Houari Korideck

Targeted radiotherapy with gold nanoparticles: current status and future perspectives

Radiation therapy (RT) is the treatment of cancer and other diseases with ionizing radiation. The ultimate goal of RT is to destroy all the disease cells while sparing healthy tissue. Towards this goal, RT has advanced significantly over the past few decades in part due to new technologies including: multileaf collimator-assisted modulation of radiation beams, improved computer-assisted inverse treatment planning, image guidance, robotics with more precision, better motion management strategies, stereotactic treatments and hypofractionation. With recent advances in nanotechnology, targeted RT with gold nanoparticles (GNPs) is actively being investigated as a means to further increase the RT therapeutic ratio. In this review, we summarize the current status of research and development towards the use of GNPs to enhance RT. We highlight the promising emerging modalities for targeted RT with GNPs and the corresponding preclinical evidence supporting such promise towards potential clinical translation. Future prospects and perspectives are discussed.

In vitro radiosensitization by gold nanoparticles during continuous low-dose-rate gamma irradiation with I-125 brachytherapy seeds

UNLABELLED This communication reports the first experimental evidence of gold nanoparticle (AuNP) radiosensitization during continuous low-dose-rate (LDR) gamma irradiation with low-energy brachytherapy sources. HeLa cell cultures incubated with and without AuNP were irradiated with an I-125 seed plaque designed to produce a relatively homogeneous dose distribution in the plane of the cell culture slide. Four sets of irradiation experiments were conducted at low-dose rates ranging from 2.1 to 4.5cGy/h. Residual γH2AX was measured 24h after irradiation and used to compare radiation damage to the cells with and without AuNP. The data demonstrate that the biological effect when irradiating in the presence of 0.2mg/ml concentration of AuNP is about 70%-130% greater than without AuNP. Meanwhile, without radiation, the AuNP showed minimal effect on the cancer cells. These findings provide in vitro evidence that AuNP may be employed as radiosensitizers during continuous LDR brachytherapy. FROM THE CLINICAL EDITOR In this basic science paper, the application of gold nanoparticles as radiosensitizing agents for low dose rate gamma radiation therapy is discussed, demonstrating efficacy in cell culture models.

DNA Damage Enhancement from Gold Nanoparticles for Clinical MV Photon Beams

In this study, we quantify the relative damage enhancement due to the presence of gold nanoparticles (GNP) in vitro in a clinical 6 MV beam for various delivery parameters and depths. It is expected that depths and delivery modes that produce a larger proportions of low-energy photons will have a larger effect on the cell samples containing GNP. HeLa cells with and without 50 nm GNP were irradiated at depths of 1.5, 5, 10, 15 and 20 cm. Conventional beams with square aperture sizes 5, 10 and 15 cm at isocenter, and flattening filter free (FFF) beams were used. Relative DNA damage enhancement with GNP was evaluated by γ-H2AX staining. Statistically significant increases in DNA damage with GNP, compared to the absence of GNP, were observed for all depths and delivery modes. Relative to the shallowest depth, damage enhancement was observed to increase as a function of increasing depth for all deliveries. For the conventional (open field) delivery, DNA damage enhancement with GNP was seen to increase as a function of field size. For FFF delivery, a substantial increase in enhancement was found relative to the conventional field delivery. The measured relative DNA damage enhancement validates the theoretically predicted trends as a function of depth and delivery mode for clinical MV photon beams. The results of this study open new possibilities for the clinical development of gold nanoparticle-aided radiation therapy.

Noninvasive Quantitative Tomography of the Therapeutic Response to Dexamethasone in Ovalbumin-Induced Murine Asthma

Animal models of pulmonary inflammation are critical for understanding the pathophysiology of asthma and for developing new therapies. Current conventional assessments in mouse models of asthma and chronic obstructive pulmonary disease rely on invasive measures of pulmonary function and terminal characterization of cells infiltrating into the lung. The ability to noninvasively visualize and quantify the underlying biological processes in mouse pulmonary models in vivo would provide a significant advance in characterizing disease processes and the effects of therapeutics. We report the utility of near-infrared imaging agents, in combination with fluorescence molecular tomography (FMT) imaging, for the noninvasive quantitative imaging of mouse lung inflammation in an ovalbumin (OVA)-induced chronic asthma model. BALB/c mice were intraperitoneally sensitized with OVA-Alum (aluminum hydroxide) at days 0 and 14, followed by daily intranasal challenge with OVA in phosphate-buffered saline from days 21 to 24. Dexamethasone and control therapies were given intraperitoneally 4 h before each intranasal inhalation of OVA from days 21 to 24. Twenty-four hours before imaging, the mice were injected intravenously with 5 nmol of the cathepsin-activatable fluorescent agent, ProSense 680. Quantification by FMT revealed in vivo cysteine protease activity within the lung associated with the inflammatory eosinophilia, which decreased in response to dexamethasone treatment. Results were correlated with in vitro laboratory tests (bronchoalveolar lavage cell analysis and immunohistochemistry) and revealed good correlation between these measures and quantification of ProSense 680 activation. We have demonstrated the ability of FMT to noninvasively visualize and quantify inflammation in the lung and monitor therapeutic efficacy in vivo.

Radiation dose enhancement of gadolinium-based AGuIX nanoparticles on HeLa cells

UNLABELLED Radiation dose enhancement of high-Z nanoparticles is an active area of research in cancer therapeutics. When kV and MV energy photon beams interact with high-Z nanoparticles in a tumor, the release of secondary electrons can injure tumor cells, leading to a higher treatment efficacy than radiation alone. We present a study that characterizes the radiation dose enhancing effects of gadolinium-based AGuIX nanoparticles on HeLa cells. Our in vitro clonogenic survival assays showed an average dose enhancement of 1.54× for 220 kVp radiation and 1.15× for 6 MV radiation. The sensitivity enhancement ratio at 4 Gy (SER4Gy) was 1.54 for 220 kVp and 1.28 for 6 MV, indicating that these nanoparticles may be useful for clinical radiation therapy. FROM THE CLINICAL EDITOR This study characterized the radiation dose enhancing effects of gadolinium-based AGuIX nanoparticles on HeLa cells, showing clear effects at 220 kV as well as 6 MV, suggesting that after additional studies, these nanoparticles may be beneficial in human radiation therapy.

Third generation gold nanoplatform optimized for radiation therapy

We report the design and fabrication of third generation ultrasmall PEGylated gold nanoparticles based platform (AuRad™) optimized for applications in radiation therapy. The AuRad™ nanoplatform has the following key features: (I) surface coating of hetero-bifunctional-PEG with amine, carboxyl, methoxy functional groups, which make this a versatile nanoplatform to conjugate various moieties like fluorophores, peptides, drugs, radiolabels; (II) size that is optimized for longer circulation, higher tumor uptake and modulated clearance; (III) high radiation enhancement. We have synthesized ultrasmall 2-3 nm gold nanoparticles, followed by attachment of hetero-bifunctional PEG and further conjugation of fluorophore AlexaFlour 647 for optical imaging, with a stability of more than 6 months. Confocal bioimaging with HeLa cells showed robust uptake of biocompatible nanoparticles in cells. Irradiation experiments X-rays showed greater than 2.8-fold cell kill enhancement as demonstrated by clonogenic survival assays. The results indicate that AuRad nanoplatform can act as potential theranostic agent in radiation therapy.

Synergy of radiotherapy and PD-1 blockade in Kras-mutant lung cancer

Radiation therapy (RT), a critical modality in the treatment of lung cancer, induces direct tumor cell death and augments tumor-specific immunity. However, despite initial tumor control, most patients suffer from locoregional relapse and/or metastatic disease following RT. The use of immunotherapy in non-small-cell lung cancer (NSCLC) could potentially change this outcome by enhancing the effects of RT. Here, we report significant (up to 70% volume reduction of the target lesion) and durable (up to 12 weeks) tumor regressions in conditional Kras-driven genetically engineered mouse models (GEMMs) of NSCLC treated with radiotherapy and a programmed cell death 1 antibody (αPD-1). However, while αPD-1 therapy was beneficial when combined with RT in radiation-naive tumors, αPD-1 therapy had no antineoplastic efficacy in RT-relapsed tumors and further induced T cell inhibitory markers in this setting. Furthermore, there was differential efficacy of αPD-1 plus RT among Kras-driven GEMMs, with additional loss of the tumor suppressor serine/threonine kinase 11/liver kinase B1 (Stk11/Lkb1) resulting in no synergistic efficacy. Taken together, our data provide evidence for a close interaction among RT, T cells, and the PD-1/PD-L1 axis and underscore the rationale for clinical combinatorial therapy with immune modulators and radiotherapy.

Image-guided radiotherapy platform using single nodule conditional lung cancer mouse models

Close resemblance of murine and human trials is essential to achieve the best predictive value of animal-based translational cancer research. Kras-driven genetically engineered mouse models of non-small-cell lung cancer faithfully predict the response of human lung cancers to systemic chemotherapy. Owing to development of multifocal disease, however, these models have not been usable in studies of outcomes following focal radiotherapy (RT). We report the development of a preclinical platform to deliver state-of-the-art image-guided RT in these models. Presence of a single tumour as usually diagnosed in patients is modelled by confined injection of adenoviral Cre recombinase. Furthermore, three-dimensional conformal planning and state-of-the-art image-guided dose delivery are performed as in humans. We evaluate treatment efficacies of two different radiation regimens and find that Kras-driven tumours can temporarily be stabilized upon RT, whereas additional loss of either Lkb1 or p53 renders these lesions less responsive to RT. Current genetic mouse models of lung cancer develop multifocal tumours in all lobes, which limits their applicability to model radiotherapy of human disease. Here Herter-Sprie et aldevelop a method to induce single lung tumours in these models, allowing precise evaluation of radiation regiment efficacy.

Comprehensive quality assurance phantom for the small animal radiation research platform (SARRP)

PURPOSE To develop and test the suitability and performance of a comprehensive quality assurance (QA) phantom for the Small Animal Radiation Research Platform (SARRP). METHODS AND MATERIALS A QA phantom was developed for carrying out daily, monthly and annual QA tasks including: imaging, dosimetry and treatment planning system (TPS) performance evaluation of the SARRP. The QA phantom consists of 15 (60 × 60 × 5 mm(3)) kV-energy tissue equivalent solid water slabs. The phantom can incorporate optically stimulated luminescence dosimeters (OSLD), Mosfet or film. One slab, with inserts and another slab with hole patterns are particularly designed for image QA. RESULTS Output constancy measurement results showed daily variations within 3%. Using the Mosfet in phantom as target, results showed that the difference between TPS calculations and measurements was within 5%. Annual QA results for the Percentage depth dose (PDD) curves, lateral beam profiles, beam flatness and beam profile symmetry were found consistent with results obtained at commissioning. PDD curves obtained using film and OSLDs showed good agreement. Image QA was performed monthly, with image-quality parameters assessed in terms of CBCT image geometric accuracy, CT number accuracy, image spatial resolution, noise and image uniformity. CONCLUSIONS The results show that the developed QA phantom can be employed as a tool for comprehensive performance evaluation of the SARRP. The study provides a useful reference for development of a comprehensive quality assurance program for the SARRP and other similar small animal irradiators, with proposed tolerances and frequency of required tests.

MOSFET assessment of radiation dose delivered to mice using the Small Animal Radiation Research Platform (SARRP).

The Small Animal Radiation Research Platform (SARRP) is a novel isocentric irradiation system that enables state-of-the-art image-guided radiotherapy research to be performed with animal models. This paper reports the results obtained from investigations assessing the radiation dose delivered by the SARRP to different anatomical target volumes in mice. Surgically implanted metal oxide semiconductor field effect transistors (MOSFET) dosimeters were employed for the dose assessment. The results reveal differences between the calculated and measured dose of −3.5 to 0.5%, −5.2 to −0.7%, −3.9 to 0.5%, −5.9 to 2.5%, −5.5 to 0.5%, and −4.3 to 0% for the left kidney, liver, pancreas, prostate, left lung, and brain, respectively. Overall, the findings show less than 6% difference between the delivered and calculated dose, without tissue heterogeneity corrections. These results provide a useful assessment of the need for tissue heterogeneity corrections in SARRP dose calculations for clinically relevant tumor model sites.