APTES-Terminated ultrasmall and iron-doped silicon nanoparticles as X-Ray dose enhancer for radiation therapy.

Silicon nanoparticles with sizes between were synthesized through wet-chemistry procedures using diverse phase transfer reagents. On the other hand, the preparation of iron-doped silicon nanoparticles was carried out using the precursor Na4Si4 containing 5% Fe. Biocompatibility of all silicon nanoparticle samples was achieved by surface-stabilizing with (3-aminopropyl)triethoxysilane. These surface structures provided positive surface charges which facilitated electrostatic binding to the negatively charged biological membranes. The mode of interaction with membranes, being either incorporation or just attachment, was found to depend on the nanoparticle size. The smallest silicon nanoparticles (ca. 1.5 nm) were embedded in the mitochondrial membrane in MCF-7 cells. When interacting with X-rays these silicon nanoparticles were observed to enhance the superoxide formation upon depolarizing the mitochondrial membrane. X-ray irradiation of MCF-7 cells loaded with the larger silicon nanoparticles was shown to increase the intracellular singlet oxygen generation. The doping of the silicon nanoparticles with iron led to additional production of hydroxyl radicals via the Fenton reaction.

Enhanced In Vitro Biocompatibility and Water Dispersibility of Magnetite and Cobalt Ferrite Nanoparticles Employed as ROS Formation Enhancer in Radiation Cancer Therapy.

Efficient magnetic reactive oxygen species (ROS) formation enhancing agents after X-ray treatment are realized by functionalizing superparamagnetic magnetite (Fe3 O4 ) and Co-ferrite (CoFe2 O4 ) nanoparticles with self-assembled monolayers (SAMs). The Fe3 O4 and CoFe2 O4 nanoparticles are synthesized using Massart's coprecipitation technique. Successful surface modification with the SAM forming compounds 1-methyl-3-(dodecylphosphonic acid) imidazolium bromide, or (2-{2-[2-hydroxy-ethoxy]-ethoxy}-ethyl phosphonic acid provides biocompatibility and long-term stability of the Fe3 O4 and CoFe2 O4 nanoparticles in cell media. The SAM-stabilized ferrite nanoparticles are characterized with dynamic light scattering, X-ray powder diffraction, a superconducting quantum interference device, Fourier transform infrared attenuated total reflectance spectroscopy, zeta potential measurements, and thermogravimetric analysis. The impact of the SAM-stabilized nanoparticles on the viability of the MCF-7 cells and healthy human umbilical vein endothelial cells (HUVECs) is assessed using the neutral red assay. Under X-ray exposure with a single dosage of 1 Gy the intracellular SAM stabilized Fe3 O4 and CoFe2 O4 nanoparticles are observed to increase the level of ROS in MCF-7 breast cancer cells but not in healthy HUVECs. The drastic ROS enhancement is associated with very low dose modifying factors for a survival fraction of 50%. This significant ROS enhancement effect by SAM-stabilized Fe3 O4 and CoFe2 O4 nanoparticles constitutes their excellent applicability in radiation therapy.

Shell-by-Shell functionalized nanoparticles as radiosensitizers and radioprotectors in radiation therapy of cancer cells and tumor spheroids.

Shell-by-Shell (SbS)-functionalized NPs can be tailor-made by combining a metal oxide NP core of choice with any desired phosphonic acids and amphiphiles as 1st or 2nd ligand shell building blocks. The complementary composition of such highly hierarchical structures makes them interesting candidates for various biomedical applications, as certain active ingredients can be incorporated into the structure. Here, we used TiO2 and CoFe2O4 NPs as drug delivery tools and coated them with a hexadecylphosphonic acid and with hexadecyl ammonium phenolates (caffeate, p-coumarate, ferulate), that possess anticancer as well as antioxidant properties. These architectures were then incubated in 2D and 3D cell cultures of non-tumorigenic and tumorigenic breast cells and irradiated to study their anticancer effect. It was found that both, the functionalized TiO2 and CoFe2O4 NPs acted as strong protective agents in non-tumorigenic spheroids. In contrast, the functionalized CoFe2O4 NPs induce a higher damage in irradiated tumor spheroids compared to the functionalized TiO2 NPs. CoFe3O4 NPs act additionally as radiosensitizing agents to the tumor spheroids. The radio-enhancement of the CoFe2O4 NPs is due to the generation of highly toxic hydroxyl radicals during X-ray irradiation. The irradiation exposed the CoFe2O4 surface, releasing the anticancer drugs into the cytoplasm and making the surface Co2+ ions accessible. These surface ions catalyze the Fenton reaction. This combination of radiosensitizer and anticancer drug delivery proved to be a very effective nanotherapeutic in 2D and 3D cell cultures of breast cancer cells.

Oxidized silicon nanoparticles for radiosensitization of cancer and tissue cells.

The applicability of ultrasmall uncapped and aminosilanized oxidized silicon nanoparticles (SiNPs and NH2-SiNPs) as radiosensitizer was studied by internalizing these nanoparticles into human breast cancer (MCF-7) and mouse fibroblast cells (3T3) that were exposed to X-rays at a single dose of 3 Gy. While SiNPs did not increase the production of reactive oxygen species (ROS) in X-ray treated cells, the NH2-SiNPs significantly enhanced the ROS formation. This is due to the amino functionality as providing positive surface charges in aqueous environment. The NH2-SiNPs were observed to penetrate into the mitochondrial membrane, wherein these nanoparticles provoked oxidative stress. The NH2-SiNPs induced mitochondrial ROS production was confirmed by the determination of an increased malondialdehyde level as representing a gauge for the extent of membrane lipid peroxidation. X-ray exposure of NH2-SiNPs incubated MCF-7 and 3T3 cells increased the ROS concentration for 180%, and 120%, respectively. Complementary cytotoxicity studies demonstrate that these silicon nanoparticles are more cytotoxic for MCF-7 than for 3T3 cells.

Acriflavine-Functionalized Silica@Manganese Ferrite Nanostructures for Synergistic Radiation and Hypoxia Therapies.

Mesoporous and nonmesoporous SiO2@MnFe2O4 nanostructures were loaded with the hypoxia-inducible factor-1 inhibitor acriflavine for combined radiation and hypoxia therapies. The X-ray irradiation of the drug-loaded nanostructures not only triggered the release of the acriflavine inside the cells but also initiated an energy transfer from the nanostructures to surface-adsorbed oxygen to generate singlet oxygen. While the drug-loaded mesoporous nanostructures showed an initial drug release before the irradiation, the drug was primarily released upon X-ray radiation in the case of the nonmesoporous nanostructures. However, the drug loading capacity was less efficient for the nonmesoporous nanostructures. Both drug-loaded nanostructures proved to be very efficient in irradiated MCF-7 multicellular tumor spheroids. The damage of these nanostructures toward the nontumorigenic MCF-10A multicellular spheroids was very limited because of the small number of nanostructures that entered the MCF-10A spheroids, while similar concentrations of acriflavine without nanostructures were toxic for the MCF-10A spheroids.

Superparamagnetic iron oxide nanoparticles as radiosensitizer via enhanced reactive oxygen species formation.

Internalization of citrate-coated and uncoated superparamagnetic iron oxide nanoparticles by human breast cancer (MCF-7) cells was verified by transmission electron microscopy imaging. Cytotoxicity studies employing metabolic and trypan blue assays manifested their excellent biocompatibility. The production of reactive oxygen species in iron oxide nanoparticle loaded MCF-7 cells was explained to originate from both, the release of iron ions and their catalytically active surfaces. Both initiate the Fenton and Haber-Weiss reaction. Additional oxidative stress caused by X-ray irradiation of MCF-7 cells was attributed to the increase of catalytically active iron oxide nanoparticle surfaces.

PD-1 and PD-L1 expression predict regression and prognosis following neoadjuvant radiochemotherapy of oesophageal adenocarcinoma.

Background and purpose: PD-1 and PD-L1 are involved in anticancer immunosurveillance, and their expression may be predictive for therapeutic effectiveness of specific antibodies. Their influence on response to neoadjuvant radiochemotherapy (RCT) and prognosis in patients with oesophageal adenocarcinoma (OAC) remains to be defined. Materials and methods: Between 10/2004 and 06/2018, complete pre-RCT biopsy-specimens were available from 76 patients with locally advanced, non-metastatic OAC scheduled for trimodality therapy. We evaluated intra- and peritumoural expression of CD8, PD-1 and PD-L1 in pre-treatment specimens to determine their influence on tumour regression grade and survival. PD-1 and PD-L1 expression were considered positive (+) if ≥1% of all cells were stained positive, otherwise negative (-); densities of CD8+ cells were categorized as being high (Hi) or low (Lo) according to the median. Results: A negative PD-L1 expression in peritumoural cells predicted a poor tumour regression (RD 0.24 [95% CI 0.03-0.44], p = 0.023). A positive PD-1 expression in intra- as well as peritumoural cells was identified as an unfavourable prognostic factor (HR 0.52 [95% CI 0.29-0.93], p = 0.028; HR 0.50 [0.25-0.99], p = 0.047, respectively). With respect to CD8+ infiltration, positive PD-1 and PD-L1 expressions attenuated its favourable prognostic effect in intratumoural area (LoCD8/PD1 + vs. HiCD8/PD1-: HR 0.25 [0.09-0.69], p = 0.007; LoCD8/PDL1+ vs. HiCD8/PDL1-: HR 0.32 [0.12-0.89], p = 0.028) and were associated with negative outcome when seen in peritumoural area (HiCD8/PD1+ vs. LoCD8/PD1-: HR 0.29 [0.11-0.74], p = 0.010); HiCD8/PDL1+ vs. LoCD8/PDL1-: HR 0.33 [0.12-0.90], p = 0.031). Conclusions: PD-1 and PD-L1 expression were identified to be of predictive and prognostic value in patients with OAC, particularly when considering CD8+ infiltration. Further validation by a large size dataset is required.

X-ray Dose-Enhancing Impact of Functionalized Au-Fe3O4 Nanoheterodimers on MCF-7 and A549 Multicellular Tumor Spheroids.

The efficiency of nanoparticle-enhanced radiotherapy was studied by loading MCF-7 and A549 multicellular tumor spheroids (MCTSs) with caffeic acid- and nitrosonium-functionalized Au-Fe3O4 nanoheterodimers (Au-Fe3O4 NHDs). Transmission electron microscope images of MCTS cross-sectional sections visualized the invasion and distribution of the nitrosonium- and caffeic acid-functionalized Au-Fe3O4 NHDs (NO- and CA-NHDs) in the A549 and MCF-7 MCTSs, whereas the iron content of the MCTSs were quantified using the ferrozine assay. The synergistic impact of intracellular NO- and CA-NHDs and X-ray irradiation on the growth dynamics of the A549 and MCF-7 MCTSs was surveyed by monitoring their temporal evolution under a light microscope over a period of 14 days. The emergence of hypoxia during the spheroid growth was followed by detecting the lactate efflux of MCTSs without and with NO- and CA-NHDs. The performance of the NO- and CA-NHDs as X-ray dose-enhancing agents in the A549 and MCF-7 MCTSs was clarified by performing clonogenic cell survival assays and determining the respective dose-modifying factors for X-ray doses of 0, 2, 4, and 6 Gy. The NO- and CA-NHDs were shown to perform as potent X-ray dose-enhancing agents in A549 and MCF-7 MCTSs. Moreover, the CA-NHDs boosted their radio-sensitizing efficacy by inhibiting the lactate efflux as impairing metabolic reprogramming. A synergistic effect on the MCTS destruction was observed for the combination of both NHDs since the surfactants differ in their antitumor effect.

Caffeic Acid, Quercetin and 5-Fluorocytidine-Functionalized Au-Fe3O4 Nanoheterodimers for X-ray-Triggered Drug Delivery in Breast Tumor Spheroids.

Au-Fe3O4 nanoheterodimers (NHD) were functionalized with the natural and synthetic anticancer drugs caffeic acid (CA), quercetin (Q) and 5-fluorocytidine (5FC). Their X-radiation dose-enhancing potential and chemotherapeutic efficacy for bimodal cancer therapy were investigated by designing multicellular tumor spheroids (MCTS) to in vitro avascular tumor models. MCTS were grown from the breast cancer cell lines MCF-7, MDA-MB-231, and MCF-10A. The MCF-7, MDA-MB-231 and MCF-10A MCTS were incubated with NHD-CA, NHD-Q, or NHD-5FC and then exposed to fractionated X-radiation comprising either a single 10 Gy dose, 2 daily single 5 Gy doses or 5 daily single 2 Gy doses. The NHD-CA, NHD-Q, and NHD-5FC affected the growth of X-ray irradiated and non-irradiated MCTS in a different manner. The impact of the NHDs on the glycolytic metabolism due to oxygen deprivation inside MCTS was assessed by measuring lactate secretion and glucose uptake by the MCTS. The NHD-CA and NHD-Q were found to act as X-radiation dose agents in MCF-7 MCTS and MDA-MB-231 MCTS and served as radioprotector in MCF-10A MCTS. X-ray triggered release of CA and Q inhibited lactate secretion and thereupon disturbed glycolytic reprogramming, whereas 5FC exerted their cytotoxic effects on both, healthy and tumor cells, after their release into the cytosol.

Cell-in-cell phenomenon: leukocyte engulfment by non-tumorigenic cells and cancer cell lines.

BACKGROUND: Research on cell-in-cell (CIC) phenomena, including entosis, emperipolesis and cannibalism, and their biological implications has increased in recent years. Homotypic and heterotypic engulfment of various target cells by numerous types of host cells has been studied in vitro and in tissue sections. This work has identified proteins involved in the mechanism and uncovered evidence for CIC as a potential histopathologic predictive and prognostic marker in cancer. Our experimental study focused on non-professional phagocytosis of leukocytes. RESULTS: We studied the engulfment of peripheral blood mononuclear cells isolated from healthy donors by counting CIC structures. Two non-tumorigenic cell lines (BEAS-2B, SBLF-9) and two tumour cell lines (BxPC3, ICNI) served as host cells. Immune cells were live-stained and either directly co-incubated or treated with irradiation or with conventional or microwave hyperthermia. Prior to co-incubation, we determined leukocyte viability for each batch via Annexin V-FITC/propidium iodide staining. All host cells engulfed their targets, with uptake rates ranging from 1.0% ± 0.5% in BxPC3 to 8.1% ± 5.0% in BEAS-2B. Engulfment rates of the cancer cell lines BxPC3 and ICNI (1.6% ± 0.2%) were similar to those of the primary fibroblasts SBLF-9 (1.4% ± 0.2%). We found a significant negative correlation between leukocyte viability and cell-in-cell formation rates. The engulfment rate rose when we increased the dose of radiotherapy and prolonged the impact time. Further, microwave hyperthermia induced higher leukocyte uptake than conventional hyperthermia. Using fluorescent immunocytochemistry to descriptively study the proteins involved, we detected ring-like formations of diverse proteins around the leukocytes, consisting, among others, of α-tubulin, integrin, myosin, F-actin, and vinculin. These results suggest the involvement of actomyosin contraction, cell-cell adhesion, and the α-tubulin cytoskeleton in the engulfment process. CONCLUSIONS: Both non-tumorigenic and cancer cells can form heterotypic CIC structures by engulfing leukocytes. Decreased viability and changes caused by microwave and X-ray irradiation trigger non-professional phagocytosis.

Pt-Fe3O4, Pd-Fe3O4, and Au-Fe3O4 Nanoheterodimers and Their Efficacy as Radiosensitizers in Cancer Therapy.

The X-radiation enhancing effect of caffeic acid-functionalized Au-Fe3O4, Pt-Fe3O4, and Pd-Fe3O4 nanoheterodimers (NHDs) on 2D and 3D breast tumor (MCF-7) and healthy breast epithelial (MCF-10A) cells was comprehensively examined by performing cell viability, reactive oxygen species (ROS) detection, enzyme activity, and clonogenic assays. Intracellular NHDs were observed to cause DNA fragmentation and to enhance superoxide and hydroxyl radical formation in MCF-7 cells when exposed to a single dose of 1 Gy. MCF-7-derived multicellular tumor spheroids (MCF-7 MCTS) and MCF-10A-derived multicellular spheroids (MCF-10A MCS) were incubated with the NHDs and irradiated with five daily doses of 2 Gy. The Au-Fe3O4 and Pt-Fe3O4 NHD-loaded MCF-7 MCTS significantly decreased in volume after being exposed to fractionated irradiation, whereas intracellular Au-Fe3O4 and Pt-Fe3O4 NHDs promoted the growth of the irradiated MCF-10A MCS. Moreover, Au-Fe3O4 and Pt-Fe3O4 NHDs were shown to impede ROS formation and inhibit DNA strand breakage in the noncancerous MCF-10A cells. On the other hand, the Pd-Fe3O4 NHDs boosted X-radiation-induced damage of MCF-10 A cells, which was ascribed to impairment of the ROS scavenging enzyme activities. In summary, caffeic acid-functionalized Au-Fe3O4 and Pt-Fe3O4 NHDs performed as excellent X-radiation enhancing agents in breast tumor cells, while they protect healthy breast epithelial cells against X-radiation.

Encapsulation of Hydrophobic Drugs in Shell-by-Shell Coated Nanoparticles for Radio-and Chemotherapy-An In Vitro Study.

Our research objective was to develop novel drug delivery vehicles consisting of TiO2 and Al2O3 nanoparticles encapsulated by a bilayer shell that allows the reversible embedment of hydrophobic drugs. The first shell is formed by covalent binding of hydrophobic phosphonic acid at the metal oxide surface. The second shell composed of amphiphilic sodium dodecylbenzenesulfonate emerges by self-aggregation driven by hydrophobic interactions between the dodecylbenzene moiety and the hydrophobic first shell. The resulting double layer provides hydrophobic pockets suited for the intake of hydrophobic drugs. The nanoparticles were loaded with the anticancer drugs quercetin and 7-amino-4-methylcoumarin. Irradiation with X-rays was observed to release the potential anticancer drugs into the cytoplasm. In Michigan Cancer Foundation (MCF)-10 A cells, quercetin and 7-amino-4-methylcoumarin acted as antioxidants by protecting the non-tumorigenic cells from harmful radiation effects. In contrast, these agents increased the reactive oxygen species (ROS) formation in cancerous MCF-7 cells. Quercetin and 7-amino-4-methylcoumarin were shown to induce apoptosis via the mitochondrial pathway in cancer cells by determining an increase in TUNEL-positive cells and a decrease in mitochondrial membrane potential after irradiation. After X-ray irradiation, the survival fraction of MCF-7 cells with drug-loaded nanoparticles considerably decreased, which demonstrates the excellent performance of the double-layer stabilized nanoparticles as drug delivery vehicles.

Cytotoxic and immunosuppressive inflammatory cells predict regression and prognosis following neoadjuvant radiochemotherapy of oesophageal adenocarcinoma.

BACKGROUND AND PURPOSE: Tumour infiltrating lymphocytes (TIL) and tumour associated macrophages (TAM) play a key role in anticancer immunosurveillance. We studied their influence on response to neoadjuvant radiochemotherapy (RCT) and prognosis in patients with oesophageal adenocarcinoma (OAC). MATERIALS AND METHODS: Between 10/2004 and 06/2018, pre-RCT biopsy-specimens were available from 76 patients with locally advanced, non-metastatic OAC scheduled for trimodality therapy. We evaluated intra- and peritumoural expression of FoxP3+-, CD8+-TIL and CD68+-, CD163+-TAM, contemplating cell density, cell ratios and cell-to-cell distances to determine a possible influence on tumour regression grade (TRG) and survival. Median follow-up time for all patients was 18 months (IQR 9-43), and 54 months (25-97) for surviving patients. Data were analysed using risk analysis, logrank test and Cox regression. RESULTS: Poor tumour regression was detected for cN+ (RR 0.77 [95% CI 0.66-0.90], p = 0.001), low intratumoural FoxP3+/CD8+ ratio (RR 0.75 [0.60-0.96], p = 0.020), high peritumoural CD163+/CD68+ ratio (RR 0.77 [0.60-0.99], p = 0.045) and high intratumoural TAM density (RD -0.44 [-0.82 to -0.06], p = 0.023). Apart from poor resection quality and TRG, pretherapeutic high peritumoural CD8+ infiltration (HR 2.36 [1.21-4.61], p = 0.012) and short intratumoural FoxP3+ to CD8+ cell-to-cell distances in middle ranged CD8+ density (HR 2.55 [1.00-6.52], p = 0.050) were significant unfavourable prognostic factors in multivariate analysis. CONCLUSIONS: Immunologic parameters, such as CD8+-, FoxP3+-TIL and CD68+-, CD163+-TAM, were identified to be of independent predictive and prognostic value in patients with OAC. Further and independent validation of these biomarkers by a large size dataset may urgently be contemplated.

Doxorubicin-transferrin conjugate selectively overcomes multidrug resistance in leukaemia cells.

Neoplastic cells frequently have an increased number of transferrin receptors. Coupling transferrin to an anti-neoplastic drug has the potential to overcome multidrug resistance (MDR). The purpose of this study was to examine the distribution and action of doxorubicin-transferrin conjugate (DOXTRF) in a leukaemia cell line (HL60), a multidrug-resistant leukaemia cell line (HL60ADR) and a normal tissue cell line (human fibroblasts). The intracellular accumulation of DOX and DOX-TRF was monitored by direct fluorescence. More DOX-TRF than free DOX was delivered to the tumour cells, and consecutively the levels of DNA double-strand breaks and apoptosis increased even in the multidrug-resistant cell line. In the normal tissue cell line, DOX-TRF did not accumulate, and therefore, the levels of DNA double-strand breaks and apoptosis did not increase. Cell viability was determined using the MTT assay. The IC(50) for DOX-TRF was lower than the IC(50) value for the free drug in both leukaemia cell lines. The IC(50) values for the HL60 cells were 0.08 microM for DOX and 0.02 microM for DOX-TRF. The IC(50) values for HL60ADR cells were 7 microM for DOX and 0.035 microM for DOX-TRF. In conclusion, DOX-TRF was able to overcome MDR in the leukaemia cell lines while having only a very limited effect on normal tissue cells.

Bifunctional Au-Fe3O4 Nanoheterodimers Acting as X-ray Protector in Healthy Cells and as X-ray Enhancer in Tumor Cells.

Bifunctional Au-Fe3O4 nanoheterodimers were synthesized by thermally decomposing Fe(III)oleate on gold nanoparticles followed by functionalizing with tiron, 2,3-dihydroxybenzoic acid, or caffeic acid. These catechol derivatives are antioxidative and thus are predicted to function as superoxide scavengers. In particular, caffeic acid lost its antioxidant capacity, although it was covalently linked through its carboxyl moiety to the Fe3O4 surface. Tiron was shown to bind via its catechol group to the Au-Fe3O4 nanoheterodimers, and 2,3-dihydroxybenzoic was just physisorbed between the oleic acid surface structures. Caffeic-acid stabilized Au-Fe3O4 nanoheterodimers turned out to act as X-ray protector in healthy cells but as X-ray enhancing agents in cancer cells. Furthermore, these functionalized Au-Fe3O4 nanoheterodimers were found to inhibit the migratory capacity of the cancer cells.

NOBF4-Functionalized Au-Fe3O4 Nanoheterodimers for Radiation Therapy: Synergy Effect Due to Simultaneous Reactive Oxygen and Nitrogen Species Formation.

Snowman-shaped Au-Fe3O4 nanoheterodimers were synthesized by thermal decomposition of iron oleate on presynthesized Au nanoparticles. Subsequently performed ligand exchange with nitrosyl tetrafluoroborate provided water solubility and enabled X-ray-induced NO release. These Au-Fe3O4 nanoheterodimers combine high- Z material with catalytically active Fe3O4 surfaces and, moreover, plasmonic properties with superparamagnetic performance. We could establish synergetic interactions between X-radiation and both the Au and Fe3O4 surfaces, which resulted in the simultaneous production of the nitric oxide radical at the Fe3O4 surface and the superoxide radical at the Au surface. The surface-confined reaction between these radicals generated peroxynitrite. This highly reactive species may cause nitration of mitochondrial proteins and lipid peroxidation and induce DNA strand breaks. Therefore, high concentrations of peroxynitrite are expected to give rise to severe cellular energetic derangements and thereupon entail rapid cell death. As providing a common platform for X-ray-induced formation of the highly reactive radical nitric oxide, superoxide, and peroxynitrite, nitrosyl tetrafluoroborate functionalized Au-Fe3O4 nanosnowmen were shown to exhibit excellent performance as X-ray-enhancing agents in radiation therapy.

Understanding the Role of Surface Charge in Cellular Uptake and X-ray-Induced ROS Enhancing of Au-Fe3O4 Nanoheterodimers.

Au-Fe3O4 nanoheterodimers were obtained by thermally decomposing iron oleate on presynthesized gold nanoparticles. Water solubility as well as surface charges were achieved by encapsulating the initially hydrophobic Au-Fe3O4 nanoheterodimers in a self-assembled bilayer shell formed either by 1-octadecylpyridinium, providing positive surface charges, or by 4-dodecylbenzenesulfonate, yielding a negatively charged surface. The surface charge and surface architecture were shown to control both the cellular entry and the intracellular trafficking of the Au-Fe3O4 nanoheterodimers. The positively charged (1-octylpyridinium-terminated) Au-Fe3O4 nanoheterodimers were internalized by both breast cancer cells (MCF-7) and epithelial cells (MCF-10 A), wherein they were electrostatically bound at the negatively charged membranes of the cell organelles and, in particular, adsorbed onto the mitochondrial membrane. The treatment of MCF-7 and MCF-10 cells with a fractional X-radiation dose of 1 Gy resulted into a large increase of superoxide production, which arose from the Au-Fe3O4 nanoheterodimer-induced mitochondrial depolarization. In contrast, the negatively charged (4-dodecylbenzenesulfonate-terminated) Au-Fe3O4 nanoheterodimers preferentially invaded the cancerous MCF-7 cells by direct permeation. X-ray treatment of MCF-7 cells, loaded with anionic Au-Fe3O4 nanoheterodimers, yielded the increase of both hydroxyl radical and cytoplasmic superoxide formation. The X-radiation-induced activation of the Fe3O4 surfaces, consisting of Fe2+ and Fe3+ cations, triggered the catalysis of the hydroxyl radical production, whereas superoxide formation presumably occurred through X-ray-induced photoelectron emission near the Au surface. Since hydroxyl radicals are highly cytotoxic and the negatively charged Au-Fe3O4 NHDs spare the healthy MCF-10A cells, these Au-Fe3O4 nanoheterodimers exhibit a higher potential for radiation therapy than the positively charged Au-Fe3O4 nanoheterodimers. Encouraging results from the clonogenic cell survival assay and DMF calculations corroborate the excellent performance of the anionic Au-Fe3O4 nanoheterodimers as an X-ray dosage enhancer.

Potential for the G2/M arrest assay to predict patient susceptibility to severe reactions following radiotherapy.

BACKGROUND AND PURPOSE: Cell-cycle regulation and checkpoint activation are crucial factors for radiation-induced DNA damage processing. The G2/M phase arrest was assessed in lymphoblastoid cell lines and phytohemagglutinin-stimulated T-lymphocytes of different radiosensitivities to study the relationship of G2/M arrest to radiosensitivity. MATERIAL AND METHODS: G2/M arrest was analyzed after in vitro irradiation by 2 and 5 Gy of ionizing radiation up to 6 days using 17 lymphoblastoid cell lines from healthy individuals, ataxia-telangiectasia (AT) patients, Nijmegen breakage syndrome (NBS) patients and cancer patients with clinically increased radiosensitivity. In a second approach, phytohemagglutinin-stimulated T-lymphocytes from 15 healthy individuals, twelve cancer patients, and five cancer patients hypersensitive to ionizing radiation were studied. Image cytometry was performed to analyze G2/M arrest. RESULTS: Two of the three AT cell lines showed markedly increased G2/M arrest compared to controls. NBS cells were comparable to controls up to day 3, but then demonstrated a slightly increased G2/M arrest. Two of the six radiosensitive lymphoblast cell lines and the five radiosensitive cancer patients' T-lymphocytes assayed showed a reduction in G2/M arrest, while healthy individuals showed no difference from cancer patients. CONCLUSION: The interrelation between G2/M arrest and radiosensitivity is not readily apparent since a variety of radiosensitive cells from patients with radiosensitive syndromes and patients identified as radiosensitive following radiation treatment showed inconsistent G2/M arrest dynamics. Secondary effects, like loss of clonogenicity, G1/S phase arrest and failure of G2/M arrest may contribute to variation of the G2/M arrest endpoint and obscure assessment of cellular radiosensitivity using this method.

Time and dose-dependent activation of p53 serine 15 phosphorylation among cell lines with different radiation sensitivity.

PURPOSE: Proper detection of DNA damage and signal transduction to other proteins following irradiation (IR) is essential for cellular integrity. The serine 15 (Ser15) on p53 is crucial for p53 stabilization and a requirement for transient and permanent cell cycle arrest. Here, we sought to determine the relationship between p53 serine 15 phosphorylation (p53-p-Ser15) on cellular sensitivity and if this modification is associated with DNA double-strand break (DSB) repair. MATERIALS AND METHODS: Eight lymphoblastoid cell lines including ataxia-telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and radiosensitive patient derived cell lines were irradiated with 1 Gy, 2 Gy and 5 Gy. Then growth inhibition, p53 induction and phosphorylation on Ser15 as assessed by immunoblotting and DNA DSB repair as assessed by constant field gel electrophoresis were examined. RESULTS: Phosphorylation of p53 at Ser15 in control cells rapidly increased, peaking at 3-6 hours and then sustained a low level of phosphorylation for up to 6 days following IR. For these cell lines, the amount of p53-p-Ser15 corresponded to the sensitivity of cells and the amount of DNA DSB. In A-T cells, p53-p-Ser15 was reduced in spite of increased DNA DSB. NBS cells had similar phosphorylation dynamics as the control cell line, which was not consistent with their increased sensitivity. Radiosensitive patients' cell lines differed only slightly from controls. CONCLUSIONS: Cells that are competent in signal transduction have p53-p-Ser15 kinetics corresponding to cellular radiosensitivity as assessed by clonogenicity and DNA DSB repair, and cells impaired in signal transduction lack this correspondence. Therefore, using p53-p-Ser15 as a general marker of radiation sensitivity has confounding factors which may impair proper radiosensitivity prediction.

Individual differences in chromosomal aberrations after in vitro irradiation of cells from healthy individuals, cancer and cancer susceptibility syndrome patients.

BACKGROUND: Radiosensitivity of normal tissue is a crucial factor of radiotherapy (RT)-related side effects. Here, we report the analysis of spontaneous and in vitro irradiation-induced chromosomal aberrations in 256,679 metaphases from 222 different individuals using three-color fluorescence in situ hybridization as a measure of radiosensitivity. MATERIALS AND METHODS: Samples were categorized into the following 6 groups: (1) healthy individuals, (2) cancer patients prior to radiotherapy, (3) RT-treated cancer patients, (4) individuals heterozygous or (5) homozygous for a mutation in the ataxia telangiectasia mutated (ATM) gene or in the Nijmegen breakage syndrome (NBS1) gene and (6) hypersensitive patients (outliers). RESULTS: A normal distribution of the number of chromosomal aberrations, measured as breaks per metaphase (B/m), was adopted for all examined groups. The mean value of the control group was 0.40B/m (SD+/-0.07). This value was lower compared to the mean breakage rate from 175 non-exposed (0.50+/-0.12B/m) and pre-exposed (0.50+/-0.16B/m) cancer patients. Nineteen of the metaphase spreads from the analyzed cancer patients had a high number of chromosomal aberrations (1.04+/-0.29B/m) and were designated as a separate hypersensitive subgroup (outliers). The aberration frequency of this group was comparable to those of ATM or NBS1 heterozygotes (0.86+/-0.26B/m). The highest incidence of aberrations was observed in ATM and NBS1 homozygous patients (2.23+/-1.03B/m). CONCLUSION: The frequency of break events in the analyzed groups resulted in a normal distribution with varying means and broadnesses defining a characteristic sensitivity pattern for each group. In the RT-relevant group of cancer patients, those patients who have cancer, about one-third of the normally distributed samples were determined to be sensitive as defined by the number of induced aberrations higher than the 99% confidence interval of the normal individual's Gaussian distribution. About 5% of these samples were outside of the 99% confidence interval for the RT-relevant group's normal distribution. These outliers with higher chromosomal breakage rates suggest a unique class of hypersensitive individuals that are susceptible to chromosomal damage and may be directly associated with an increased risk to suffer from radiotherapy-related complications.