Ultrasound Molecular Imaging of Renal Cell Carcinoma: VEGFR targeted therapy monitored with VEGFR1 and FSHR targeted microbubbles

BR55 Ultrasound Molecular Imaging of Clear Cell Renal Cell Carcinoma Reflects Tumor Vascular Expression of VEGFR-2 in a Patient-Derived Xenograft Model

Standard imaging cannot reliably predict the nature of renal tumors. Among malignant renal tumors, clear cell renal cell carcinoma (ccRCC) is the most common histological subtype, in which the vascular endothelial growth factor 2 (VEGFR-2) is highly expressed in the vascular endothelium. BR55, a contrast agent for ultrasound imaging, consists of gas-core lipid microbubbles that specifically target and bind to the extracellular portion of the VEGFR-2. The specific information provided by ultrasound molecular imaging (USMI) using BR55 was compared with the vascular tumor expression of the VEGFR-2 by immunohistochemical (IHC) staining in a preclinical model of ccRCC. Patients' ccRCCs were orthotopically grafted onto Nod-Scid-Gamma (NSG) mice to generate patient-derived xenografts (PdX). Mice were divided into four groups to receive either vehicle or axitinib an amount of 2, 7.5 or 15 mg/kg twice daily. Perfusion parameters and the BR55 ultrasound contrast signal on PdX renal tumors were analyzed at D0, D1, D3, D7 and D11, and compared with IHC staining for the VEGFR-2 and CD34. Significant Pearson correlation coefficients were observed between the area under the curve (AUC) and the CD34 (0.84, p < 10-4), and between the VEGFR-2-specific signal obtained by USMI and IHC (0.72, p < 10-4). USMI with BR55 could provide instant, quantitative information on tumor VEGFR-2 expression to characterize renal masses non-invasively.

Intraoperative Imaging in Hepatopancreatobiliary Surgery

Hepatopancreatobiliary surgery belongs to one of the most complex fields of general surgery. An intricate and vital anatomy is accompanied by difficult distinctions of tumors from fibrosis and inflammation; the identification of precise tumor margins; or small, even disappearing, lesions on currently available imaging. The routine implementation of ultrasound use shifted the possibilities in the operating room, yet more precision is necessary to achieve negative resection margins. Modalities utilizing fluorescent-compatible dyes have proven their role in hepatopancreatobiliary surgery, although this is not yet a routine practice, as there are many limitations. Modalities, such as photoacoustic imaging or 3D holograms, are emerging but are mostly limited to preclinical settings. There is a need to identify and develop an ideal contrast agent capable of differentiating between malignant and benign tissue and to report on the prognostic benefits of implemented intraoperative imaging in order to navigate clinical translation. This review focuses on existing and developing imaging modalities for intraoperative use, tailored to the needs of hepatopancreatobiliary cancers. We will also cover the application of these imaging techniques to theranostics to achieve combined diagnostic and therapeutic potential.

Ultrasound Molecular Imaging of Epithelial Mesenchymal Transition for Evaluating Tumor Metastatic Potential via Targeted Biosynthetic Gas Vesicles

Epithelial mesenchymal transition (EMT) of tumor cells is recognized as the main driver to promote metastasis. Extensive researches suggest that gradually decreased E-cadherin (E-cad) and increased N-cadherin (N-cad) exist in the tumor cells during the EMT process. However, there still lacks suitable imaging methods to monitor the status of EMT for evaluating tumor metastatic potentials. Herein, the E-cad-targeted and N-cad-targeted gas vesicles (GVs) are developed as the acoustic probes to monitor the EMT status in tumor. The resulting probes have ≈200 nm particle size and good tumor cell targeting performance. Upon systemic administration, E-cad-GVs and N-cad-GVs can traverse through blood vessels and bind to the tumor cells, producing strong contrast imaging signals in comparison with the nontargeted GVs. The contrast imaging signals correlate well with the expression levels of E-cad and N-cad and tumor metastatic ability. This study provides a new strategy to noninvasively monitor the EMT status and help to evaluate tumor metastatic potential in vivo.

Microbubbles for human diagnosis and therapy

Microbubbles (MBs) were observed for the first time in vivo as a curious consequence of quick saline injection during ultrasound (US) imaging of the aortic root, more than 50 years ago. From this serendipitous event, MBs are now widely used as contrast enhancers for US imaging. Their intrinsic properties described in this review, allow a multitude of designs, from shell to gas composition but also from grafting targeting agents to drug payload encapsulation. Indeed, the versatile MBs are deeply studied for their dual potential in imaging and therapy. As presented in this paper, new generations of MBs now opens perspectives for targeted molecular imaging along with the development of new US imaging systems. This review also presents an overview of the different therapeutic strategies with US and MBs for cancer, cardiovascular diseases, and inflammation. The overall aim is to overlap those fields in order to find similarities in the MBs application for treatment enhancement associated with US. To conclude, this review explores the new scales of MBs technologies with nanobubbles development, and along concurrent advances in the US imaging field. This review ends by discussing perspectives for the booming future uses of MBs.

Characterization of spatially mapped volumetric molecular ultrasound signals for predicting response to anti-vascular therapy

Quantitative three-dimensional molecular ultrasound is a promising technology for longitudinal imaging applications such as therapy monitoring; the risk profile is favorable compared to positron emission tomography and computed tomography. However, clinical translation of quantitative methods for this technology are limited in that they assume that tumor tissues are homogeneous, and often depend on contrast-destruction events that can produce unintended bioeffects. Here, we develop quantitative features (henceforth image features) that capture tumor spatial information, and that are extracted without contrast destruction. We compare these techniques with the contrast-destruction derived differential targeted enhancement parameter (dTE) in predicting response to therapy. We found thirty-three reproducible image features that predict response to antiangiogenic therapy, without the need for a contrast agent disruption pulse. Multiparametric analysis shows that several of these image features can differentiate treated versus control animals with comparable performance to post-destruction measurements, suggesting that these can potentially replace parameters such as the dTE. The highest performing pre-destruction image features showed strong linear correlations with conventional dTE parameters with less overall variance. Thus, our study suggests that image features obtained during the wash in of the molecular agent, pre-destruction, may replace conventional post-destruction image features or the dTE parameter.

Targeted Nanobubbles of PD-L1 mAb Combined with Doxorubicin as a Synergistic Tumor Repressor in Hepatocarcinoma

Purpose

Ultrasound nanobubbles (NBs) can kill tumor cells, mediated by their effects of cavitation and acoustic perforation through ultrasound, while as novel drug carriers, biomaterial-modified NBs release drugs at a target region. In this work, the ultrasound NBs bridged by biotin-streptavidin were prepared simultaneously to be loaded with both programmed death ligand 1 monoclonal antibody (PD-L1 mAb) and doxorubicin (DOX), which are immune checkpoint inhibitors (ICIs) and chemotherapeutic agents, to synergize immunotherapy and chemotherapy combined with sonodynamic therapy (SDT).

Methods

The PD-L1 mAb/DOX NBs, using bridging affinity biotin (BRAB) technology as a bridge, were prepared by thin-film hydration and mechanical oscillation for the targeted delivery of biotinylated PD-L1 mAb and DOX. Characterization and pharmacokinetic studies of PD-L1 mAb/DOX NBs were performed in vitro and in vivo. The antitumor effect of ultrasound-mediated PD-L1 mAb/DOX-NBs was studied in the subcutaneously transplanted tumor of the H22 hepatoma model, and the mechanism of synergistic tumor repression was investigated.

Results

The data of in vitro targeting experiments, contrast-enhanced ultrasound imaging (CEUS), in vivo imaging of the small animals imaging system (IVIS), and frozen sections showed that PD-L1 mAb/DOX-NBs have well-targeted aggregation in the tumor. By observing tumor inhibition rate, tissue cell apoptosis, and apoptosis-related gene and protein expression, the PD-L1 mAb/DOX-NBs group showed the best immunotherapy effects, and its tumor volume and mass inhibition rates were about 69.64% and 75.97%, respectively (P < 0.01). Therefore, blocking the PD-1/PD-L1 pathway could improve immune cells’ tumor-killing ability. Antitumor immune cytokines were further enhanced when combined with DOX-induced tumor cell apoptosis and immunogenic cell death (ICD).

Conclusion

In summary, ultrasound-mediated PD-L1 mAb/DOX-NBs showed significant synergistic antitumor effects, providing a potential combined immunotherapy strategy for HCC.

Optimizing the performance of 68Ga labeled FSHR ligand in Prostate Cancer Model by Co-Administration of Aprotinin

PURPOSE

Radiolabeled FSH1 peptides are potential specific probes for FSHR imaging. However, moderate uptakes and fast washout from the tumors may limit its widespread use. In this study, ⁶⁸Ga labeled modified FSH1 analogs was prepared and the imaging properties were determined in the prostate cancer model with or without aprotinin.

METHODS

NOTA-MAL-FSH4 was synthesized and labeled with ⁶⁸Ga. The pharmacokinetic profile of the peptide after co-administration with aprotinin was determined through metabolism analyses and microPET imaging.

RESULTS

⁶⁸Ga-NOTA-MAL-FSH4 was successfully prepared. The IC50 value of displacement ⁶⁸Ga-NOTA-MAL-FSH4 with FSH1 was 139.4 ± 1.16 nM. The PC-3 prostate tumor was visible after administration of the ⁶⁸Ga labeled tracer. In vitro RP-HPLC analysis revealed that the average percentage of intact peptide in the plasma, liver and tumor was 8.30, 9.57 and 7.06% respectively. In presence of aprotinin, the amounts of intact peptide increased to 34.32%, 20.63% and 15.39% in the counterparts respectively. MicroPET imaging showed that the uptakes of PC-3 tumors at 60mins after co-administration of 100μg, 200μg or 400μg enzyme inhibitors were 2.91 ± 0.21%ID/g, 3.89 ± 0.16%ID/g and 9.21 ± 0.22%ID/g respectively.

CONCLUSION

With the aid of a serine protease inhibitor, the performance of the ⁶⁸Ga labeled peptide was optimized, which may benefit further clinical application.

Protein-conjugated microbubbles for the selective targeting of S. aureus biofilms

Staphylococcus aureus (S. aureus) is an important human pathogen and a common cause of bloodstream infection. The ability of S. aureus to form biofilms, particularly on medical devices, makes treatment difficult, as does its tendency to spread within the body and cause secondary foci of infection. Prolonged courses of intravenous antimicrobial treatment are usually required for serious S. aureus infections. This work investigates the in vitro attachment of microbubbles to S. aureus biofilms via a novel Affimer protein, AClfA1, which targets the clumping factor A (ClfA) virulence factor – a cell-wall anchored protein associated with surface attachment. Microbubbles (MBs) are micron-sized gas-filled bubbles encapsulated by a lipid, polymer, or protein monolayer or other surfactant-based material. Affimers are small (∼12 kDa) heat-stable binding proteins developed as replacements for antibodies. The binding kinetics of AClfA1 against S. aureus ClfA showed strong binding affinity (K_D = 62 ± 3 nM). AClfA1 was then shown to bind S. aureus biofilms under flow conditions both as a free ligand and when bound to microparticles (polymer beads or microbubbles). Microbubbles functionalized with AClfA1 demonstrated an 8-fold increase in binding compared to microbubbles functionalized with an identical Affimer scaffold but lacking the recognition groups. Bound MBs were able to withstand flow rates of 250 μL/min. Finally, ultrasound was applied to burst the biofilm bound MBs to determine whether this would lead to biofilm biomass loss or cell death. Application of a 2.25 MHz ultrasound profile (with a peak negative pressure of 0.8 MPa and consisting of a 22-cycle sine wave, at a pulse repetition rate of 10 kHz) for 2 s to a biofilm decorated with targeted MBs, led to a 25% increase in biomass loss and a concomitant 8% increase in dead cell count. The results of this work show that Affimers can be developed to target S. aureus biofilms and that such Affimers can be attached to contrast agents such as microbubbles or polymer beads and offer potential, with some optimization, for drug-free biofilm treatment.

Expanding the Role of Ultrasound for the Characterization of Renal Masses

The incidental detection of renal masses has been steadily rising. As a significant proportion of renal masses that are surgically treated are benign or indolent in nature, there is a clear need for better presurgical characterization of renal masses to minimize unnecessary harm. Ultrasound is a widely available and relatively inexpensive real-time imaging technique, and novel ultrasound-based applications can potentially aid in the non-invasive characterization of renal masses. Evidence acquisition: We performed a narrative review on novel ultrasound-based techniques that can aid in the non-invasive characterization of renal masses. Evidence synthesis: Contrast-enhanced ultrasound (CEUS) adds significant diagnostic value, particularly for cystic renal masses, by improving the characterization of fine septations and small nodules, with a sensitivity and specificity comparable to magnetic resonance imaging (MRI). Additionally, the performance of CEUS for the classification of benign versus malignant renal masses is comparable to that of computed tomography (CT) and MRI, although the imaging features of different tumor subtypes overlap significantly. Ultrasound molecular imaging with targeted contrast agents is being investigated in preclinical research as an addition to CEUS. Elastography for the assessment of tissue stiffness and micro-Doppler imaging for the improved detection of intratumoral blood flow without the need for contrast are both being investigated for the characterization of renal masses, though few studies have been conducted and validation is lacking. Conclusions: Several novel ultrasound-based techniques have been investigated for the non-invasive characterization of renal masses. CEUS has several advantages over traditional grayscale ultrasound, including the improved characterization of cystic renal masses and the potential to differentiate benign from malignant renal masses to some extent. Ultrasound molecular imaging offers promise for serial disease monitoring and the longitudinal assessment of treatment response, though this remains in the preclinical stages of development. While elastography and emerging micro-Doppler techniques have shown some encouraging applications, they are currently not ready for widespread clinical use.

Theranostic Microbubbles with Homogeneous Ligand Distribution for Higher Binding Efficacy

Phospholipid-coated targeted microbubbles are used for ultrasound molecular imaging and locally enhanced drug delivery, with the binding efficacy being an important trait. The use of organic solvent in microbubble production makes the difference between a heterogeneous or homogeneous ligand distribution. This study demonstrates the effect of ligand distribution on the binding efficacy of phospholipid-coated ανβ3-targeted microbubbles in vitro using a monolayer of human umbilical-vein endothelial cells and in vivo using chicken embryos. Microbubbles with a homogeneous ligand distribution had a higher binding efficacy than those with a heterogeneous ligand distribution both in vitro and in vivo. In vitro, 1.55× more microbubbles with a homogeneous ligand distribution bound under static conditions, while this was 1.49× more under flow with 1.25 dyn/cm2, 1.56× more under flow with 2.22 dyn/cm2, and 1.25× more in vivo. The in vitro dissociation rate of bound microbubbles with homogeneous ligand distribution was lower at low shear stresses (1–5 dyn/cm2). The internalized depth of bound microbubbles was influenced by microbubble size, not by ligand distribution. In conclusion, for optimal binding the use of organic solvent in targeted microbubble production is preferable over directly dispersing phospholipids in aqueous medium.

Highlights of the development in ultrasound during the last 70 years: A historical review

This review looks at highlights of the development in ultrasound, ranging from interventional ultrasound and Doppler to the newest techniques like contrast-enhanced ultrasound and elastography, and gives reference to some of the valuable articles in Acta Radiologica. Ultrasound equipment is now available in any size and for any purpose, ranging from handheld devices to high-end devices, and the scientific societies include ultrasound professionals of all disciplines publishing guidelines and recommendations. Interventional ultrasound is expanding the field of use of ultrasound-guided interventions into nearly all specialties of medicine, from ultrasound guidance in minimally invasive robotic procedures to simple ultrasound-guided punctures performed by general practitioners. Each medical specialty is urged to define minimum requirements for equipment, education, training, and maintenance of skills, also for medical students. The clinical application of contrast-enhanced ultrasound and elastography is a topic often seen in current research settings.

Comprehensive review on ultrasound-responsive theranostic nanomaterials: mechanisms, structures and medical applications

The field of theranostics has been rapidly growing in recent years and nanotechnology has played a major role in this growth. Nanomaterials can be constructed to respond to a variety of different stimuli which can be internal (enzyme activity, redox potential, pH changes, temperature changes) or external (light, heat, magnetic fields, ultrasound). Theranostic nanomaterials can respond by producing an imaging signal and/or a therapeutic effect, which frequently involves cell death. Since ultrasound (US) is already well established as a clinical imaging modality, it is attractive to combine it with rationally designed nanoparticles for theranostics. The mechanisms of US interactions include cavitation microbubbles (MBs), acoustic droplet vaporization, acoustic radiation force, localized thermal effects, reactive oxygen species generation, sonoluminescence, and sonoporation. These effects can result in the release of encapsulated drugs or genes at the site of interest as well as cell death and considerable image enhancement. The present review discusses US-responsive theranostic nanomaterials under the following categories: MBs, micelles, liposomes (conventional and echogenic), niosomes, nanoemulsions, polymeric nanoparticles, chitosan nanocapsules, dendrimers, hydrogels, nanogels, gold nanoparticles, titania nanostructures, carbon nanostructures, mesoporous silica nanoparticles, fuel-free nano/micromotors.

Phospholipid-coated targeted microbubbles for ultrasound molecular imaging and therapy

Phospholipid-coated microbubbles are ultrasound contrast agents that, when functionalized, adhere to specific biomarkers on cells. In this concise review, we highlight recent developments in strategies for targeting the microbubbles and their use for ultrasound molecular imaging (UMI) and therapy. Recently developed novel targeting strategies include magnetic functionalization, triple targeting, and the use of several new ligands. UMI is a powerful technique for studying disease progression, diagnostic imaging, and monitoring of therapeutic responses. Targeted microbubbles (tMBs) have been used for the treatment of cardiovascular diseases and cancer, with therapeutics either coadministered or loaded onto the tMBs. Regardless of which disease was treated, the use of tMBs always resulted in a better therapeutic outcome than non-tMBs when compared in vitro or in vivo.

Ultrasound targeting of microbubble-bound anti PD-L1 mAb to enhance anti-tumor effect of cisplatin in cervical cancer xenografts treatment

AIMS

Anti-PD-L1 monoclonal antibody (mAb)-conjugated ultrasound (US) lipid-shelled microbubbles (PD-L1-MBs) were successfully synthesized to investigate whether that PD-L1-MBs could enhance anti-tumor effect in combination therapy with cisplatin (CDDP) under ultrasound mediation.

MAIN METHODS

Based on affinity between biotin and streptavidin, we prepared microbubbles conjugated with anti-PD-L1 mAb by membrane hydration and mechanical oscillation. A subcutaneous tumor model was established to test the anti-tumor effect and immunological activity of this combination therapy. Bax and Bcl-2 expression were detected by RT-qPCR and Immunohistochemistry. Cells undergoing apoptosis in tissue section were determined by TUNEL. Proliferation of splenocytes was analyzed by Flow cytometry. A cytotoxic T lymphocyte assay was performed by CTL. Expression of PD-L1 and CD8 in tissue section was examined by immunologfluorescence. Expression of IFN-γ, TNF-α, CD86 and CD80 was also detected by RT-qPCR.

KEY FINDINGS

We observed that the growth of the subcutaneous tumor was significantly slower in combined group than that in the group treated with either drug or microbubbles. Moreover, higher antitumor activity was observed in the combined group than that in cisplatin alone, which could be reflected by the number of apoptotic cells in tumor tissues and over expression of bax in the combined group. This combination treatment also exhibited a better immunological activity, increasing the infiltration of CD8⁺ T cells and the expression of several revelant cytokines.

SIGNIFICANCE

The ultrasound lipid-shelled PD-L1-MBs may enhance anti-tumor effects of cisplatin by blocking the PD-L1 site and improving immune function.