or mechanical effects on the extracellular matrix and the vasculature. Furthermore, we provide a review on techniques in which ultrasound imaging may be used to diagnose elevated interstitial fluid pressure within solid tumors. Ultrasound-based techniques show high promise in diagnosing and treating elevated interstitial pressure to enhance drug delivery.

Relaxin-expressing oncolytic adenovirus induces remodeling of physical and immunological aspects of cold tumor to potentiate PD-1 blockade

Background

Currently, several antibody (Ab)-based therapies have shown excellent therapeutic effects in the clinic. Nonetheless, Ab penetration into tumor tissues is limited due to abnormal vasculature, tumor interstitial pressure, and excessive extracellular matrix (ECM) accumulation, thus demanding novel strategies to overcome these barriers.

Methods

The intratumoral distribution of therapeutic Abs were detected by fluorescence microscopy or positron emission tomography in both human gastric xenograft and syngeneic pancreatic hamster tumor models. The antitumor efficacy by combination of oncolytic adenovirus (Ad), which coexpresses relaxin (RLX), interleukin (IL)-12, and granulocyte macrophage colony-stimulating factor (GM-CSF) (oAd/IL12/GM-RLX) and antibody against the programmed cell death protein 1 (αPD-1) was examined in hamster subcutaneous and orthotopic pancreatic tumor models. The immunological aspects of these combination therapy regimen were assessed by flow cytometry or immunohistochemistry in subcutaneous hamster tumor models.

Results

Relaxin-expressing oncolytic Ad effectively degraded tumor ECM and enhanced the tumor penetration of trastuzumab in comparison with trastuzumab monotherapy. Based on these results, an oAd/IL12/GM-RLX was used to enhance the potency of immune checkpoint blockade. The combination of the oAd/IL12/GM-RLX and αPD-1 promoted a concomitant degradation of the tumor ECM and amelioration of the immunosuppressive tumor niches, ultimately enhanced intratumoral infiltration of both αPD-1 and activated T cells. Of note, the combination therapy was able to elicit a potent and durable antitumor immune response against cold tumors that were refractory to immune checkpoint inhibitor monotherapy.

Conclusions

Our findings are the first to demonstrate that expression of four genes (IL-12p35, IL-12p40, GM-CSF, and RLX) mediated by a single oncolytic Ad vector can promote remodeling of both physical and immunological aspects of the tumor niches to overcome the major limitations of Ab-based therapies that have emerged in recent clinical trials.

Tumor treating fields can effectively overcome trastuzumab resistant breast cancer multiplication

The Human Epidermal Growth Receptor 2, or the HER2 is one of the highest expressed negative receptor that constitutes approximately 15-20% of malevolent breast cancerous tumors among women. The prevalence of HER2 has untimely and unfavorable consequences on breast cancer, and its underlying carcinomous cell processes, structures, and growth. Trastuzumab (TRZ), a humanized antibody that is rooted in relatively recent foundations, has been found operational in its construction of treatments against HER2-positive breast cancer. This drug is combined with radiotherapy or chemotherapy to deregulate HER2 genes in the body. However, patients who suffer from evolved tumors in advanced stages of cancer exhibit a good amount of tolerance towards singularly used TRZ treatment. Inversely, the factorization of Tumor Testing Fields (TTFields or TTFs) into cancer therapy revives the functions of a TRZ treatment plan, by sensitizing the HER2 genes to the drug. In turn, this facilitates TRZ to continue limiting cancerous cell multiplication and toxicity levels within the treatment. This research evaluates the aspects and effects of this pairing, both in vivo and in vitro through BT474 cells. The TTFields conduct an electromagnetic boundary, which generates sine-wave radiations to manipulate the HER2 gene structure. The methods followed in the research also examines the gene cell cultures and their viability through solutions like Tryptophan blue, or the Crystal violet which may or may not deliver certain testmants to the experiment. The Western Blot Test and the IHC confirm the presence of antibodies and negative receptors in the BT474 cells. These procedures contribute to the formulation of a treatment plan that overcomes the TRZ-resistant nature of the tumor, which is essentially the aim of the research. Thus, the paper substantiates that a healthy combination of TTF's with TRZ can enhance the penetration of TRZ after inducing apoptosis due to TTFields therapy. The success of a TTField in undertaking this pursuit makes room for more utilization of it in future cancerous treatment ventures.

Drug Delivery by Ultrasound-Responsive Nanocarriers for Cancer Treatment

Conventional cancer chemotherapies often exhibit insufficient therapeutic outcomes and dose-limiting toxicity. Therefore, there is a need for novel therapeutics and formulations with higher efficacy, improved safety, and more favorable toxicological profiles. This has promoted the development of nanomedicines, including systems for drug delivery, but also for imaging and diagnostics. Nanoparticles loaded with drugs can be designed to overcome several biological barriers to improving efficiency and reducing toxicity. In addition, stimuli-responsive nanocarriers are able to release their payload on demand at the tumor tissue site, preventing premature drug loss. This review focuses on ultrasound-triggered drug delivery by nanocarriers as a versatile, cost-efficient, non-invasive technique for improving tissue specificity and tissue penetration, and for achieving high drug concentrations at their intended site of action. It highlights aspects relevant for ultrasound-mediated drug delivery, including ultrasound parameters and resulting biological effects. Then, concepts in ultrasound-mediated drug delivery are introduced and a comprehensive overview of several types of nanoparticles used for this purpose is given. This includes an in-depth compilation of the literature on the various in vivo ultrasound-responsive drug delivery systems. Finally, toxicological and safety considerations regarding ultrasound-mediated drug delivery with nanocarriers are discussed.

Effect of Acoustic Radiation Force on the Distribution of Nanoparticles in Solid Tumors

Acoustic radiation force (ARF) might improve the distribution of nanoparticles (NPs) in tumors. To study this, tumors growing subcutaneously in mice were exposed to focused ultrasound (FUS) either 15 min or 4 h after the injection of NPs, to investigate the effect of ARF on the transport of NPs across the vessel wall and through the extracellular matrix. Quantitative analysis of confocal microscopy images from frozen tumor sections was performed to estimate the displacement of NPs from blood vessels. Using the same experimental exposure parameters, ARF was simulated and compared with the experimental data. Enhanced interstitial transport of NPs in tumor tissues was observed when FUS (10 MHz, acoustic power 234 W/cm², 3.3% duty cycle) was given either 15 min or 4 h after NP administration. According to acoustic simulations, the FUS generated an ARF per unit volume of 2.0×10⁶ N/m³. The displacement of NPs was larger when FUS was applied 4 h after NP injection compared with after 15 min. This study shows that ARF might contribute to a modest improved distribution of NPs into the tumor interstitium.

Improved therapeutic antibody delivery to xenograft tumors using cavitation nucleated by gas-entrapping nanoparticles

Aims: Testing ultrasound-mediated cavitation for enhanced delivery of the therapeutic antibody cetuximab to tumors in a mouse model. Methods: Tumors with strong EGF receptor expression were grown bilaterally. Cetuximab was coadministered intravenously with cavitation nuclei, consisting of either the ultrasound contrast agent Sonovue or gas-stabilizing nanoscale SonoTran Particles. One of the two tumors was exposed to focused ultrasound. Passive acoustic mapping localized and monitored cavitation activity. Both tumors were then excised and cetuximab concentration was quantified. Results: Cavitation increased tumoral cetuximab concentration. When nucleated by Sonovue, a 2.1-fold increase (95% CI 1.3- to 3.4-fold) was measured, whereas SonoTran Particles gave a 3.6-fold increase (95% CI 2.3- to 5.8-fold). Conclusions: Ultrasound-mediated cavitation, especially when nucleated by nanoscale gas-entrapping particles, can noninvasively increase site-specific delivery of therapeutic antibodies to solid tumors.

PET imaging facilitates antibody screening for synergistic radioimmunotherapy with a 177Lu-labeled αPD-L1 antibody

Rationale: The low response rate of immunotherapy, such as anti-PD-L1/PD-1 and anti-CTLA4, has limited its application to a wider population of cancer patients. One widely accepted view is that inflammation within the tumor microenvironment is low or ineffective for inducing the sufficient infiltration and/or activation of lymphocytes. Here, a highly tumor-selective anti-PD-L1 (αPD-L1) antibody was developed through PET imaging screening, and it was radiolabeled with Lu-177 for PD-L1-targeted radioimmunotherapy (RIT) and radiation-synergized immunotherapy. Methods: A series of αPD-L1 antibodies were radiolabeled with zirconium-89 for PET imaging to screen the most suitable antibodies for RIT. Mice were divided into an immunotherapy group, a RIT group and a radiation-synergized immunotherapy group to evaluate the therapeutic effect. Alterations in the tumor microenvironment after treatment were assessed using flow cytometry and immunofluorescence microscopy. Results: Radiation-synergistic RIT can achieve a significantly better therapeutic effect than immunotherapy or RIT alone. The dosages of the radiopharmaceuticals and αPD-L1 antibodies were reduced, the infiltration of CD4⁺ and CD8⁺ T cells in the tumor microenvironment was increased, and no side effects were observed. This radiation-synergistic RIT strategy successfully showed a strong synergistic effect with αPD-L1 checkpoint blockade therapy, at least in the mouse model. Conclusions: PET imaging of ⁸⁹Zr-labeled antibodies is an effective method for antibody screening. RIT with a ¹⁷⁷Lu-labeled αPD-L1 antibody could successfully upregulate antitumor immunity in the tumor microenvironment and turn "cold" tumors "hot" for immunotherapy.

Tumor-mesoporous silica nanoparticle interactions following intraperitoneal delivery for targeting peritoneal metastasis

The use of intraperitoneal administration of nanoparticles has been reported to facilitate higher concentrations of nanoparticles in metastatic peritoneal tumors. While this strategy is appealing for limiting systemic exposure of nanocarrier delivered toxic cargoes and increasing nanoparticle concentrations in avascular peritoneal tumors, little is known about the mechanism of nanoparticle accumulation on tumor tissues and currently, no nanoparticle-based product has been approved for intraperitoneal delivery. Here, we investigated the nanoparticle-specific characteristics that led to increased peritoneal tumor accumulation using MCM-41 type mesoporous silica nanoparticles as our model system. We also investigated the components of the peritoneal tumor stroma that facilitated nanoparticle-tumor interaction. The tumor extracellular matrix is the main factor driving these interactions, specifically the interaction of nanoparticles with collagen. Upon disruption of the collagen matrix, nanoparticle accumulation was reduced by 50%. It is also notable that the incorporation of targeting ligands did not increase overall tumor accumulation in vivo while it significantly increased nanoparticle accumulation in vitro. The use of other particle chemistries did not grossly affect the tumor targetability, but additional concerns arose when those tested particles exhibited significant systemic exposure. Mesoporous silica nanoparticles are advantageous for intraperitoneal administration for the treatment of peritoneal metastasis due to their physical stability, tumor targetability, strong interaction with the collagen matrix, and extended peritoneal residence time. Maximizing nanoparticle interaction with the tumor extracellular matrix is critical for developing strategies to deliver emerging therapeutics for peritoneal cancer treatment using nanocarriers.

Deep Tumor Penetration of Doxorubicin-Loaded Glycol Chitosan Nanoparticles Using High-Intensity Focused Ultrasound

The dense extracellular matrix (ECM) in heterogeneous tumor tissues can prevent the deep tumor penetration of drug-loaded nanoparticles, resulting in a limited therapeutic efficacy in cancer treatment. Herein, we suggest that the deep tumor penetration of doxorubicin (DOX)-loaded glycol chitosan nanoparticles (CNPs) can be improved using high-intensity focused ultrasound (HIFU) technology. Firstly, we prepared amphiphilic glycol chitosan-5β-cholanic acid conjugates that can self-assemble to form stable nanoparticles with an average of 283.7 ± 5.3 nm. Next, the anticancer drug DOX was simply loaded into the CNPs via a dialysis method. DOX-loaded CNPs (DOX-CNPs) had stable nanoparticle structures with an average size of 265.9 ± 35.5 nm in aqueous condition. In cultured cells, HIFU-treated DOX-CNPs showed rapid drug release and enhanced cellular uptake in A549 cells, resulting in increased cytotoxicity, compared to untreated DOX-CNPs. In ECM-rich A549 tumor-bearing mice, the tumor-targeting efficacy of intravenously injected DOX-CNPs with HIFU treatment was 1.84 times higher than that of untreated DOX-CNPs. Furthermore, the deep tumor penetration of HIFU-treated DOX-CNPs was clearly observed at targeted tumor tissues, due to the destruction of the ECM structure via HIFU treatment. Finally, HIFU-treated DOX-CNPs greatly increased the therapeutic efficacy at ECM-rich A549 tumor-bearing mice, compared to free DOX and untreated DOX-CNPs. This deep penetration of drug-loaded nanoparticles via HIFU treatment is a promising strategy to treat heterogeneous tumors with dense ECM structures.

Pulsed focused ultrasound lowers interstitial fluid pressure and increases nanoparticle delivery and penetration in head and neck squamous cell carcinoma xenograft tumors

Nanocarriers offer a promising approach to significantly improve therapeutic delivery to solid tumors as well as limit the side effects associated with anti-cancer agents. However, their relatively large size can negatively affect their ability to efficiently penetrate into more interior tumor regions, ultimately reducing therapeutic efficacy. Poor penetration of large agents such as nanocarriers is attributed to factors in the tumor microenvironment such as elevated interstitial fluid pressure (IFP) and fibrillar collagen in the extracellular matrix. Our previous studies reported that pretreatment of solid tumor xenografts with nondestructive pulsed focused ultrasound (pFUS) can improve the delivery and subsequent therapy of a variety of therapeutic formulations in different tumor models, where the results were associated with expanded extracellular spaces (ECS), an increase in hydraulic conductivity, and decrease in tissue stiffness. Here, we demonstrate the inverse relationship between IFP and the penetration of systemically administered nanoparticle (NP) probes, where IFP increased from the tumor periphery to their center. Furthermore, we show that pretreatment with pFUS can safely reduce IFP and improve NP delivery; especially into the center of the tumors. These results coincide with effects generated in the fibrillar collagen network microstructure in the ECS as determined by quantitative polarized light microscopy. Whole tumor and histomorphometric analysis, however, did not show significant differences in collagen area fraction or collagen feature solidity, as well as tumor cross-sectional area and aspect ratio, as a result of the treatments. We present a biophysical model connecting the experimental results, where pFUS-mediated cytoarchitectural changes are associated with improved redistribution of the interstitial fluid and lower IFP. The resulting improvement in NP delivery supports our previous therapeutic studies and may have implications for clinical applications to improve therapeutic outcomes in cancer therapy.

Inhibition of HIF-1α by Atorvastatin During 131I-RTX Therapy in Burkitt's Lymphoma Model

Backgrounds: Radioimmunotherapy (RIT) serves as a targeted therapy for non-Hodgkin lymphomas (NHL). Although HIF(Hypoxia-inducible factors)-1α is an important biomarker during radiation therapy, its role in NHL is unclear. Atorvastatin (ATV) is used as a combination drug for chemotherapy. Methods: We investigated whether ATV downregulated tumor radio-resistance and enhanced the anticancer effect of ¹³¹I-RTX (rituximab) in Raji xenograft mouse models. First, the increased uptake and enhanced therapeutic effect of ¹³¹I-RTX by ATV was confirmed using molecular imaging in Raji xenograft subcutaneous model and orthotropic model with SPECT and IVIS images. Second, we examined the profile of differentially expressed miRNAs using miRNA array. Results: We found that miR-346 inhibited HIF-1α/VEGF (Vascular endothelial growth factor) during ATV combination therapy with ¹³¹I-RTX. The underlying mechanism of ATV involved induction of anti-angiogenesis and radiosensitivity by downregulating HIF-1α in Raji cells. Conclusion: Our findings suggested that combination therapy with ATV and ¹³¹I-RTX is a promising strategy for enhancing the potency of ¹³¹I-RTX therapy in poorly responding patients and those with radio-resistance.

Micro/nano-bubble-assisted ultrasound to enhance the EPR effect and potential theranostic applications

Drug delivery for tumor theranostics involves the extensive use of the enhanced permeability and retention (EPR) effect. Previously, various types of nanomedicines have been demonstrated to accumulate in solid tumors via the EPR effect. However, EPR is a highly variable phenomenon because of tumor heterogeneity, resulting in low drug delivery efficacy in clinical trials. Because ultrasonication using micro/nanobubbles as contrast agents can disrupt blood vessels and enhance the specific delivery of drugs, it is an effective approach to improve the EPR effect for the passive targeting of tumors. In this review, the basic thermal effect, acoustic streaming, and cavitation mechanisms of ultrasound, which are characteristics that can be utilized to enhance the EPR effect, are briefly introduced. Second, micro/nanobubble-enhanced ultrasound imaging is discussed to understand the validity and variability of the EPR effect. Third, because the tumor microenvironment is complicated owing to elevated interstitial fluid pressure and the deregulated extracellular matrix components, which may be unfavorable for the EPR effect, few new trends in smart bubble drug delivery systems, which may improve the accuracy of EPR-mediated passive drug targeting, are summarized. Finally, the challenging and major concerns that should be considered in the next generation of micro/nanobubble-contrast-enhanced ultrasound theranostics for EPR-mediated passive drug targeting are also discussed.

Nano-Enhanced Drug Delivery and Therapeutic Ultrasound for Cancer Treatment and Beyond

While ultrasound is most widely known for its use in diagnostic imaging, the energy carried by ultrasound waves can be utilized to influence cell function and drug delivery. Consequently, our ability to use ultrasound energy at a given intensity unlocks the opportunity to use the ultrasound for therapeutic applications. Indeed, in the last decade ultrasound-based therapies have emerged with promising treatment modalities for several medical conditions. More recently, ultrasound in combination with nanomedicines, i.e., nanoparticles, has been shown to have substantial potential to enhance the efficacy of many treatments including cancer, Alzheimer disease or osteoarthritis. The concept of ultrasound combined with drug delivery is still in its infancy and more research is needed to unfold the mechanisms and interactions of ultrasound with different nanoparticles types and with various cell types. Here we present the state-of-art in ultrasound and ultrasound-assisted drug delivery with a particular focus on cancer treatments. Notably, this review discusses the application of high intensity focus ultrasound for non-invasive tumor ablation and immunomodulatory effects of ultrasound, as well as the efficacy of nanoparticle-enhanced ultrasound therapies for different medical conditions. Furthermore, this review presents safety considerations related to ultrasound technology and gives recommendations in the context of system design and operation.

Optimization of osmotic blood-brain barrier opening to enable intravital microscopy studies on drug delivery in mouse cortex

Intra-arterial (IA) infusion of mannitol induces osmotic blood-brain barrier opening (OBBBO) and that method has been used for decades to improve drug delivery to the brain. However, high variability of outcomes prevented vast clinical adoption. Studies on dynamic multi-scale imaging of OBBBO as well as extravasation of IA injected therapeutic agents are essential to develop strategies assuring precision and reproducibility of drug delivery. Intravital microscopy is increasingly used to capture the dynamics of biological processes at the molecular level in convenient mouse models. However, until now OBBBO has been achieved safely in subcortical structures, which prevented direct insight into the process of extravasation through the skull window. Here, we used our previously developed real-time MRI to adjust the procedure to achieve robust cortical OBBBO. We found that catheter-mediated delivery to the cortex from the ipsilateral carotid artery can be improved by temporarily occluding the contralateral carotid artery. The reproducibility and safety of the method were validated by MRI and histology. This experimental platform was further exploited for studying with intravital microscopy the extravasation of 0.58 kDa rhodamine and 153 kDa anti-VEGF monoclonal antibody (bevacizumab) upon IA injection. Dynamic imaging during IA infusion captured the spatiotemporal dynamic of infiltration for each molecule into the brain parenchyma upon OBBBO. Small-sized rhodamine exhibited faster and higher penetration than the antibody. Histological analysis showed some uptake of the monoclonal antibody after IA delivery, and OBBBO significantly amplified the extent of its uptake. For quantitative assessment of cortical uptake, bevacizumab was radiolabeled with zirconium-89 and infused intraarterially. As expected, OBBBO potentiated brain accumulation, providing 33.90 ± 9.06% of injected dose per gram of brain tissue (%ID/g) in the cortex and 17.09 ± 7.22%ID/g in subcortical structures. In contrast IA infusion with an intact BBB resulted in 3.56 ± 1.06%ID/g and 3.57 ± 0.59%ID/g in the same brain regions, respectively. This study established reproducible cortical OBBBO in mice, which enabled multi-photon microscopy studies on OBBBO and drug targeting. This approach helped demonstrate in a dynamic fashion extravasation of fluorescently-tagged antibodies and their effective delivery into the brain across an osmotically opened BBB.

Combination Radioimmunotherapy Strategies for Solid Tumors

Combination radioimmunotherapy is an emerging approach for the treatment of solid tumors where radio immunotherapy alone has proven to be reasonably ineffective. Radioimmunotherapy (RIT) using monoclonal antibodies (mAbs) labeled with radionuclides is an attractive approach for cancer treatment because tumor-associated mAbs with cytotoxic radionuclides can selectively bind to tumor antigens. However, due to various limitations, mAbs cannot reach solid tumors, consequently reducing RIT efficacy. Combination RIT is a pragmatic approach through which the addition of drugs or other agents not only help mAbs to reach the targeted site but also improves its efficacy. Thus, the combination of drugs or moieties with RIT can be applied to overcome the barriers that RIT faces for solid tumors. This review covers the RIT approach, along with the mechanism of action of mAb used in RIT, limitations of solid tumors, and strategies that can be used in combination RIT to enhance the treatment regimen for solid tumors.

Comparison between Fractionated Dose and Single Dose of Cu-64 Trastuzumab Therapy in the NCI-N87 Gastric Cancer Mouse Model

For optimum radioimmunotherapy (RIT), deep penetration and uniform distribution into the tumor core is important. The solid tumor microenvironment, consisting of a highly fibrotic or desmoplastic tumor, abnormal tumor vasculature, high fluid pressure, and the absence of fluid lymphatics, limits the distribution of monoclonal antibodies mAbs to the tumor core. To investigate the optimal rationale for therapeutic mAbs administration and the microdistribution of mAbs, single and serial fractional dosage regimens of Cu-64-trastuzumab (TRZ) with paclitaxel were evaluated. Groups of nude mice were inoculated with gastric cancer cell line NCI-N87 tumor cells. When the tumor size reached 200 ± 20 mm³, the mice were divided into two groups for injection of Alexa-647-TRZ. One group (n = 5) was injected with 15 mg/kg in a single dose (SD), and the other group (n = 5) with two doses of 7.5 mg/kg (fractionated dose (FD)). In both cases, the injections were done intravenously in combination with intraperitoneal paclitaxel either as a SD of 70 mg/kg or fractionated into two doses of 40 and 30 mg/kg. Tumors were harvested, flash frozen, and sectioned (8 µm) five days after Alexa-647-TRZ injection. Rhodamine lectin (rhodamine-labeled Ricinus communis agglutinin I, 1 mg in 0.2 mL of phosphate-buffered saline (PBS)) was intravenously injected to delineate the functional vessel for a wait time of 5 min before animal euthanization. Microscopic images were acquired with an IN Cell Analyzer. The amount of TRZ that penetrated the tumor surface and the tumor vessel was calculated by area under the curve (AUC) analysis. For RIT efficacy (n = 21), Cu-64-TRZ was injected following the same dose schedule to observe tumor volume and survival ratio for 30 days. The SD and FD regimens of Alexa-647-TRZ were observed to have no significant difference in penetration of mAbs from the tumor edge and vessel, nor was the total accumulation across the whole tumor tissue significantly different. Additionally, the SD and FD regimens of Cu-64-TRZ were not proven to be significantly efficacious. Our study reveals that SD and FD in a treatment design with Cu-64-TRZ and paclitaxel shows no significant difference in therapeutic efficacy on tumor growth inhibition in vivo in mice bearing human gastric cancer xenografts overexpressing HER2 antigen.

Near-infrared-light induced nanoparticles with enhanced tumor tissue penetration and intelligent drug release

Tumor tissue presents much denser and stiffer extracellular matrix (ECM), which can hinder the penetration of most nanoparticles (NPs) and contribute to the tumor cell proliferation. Here, NIR-activated losartan was encapsulated in hollow mesoporous prussian blue nanoparticles (HMPBs) to degrade ECM. The results showed that losartan enhanced the penetration of DOX, 1.47% of the injected dose (ID) of DOX reached the tumor tissues, which was 3.00-fold higher than the control group (0.49%). In addition, as the existence of thermo-sensitive lauric acid, (Losartan + DOX)@HMPBs could achieve near "zero drug leakage" during blood circulation, so as to reduce the damage of DOX to normal tissues. Furthermore, the animal experiments proved tumor inhibition ability of (Losartan + DOX)@HMPBs in synergistic of photothermal/chemotherapy, with the tumor growth inhibition rate of 81.3%. Taken together, these findings can be a candidate for developing vectors with enhanced tumor penetration and therapeutic effect in future clinical application. STATEMENT OF SIGNIFICANCE: Due to the existence of denser extracellular matrices (ECM), only 0.7% of the administered nanoparticles dose is delivered to tumor, which will limit the tumors' therapeutic effect. Degradation of ECM can improve the penetration of nanoparticles in tumors. However, no researchers has encapsulated losartan in nanoparticles to degrade ECM. Herein, we developed a NIR induced losartan and DOX co-delivery system based on hollow mesoporous prussian blue nanoparticles (HMPBs) to degrade ECM and improve the penetration of nanoparticles in tumors. The prepared nanoparticles can also acheive near "zero drug leakage" during blood circulation and "fixed-point drug release" in tumor, so as to reduce the damage of DOX to normal tissues. We believe the prepared nanoparticles provide a new platform for cancer treatment.

Pharmacokinetics and Tissue Transport of Intraperitoneal Chemotherapy

The presence of a peritoneal barrier results in a pharmacokinetic advantage associated with intraperitoneal (IP) delivery of anticancer drugs. The anticancer efficacy of IP chemotherapy depends, however, on its ability to penetrate the tumor stroma. Tumor tissue transport is governed by diffusion and convection and is affected by numerous physical, biological, and pharmaceutical variables. From preclinical and clinical studies, it appears that tissue penetration after IP chemotherapy delivery is very limited. Several approaches are studied in order to improve tissue penetration of small molecular and macromolecular anticancer drugs after IP instillation.

Influence of the dissociation rate constant on the intra-tumor distribution of antibody-drug conjugate against tissue factor

Antibody-drug conjugates (ADCs) are currently considered to be promising agents for cancer therapy. However, especially in solid tumors, the uneven distribution of ADCs would decrease their efficacy in clinical studies. We suggest that in addition to optimizing ADC components, such as the linker structure and anticancer agent, it is necessary to consider the distribution of the ADC within tumor tissue. In this study, we established three kinds of anti-tissue factor (TF) ADCs: 1849ADC with a low k_d, 444ADC with an intermediate k_d, and 1084ADC with a high k_d. All three of the anti-TF ADCs exhibited almost the same in vitro cytotoxicity and pharmacological and biochemical characteristics, although the binding kinetics parameters differed. In vivo, all ADCs exerted equivalent antitumor effects against small BxPC3 tumors. However, on larger BxPC3 tumors, 1084ADC (higher k_d) exerted higher antitumor activity than 1849ADC (lower k_d). Furthermore, immunofluorescence staining indicated that 1084ADC was distributed throughout the whole tumor, whereas 1849ADC was mainly localized close to tumor vessels. We conclude that the ADC with a higher k_d increased the antitumor effect of because it penetrated and distributed evenly throughout the entire solid tumor. These findings highlight the importance of the k_d of a mAb in ADC design.

Tumour tissue transport after intraperitoneal anticancer drug delivery

Intraperitoneal (IP) drug delivery, either as an intraoperative chemoperfusion or as an adjuvant, repeated instillation, is an established treatment modality in patients with peritoneal carcinomatosis. The efficacy of IP drugs depends on its ability to penetrate the tumour stroma in order to reach their (sub)cellular target. It is known, that drug penetration after IP delivery is limited to a few millimetres. Here, we review the basic tissue transport mechanisms after IP delivery and discuss the biophysical barriers and obstacles that limit penetration distance. In addition, we review the physical and pharmaceutical interventions that have been studied in order to improve delivery of small molecular and macromolecular drugs after IP instillation. These interventions could inform the design of future clinical trials aiming at an improved efficacy of IP-based drug delivery in carcinomatosis patients.

Tumor-Shed Antigen Affects Antibody Tumor Targeting: Comparison of Two 89Zr-Labeled Antibodies Directed against Shed or Nonshed Antigens

We investigated the effect of shed antigen mesothelin on the tumor uptake of amatuximab, a therapeutic anti-mesothelin mAb clinically tested in mesothelioma patients. The B3 mAb targeting a nonshed antigen was also analyzed for comparison. The mouse model implanted with A431/H9 tumor, which expresses both shed mesothelin and nonshed Lewis-Y antigen, provided an ideal system to compare the biodistribution and PET imaging profiles of the two mAbs. Our study demonstrated that the tumor and organ uptakes of 89Zr-B3 were dose-independent when 3 doses, 2, 15, and 60 μg B3, were compared at 24 h after injection. In contrast, tumor and organ uptakes of 89Zr-amatuximab were dose-dependent, whereby a high dose (60 μg) was needed to achieve tumor targeting comparable to the low dose (2 μg) of 89Zr-B3, suggesting that shed mesothelin may affect amatuximab tumor targeting as well as serum half-life. The autoradiography analysis showed that the distribution of 89Zr-B3 was nonuniform with the radioactivity primarily localized at the tumor periphery independent of the B3 dose. However, the autoradiography analysis for 89Zr-amatuximab showed dose-dependent distribution profiles of the radiolabel; at 10 μg dose, the radiolabel penetrated toward the tumor core with its activity comparable to that at the tumor periphery, whereas at 60 μg dose, the distribution profile became similar to those of 89Zr-B3. These results suggest that shed antigen in blood may act as a decoy requiring higher doses of mAb to improve serum half-life as well as tumor targeting. Systemic mAb concentration should be at a severalfold molar excess to the shed Ag in blood to overcome the hepatic processing of mAb-Ag complexes. On the other hand, mAb concentration should remain lower than the shed Ag concentration in the tumor ECS to maximize tumor penetration by passing binding site barriers.

Size shrinkable drug delivery nanosystems and priming the tumor microenvironment for deep intratumoral penetration of nanoparticles

The penetration of nanomedicine into solid tumor still constitutes a great challenge for cancer therapy, which lead to the failure of thorough clearance of tumor cells. Aiming at solving this issue, lots of encouraging progress has been made in the development of multistage nanoparticles triggered by various stimuli in the past few years. Besides, the therapeutical effects of nanoagents are also greatly impacted by the complex tumor microenvironment, and remodeling tumor microenvironment has become another important approach for promoting nanoparticles penetration. In this review, we summarize and analyze recent research progress and challenges in promoting nanoparticle penetration based on two kinds of different strategies, which include size shrinkable nanoparticles and priming tumor microenvironments. Especially, many recent reported multi-strategy approaches based on particle size reduction in conjugated with other therapeutic strategies are discussed. And we expect to provide some useful enlightenments and proposals on nanotechnology-based drug delivery systems for more effective therapy of solid tumors.

MR-guided transcranial focused ultrasound safely enhances interstitial dispersion of large polymeric nanoparticles in the living brain

Generating spatially controlled, non-destructive changes in the interstitial spaces of the brain has a host of potential clinical applications, including enhancing the delivery of therapeutics, modulating biological features within the tissue microenvironment, altering fluid and pressure dynamics, and increasing the clearance of toxins, such as plaques found in Alzheimer's disease. Recently we demonstrated that ultrasound can non-destructively enlarge the interstitial spaces of the brain ex vivo. The goal of the current study was to determine whether these effects could be reproduced in the living brain using non-invasive, transcranial MRI-guided focused ultrasound (MRgFUS). The left striatum of healthy rats was treated using MRgFUS. Computer simulations facilitated treatment planning, and targeting was validated using MRI acoustic radiation force impulse imaging. Following MRgFUS treatments, Evans blue dye or nanoparticle probes were infused to assess changes in the interstitial space. In MRgFUS-treated animals, enhanced dispersion was observed compared to controls for 70 nm (12.8 ± 0.9 mm3 vs. 10.6 ± 1.0 mm3, p = 0.01), 200 nm (10.9 ± 1.4 mm3 vs. 7.4 ± 0.7 mm3, p = 0.01) and 700 nm (7.5 ± 0.4 mm3 vs. 5.4 ± 1.2 mm3, p = 0.02) nanoparticles, indicating enlargement of the interstitial spaces. No evidence of significant histological or electrophysiological injury was identified. These findings suggest that transcranial ultrasound can safely and effectively modulate the brain interstitium and increase the dispersion of large therapeutic entities such as particulate drug carriers or modified viruses. This has the potential to expand the therapeutic uses of MRgFUS.

Treatment of Movement Disorders With Focused Ultrasound

Although the use of ultrasound as a potential therapeutic modality in the brain has been under study for several decades, relatively few neuroscientists or neurologists are familiar with this technology. Stereotactic brain lesioning had been widely used as a treatment for medically refractory patients with essential tremor (ET), Parkinson disease (PD), and dystonia but has been largely replaced by deep brain stimulation (DBS) surgery, with advantages both in safety and efficacy. However, DBS is associated with complications including intracerebral hemorrhage, infection, and hardware malfunction. The occurrence of these complications has spurred interest in less invasive stereotactic brain lesioning methods including magnetic resonance imaging–guided high intensity–focused ultrasound (FUS) surgery. Engineering advances now allow sound waves to be targeted noninvasively through the skull to a brain target. High intensities of sonic energy can create a coagulation lesion similar to that of older radiofrequency stereotactic methods, but without opening the skull, recent Food and Drug Administration approval of unilateral thalamotomy for treatment of ET. Clinical studies of stereotactic FUS for aspects of PD are underway. Moderate intensity, pulsed FUS has also demonstrated the potential to safely open the blood-brain barrier for localized delivery of therapeutics including proteins, genes, and cell-based therapy for PD and related disorders. The goal of this review is to provide basic and clinical neuroscientists with a level of understanding to interact with medical physicists, biomedical engineers, and radiologists to accelerate the application of this powerful technology to brain disease

Enhancing Tumor Penetration of Nanomedicines

Tumor-targeted nanomedicines have been extensively applied to alter the drawbacks and enhance the efficacy of chemotherapeutics. Despite the large number of preclinical nanomedicine studies showing initial success, their therapeutic benefit in the clinic has been rather modest, which is partially due to the inefficient tumor penetration caused by the tumor microenvironment (high density of cells and extracellular matrix, increased interstitial fluid pressure). Furthermore, tumor penetration of nanomedicines is significantly influenced by physicochemical characteristics, such as size, surface chemistry, and shape. The effect of size on tumor penetration has been exploited to design nanomedicines with switchable size to tackle this challenge. Moreover, several pharmacological and physical approaches have been developed to enhance the tumor penetration of nanomedicines, by penetration-promoting ligands, intratumoral drug release, and modulating the tumor microenvironment and vasculature. Overall, these efforts have resulted in nanomedicines with better tumor penetration properties and with enhanced therapeutic efficacy. Future research should be directed to penetration-promoting strategies with broad applicability and with high translational potential.

Extracellular matrix remodeling in vivo for enhancing tumor-targeting efficiency of nanoparticle drug carriers using the pulsed high intensity focused ultrasound

Dense and stiff extracellular matrix (ECM) in heterogeneous tumor tissues can inhibit deep penetration of nanoparticle drug carriers and decreases their therapeutic efficacy. Herein, we suggest the ECM remodeling strategy by the pulsed high intensity focused ultrasound (Pulsed-HIFU) technology for enhanced tumor-targeting of nanoparticles. First, we clearly observed that the tumor-targeting efficacy and tissue penetration of intravenously injected Cy5.5-labled glycol chitosan nanoparticles (Cy5.5-CNPs) were greatly inhibited in tumor tissue containing high collagen and hyaluronan contents in ECM-rich A549 tumor-bearing mice, compared to in ECM-less SCC7. When collagenase or hyaluronidase was treated by intra-tumoral injection, the amount of collagen and hyaluronan decreased in ECM-rich A549 tumor tissues and more Cy5.5-CNPs penetrated inside the tumor tissue, confirmed using non-invasive optical imaging. Finally, in order to break down the stiff ECM structure, ECM-rich A549 tumor tissues were treated with the relatively low power of Pulse-HIFU (20W/cm²), wherein acute tissue damage was not observed. As we expected, the A549 tumor tissues showed the remodeling of ECM structure after non-invasive Pulsed-HIFU exposure, which resulted in the increased blood flow, decreased collagen contents, and enhanced penetration of CNP_S. Importantly, the tumor targeting efficiency in Pulsed-HIFU-treated A549 tumor tissues was 2.5 times higher than that of untreated tumor tissues. These overall results demonstrate that ECM remodeling and disruption of collagen structure by Pulse-HIFU is promising strategy to enhance the deep penetration and enhanced tumor targeting of nanoparticles in ECM-rich tumor tissues.

Direct brain infusion can be enhanced with focused ultrasound and microbubbles

The delivery of most therapeutic agents is rendered ineffective for the treatment of brain diseases due to the presence of the blood-brain barrier (BBB). The goal of this study was to investigate the effect of pre-infusion focused ultrasound (FUS) and microbubbles on the distribution of direct brain infusion in vivo. A single-element FUS transducer was used in all sonications, which were carried out immediately prior to direct infusion procedures. Mice received direct infusion of either Gadolinium-labeled albumin (Gd-albumin, 74 kDa) or adeno-associated virus (AAV, ∼4 MDa). The volumes of Gd-albumin at 30 min were deemed comparable ( P = 0.334) between the direct infusion (DI)-only group and the FUS + DI group. At 120 min, the FUS + DI group showed significantly higher contrast-enhanced volume (9.76 ± 0.74 mm³) than the DI-only group (7.14 ± 0.34 mm³). For mice infused with AAV, the total volume of transduction was estimated as GFP-positive regions and FUS + DI group demonstrated significantly higher ( P = 0.017) transduction efficiency in vivo. In conclusion, enhanced bio-distribution of directly infused agents was observed when the targeted region was pre-conditioned with FUS and microbubbles. Focused ultrasound has the potential, as an adjuvant technique, to significantly enhance direct brain infusion and achieve the desired therapeutic outcomes.

Focused ultrasound induced hyperthermia accelerates and increases the uptake of anti-HER-2 antibodies in a xenograft model

Image guided drug delivery has gained significant attention during the last few years. Labelling nanoparticles or macromolecules and monitoring their fate in the body provides information that can be used to modulate their biodistribution and improve their pharmacokinetics. In this study we label antibodies and monitor their distribution in the tumours post intravenous injection. Using Focused Ultrasound (FUS, a non-invasive method of hyperthermia) we increase the tumour temperature to 42°C for a short period of time (3-5min) and we observe an increased accumulation of labelled antibody. Repetition of focused ultrasound induced hyperthermic treatment increased still further the accumulation of the antibodies in the tumour. This treatment also augmented the accumulation of other macromolecules non-specific to the tumour, such as IgG and albumin. These effects may be used to enhance the therapeutic efficiency of antibodies and/or targeted nanoparticles.

Peptide mediated active targeting and intelligent particle size reduction-mediated enhanced penetrating of fabricated nanoparticles for triple-negative breast cancer treatment

Triple-negative breast cancer (TNBC) is one of the most invasively malignant human cancers and its incidence increases year by year. Effective therapeutics against them needs to be developed urgently. In this study, a kind of angiopep-2 modified and intelligently particle size-reducible NPs, Angio-DOX-DGL-GNP, was designed for accomplishing both high accumulation and deep penetration within tumor tissues. On one hand, for improving the cancerous targeting efficiency of NPs, angiopep-2 was anchored on the surface of NPs to facilitate their accumulation via binding with low density lipoprotein-receptor related protein (LRP) overexpressed on TNBC. On the other hand, for achieving high tumor retention and increasing tumor penetration, an intelligently particle size-reducible NPs were constructed through fabricating gelatin NPs (GNP) with doxorubicin (DOX) loaded dendrigraft poly-lysine (DGL). In vitro cellular uptake and ex-vivo imaging proved the tumor targeting effect of Angio-DOX-DGL-GNP. Additionally, the degradation of large-sized Angio-DOX-DGL-GNP by matrix metalloproteinase-2 (MMP-2) led to the size reduction from 185.7 nm to 55.6 nm. More importantly, the penetration ability of Angio-DOX-DGL-GNP after incubation with MMP-2 was dominantly enhanced in tumor spheroids. Due to a combinational effect of active targeting and deep tumor penetration, the tumor growth inhibition rate of Angio-DOX-DGL-GNP was 74.1% in a 4T1 breast cancer bearing mouse model, which was significantly higher than other groups. Taken together, we successfully demonstrated a promising and effective nanoplatform for TNBC treatment.

Combination Radioimmunotherapy Approaches and Quantification of Immuno-PET

Monoclonal antibodies (mAbs), which play a prominent role in cancer therapy, can interact with specific antigens on cancer cells, thereby enhancing the patient's immune response via various mechanisms, or mAbs can act against cell growth factors and, thereby, arrest the proliferation of tumor cells. Radionuclide-labeled mAbs, which are used in radioimmunotherapy (RIT), are effective for cancer treatment because tumor associated-mAbs linked to cytotoxic radionuclides can selectively bind to tumor antigens and release targeted cytotoxic radiation. Immunological positron emission tomography (immuno-PET), which is the combination of PET with mAb, is an attractive option for improving tumor detection and mAb quantification. However, RIT remains a challenge because of the limited delivery of mAb into tumors. The transport and uptake of mAb into tumors is slow and heterogeneous. The tumor microenvironment contributed to the limited delivery of the mAb. During the delivery process of mAb to tumor, mechanical drug resistance such as collagen distribution or physiological drug resistance such as high intestinal pressure or absence of lymphatic vessel would be the limited factor of mAb delivery to the tumor at a potentially lethal mAb concentration. When α-emitter-labeled mAbs were used, deeper penetration of α-emitter-labeled mAb inside tumors was more important because of the short range of the α emitter. Therefore, combination therapy strategies aimed at improving mAb tumor penetration and accumulation would be beneficial for maximizing their therapeutic efficacy against solid tumors.

Inkjet printing based assembly of thermoresponsive core–shell polymer microcapsules for controlled drug release

A thermoresponsive polymer microcapsule with a hollow core–porous shell structure was fabricated based on inkjet printing, which can be used to control drug release by changing the temperature at around 38 °C.

Ultrasound ablation enhances drug accumulation and survival in mammary carcinoma models

Magnetic resonance-guided focused ultrasound (MRgFUS) facilitates noninvasive image-guided conformal thermal therapy of cancer. Yet in many scenarios, the sensitive tissues surrounding the tumor constrain the margins of ablation; therefore, augmentation of MRgFUS with chemotherapy may be required to destroy remaining tumor. Here, we used 64Cu-PET-CT, MRI, autoradiography, and fluorescence imaging to track the kinetics of long-circulating liposomes in immunocompetent mammary carcinoma-bearing FVB/n and BALB/c mice. We observed a 5-fold and 50-fold enhancement of liposome and drug concentration, respectively, within MRgFUS thermal ablation-treated tumors along with dense accumulation within the surrounding tissue rim. Ultrasound-enhanced drug accumulation was rapid and durable and greatly increased total tumor drug exposure over time. In addition, we found that the small molecule gadoteridol accumulates around and within ablated tissue. We further demonstrated that dilated vasculature, loss of vascular integrity resulting in extravasation of blood cells, stromal inflammation, and loss of cell-cell adhesion and tissue architecture all contribute to the enhanced accumulation of the liposomes and small molecule probe. The locally enhanced liposome accumulation was preserved even after a multiweek protocol of doxorubicin-loaded liposomes and partial ablation. Finally, by supplementing ablation with concurrent liposomal drug therapy, a complete and durable response was obtained using protocols for which a sub-mm rim of tumor remained after ablation.

Increasing the density of nanomedicines improves their ultrasound-mediated delivery to tumours

Nanomedicines have provided fresh impetus in the fight against cancer due to their selectivity and power. However, these agents are limited when delivered intravenously due to their rapid clearance from the bloodstream and poor passage from the bloodstream into target tumours. Here we describe a novel stealthing strategy which addresses both these limitations and thereby demonstrate that both the passive and mechanically-mediated tumour accumulation of the model nanomedicine adenovirus (Ad) can be substantially enhanced. In our strategy gold nanoparticles were thoroughly modified with 2kDa polyethyleneglycol (PEG) and then linked to Ad via a single reduction-cleavable 5kDa PEG. The resulting Ad-gold-PEG construct was compared to non-modified Ad or conventionally stealthed Ad-poly[N-(2-hydroxypropyl)methacrylamide] (Ad-PHPMA). Notably, although Ad-gold-PEG was of similar size and surface charge to Ad-PHPMA the increase in density, resulting from the inclusion of the gold nanoparticles, provided a substantial enhancement of ultrasound-mediated transport. In an in vitro tumour mimicking phantom, the level and distance of Ad-gold-PEG transport was shown to be substantially greater than achieved with Ad-PHPMA. In in vivo studies 0.1% of an unmodified Ad dose was shown to accumulate in tumours, whereas over 12% of the injected dose was recovered from the tumours of mice treated with Ad-gold-PEG and ultrasound. Ultimately, a significant increase in anti-tumour efficacy resulted from this strategy. This stealthing and density-increasing technology could ultimately enhance clinical utility of intravenously delivered nanoscale medicines including viruses, liposomes and antibodies.

The effects of low-frequency ultrasound and microbubbles on rabbit hepatic tumors

High-intensity focused ultrasound in combination with microbubbles (MBs) is able to inhibit the growth of VX2 rabbit liver tumors in vivo and prolong the survival time of the animals. In this study, we attempt to investigate the feasibility of VX2 tumor growth inhibition using low-frequency ultrasound (US)-mediated MB disruption. Forty-eight New Zealand rabbits with hepatic VX2 tumors were divided into four groups: control, MBs group, low-frequency US group, and US + MB group. The parameters of the US were 20 kHz, 2 W/cm², 40% duty cycle, 5 min, and once every other day for 2 weeks. At the end of the therapy experiment, 24 rabbits were euthanized, and the cancers were collected and cut into five sections for histological examination, immunohistochemistry, laser confocal microscopy, western blotting assays, and transmission electron microscopy (TEM). Another 24 rabbits were saved, and overall survival time was recorded. The tumor volumes in control, MB, US, and US + MB groups were 6.36 ± 0.58, 5.68 ± 0.42, 5.29 ± 0.26, and 2.04 ± 0.14 cm³, respectively (US + MB versus the other three groups, P < 0.01). Tumor cells manifested coagulation necrosis with internal calcification. Hematoxylin and eosin (H–E) staining revealed interstitial hemorrhage and intravascular thrombosis. The intensity of cyclooxygenase-2 (COX-2), and vascular endothelial growth factor (VEGF) in the US + MB group in the immunohistochemical staining, laser confocal microscopy, and western blotting assays was lower than that of the other three groups (P < 0.05). TEM of the US + MB group revealed vascular endothelial cell wall rupture, widened endothelial cell gaps, interstitial erythrocyte leakage, and microvascular thrombosis, while intact vascular endothelial cells and normal erythrocytes in the tumor vessels were observed in control, MB, and US groups. Rabbits treated with US + MB had a significantly longer overall survival than those in the other three groups (χ2 = 9.328, P = 0.0242). VX2 tumor growth could be inhibited by cavitation induced using low-frequency US and MB.

Quantification of recombinant immunotoxin delivery to solid tumors allows for direct comparison of in vivo and in vitro results

Solid tumors present challenges for delivery of protein therapeutics; current methods cannot quantify the functional effects of these agents. RG7787 (anti-mesothelin recombinant immunotoxin) is highly cytotoxic to pancreatic cancer cell lines, but with limited activity in vivo. To investigate this discrepancy, we developed a flow cytometry method to quantify the amount of RG7787 internalized per cell in tumors and used it to analyze tumor responses by determining the number of molecules of RG7787 internalized per cell in vivo and comparing it to that needed to kill cells in vitro. At a maximum tolerated dose of 7.5 mg/kg, tumor cells in vivo internalized a wide range of RG7787 with the average amount equivalent to the amount that induced growth arrest in vitro. However, 20% of cells accumulated 20,300 ITs per cell, sufficient to kill cells in vitro. At 2.5 mg/kg the top 20% of cells internalized enough RG7787 to only induce growth arrest. These data are in agreement with tumor responses; 22% regression following a 7.5 mg/kg dose and growth stabilization following 2.5 mg/kg. Comparing amounts of RIT delivered in vivo and in vitro can explain tumor responses and should facilitate the development of more active immunotoxins and other antibody based agents.

Mechanical high-intensity focused ultrasound destruction of soft tissue: working mechanisms and physiologic effects

The best known method of high-intensity focused ultrasound is thermal ablation, but interest in non-thermal, mechanical destruction is increasing. The advantages of mechanical ablation are that thermal protein denaturation remains limited and less damage is created to the surrounding tissue by thermal diffusion. The two main techniques for mechanical fragmentation of tissue are histotripsy and boiling histotripsy. These techniques can be used for complete liquefaction of tumor tissue into submicron fragments, after which the fragmented tissue can be easily removed by natural (immunologic) responses. Interestingly it seems that there is a correlation between the degree of destruction and tissue specific characteristics based on the treatment settings used. In this review article, the technical aspects of these two techniques are described, and an overview of the in vivo pathologic and immunologic responses is provided.

Sonosensitive theranostic liposomes for preclinical in vivo MRI-guided visualization of doxorubicin release stimulated by pulsed low intensity non-focused ultrasound

The main goal of this study was to assess the theranostic performance of a nanomedicine able to generate MRI contrast as a response to the release from liposomes of the antitumor drug Doxorubicin triggered by the local exposure to pulsed low intensity non focused ultrasounds (pLINFU). In vitro experiments showed that Gadoteridol was an excellent imaging agent for probing the release of Doxorubicin following pLINFU stimulation. On this basis, the theranostic system was investigated in vivo on a syngeneic murine model of TS/A breast cancer. MRI offered an excellent guidance for monitoring the pLINFU-stimulated release of the drug. Moreover, it provided: i) an in vivo proof of the effective release of the liposomal content, and ii) a confirmation of the therapeutic benefits of the overall protocol. Ex vivo fluorescence microscopy indicated that the good therapeutic outcome was originated from a better diffusion of the drug in the tumor following the pLINFU stimulus. Very interestingly, the broad diffusion of the drug in the tumor stroma appeared to be mediated by the presence of the liposomes themselves. The results of this study highlighted either the great potential of US-based stimuli to safely trigger the release of a drug from its nanocarrier or the associated significant therapeutic improvement. Finally, MRI demonstrated to be a valuable technique to support chemotherapy and monitoring the outcome. Furthermore, in this specific case, the theranostic agent developed has a high clinical translatability because the MRI agent utilized is already approved for human use.

Modulation of the interstitial fluid pressure by high intensity focused ultrasound as a way to alter local fluid and solute movement: insights from a mathematical model

High intensity focused ultrasound (HIFU) operated in thermal mode has been reported to reduce interstitial fluid pressure and improve the penetration of large macromolecules and nanoparticles in tumor and normal tissue. Little is understood about how the interstitial fluid pressure and velocity as well as the interstitial macromolecule transport are affected by HIFU exposure. A mathematical model is presented here which sheds light on the initial biophysical changes brought about HIFU. Our continuum model treats tissue as an effective poro-elastic material that reacts to elevated temperatures with a rapid drop in interstitial elastic modulus. Using parameters from the literature, the model is extrapolated to derive information on the effect in tumors, and to predict its impact on the convective and diffusive transport of macromolecular drugs. The model is first solved using an analytical approximation with step-wise changes at each boundary, and then solved numerically starting from a Gaussian beam approximation of the ultrasound treatment. Our results indicate that HIFU causes a rapid drop in interstitial fluid pressure that may be exploited to facilitate convection of macromolecules from vasculature to the exposed region. However, following a short recovery period in which the interstitial fluid pressure is normalized, transport returns to normal and the advantages disappear over time. The results indicate that this effect is strongest for the delivery of large molecules and nanoparticles that are in the circulation at the time of treatment. The model may be easily applied to more complex situations involving effects on vascular permeability and diffusion.