Sensitizer Enhancement Ratio Research Articles

Albumin-Modified Gold Nanoparticles as Novel Radiosensitizers for Enhancing Lung Cancer Radiotherapy.

Considering the strong attenuation of photons and the potential to increase the deposition of radiation, high-atomic number nanomaterials are often used as radiosensitizers in cancer radiotherapy, of which gold nanoparticles (GNPs) are widely used. We prepared albumin-modified GNPs (Alb-GNPs) and observed their radiosensitizing effects and biotoxicity in human non-small-cell lung carcinoma tumor-bearing mice models. The prepared nanoparticles (Alb-GNPs) demonstrated excellent colloidal stability and biocompatibility at the mean size of 205.06 ± 1.03 nm. Furthermore, clone formation experiments revealed that Alb-GNPs exerted excellent radiosensitization, with a sensitization enhancement ratio (SER) of 1.432, which is higher than X-ray alone. Our in vitro and in vivo data suggested that Alb-GNPs enabled favorable accumulation in tumors, and the combination of Alb-GNPs and radiotherapy exhibited a relatively greater radiosensitizing effect and anti-tumor activity. In addition, no toxicity or abnormal irritating response resulted from the application of Alb-GNPs. Alb-GNPs can be used as an effective radiosensitizer to improve the efficacy of radiotherapy with minimal damage to healthy tissues.

Application of Gold Nanoparticles as Radiosensitizer for Metastatic Prostate Cancer Cell Lines

More than 50% of all prostate cancer (PCa) patients are treated by radiotherapy (RT). Radioresistance and cancer recurrence are two consequences of the therapy and are related to dose heterogeneity and non-selectivity between normal and tumoral cells. Gold nanoparticles (AuNPs) could be used as potential radiosensitizers to overcome these therapeutic limitations of RT. This study assessed the biological interaction of different morphologies of AuNPs with ionizing radiation (IR) in PCa cells. To achieve that aim, three different amine-pegylated AuNPs were synthesized with distinct sizes and shapes (spherical, AuNPsp-PEG, star, AuNPst-PEG, and rods, AuNPr-PEG) and viability, injury and colony assays were used to analyze their biological effect on PCa cells (PC3, DU145, and LNCaP) when submitted to the accumulative fraction of RT. The combinatory effect of AuNPs with IR decreased cell viability and increased apoptosis compared to cells treated only with IR or untreated cells. Additionally, our results showed an increase in the sensitization enhancement ratio by cells treated with AuNPs and IR, and this effect is cell line dependent. Our findings support that the design of AuNPs modulated their cellular behavior and suggested that AuNPs could improve the RT efficacy in PCa cells.

Self-synthesized second mitochondria-derived activator of caspase (SMAC) mimetic TP-WY-1345 enhances the radiosensitivity of NSCLC cells H1299 by targeting anti-apoptotic protein cIAP1

ObjectiveTo explore the toxicity and cellular uptake of the self-synthesized second mitochondria-derived activator of caspase (SMAC) mimetic TP-WY-1345 polypeptide and its radiosensitizing effect on non-small cell lung cancer (NSCLC). MethodsA fluorescence microscope was used to observe the uptake efficiency of TP-WY-1345 by human NSCLC cells H1299. Toxicity of the TP-WY-1345 peptide in normal cells was examined in human embryonic lung fibroblasts MRC5. CCK-8 and clone formation experiments were performed to detect the radiosensitizing effect of TP-WY-1345 in the H1299 ​cells. The AutoDock Vina simulation software was employed to predict the binding efficiency of TP-WY-1345 to the inhibitor of apoptosis proteins (IAPs). Moreover, Western blot and qPCR experiments were carried out to determine the protein and gene expressions, and the flow cytometry (FCM) technique was used to detect the apoptosis level under different conditions. ResultsTP-WY-1345 can be self-synthesized, and significant green fluorescence was observed in H1299 2 ​h and 6 ​h after incubation with TP-WY-1345. The cell counting and CCK-8 results showed that 10 ​μmol/L and 20 ​μmol/L TP-WY-1345 did not produce a significant toxic effect on the MRC5 cells (P ​> ​0.05). Compared with the single ionizing radiation group, the cell viability and clone formation of H1299 ​cells were significantly inhibited after treatment with TP-WY-1345 at a concentration of 50 ​μmol/L (P ​< 0.05). The sensitivity enhancement ratio (SER) was calculated to be 1.14. Moreover, the binding efficiency of TP-WY-1345 to cIAP1 protein was predicted to be −7.3, and this strong binding force was demonstrated by Western blot. TP-WY-1345 inhibited the protein and mRNA expressions of cIAP1 and further increased the apoptosis level of the H1299 ​cells at 24 ​h ​(P ​< ​0.01) and 48 ​h after radiation (P ​< ​0.05). ConclusionSMAC mimetic TP-WY-1345 can enter the H1299 ​cells and produce a radiosensitizing effect by increasing the level of radiation-induced apoptosis of the cells. There, TP-WY-1345 is expected to become a new generation of radiosensitizing drugs.

Irradiation-induced exosomal HMGB1 to confer radioresistance via the PI3K/AKT/FOXO3A signaling pathway in ESCC

BackgroundRadioresistance is a major cause of treatment failure in esophageal squamous cell carcinoma (ESCC) radiotherapy, and the underlying mechanisms of radioresistance are still unclear. Irradiation (IR) stimulates changes in tumor-derived exosome contents, which can be taken up by recipient cells, playing an important role in the proliferation, cell cycle and apoptosis of recipient cells. This study investigated the effect of IR-induced exosomal high mobility group box 1 (HMGB1) on radioresistance in ESCC cells.MethodsPlasma exosomes were isolated from 21 ESCC patients and 24 healthy volunteers, and the expression of HMGB1 was examined. Then, the therapeutic effect of radiotherapy was analyzed according to the different expression levels of plasma exosomal HMGB1 in ESCC patients. The uptake of exosomes by recipient cells was verified by immunofluorescence staining, and the localization of exosomes and HMGB1 in cells before and after IR was evaluated. The effects of IR-induced exosomes on cell proliferation, invasion, apoptosis, cell cycle distribution and radioresistance after HMGB1 knockdown were verified. Moreover, western blotting was used to measure changes in the expression of cyclin B1, CDK1, Bax, Bcl2, phosphorylated histone H2AX and the PI3K/AKT/FOXO3A pathway in the HMGB1-knockdown exosome group and the negative control group.ResultsThe expression of HMGB1 in ESCC plasma exosomes was significantly increased compared with that in healthy volunteers, and high expression of HMGB1 in plasma exosomes was associated with radioresistance (P = 0.016). IR-induced the release of exosomal HMGB1 and promoted proliferation and radioresistance in recipient cells, with a sensitization enhancement ratio (SER) of 0.906 and 0.919, respectively. In addition, IR-induced exosomal HMGB1 promotes G2/M phase arrest by regulating the proteins cyclin B1 and CDK1, cooperating with the proteins Bax and Bcl2 to reduce the apoptosis rate through the PI3K/AKT/FOXO3A signaling pathway, and participated in IR-induced DNA damage repair through γH2AX.ConclusionThese findings indicate that high expression of plasma exosomal HMGB1 is associated with an adverse radiotherapy response. IR-induced exosomal HMGB1 enhances the radioresistance of ESCC cells.

Quantifying Radiosensitization of PSMA-Targeted Gold Nanoparticles on Prostate Cancer Cells at Megavoltage Radiation Energies by Monte Carlo Simulation and Local Effect Model.

Active targeting gold nanoparticles (AuNPs) are a very promising avenue for cancer treatment with many publications on AuNP mediated radiosensitization at kilovoltage (kV) photon energies. However, uncertainty on the effectiveness of AuNPs under clinically relevant megavoltage (MV) radiation energies hinders the clinical translation of AuNP-assisted radiation therapy (RT) paradigm. The aim of this study was to investigate radiosensitization mediated by PSMA-targeted AuNPs irradiated by a 6 MV radiation beam at different depths to explore feasibility of AuNP-assisted prostate cancer RT under clinically relevant conditions. PSMA-targeted AuNPs (PSMA-AuNPs) were synthesized by conjugating PSMA antibodies onto PEGylated AuNPs through EDC/NHS chemistry. Confocal fluorescence microscopy was used to verify the active targeting of the developed PSMA-AuNPs. Transmission electron microscopy (TEM) was used to demonstrate the intracellular biodistribution of PSMA-AuNPs. LNCaP prostate cancer cells treated with PSMA-AuNPs were irradiated on a Varian 6 MV LINAC under varying depths (2.5 cm, 10 cm, 20 cm, 30 cm) of solid water. Clonogenic assays were carried out to determine the in vitro cell survival fractions. A Monte Carlo (MC) model developed on TOPAS platform was then employed to determine the nano-scale radial dose distribution around AuNPs, which was subsequently used to predict the radiation dose response of LNCaP cells treated with AuNPs. Two different cell models, with AuNPs located within the whole cell or only in the cytoplasm, were used to assess how the intracellular PSMA-AuNP biodistribution impacts the prostate cancer radiosensitization. Then, MC-based microdosimetry was combined with the local effect model (LEM) to calculate cell survival fraction, which was benchmarked against the in vitro clonogenic assays at different depths. In vitro clonogenic assay of LNCaP cells demonstrated the depth dependence of AuNP radiosensitization under clinical megavoltage beams, with sensitization enhancement ratio (SER) of 1.14 ± 0.03 and 1.55 ± 0.05 at 2.5 cm depth and 30 cm depth, respectively. The MC microdosimetry model showed the elevated percent of low-energy photons in the MV beams at greater depth, consequently resulting in increased dose enhancement ratio (DER) of AuNPs with depth. The AuNP-induced DER reached ~5.7 and ~8.1 at depths of 2.5 cm and 30 cm, respectively. Microdosimetry based LEM accurately predicted the cell survival under 6 MV beams at different depths, for the cell model with AuNPs placed only in the cell cytoplasm. TEM results demonstrated the distribution of PSMA-AuNPs in the cytoplasm, confirming the accuracy of MC microdosimetry based LEM with modelled AuNPs distributed within the cytoplasm. We conclude that AuNP radiosensitization can be achieved under megavoltage clinical radiotherapy energies with a dependence on tumor depth. Furthermore, the combination of Monte Carlo microdosimetry and LEM will be a valuable tool to assist with developing AuNP-aided radiotherapy paradigm and drive clinical translation.

Natural Baicalein-Rich Fraction as Radiosensitizer in Combination with Bismuth Oxide Nanoparticles and Cisplatin for Clinical Radiotherapy.

PurposeChemotherapy has been used in conjunction with radiation therapy to improve the treatment outcomes of cancers. Cisplatin (Cis) is a standard treatment that has been used as a chemotherapeutic drug in medical settings. However, the possibility of complications constrains the treatment due to the exposure of healthy organs to unnecessary radiation and the drugs’ toxicities. As a result, researchers have been looking for non-toxic chemotherapeutic agents which can be used as radiosensitizers, possibly produced from natural derivatives and nano sized materials.MethodsBRF, Cis, and BiONPs were irradiated individually and in combinations with 6 MV of photon beam and 6 MeV of electron beams with 0 to 10 Gy radiation doses on MCF-7, MDA-MB-231, and NIH/3T3 cell lines. Then, the experimental sensitization enhancement ratios (SER) of each treatment obtained were compared to the theoretical dose enhancement factor (DEF). The interactions within the BRF-BiONPs (BB) and BRF-Cis-BiONPs (BCB) combinations were also estimated using the Combination Index (CI).ResultsBRF induced radiosensitization in all cells under 6 MV photon beam (SER of 1.06 to 1.35), and MDA-MB-231 cells only under 6 MeV electron beam (SER = 1.20). The highest SER values for BiONPs and Cis were obtained from MCF-7 cells under a 6 MeV electron beam (SER of 1.50 and 2.24, respectively). The theoretical DEFs were generally lower than the experimental SERs. Based on the SER and CI relationships, it was estimated that BB and BCB therapy methods interacted in either a synergistic or additive manner.ConclusionThe BRF is found to induce relatively less radiosensitization effects compared to the BiONPs and Cis. The BB and BCB combinations have shown better effects with potential for becoming competently suitable radiosensitizers in breast cancer therapies.

Improve the cytotoxic effects of megavoltage radiation treatment by Fe3O4@Cus–PEG nanoparticles as a novel radiosensitizer in colorectal cancer cells

BackgroundTo enhance the performance of radiotherapy, emerging nanoparticles that can professionally enhance X-ray irradiation to destruct cancer cells are extremely necessary. Here, we examined the potential of PEG-coated magnetite copper sulfide hetero-nanoparticles (Fe3O4@Cus–PEG) as a radiosensitizer agent.MethodsFe3O4@Cus–PEG nanoparticles were synthesized and characterized. The toxicity of nanoparticles on HT-29 colorectal cancer cells was assessed by the MTT assay. The radio-sensitizing effects of Fe3O4@Cus–PEG nanoparticles on HT-29 cancer cells were investigated by the MTT and colony formation assays. Moreover, the underlying mechanisms for Fe3O4@Cus–PEG nanoparticles to improve the radiation sensitivity of cells were evaluated.ResultsThe results demonstrated that nanoparticles enhanced the effects of X-ray irradiation in a dose-dependent manner. The effects of combined treatments (nanoparticles and X-ray radiation) were strongly synergistic. The sensitizing enhancement ratio (SER) of nanoparticles was 2.02. Our in vitro assays demonstrated that the nitric oxide production, the intracellular hydrogen peroxide concentration, and the expression level of Bax and Caspase-3 genes significantly increased in the cells treated with the combination of nanoparticles and radiation. Whereas, the Glutathione peroxidase enzyme activity and the expression level of the Bcl-2 gene in the combined treatment significantly decreased compared to the radiation alone.ConclusionsOur study suggests that Fe3O4@Cus–PEG nanoparticles are the promising nano radio-sensitizing agents for the treatment of cancer cells to enhance the efficacy of radiation therapy through increasing the reactive oxygen species generation, nitric oxide production, and inducing apoptosis.Graphical

Radiosensitizing effect of dendrosomal nanoformulation of curcumin on cancer cells.

Curcumin was found to possess numerous pharmacological activities in clinical research, however, its biological effects together with radiation are yet to be addressed. The present study investigated whether the combined treatment of dendrosomal nanoformulation of curcumin (DNC) and gamma radiation can enhance the radiosensitivity of U87MG and MDA-MB-231 cell lines. U87MG and MDA-MB-231 cell lines were exposed to 2 Gray (Gy) and 10μM DNC determined by MTT assay, then subjected to clonogenic assay, cell cycle assay, and flow cytometric apoptosis analysis. Acridine Orange/Ethidium Bromide (AO/EB) and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) stained cells were used to study morphologic changes. The expression evaluation of putative cell cycle genes, i.e., P53, P21, CCND1, and CCNB1 was carried out by RT-qPCR. Our findings indicated that the combined treatment with DNC and radiation might cooperatively augment the efficacy of ionizing radiation in the cancer cells and notably decrease the survival and viability of the cells in a time- and concentration-dependent manner. In addition to a synergistic effect deducted by sensitizer enhancement ratio (SER) assessment, co-treatment resulted in greater apoptotic cells than the individual treatments. Further experiments then indicated that DNC could effectively induce G2/M phase cell cycle arrest and apoptosis following irradiation. Conformably, there was a decrement of CCND1 and CCNB1 expression, and an increment of P53, P21 expression. The data implied that DNC as a radiosensitizer can enhance the lethal effect of ionizing radiation on cancer cells which could be a promising adjuvant therapy in clinical treatments.

Effect of boron compounds on the biological effectiveness of proton therapy.

We assessed whether adding sodium borocaptate (BSH) or 4-borono-l-phenylalanine (BPA) to cells irradiated with proton beams influenced the biological effectiveness of those beams against prostate cancer cells to investigate if the alpha particles generated through proton-boron nuclear reactions would be sufficient to enhance the biological effectiveness of the proton beams. We measured clonogenic survival in DU145 cells treated with 80.4-ppm BSH or 86.9-ppm BPA, or their respective vehicles, after irradiation with 6-MV X-rays, 1.2-keV/μm (low linear energy transfer [LET]) protons, or 9.9-keV/μm (high-LET) protons. We also measured γH2AX and 53BP1 foci in treated cells at 1 and 24h after irradiation with the same conditions. We found that BSH radiosensitized DU145 cells across all radiation types. However, no difference was found in relative radiosensitization, characterized by the sensitization enhancement ratio or the relative biological effectiveness, for vehicle- versus BSH-treated cells. No differences were found in numbers of γH2AX or 53BP1 foci or γH2AX/53BP1 colocalized foci for vehicle- versus BSH-treated cells across radiation types. BPA did not radiosensitize DU145 cells nor induced any significant differences when comparing vehicle- versus BPA-treated cells for clonogenic cell survival or γH2AX and 53BP1 foci or γH2AX/53BP1 colocalized foci. Treatment with 11 B, at concentrations of 80.4ppm from BSH or 86.9ppm from BPA, had no effect on the biological effectiveness of proton beams in DU145 prostate cancer cells. Our results agree with published theoretical calculations indicating that the contribution of alpha particles from such reactions to the total absorbed dose and biological effectiveness is negligible. We also found that BSH radiosensitized DU145 cells to X-rays, low-LET protons, and high-LET protons but that the radiosensitization was not related to DNA damage.

Intercomparison of radiosensitization induced by gold and iron oxide nanoparticles in human glioblastoma cells irradiated by 6 MV photons

In this work, an intercomparison of sensitization effects produced by gold (GNP) and dextran-coated iron oxide (SPION-DX) nanoparticles in M059J and U87 human glioblastoma cells was performed using 6 MV-photons. Three variables were mapped: the nanoparticle material, treatment concentration, and cell radiosensitivity. For U87, GNP treatments resulted in high sensitization enhancement ratios (SER_{10%} up to 2.04). More modest effects were induced by SPION-DX, but still significant reductions in survival were achieved (maximum SER_{10%}=1.61 ). For the radiosensitive M059J, sensitization by both NPs was poor. SER_{10%} increased with the degree of elemental uptake in the cells, but not necessarily with treatment concentration. For GNP, where exposure concentration and elemental uptake were found to be proportional, SER_{10%} increased linearly with concentration in both cell lines. For SPION-DX, saturation of sensitization enhancement and metal uptake occurred at high exposures. Fold change in the alpha /beta ratios extracted from survival curves are reduced by the presence of SPION-DX but strongly increased by GNPs , suggesting that sensitization by GNPs occurs mainly via promotion of lethal damage, while for SPION-DX repairable damage dominates. The NPs were more effective in eliminating the radioresistant glioblastoma cells, an interesting finding, as resistant cells are key targets to improve treatment outcome.

Oleanolic acid combined with olaparib enhances radiosensitization in triple negative breast cancer and hypoxia imaging with 18F-FETNIM micro PET/CT.

The heterogeneity of triple negative breast cancer (TNBC) results in the worst prognosis among breast cancer types, making its treatment strategy very challenging. A recent study showed that oleanolic acid (OA) has a radiosensitizing effect on tumor cells, but it does not show a good clinical effect when used alone in radiotherapy. The cytotoxicity of radiotherapy can be enhanced by modulating DNA repair, so new treatment options are being investigated to inhibit DNA repair pathways and sensitize tumors to radiation. Radiation induces DNA double-strand breaks (DSBs), and inhibition of Poly (ADP-Ribose) polymerase (PARP) can prevent the repair of these lesions. Hence, we evaluated the radiosensitization and the underlying mechanism of combination treatment with OA and olaparib in TNBC. Meanwhile, tumor hypoxia was monitored with 18F-Fluoroerythronitroimidazole (FETNIM) positron emission tomography/computed tomography (PET/CT) during radiosensitization therapy. Here, we found that OA and olaparib in combination with radiotherapy significantly inhibited cell proliferation compared with other groups. The results were observed using colony formation assays [sensitization enhancement ratios (SER) 1.16-1.65]. In vivo, tumor growth was significantly delayed in transplanted tumors receiving irradiation (IR) with OA and olaparib. 18F-FETNIM PET/CT can be utilized for tumor hypoxia monitoring and radiosensitization response evaluation. In conclusion, these results suggest that the combination of OA and olaparib with IR enhances the inhibition of MDA-MB-231 in cell culture and in mice, providing a potentially novel combination for the effective treatment of TNBC patients.

Blocking PARP activity with the inhibitor veliparib enhances radiotherapy sensitivity in endometrial carcinoma.

ObjectiveOur study aimed to investigate the potential clinical utility of a poly(ADP‐ribose) polymerase (PARP) inhibitor, veliparib (ABT‐888), as a radiosensitizer in the medication of endometrial carcinoma (EC).MethodsHuman Ishikawa endometrial adenocarcinoma cells were treated with veliparib, radiotherapy (RT), or combination treatment. The viabilities, radiosensitivity enhancement ratio (sensitizer enhancement ratio (SER), and apoptosis of Ishikawa cells were, respectively, evaluated by Cell Counting Kit‐8 (CCK‐8), colony formation experiment, and flow cytometry. The tumor growth was assessed by xenograft mice models. Western blot assay investigated the expression of DNA damage and apoptosis‐related proteins in vivo and in vitro.ResultsCell Counting Kit‐8 revealed that the 10% inhibition concentration (IC10) and 50% inhibition concentration (IC50) values of veliparib‐treated Ishikawa cells were 1.7 and 133.5 µM, respectively. The SER of veliparib combined with RT was 1.229 in vitro. Flow cytometry analysis results indicated that the apoptosis rate of the veliparib + RT group was markedly higher than that of the RT group in vitro (p < 0.05). Furthermore, in vivo data revealed that veliparib + RT treatment significantly decreased tumor growth compared with single treatments of veliparib or RT and with the control group (p < 0.05). Then western blot confirmed the levels of anti‐phospho‐histone (γH2AX), caspase‐3, and B‐cell lymphoma 2 (Bcl‐2) associated protein X (Bax) were significantly higher in the veliparib + RT group, while the level of Bcl‐2 was lower compared with that of the RT group (p < 0.05), both in vivo and in vitro.ConclusionOur results indicate that veliparib in combination with RT markedly improved the therapeutic efficiency in human endometrial carcinoma.

In vitro radiosensitization by eribulin in human cancer cell lines.

BackgroundThe objective was to to determine the radiosensitizing properties of eribulin and the potential mechanisms of radiosensitization in cervical (HeLa) and pharyngeal (FaDu) cancer cell lines.Materials and methodsCytotoxicity was evaluated by the crystal violet method. The 10% and 50% inhibitory concentration (IC10, IC50) for 24-hour drug exposure were determined. The surviving fraction at 2 Gy (SF2) and the sensitizer enhancement ratio (SER) were calculated from radiation cell survival curves in the presence or absence of eribulin. Combination index (CI) was calculated to determine if there is a true synergistic interaction between eribulin and irradiation. Cell cycle changes were assessed by propidium iodide staining and flow cytometry. Apoptotic cells were detected by annexin V and TUNEL-assay.ResultsMean IC50s and IC10s were 1.58 nM and 0.7 nM and 0.7 nM and 0.27 nM for HeLa and FaDu cells, respectively. Radiosensitization was observed in both lines with a SER up to 2.71 and 2.32 for HeLa and FaDu cells, respectively. A true synergistic effect was showed with a CI of 0.82 and 0.76 for HeLa and FaDu cells, respectively. Eribulin induced significant G2/M cell arrest and marked apoptosis. Irradiation combined with 3 nM eribulin increased the apoptotic response to radiation in Hela cells.ConclusionEribulin shows a true in vitro radiosensitizing effect in HeLa and FaDu cells by inducing significant G2/M phase arrest. In HeLa, the enhancement radiation-induced apoptosis could be an additional mechanism of radiosensitization. Further studies are needed to evaluate the clinical benefits of concurrent eribulin and radiotherapy as a novel therapeutic strategy for cancer.

GMT8 aptamer conjugated PEGylated Ag@Au core-shell nanoparticles as a novel radiosensitizer for targeted radiotherapy of glioma

Radiotherapy is one of the main treatment modalities for glioma, but the therapeutic efficacy is often limited by the radioresistance of tumor cells. The radiosensitization effects of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) on tumors have been confirmed by previous studies. To enhance the specific killing effect of irradiation on tumor cells, targeted modification of radiosensitizers is urgently needed. Herein, we developed polyethylene glycol (PEG)-coated Ag@Au core-shell nanoparticles (PSGNPs) modified with GMT8 aptamer (GSGNPs) and evaluated their radiosensitization effects on glioma cells through in vivo and in vitro experiments. Transmission electron microscope image showed that the prepared PSGNPs had a spherical core-shell structure with an average size of 11 nm. The ultraviolet-visible absorption spectra and Fourier transform infrared spectra displayed that GMT8 was successfully conjugated to PSGNPs. The results of dark-field imaging revealed that the targeting ability of GSGNPs to U87 glioma cells was much better than that to normal human microvascular endothelial cells. Additionally, it was also found that the endocytic pathways of GSGNPs mainly involved clathrin-mediated endocytosis and macropinocytosis. The sensitization enhancement ratio of GSGNPs was calculated to be 1.62, which was higher than that of PSGNPs. In vivo imaging results showed that GSGNPs exhibited good tumor targeting and retention capabilities, and the fluorescence intensity ratio of Cy5-GSGNPs to Cy5-PSGNPs reached a peak at 4 h after injection. More importantly, the median survival time of mice bearing U87 glioma was significantly prolonged after intravenous administration of GSGNPs combined with radiotherapy. This work demonstrated that GSGNPs could be used as an effective nano-radiosensitizer for targeted radiotherapy of glioma.

Supramolecular Radiosensitizer Based on Hypoxia-Responsive Macrocycle.

Radiotherapy (RT) has been viewed as one of the most effective and extensively applied curatives in clinical cancer therapy. However, the radioresistance of tumor severely discounts the radiotherapy outcomes. Here, an innovative supramolecular radiotherapy strategy, based on the complexation of a hypoxia‐responsive macrocycle with small‐molecule radiosensitizer, is reported. To exemplify this tactic, a carboxylated azocalix[4]arene (CAC4A) is devised as molecular container to quantitatively package tumor sensitizer banoxantrone dihydrochloride (AQ4N) through reversible host–guest interaction. Benefited from the selective reduction of azo functional groups under hypoxic microenvironment, the supramolecular prodrug CAC4A•AQ4N exhibits high tumor accumulation and efficient cellular internalization, thereby significantly amplifying radiation‐mediated tumor destruction without appreciable systemic toxicity. More importantly, this supramolecular radiotherapy strategy achieves an ultrahigh sensitizer enhancement ratio (SER) value of 2.349, which is the supreme among currently reported noncovalent‐based radiosensitization approach. Further development by applying different radiosensitizing drugs can make this supramolecular strategy become a general platform for boosting therapeutic effect in cancer radiotherapies, tremendously promising for clinical translation.

Mitochondrion-targeted supramolecular "nano-boat" simultaneously inhibiting dual energy metabolism for tumor selective and synergistic chemo-radiotherapy.

Rationale: Tumor energy metabolism has been a well-appreciated target of cancer therapy; however, the metabolism change of cancer cells between oxidative phosphorylation and glycolysis poses a challenge to the above. In this study, we constructed an innovative mitochondrion-targeted supramolecular “nano-boat” based on peptide self-assembly for tumor combined chemo-radiotherapy by simultaneously inhibiting the dual energy metabolism.Methods: A lipophilic self-assembled peptide and a positively charged cyclen were integrated to fabricate a brand new mitochondrion-targeted nano-platform for the first time. The indices of mitochondrial dysfunction including mitochondrial membrane potential, apoptosis proteins expression and ultrastructure change were evaluated using a JC-1 probe, western blotting and biological transmission electron microscopy, respectively. Energy metabolism assays were conducted on a Seahorse XF24 system by detecting the oxygen consumption rate and the glycolytic proton efflux rate. The radio-sensitization effect was investigated by colony formation, the comet assay, and γ-H2AX staining.Results: The supramolecular “nano-boat” could selectively kill cancer cells by much higher enrichment and reactive oxygen species generation than those in normal cells. In the cancer cells treated with the supramolecular “nano-boat”, the dysfunctional morphological changes of the mitochondrial ultrastructure including swelling and pyknosis were evidently observed, and the endogenous mitochondrial apoptosis pathway was effectively triggered by abundant of cytochrome C leaking out. Concurrently, the dual metabolic pathways of glycolysis and oxidative phosphorylation were severely inhibited. More importantly, the supramolecular “nano-boat” displayed an excellent radio-sensitization effect with a sensitization enhancement ratio value as high as 2.58, and hence, in vivo efficiently combining radiotherapy yielded an enhanced chemo-radiotherapy effect.Conclusion: Our study demonstrated that the rationally designed peptide-based “nano-boat” could efficiently induce cancer cell apoptosis by the energy metabolism inhibition involving multiple pathways, which may provide the motivation for designing novel and universal mitochondria-targeted drug delivery systems for cancer therapy.

DNA repair inhibitors sensitize cells differently to high and low LET radiation

The aim of this study was to investigate effects of high LET α-radiation in combination with inhibitors of DDR (DNA-PK and ATM) and to compare the effect with the radiosensitizing effect of low LET X-ray radiation. The various cell lines were irradiated with α-radiation and with X-ray. Clonogenic survival, the formation of micronuclei and cell cycle distribution were studied after combining of radiation with DDR inhibitors. The inhibitors sensitized different cancer cell lines to radiation. DNA-PKi affected survival rates in combination with α-radiation in selected cell lines. The sensitization enhancement ratios were in the range of 1.6–1.85 in cancer cells. ATMi sensitized H460 cells and significantly increased the micronucleus frequency for both radiation qualities. ATMi in combination with α-radiation reduced survival of HEK293. A significantly elicited cell cycle arrest in G2/M phase after co-treatment of ATMi with α-radiation and X-ray. The most prominent treatment effect was observed in the HEK293 by combining α-radiation and inhibitions. ATMi preferentially sensitized cancer cells and normal HEK293 cells to α-radiation. DNA-PKi and ATMi can sensitize cancer cells to X-ray, but the effectiveness was dependent on cancer cells itself. α-radiation reduced proliferation in primary fibroblast without G2/M arrest.

Impact of PSMA Targeted Gold Nanoparticles on Prostate Cancer Radiation Bystander Effect

Gold nanoparticles (GNPs) are effective radiosensitizers due to their ability to enhance ionizing radiation absorptance and deposit elevated dose in their vicinity. Radiation induced bystander effect (RIBE) expands radiation effects to non-targeted cells close to radiation-targeted cells, further improving radiation outcome. In this study, we investigated the impact of PSMA-targeted GNPs on RIBE. We hypothesize that the PSMA-targeted GNPs would intensify radiation effects by augmenting RIBE consequence as well as enhancing sensitivity of bystander cells to RIBE.Anti-prostate-specific membrane antigen (PSMA) antibodies were conjugated onto PE Gylated GNPs through EDC/NHS chemistry. UV-Vis spectrophotometry and real time cell analysis were employed to evaluate the cellular uptake and biocompatibility, respectively, when LNCaP prostate cancer cells were treated with PSMA-targeted GNPs at varying concentrations. Then GNPs with biocompatible dosage were used for cancer cell treatments. The media transfer technique was performed to induce the RIBE effects on bystander cells. First, LNCaP cells pretreated with phosphate buffered saline (PBS) or GNPs for 24hrs were irradiated with 160kvP X-rays at varying doses (0∼8 Gy). The culture media from irradiated cells were collected and filtered (sterile 0.2µm polyethersulfone) to acquire PBS conditioned media (PBS-CM) and GNP conditioned media (GNP-CM). Then, the collected PBS-/GNP-CMs were transferred to non-irradiated LNCaP cells with/without GNPs for 24hrs to investigate RIBE effect. The final GNP-induced RIBE was evaluated via MTT cellular viability assay, clonogenic assay, γ-H2AX assay, as well as reactive oxygen species (ROS) assessment through 2',7'-dichlorofluorescein diacetate staining.PSMA-targeted GNPs showed minimal cytotoxicity in LNCaP cells up to 1mg/mL concentrations. Cellar uptake analysis demonstrated that GNPs were bound to cells within 30 mins, with maximum uptake at 250µg/mL. Compared to 2 Gy PBS-CM, 8 Gy PBS-CM demonstrated much higher RIBE response on the non-irradiated cells, showing the dose dependent RIBE in LNCaP cells. Compared to PBS-CM, GNP-CM exhibited much higher cell death in MTT assay, as well as demonstrated RIBE enhancement in γ-H2AX (133%) and clonogenic assays (120%) analysis. Moreover, GNP-CM showed elevated ROS expression (125%) than PBS-CM. In the presence of PBS-CM, the non-irradiated cells with GNPs showed increased cell death compared to that without GNPs, indicating that GNP would enhance the sensitivity of bystander cells to RIBE. This sensitivity enhancement ratio was also validated in γ-H2AX (120%) and clonogenic assays (120%).PSMA directed GNPs were associated with physical dose enhancement along with the enhanced RIBE, playing a critical role in increasing the overall radiosensitivity of prostate cancer cells. Our results also showed that PSMA-targeted GNPs enhanced the sensitivity of bystander cells to RIBE.

AMG-510 Plus Cetuximab Enhance Radiosensitivity in KRAS p.G12C Mutant Colorectal Carcinoma Cell Lines via Increasing Apoptosis and Inducing G1/S Arrest

<h3>Purpose/Objective(s)</h3> KRAS p.G12C mutation is rare (∼3%) but with a dismal prognosis in colorectal carcinoma (CRC). AMG-510 is a first-in-class KRAS p.G12C inhibitor, which shows clinical efficacy in KRAS p.G12C mutant solid tumors including non-small cell lung cancer and CRC. The addition of cetuximab could revert resistance to AMG-510 in CRC. Herein, we evaluate the anti-cancer effect of AMG-510 plus cetuximab in combination with radiation in CRC. <h3>Materials/Methods</h3> Two KRAS p.G12C mutant CRC cell lines were treated with AMG-510, AMG-510 plus cetuximab, irradiation (IR), and the combination of IR and AMG-510 plus cetuximab. Clonogenic assays were used to study the radiosensitizing effect of AMG-510 combined with cetuximab. Immunofluorescence staining of rH2AX was used to detect double-strand break (DSB) repair. Cell proliferation was performed using a cell counting kit. Then, we performed flow cytometry analysis to detect cell apoptosis rate and cell cycle distribution. <h3>Results</h3> First, we found that AMG-510 plus cetuximab enhanced the radiosensitivity of X-ray in the SW837 cell line (sensitization enhancement ratio: 1.32). The combination of AMG-510 and cetuximab reduced cell proliferation and increased cell apoptosis rate and DNA damage, with or without irradiation. The flow cytometry analysis of the cell cycle showed G1/S phase arrest after AMG-510 monotherapy and AMG-510 plus cetuximab treatment. Moreover, the P53/Rb/P21 pathway was activated after the addition of AMG-510 with or without cetuximab. <h3>Conclusion</h3> The combination of AMG-510 and cetuximab might be a potent treatment as a radiosensitizer. However, more studies in vivo and clinical trials should be performed to further evaluate this regimen in the future.

Radiosensitization effects by bismuth oxide nanorods of different sizes in megavoltage external beam radiotherapy.

Nanotechnology application has successfully reached numerous scientific breakthroughs including in radiotherapy. However, the clinical application of nanoparticles requires more diligent research primarily on the crucial parameters such as nanoparticle sizes. This study is aimed to investigate the influence of bismuth oxide nanorod (Bi2O3-NR) sizes on radiosensitization effects on MCF-7 and HeLa cell lines for megavoltage photon and electron beam radiotherapy. MCF-7 and HeLa cells were treated with and without 0.5 μMol/L of Bi2O3-NR of varying sizes (60, 70, 80, and 90 nm). The samples, including the control groups, were exposed to different radiation doses (0-10 Gy), using photon (6 MV and 10 MV), and electron beam (6 MeV and 12 MeV) radiotherapy. Clonogenic assay was performed, and sensitization enhancement ratio (SER) was determined from linear quadratic based cell survival curves. The results depicted that 60 nm Bi2O3-NR yields the most excellent SER followed by 70 nm Bi2O3-NR. Meanwhile, the 80 and 90 nm Bi2O3-NR showed an insignificant difference between treated and untreated cell groups. This study also found that MCF-7 was subjected to more cell death compared to HeLa. 60 nm Bi2O3-NR was the optimal Bi2O3-NR size to induce radiosensitization effects for megavoltage external beam radiotherapy. The SER in photon beam radiotherapy marked the highest compared to electron beam radiotherapy due to decreased primary radiation energy from multiple radiation interaction and higher Compton scattering.