Identification of 6-Anilino Imidazo[4,5-c]pyridin-2-ones as Selective DNA-Dependent Protein Kinase Inhibitors and Their Application as Radiosensitizers.

The dominant role of non-homologous end-joining in the repair of radiation-induced double-strand breaks identifies DNA-dependent protein kinase (DNA-PK) as an excellent target for the development of radiosensitizers. We report the discovery of a new class of imidazo[4,5-c]pyridine-2-one DNA-PK inhibitors. Structure-activity studies culminated in the identification of 78 as a nM DNA-PK inhibitor with excellent selectivity for DNA-PK compared to related phosphoinositide 3-kinase (PI3K) and PI3K-like kinase (PIKK) families and the broader kinome, and displayed DNA-PK-dependent radiosensitization of HAP1 cells. Compound 78 demonstrated robust radiosensitization of a broad range of cancer cells in vitro, displayed high oral bioavailability, and sensitized colorectal carcinoma (HCT116/54C) and head and neck squamous cell carcinoma (UT-SCC-74B) tumor xenografts to radiation. Compound 78 also provided substantial tumor growth inhibition of HCT116/54C tumor xenografts in combination with radiation. Compound 78 represents a new, potent, and selective class of DNA-PK inhibitors with significant potential as radiosensitizers for cancer treatment.

Preclinical Systemic Pharmacokinetics, Dose Proportionality, and Central Nervous System Distribution of the ATM Inhibitor WSD0628, a Novel Radiosensitizer for the Treatment of Brain Tumors.

Radiation therapy, a standard treatment option for many cancer patients, induces DNA double-strand breaks (DSBs), leading to cell death. Ataxia telangiectasia mutated (ATM) kinase is a key regulator of DSB repair, and ATM inhibitors are being explored as radiosensitizers for various tumors, including primary and metastatic brain tumors. Efficacy of radiosensitizers for brain tumors may be influenced by a lack of effective drug delivery across the blood-brain barrier. The objective of this study was to evaluate the systemic pharmacokinetics and mechanisms that influence the central nervous system (CNS) distribution of WSD0628, a novel and potent ATM inhibitor, in the mouse. Further, we have used these observations to form the basis of predicting effective exposures for clinical application. We observed a greater than dose proportional increase in exposure, likely due to saturation of clearance processes. Our results show that WSD0628 is orally bioavailable and CNS penetrant, with unbound partitioning in CNS (i.e., unbound tissue partition coefficient) between 0.15 and 0.3. CNS distribution is not limited by the efflux transporters P-glycoprotein and breast cancer resistant protein. WSD0628 is distributed uniformly among different brain regions. Thus, WSD0628 has favorable pharmacokinetic properties and potential for further exploration to determine the pharmacodynamics-pharmacokinetics efficacy relationship in CNS tumors. This approach will provide critical insights for the clinical translation of WSD0628 for the treatment of primary and secondary brain tumors. SIGNIFICANCE STATEMENT: This study evaluates the preclinical systemic pharmacokinetics, dose proportionality, and mechanisms influencing CNS distribution of WSD0628, a novel ATM inhibitor for the treatment of brain tumors. Results indicate that WSD0628 is orally bioavailable and CNS penetrant without efflux transporter liability. We also observed a greater than dose proportional increase in exposure in both the plasma and brain. These favorable pharmacokinetic properties indicate WSD0628 has potential for further exploration for use as a radiosensitizer in the treatment of brain tumors.

Differential Distribution of the DNA-PKcs Inhibitor Peposertib Selectively Radiosensitizes Patient-derived Melanoma Brain Metastasis Xenografts.

Radioresistance of melanoma brain metastases limits the clinical utility of conventionally fractionated brain radiation in this disease, and strategies to improve radiation response could have significant clinical impact. The catalytic subunit of DNA-dependent protein kinase (DNA-PKcs) is critical for repair of radiation-induced DNA damage, and inhibitors of this kinase can have potent effects on radiation sensitivity. In this study, the radiosensitizing effects of the DNA-PKcs inhibitor peposertib were evaluated in patient-derived xenografts of melanoma brain metastases (M12, M15, M27). In clonogenic survival assays, peposertib augmented radiation-induced killing of M12 cells at concentrations ≥100 nmol/L, and a minimum of 16 hours exposure allowed maximal sensitization. This information was integrated with pharmacokinetic modeling to define an optimal dosing regimen for peposertib of 125 mpk dosed just prior to and 7 hours after irradiation. Using this drug dosing regimen in combination with 2.5 Gy × 5 fractions of radiation, significant prolongation in median survival was observed in M12-eGFP (104%; P = 0.0015) and M15 (50%; P = 0.03), while more limited effects were seen in M27 (16%, P = 0.04). These data support the concept of developing peposertib as a radiosensitizer for brain metastases and provide a paradigm for integrating in vitro and pharmacokinetic data to define an optimal radiosensitizing regimen for potent DNA repair inhibitors.

A multifunctional AIE gold cluster-based theranostic system: tumor-targeted imaging and Fenton reaction-assisted enhanced radiotherapy.

BACKGROUND: As cancer is one of the main leading causes of mortality, a series of monotherapies such as chemotherapy, gene therapy and radiotherapy have been developed to overcome this thorny problem. However, a single treatment approach could not achieve satisfactory effect in many experimental explorations. RESULTS: In this study, we report the fabrication of cyclic RGD peptide (cRGD) modified Au4-iron oxide nanoparticle (Au4-IO NP-cRGD) based on aggregation-induced emission (AIE) as a multifunctional theranostic system. Besides Au4 cluster-based fluorescence imaging and enhanced radiotherapy, iron oxide (IO) nanocluster could realize magnetic resonance (MR) imaging and Fenton reaction-based chemotherapy. Abundant toxic reactive oxygen species generated from X-ray irradiation and in situ tumor-specific Fenton reaction under acidic microenvironment leads to the apoptotic and necrotic death of cancer cells. In vivo studies demonstrated good biocompatibility of Au4-IO NP-cRGD and a high tumor suppression rate of 81.1% in the synergistic therapy group. CONCLUSIONS: The successful dual-modal imaging and combined tumor therapy demonstrated AIE as a promising strategy for constructing multifunctional cancer theranostic platform.

Redox-sensitive iodinated polymersomes carrying histone deacetylase inhibitor as a dual-functional nano-radiosensitizer for enhanced radiotherapy of breast cancer.

Radiotherapy (RT) is a frequently used means in clinical tumor treatment. The outcome of RT varies, however, to a great extent, due to RT resistance or intolerable dose, which might be resolved by the development of radio-sensitizing strategies. Here, we report redox-sensitive iodinated polymersomes (RIP) carrying histone deacetylase inhibitor, suberoylanilide hydroxamic acid (SAHA, vorinostat), as a new dual-functional nano-radiosensitizer for breast cancer radiotherapy. SAHA-loaded RIP (RIP-SAHA) with a size of about 101 nm exhibited good colloidal stability while the reduction-activated release of SAHA, giving rise to better antitumor effect to 4T1 breast carcinoma cells than free SAHA. Accordingly, RIP-SAHA combined with a 4 Gy dose of X-ray radiation led to significantly enhanced suppression of 4T1 cells compared with SAHA combined 4 Gy of X-ray radiation, as a result of enhanced DNA damage and impeded DNA damage repair. The pharmacokinetics and biodistribution studies by single-photon emission computed tomography (SPECT) with 125I-labeled SAHA (125I-SAHA) showed a 17.3-fold longer circulation and 237.7-fold better tumor accumulation of RIP-SAHA over SAHA. The systemic administration of RIP-SAHA greatly sensitized radiotherapy of subcutaneous 4T1 breast tumors and brought about significant inhibition of tumor growth, without causing damages to major organs, compared with radiotherapy alone. RIP not only enhanced SAHA delivery but also acted as a radiosensitizer. RIP-SAHA emerges as a smart dual-functional nano-radiosensitizer to effectively enhance tumor radiotherapy.

IEDDA: An Attractive Bioorthogonal Reaction for Biomedical Applications.

The pretargeting strategy has recently emerged in order to overcome the limitations of direct targeting, mainly in the field of radioimmunotherapy (RIT). This strategy is directly dependent on chemical reactions, namely bioorthogonal reactions, which have been developed for their ability to occur under physiological conditions. The Staudinger ligation, the copper catalyzed azide-alkyne cycloaddition (CuAAC) and the strain-promoted [3 + 2] azide-alkyne cycloaddition (SPAAC) were the first bioorthogonal reactions introduced in the literature. However, due to their incomplete biocompatibility and slow kinetics, the inverse-electron demand Diels-Alder (IEDDA) reaction was advanced in 2008 by Blackman et al. as an optimal bioorthogonal reaction. The IEDDA is the fastest bioorthogonal reaction known so far. Its biocompatibility and ideal kinetics are very appealing for pretargeting applications. The use of a trans-cyclooctene (TCO) and a tetrazine (Tz) in the reaction encouraged researchers to study them deeply. It was found that both reagents are sensitive to acidic or basic conditions. Furthermore, TCO is photosensitive and can be isomerized to its cis-conformation via a radical catalyzed reaction. Unfortunately, the cis-conformer is significantly less reactive toward tetrazine than the trans-conformation. Therefore, extensive research has been carried out to optimize both click reagents and to employ the IEDDA bioorthogonal reaction in biomedical applications.

Targeting a Radiosensitizing Antibody-Drug Conjugate to a Radiation-Inducible Antigen.

PURPOSE: We recently discovered that anti-TIP1 antibody activates endocytosis in cancer cells, which facilitates retention of antibody and dissociation of a conjugated drug. To improve the pharmacokinetics and cancer specificity of radiosensitizing drugs, we utilized antibody-drug conjugates (ADCs) that bind specifically to radiation-inducible antigen, TIP1, on non-small cell lung cancer (NSCLC). This approach exploits the long circulation time of antibodies to deliver a radiosensitizing drug to cancer each day during radiotherapy. EXPERIMENTAL DESIGN: Antibodies to TIP1 were prioritized based on affinity, cancer-specific binding, and internalization. The lead antibody, 7H5, was conjugated with a cytotoxic drug MMAE because of its ability to radiosensitize cancer. Cytotoxicity, colony formation, and tumor growth studies were performed with 7H5-VcMMAE in combination with radiation. RESULTS: 7H5 showed a high affinity to recombinant TIP1 protein and radiation-inducible TIP1 on the cancer cell surface. 7H5 undergoes endocytosis in NSCLC cells in vitro. We obtained an average drug-to-antibody ratio (DAR) of 4.25 for 7H5-VcMMAE. A 70% reduction in viable cells was observed following 7H5-VcMMAE treatment compared with 7H5 alone in both A549 and H1299 cells. 7H5-VcMMAE sensitized NSCLC cells to radiation, thereby significantly decreasing the surviving fraction. The ADC combined with radiation showed a prolonged delay in tumor growth and improved survival in A549 and H1299 tumor models. CONCLUSIONS: Targeting radiation-inducible TIP1 with a radiosensitizing ADC is a promising strategy to enhance the therapeutic efficacy of NSCLC. This novel approach of targeting with ADCs to radiation-inducible antigens will lead to clinical trials in lung cancer patients treated with radiotherapy.

Au-Pt Nanoparticle Formulation as a Radiosensitizer for Radiotherapy with Dual Effects.

BACKGROUND: Radiotherapy occupies an essential position as one of the most significant approaches for the clinical treatment of cancer. However, we cannot overcome the shortcoming of X-rays which is the high value of the oxygen enhancement ratio (OER). Radiosensitizers with the ability to enhance the radiosensitivity of tumor cells provide an alternative to changing X-rays to protons and heavy ion radiotherapy. MATERIALS AND METHODS: We prepared the Au-Pt nanoparticles (Au-Pt NPs) using a one-step method. The characteristics of the Au-Pt NPs were determined using TEM, HAADF-STEM, elemental mapping images, and DLS. The enhanced radiotherapy was demonstrated in vitro using MTT assays, colony formation assays, fluorescence imaging, and flow cytometric analyses of the apoptosis. The biodistribution of the Au-Pt NPs was analyzed using ICP-OES, and thermal images. The enhanced radiotherapy was demonstrated in vitro using immunofluorescence images, tumor volume and weigh, and hematoxylin & eosin (H&E) staining. RESULTS: Polyethylene glycol (PEG) functionalized nanoparticles composed of the metallic elements Au and Pt were designed to increase synergistic radiosensitivity. The mechanism demonstrated that heavy metal NPs possess a high X-ray photon capture cross-section and Compton scattering effect which increased DNA damage. Furthermore, the Au-Pt NPs exhibited enzyme-mimicking activities by catalyzing the decomposition of endogenous H2O2 to O2 in the solid tumor microenvironment (TME). CONCLUSION: Our work provides a systematically administered radiosensitizer that can selectively reside in a tumor via the EPR effect and enhances the efficiency of treating cancer with radiotherapy.

Localized Delivery of Cisplatin to Cervical Cancer Improves Its Therapeutic Efficacy and Minimizes Its Side Effect Profile.

PURPOSE: Cervical cancer represents the fourth most frequent malignancy in the world among women, and mortality has remained stable for the past 4 decades. Intravenous cisplatin with concurrent radiation therapy is the standard-of-care for patients with local and regional cervical cancer. However, cisplatin induces serious dose-limiting systemic toxicities and recurrence frequently occurs. In this study, we aimed to develop an intracervical drug delivery system that allows cisplatin release directly into the tumor and minimize systemic side effects. METHODS AND MATERIALS: Twenty patient biopsies and 5 cell lines treated with cisplatin were analyzed for platinum content using inductively coupled plasma mass spectrometry. Polymeric implants loaded with cisplatin were developed and evaluated for degradation and drug release. The effect of local or systemic cisplatin delivery on drug biodistribution as well as tumor burden were evaluated in vivo, in combination with radiation therapy. RESULTS: Platinum levels in patient biopsies were 6-fold lower than the levels needed for efficacy and radiosensitization in vitro. Cisplatin local delivery implant remarkably improved drug specificity to the tumor and significantly decreased accumulation in the blood, kidney, and other distant normal organs, compared with traditional systemic delivery. The localized treatment further resulted in complete inhibition of tumor growth. CONCLUSIONS: The current standard-of-care systemic administration of cisplatin provides a subtherapeutic dose. We developed a polymeric drug delivery system that delivered high doses of cisplatin directly into the cervical tumor, while lowering drug accumulation and consequent side effects in normal tissues. Moving forward, these data will be used as the basis of a future first-in-human clinical trial to test the efficacy of localized cisplatin as adjuvant or neoadjuvant chemotherapy in local and regional cervical cancer.

In vitro evaluation of the metabolic enzymes and drug interaction potential of triapine.

PURPOSE: To investigate the metabolic pathways of triapine in primary cultures of human hepatocytes and human hepatic subcellular fractions; to investigate interactions of triapine with tenofovir and emtricitabine; and to evaluate triapine as a perpetrator of drug interactions. The results will better inform future clinical studies of triapine, a radiation sensitizer currently being studied in a phase III study. METHODS: Triapine was incubated with human hepatocytes and subcellular fractions in the presence of a number of inhibitors of drug metabolizing enzymes. Triapine depletion was monitored by LC-MS/MS. Tenofovir and emtricitabine were co-incubated with triapine in primary cultures of human hepatocytes. Triapine was incubated with a CYP probe cocktail and human liver microsomes, followed by LC-MS/MS monitoring of CYP specific metabolite formation. RESULTS: Triapine was not metabolized by FMO, AO/XO, MAO-A/B, or NAT-1/2, but was metabolized by CYP450s. CYP1A2 accounted for most of the depletion of triapine. Tenofovir and emtricitabine did not alter triapine depletion. Triapine reduced CYP1A2 activity and increased CYP2C19 activity. CONCLUSION: CYP1A2 metabolism is the major metabolic pathway for triapine. Triapine may be evaluated in cancer patients in the setting of HIV with emtricitabine or tenofovir treatment. Confirmatory clinical trials may further define the in vivo triapine metabolic fate and quantify any drug-drug interactions.

Synergy of Tumor Microenvironment Remodeling and Autophagy Inhibition to Sensitize Radiation for Bladder Cancer Treatment.

Tumor hypoxia, acidosis, and excessive reactive oxygen species (ROS) were the main characteristics of the bladder tumor microenvironment (TME), and abnormal TME led to autophagy activation, which facilitated cancer cell proliferation. The therapeutic efficacy of autophagy inhibitors might also be impeded by abnormal TME. To address these issues, we proposed a new strategy that utilized manganese dioxide (MnO2) nanoparticles to optimize the abnormal TME and revitalize autophagy inhibitors, and both oxygenation and autophagy inhibition may sensitize the tumor cells to radiation therapy. Methods: By taking advantage of the strong affinity between negatively charged MnO2 and positively charged chloroquine (CQ), the nanoparticles were fabricated by integrating MnO2 and CQ in human serum albumin (HSA)-based nanoplatform (HSA-MnO2-CQ NPs). Results: HSA-MnO2-CQ NPs NPs efficiently generated O2 and increased pH in vitro after reaction with H+/H2O2 and then released the encapsulated CQ in a H+/H2O2 concentration-dependent manner. The NPs restored the autophagy-inhibiting activity of chloroquine in acidic conditions by increasing its intracellular uptake, and markedly blocked hypoxia-induced autophagic flux. In vivo studies showed the NPs improved pharmacokinetic behavior of chloroquine and effectively accumulated in tumor tissues. The NPs exhibited significantly decreased tumor hypoxia areas and increased tumor pH, and had remarkable autophagy inhibition efficacy on bladder tumors. Finally, a significant anti-tumor effect achieved by the enhanced autophagy inhibition and radiation sensitization. Conclusions: HSA-MnO2-CQ NPs synergistically regulated the abnormal TME and inhibited autophagic flux, and effectively sensitized radiation therapy to treat bladder cancers.

One-stop radiotherapeutic targeting of primary and distant osteosarcoma to inhibit cancer progression and metastasis using 2DG-grafted graphene quantum dots.

The application of radiotherapy (RT) to treat osteosarcoma (OS) has been limited, but this is starting to change as the ability to target radiation energy to niches improves. Furthermore, lung cancer from highly metastatic OS is a major cause of death, so it is critical to explore new strategies to tackle metastasis. In this study, we designed a nanoscale radiosensitizer by grafting 2-deoxy-d-glucose (2DG) onto graphene quantum dots (GQD) to achieve OS targeting and boost RT efficacy. Combining the use of 2DG-grafted GQDs (2DG-g-GQD) with RT produced a significant increase in oxidative stress response and DNA damage in the 143B OS cell line compared with RT alone. Moreover, 2DG-g-GQDs selectively associated with 143B cells, and demonstrated the inhibition of migration in a scratch assay. We also demonstrated remarkable improvement in their ability to inhibit tumour progression and lung metastasis in an OS xenograft mouse model. Our results show that the use of 2DG-g-GQDs as OS-targeting radiosensitizers improves their therapeutic outcome and exhibits potential for use in low-dose precision RT for OS.

Protein-drug conjugate programmed by pH-reversible linker for tumor hypoxia relief and enhanced cancer combination therapy.

Combining functional proteins with small molecular drugs into one entity may endow distinct synergistic advantages. However, on account of completely different physicochemical properties of such payloads, co-delivery through systemic administration for therapeutic purpose is challenging. Herein, we designed the protein-drug conjugate HSAP-DC-CAT (human serum albumin/Pt (IV)-dibenzocyclooctyne/chlorin e6-catalase) by modification of CAT and cisplatin pro-drug loaded HSA with pH-sensitive azide linker 3-(azidomethyl)-4-methyl-2,5-furandione (AzMMMan) followed by click chemistry assembly with DC. The dynamic covalent bonds between linker and proteins, on the one hand, can bridge proteins and small molecular drugs in the intermediate state for systemic delivery in the harsh in vivo environment; on the other hand, it can trigger traceless cleavage and release of drugs and proteins with full bioactivity in acidic microenvironment of tumor. The multifunctional HSAP-DC-CAT provides efficient cytosolic transduction in vitro, excellent blood half-lives after systemic administration, and significant antitumor outcome via integrated cisplatin-based chemotherapy and Ce6-based photodynamic therapy enhanced by catalase-induced manipulation of tumor hypoxia microenvironment. This study describes a universal formulation strategy for protein and small molecular drug by a bifunctional linker through amide reaction and click chemistry, with traceless in vivo release of therapeutic units.

Enhancement radiation-induced apoptosis in C6 glioma tumor-bearing rats via pH-responsive magnetic graphene oxide nanocarrier.

5-iodo-2-deoxyuridine (IUdR) has been demonstrated to induce an appreciable radiosensitizing effect on glioblastoma patients, but due to the short circulation half-life times and failure to pass through the blood-brain barrier (BBB), its clinical use is limited. Accordingly, in this study, we used magnetic graphene oxide (NGO/SPIONs) nanoparticles coated with PLGA polymer as a dynamic nanocarrier for IUdR and, evaluated its sensitizing enhancement ratio in combination with a single dose X-ray at clinically megavoltage energies for treatment of C6 glioma rats. Nanoparticles were characterized using Zetasizer and TEM microscopy, and in vitro biocompatibility of nanoparticles was assessed with MTT assay. IUdR/MNPs were intravenously administered under a magnetic field (1.3 T) on day 13 after the implantation of C6 cells. After a day following the injection, rats exposed with radiation (8 Gy). ICP-OES analysis data indicated an effective magnetic targeting, leading to remarkably improved penetration through the BBB. In vivo release analysis with HPLC indicated sustained release of IUdR and, prolonged the lifespan in plasma (P < .01). In addition, our findings revealed a synergistic effect for IUdR/MNPs coupled with radiation, which significantly inhibited the tumor expansion (>100%), prolonged the survival time (>100%) and suppressed the anti-apoptotic response of glioma rats by increasing Bax/Bcl-2 ratio (2.13-fold) in compared with the radiation-only. In conclusion, besides high accumulation in targeted tumor sites, the newly developed IUdR/MNPs, also exhibited the ability of IUdR/MNPs to significantly enhance radiosensitizing effect, improve therapeutic efficacy and increase toxicity for glioma-bearing rats.

Surface functionalization of gold nanoclusters with arginine: a trade-off between microtumor uptake and radiotherapy enhancement.

Ultra-small gold nanoclusters (AuNCs) are increasingly investigated for cancer imaging and radiotherapy enhancement. While fine-tuning the AuNC surface chemistry can optimize their pharmacokinetics, its effects on radiotherapy enhancement remain largely unexplored. This study demonstrates that optimizing the surface chemistry of AuNCs for increased tumor uptake can significantly affect its potential to augment radiotherapy outcomes.

Poly(vinyl alcohol) boosting therapeutic potential of p-boronophenylalanine in neutron capture therapy by modulating metabolism.

In the current clinical boron neutron capture therapy (BNCT), p-boronophenylalanine (BPA) has been the most powerful drug owing to its ability to accumulate selectively within cancers through cancer-related amino acid transporters including LAT1. However, the therapeutic success of BPA has been sometimes compromised by its unfavorable efflux from cytosol due to their antiport mechanism. Here, we report that poly(vinyl alcohol) (PVA) can form complexes with BPA through reversible boronate esters in aqueous solution, and the complex termed PVA-BPA can be internalized into cancer cells through LAT1-mediated endocytosis, thereby enhancing cellular uptake and slowing the untoward efflux. In in vivo study, compared with clinically used fructose-BPA complexes, PVA-BPA exhibited efficient tumor accumulation and prolonged tumor retention with quick clearance from bloodstream and normal organs. Ultimately, PVA-BPA showed critically enhanced antitumor activity in BNCT. The facile technique proposed in this study offers an approach for drug delivery focusing on drug metabolism.

Modulation of nanoparticle uptake, intracellular distribution, and retention with docetaxel to enhance radiotherapy.

OBJECTIVE: One of the major issues in current radiotherapy (RT) is the normal tissue toxicity. A smart combination of agents within the tumor would allow lowering the RT dose required while minimizing the damage to healthy tissue surrounding the tumor. We chose gold nanoparticles (GNPs) and docetaxel (DTX) as our choice of two radiosensitizing agents. They have a different mechanism of action which could lead to a synergistic effect. Our first goal was to assess the variation in GNP uptake, distribution, and retention in the presence of DTX. Our second goal was to assess the therapeutic results of the triple combination, RT/GNPs/DTX. METHODS: We used HeLa and MDA-MB-231 cells for our study. Cells were incubated with GNPs (0.2 nM) in the absence and presence of DTX (50 nM) for 24 h to determine uptake, distribution, and retention of NPs. For RT experiments, treated cells were given a 2 Gy dose of 6 MV photons using a linear accelerator. RESULTS: Concurrent treatment of DTX and GNPs resulted in over 85% retention of GNPs in tumor cells. DTX treatment also forced GNPs to be closer to the most important target, the nucleus, resulting in a decrease in cell survival and increase in DNA damage with the triple combination of RT/ GNPs/DTX vs RT/DTX. Our experimental therapeutic results were supported by Monte Carlo simulations. CONCLUSION: The ability to not only trap GNPs at clinically feasible doses but also to retain them within the cells could lead to meaningful fractionated treatments in future combined cancer therapy. Furthermore, the suggested triple combination of RT/GNPs/DTX may allow lowering the RT dose to spare surrounding healthy tissue. ADVANCES IN KNOWLEDGE: This is the first study to show intracellular GNP transport disruption by DTX, and its advantage in radiosensitization.

Uptake and excretion dynamics of gold nanoparticles in cancer cells and fibroblasts.

Radiotherapy is one of the main treatments used to fight cancer. A major limitation of this modality is the lack of selectivity between cancerous and healthy tissues. One of the most promising strategies proposed in this last decade is the addition of nanoparticles with high-atomic number to enhance radiation effects in tumors. Gold nanoparticles (AuNPs) are considered as one of the best candidates because of their high radioenhancing property, simple synthesis and low toxicity. Ultra small AuNPs (core size of 2.4 nm and hydrodynamic diameter of 4.5 nm) covered with dithiolated diethylenetriaminepentaacetic acid (Au@DTDTPA) are of high interest because of their properties to bind MRI active or PET active compounds at their surface, to concentrate in some tumors and be eliminated via renal clearance thanks to their small size. These key figures make Au@DTDTPA the best candidate to develop image-guided radiotherapy. Surprisingly the capacity of the nanoparticles to penetrate cells, an important issue to predict radioenhancement, has not been established yet. Here, we report the uptake dynamics, internalization routes and excretion dynamics of Au@DTDTPA nanoparticles in various cancer cell lines including glioblastoma (U87-MG), chordoma (UM-Chor1), cervix (HeLa), prostate (PC3), and pancreatic (BxPC-3) cell lines as well as fibroblasts (Dermal fibroblasts). This study demonstrates a strong cell line dependence of the nanoparticle uptake and excretion dynamics. Different pathways of cell internalization evidenced here explain this dependence. As a major finding, the retention of Au@DTDTPA nanoparticles was found to be higher in cancer cells than in fibroblasts. This result strengthens the strategy of using nanoagents to improve tumor selectivity of radiation treatments. In particular Au@DTDTPA nanoparticles are good candidates to improve the treatment of radioresitant gliobastoma, pancreatic and prostate cancer in particular. In conclusion, the variability of cell-to-nanoparticle interaction is a new parameter to consider in the choice of nanoagents in a combined treatment.

Analysis of DNA Damage Responses After Boric Acid-mediated Boron Neutron Capture Therapy in Hepatocellular Carcinoma.

BACKGROUND: Boron neutron capture therapy (BNCT) selectively kills tumor cells while sparing adjacent normal cells. Boric acid (BA)-mediated BNCT showed therapeutic efficacy in treating hepatocellular carcinoma (HCC) in vivo. However, DNA damage and corresponding responses induced by BA-mediated BNCT remained unclear. This study aimed to investigate whether BA-mediated BNCT induced DNA double-strand breaks (DSBs) and to explore DNA damage responses in vitro. MATERIALS AND METHODS: Huh7 Human HCC cells were treated with BA and irradiated with neutrons during BA-BNCT. Cell survival and DNA DSBs were examined by clonogenic assay and expression of phosphorylated H2A histone family member X (γH2AX), respectively. The DNA damage response was explored by determining the expression levels of DNA repair- and apoptosis-associated proteins and conducting a cell-cycle analysis. RESULTS: DNA DSBs induced by BA-mediated BNCT were primarily repaired through the homologous recombination pathway. BA-mediated BNCT induced G2/M arrest and apoptosis in HCC. CONCLUSION: Our findings may enable the identification of radiosensitizers or adjuvant drugs for potentiating the therapeutic effectiveness of BA-mediated BNCT for HCC.

Synthesis and Initial Biological Evaluation of Boron-Containing Prostate-Specific Membrane Antigen Ligands for Treatment of Prostate Cancer Using Boron Neutron Capture Therapy.

Boron neutron capture therapy (BNCT) is a therapeutic modality which has been used for the treatment of cancers, including brain and head and neck tumors. For effective treatment via BNCT, efficient and selective delivery of a high boron dose to cancer cells is needed. Prostate-specific membrane antigen (PSMA) is a target for prostate cancer imaging and drug delivery. In this study, we conjugated boronic acid or carborane functional groups to a well-established PSMA inhibitor scaffold to deliver boron to prostate cancer cells and prostate tumor xenograft models. Eight boron-containing PSMA inhibitors were synthesized. All of these compounds showed a strong binding affinity to PSMA in a competition radioligand binding assay (IC50 from 555.7 to 20.3 nM). Three selected compounds 1a, 1d, and 1f were administered to mice, and their in vivo blocking of 68Ga-PSMA-11 uptake was demonstrated through a positron emission tomography (PET) imaging and biodistribution experiment. Biodistribution analysis demonstrated boron uptake of 4-7 µg/g in 22Rv1 prostate xenograft tumors and similar tumor/muscle ratios compared to the ratio for the most commonly used BNCT compound, 4-borono-l-phenylalanine (BPA). Taken together, these data suggest a potential role for PSMA targeted BNCT agents in prostate cancer therapy following suitable optimization.