Effect of titanium dioxide nanoparticles on DNA methylation in multiple human cell lines.

Nanoscale titanium dioxide (TiO2) is manufactured in wide scale, with a range of applications in consumer products. Significant toxicity of TiO2 nanoparticles has, however, been recognized, suggesting considerable risk to human health. To evaluate fully their toxicity, assessment of the epigenetic action of these nanoparticles is critical. However, only few studies are available examining capability of nanoparticles to alter epigenetic integrity. In the present study, the effect of TiO2 nanoparticles exposure on DNA methylation, a major epigenetic mechanism, was investigated in in vitro cellular model systems. A panel of cells relevant to portals of human exposure (Caco-2 (colorectal), HepG2 (liver), NL20 (lung), and A-431 (skin)) was exposed to TiO2 nanoparticles to assess effects on global methylation, gene-specific methylation, and expression levels of DNA methyltransferases, MBD2, and UHRF1. Global methylation was determined by enzyme-linked immunosorbent assay-based immunochemical analysis. Degree of promoter methylation across a defined panel of genes was evaluated using EpiTect Methyl II Signature PCR System Array technology. Expression of DNMT1, DNMT3a, DNMT3b, MBD2, and URHF1 was quantified by qRT-PCR. Decrease in global DNA methylation in cell lines Caco-2, HepG2, and A-431 exposed to TiO2 nanoparticles was shown. Across four cell lines, eight genes (CDKN1A, DNAJC15, GADD45A, GDF15, INSIG1, SCARA3, TP53, and BNIP3) were identified in which promotors were methylated after exposure. Altered expression of these genes is associated with disease etiology. The results also revealed aberrant expression of epigenetic regulatory genes involved in DNA methylation (DNMT1, DNMT3a, DNMT3b, MBD2, and UHRF1) in TiO2 exposed cells, which was cell type dependent. Findings from this study clearly demonstrate the impact of TiO2 nanoparticles exposure on DNA methylation in multiple cell types, supporting potential involvement of this epigenetic mechanism in the toxicity of TiO2 nanoparticles. Hence for complete assessment of potential risk from nanoparticle exposure, epigenetic studies are critical.

Galectin-1 Inhibitor OTX008 Induces Tumor Vessel Normalization and Tumor Growth Inhibition in Human Head and Neck Squamous Cell Carcinoma Models.

Galectin-1 is a hypoxia-regulated protein and a prognostic marker in head and neck squamous cell carcinomas (HNSCC). Here we assessed the ability of non-peptidic galectin-1 inhibitor OTX008 to improve tumor oxygenation levels via tumor vessel normalization as well as tumor growth inhibition in two human HNSCC tumor models, the human laryngeal squamous carcinoma SQ20B and the human epithelial type 2 HEp-2. Tumor-bearing mice were treated with OTX008, Anginex, or Avastin and oxygen levels were determined by fiber-optics and molecular marker pimonidazole binding. Immuno-fluorescence was used to determine vessel normalization status. Continued OTX008 treatment caused a transient reoxygenation in SQ20B tumors peaking on day 14, while a steady increase in tumor oxygenation was observed over 21 days in the HEp-2 model. A >50% decrease in immunohistochemical staining for tumor hypoxia verified the oxygenation data measured using a partial pressure of oxygen (pO2) probe. Additionally, OTX008 induced tumor vessel normalization as tumor pericyte coverage increased by approximately 40% without inducing any toxicity. Moreover, OTX008 inhibited tumor growth as effectively as Anginex and Avastin, except in the HEp-2 model where Avastin was found to suspend tumor growth. Galectin-1 inhibitor OTX008 transiently increased overall tumor oxygenation via vessel normalization to various degrees in both HNSCC models. These findings suggest that targeting galectin-1-e.g., by OTX008-may be an effective approach to treat cancer patients as stand-alone therapy or in combination with other standards of care.

Real-time monitoring of circulating tumor cell (CTC) release after nanodrug or tumor radiotherapy using in vivo flow cytometry.

Noninvasive biological readouts of tumor metastatic risk and therapeutic efficacy are needed as healthcare costs rise. CTCs are the source of metastasis in distant organs that are responsible for the majority of cancer-related deaths. Here we demonstrate the acute and long-term effect of vascular disrupting therapies (high-dose radiotherapy and tumor necrosis factor-alpha (TNF)) on CTCs released from the primary tumor with a non-invasive real-time in vivo flow cytometry system. Using our innovative flow cytometry platform, we show here that radiation and nanodrug treatment can lead to short term release of CTC from the primary tumor. There was no increase in metastasis frequency or extent between control and TNF-treated mice; however, a significant reduction in lung metastasis was noted in the radiotherapy alone group. Mice treated with both TNF and radiotherapy had a slightly elevated metastatic profile between that of radiation alone and control (untreated) tumors. Possible mechanisms based on therapy specific vessel disruption and cell death are discussed. Overall, CTCs correlated with tumor progression and suggest CTC enumeration described herein may be useful in clinical management of solid tumor malignancies.

Combination of Gold Nanoparticle-Conjugated Tumor Necrosis Factor-α and Radiation Therapy Results in a Synergistic Antitumor Response in Murine Carcinoma Models.

PURPOSE: Although remarkable preclinical antitumor effects have been shown for tumor necrosis factor-α (TNF) alone and combined with radiation, its clinical use has been hindered by systemic dose-limiting toxicities. We investigated the physiological and antitumor effects of radiation therapy combined with the novel nanomedicine CYT-6091, a 27-nm average-diameter polyethylene glycol-TNF-coated gold nanoparticle, which recently passed through phase 1 trials. METHODS AND MATERIALS: The physiologic and antitumor effects of single and fractionated radiation combined with CYT-6091 were studied in the murine 4T1 breast carcinoma and SCCVII head and neck tumor squamous cell carcinoma models. RESULTS: In the 4T1 murine breast tumor model, we observed a significant reduction in the tumor interstitial fluid pressure (IFP) 24 hours after CYT-6091 alone and combined with a radiation dose of 12 Gy (P<.05 vs control). In contrast, radiation alone (12 Gy) had a negligible effect on the IFP. In the SCCVII head and neck tumor model, the baseline IFP was not markedly elevated, and little additional change occurred in the IFP after single-dose radiation or combined therapy (P>.05 vs control) despite extensive vascular damage observed. The IFP reduction in the 4T1 model was also associated with marked vascular damage and extravasation of red blood cells into the tumor interstitium. A sustained reduction in tumor cell density was observed in the combined therapy group compared with all other groups (P<.05). Finally, we observed a more than twofold delay in tumor growth when CYT-6091 was combined with a single 20-Gy radiation dose-notably, irrespective of the treatment sequence. Moreover, when hypofractionated radiation (12 Gy × 3) was applied with CYT-6091 treatment, a more than five-fold growth delay was observed in the combined treatment group of both tumor models and determined to be synergistic. CONCLUSIONS: Our results have demonstrated that TNF-labeled gold nanoparticles combined with single or fractionated high-dose radiation therapy is effective in reducing IFP and tumor growth and shows promise for clinical translation.

Targeting Artificial Tumor Stromal Targets for Molecular Imaging of Tumor Vascular Hypoxia.

Developed and tested for many years, a variety of tumor hypoxia detection methods have been inconsistent in their ability to predict treatment outcomes or monitor treatment efficacy, limiting their present prognostic capability. These variable results might stem from the fact that these approaches are based on inherently wide-ranging global tumor oxygenation levels based on uncertain influences of necrotic regions present in most solid tumors. Here, we have developed a novel non-invasive and specific method for tumor vessel hypoxia detection, as hypoxemia (vascular hypoxia) has been implicated as a key driver of malignant progression, therapy resistance and metastasis. This method is based on high-frequency ultrasound imaging of α-pimonidazole targeted-microbubbles to the exogenously administered hypoxia marker pimonidazole. The degree of tumor vessel hypoxia was assessed in three mouse models of mammary gland carcinoma (4T1, SCK and MMTV-Wnt-1) and amassed up to 20% of the tumor vasculature. In the 4T1 mammary gland carcinoma model, the signal strength of α-pimonidazole targeted-microbubbles was on average 8-fold fold higher in tumors of pimonidazole-injected mice than in non-pimonidazole injected tumor bearing mice or non-targeted microbubbles in pimonidazole-injected tumor bearing mice. Overall, this provides proof of principle for generating and targeting artificial antigens able to be 'created' on-demand under tumor specific microenvironmental conditions, providing translational diagnostic, therapeutic and treatment planning potential in cancer and other hypoxia-associated diseases or conditions.

Indirect Tumor Cell Death After High-Dose Hypofractionated Irradiation: Implications for Stereotactic Body Radiation Therapy and Stereotactic Radiation Surgery.

PURPOSE: The purpose of this study was to reveal the biological mechanisms underlying stereotactic body radiation therapy (SBRT) and stereotactic radiation surgery (SRS). METHODS AND MATERIALS: FSaII fibrosarcomas grown subcutaneously in the hind limbs of C3H mice were irradiated with 10 to 30 Gy of X rays in a single fraction, and the clonogenic cell survival was determined with in vivo--in vitro excision assay immediately or 2 to 5 days after irradiation. The effects of radiation on the intratumor microenvironment were studied using immunohistochemical methods. RESULTS: After cells were irradiated with 15 or 20 Gy, cell survival in FSaII tumors declined for 2 to 3 days and began to recover thereafter in some but not all tumors. After irradiation with 30 Gy, cell survival declined continuously for 5 days. Cell survival in some tumors 5 days after 20 to 30 Gy irradiation was 2 to 3 logs less than that immediately after irradiation. Irradiation with 20 Gy markedly reduced blood perfusion, upregulated HIF-1α, and increased carbonic anhydrase-9 expression, indicating that irradiation increased tumor hypoxia. In addition, expression of VEGF also increased in the tumor tissue after 20 Gy irradiation, probably due to the increase in HIF-1α activity. CONCLUSIONS: Irradiation of FSaII tumors with 15 to 30 Gy in a single dose caused dose-dependent secondary cell death, most likely by causing vascular damage accompanied by deterioration of intratumor microenvironment. Such indirect tumor cell death may play a crucial role in the control of human tumors with SBRT and SRS.

Hyperthermia-enhanced indocyanine green delivery for laser-induced thermal ablation of carcinomas.

PURPOSE: Intravenous administration of indocyanine green (ICG) dye can effectively convert near-infrared (NIR) laser light into heat and enhance thermal injury of blood vessels; however, there is no selective uptake of ICG by the tumour compared to the other tissues, which impacts the therapeutic ratio of this strategy unless uptake can be selectively increased in tumour tissue. Here we investigated the use of local hyperthermia prior to intravenous ICG administration to enhance ICG uptake in tumour tissue, thereby enhancing laser thermal ablation of solid tumours. METHODS: Murine SCK breast or SCCVII head and neck tumours were treated with a 755-nm laser light either alone or with prior intravenous administration of 4 mg/kg ICG and/or local tumour hyperthermia at 42.5 °C for 60 min. Retention of ICG was quantified using a NIR animal imaging system. Treatment effects were assessed by growth delay and histology. RESULTS: ICG accumulation in the heated tumours was 1.23-fold greater on average compared to non-heated tumours, in both models. In SCK tumours, animals receiving either laser irradiation alone or in conjunction with ICG had a 1.86- or 3.91-fold increase in tumour growth delay, respectively. The addition of local hyperthermia before ICG injection resulted in complete regression of SCK tumours. Uptake of ICG increased in SCCVII tumours; however, little change in tumour growth delay was observed. CONCLUSION: Using local hyperthermia may improve the delivery of ICG to the tumour and thereby increase the extent of laser thermal ablation of smaller superficial malignancies that can be effectively exposed to laser therapy.

Nanoparticle delivered vascular disrupting agents (VDAs): use of TNF-alpha conjugated gold nanoparticles for multimodal cancer therapy.

Surgery, radiation and chemotherapy remain the mainstay of current cancer therapy. However, treatment failure persists due to the inability to achieve complete local control of the tumor and curtail metastatic spread. Vascular disrupting agents (VDAs) are a class of promising systemic agents that are known to synergistically enhance radiation, chemotherapy or thermal treatments of solid tumors. Unfortunately, there is still an unmet need for VDAs with more favorable safety profiles and fewer side effects. Recent work has demonstrated that conjugating VDAs to other molecules (polyethylene glycol, CNGRCG peptide) or nanoparticles (liposomes, gold) can reduce toxicity of one prominent VDA (tumor necrosis factor alpha, TNF-α). In this report, we show the potential of a gold conjugated TNF-α nanoparticle (NP-TNF) to improve multimodal cancer therapies with VDAs. In a dorsal skin fold and hindlimb murine xenograft model of prostate cancer, we found that NP-TNF disrupts endothelial barrier function and induces a significant increase in vascular permeability within the first 1-2 h followed by a dramatic 80% drop in perfusion 2-6 h after systemic administration. We also demonstrate that the tumor response to the nanoparticle can be verified using dynamic contrast-enhanced magnetic resonance imaging (MRI), a technique in clinical use. Additionally, multimodal treatment with thermal therapies at the perfusion nadir in the sub- and supraphysiological temperature regimes increases tumor volumetric destruction by over 60% and leads to significant tumor growth delays compared to thermal therapy alone. Lastly, NP-TNF was found to enhance thermal therapy in the absence of neutrophil recruitment, suggesting that immune/inflammatory regulation is not central to its power as part of a multimodal approach. Our data demonstrate the potential of nanoparticle-conjugated VDAs to significantly improve cancer therapy by preconditioning tumor vasculature to a secondary insult in a targeted manner. We anticipate our work to direct investigations into more potent tumor vasculature specific combinations of VDAs and nanoparticles with the goal of transitioning optimal regimens into clinical trials.

Radiation-induced galectin-1 by endothelial cells: a promising molecular target for preferential drug delivery to the tumor vasculature.

The present study reports on a new strategy for selective, radiation therapy-amplified drug delivery using an antiangiogenic 33-a.a., tumor vasculature-targeting ligand, anginex, to improve the therapeutic ratio for strategies developed against solid tumors. Our findings indicate that galectin-1 is (a) one of the major receptors for anginex (b) overexpressed by tumor neovasculature and (c) further specifically upregulated in endothelial cells in response to radiation exposure as low as 0.5 Gy. An investigation of [18]-F-labeled anginex biodistribution in SCK tumors indicates that anginex is an effective targeting molecule for image and radiation-guided therapy of solid tumors. An anginex-conjugated liposome capable of being loaded with drug was shown to selectively target endothelial cells post-radiation. The presence of endothelial cells in a three-dimensional co-culture system with tumor cells developed to study tumor/endothelial cell interactions in vitro led to higher levels of galectin-1 and showed a further increase in expression upon radiation exposure when compared to tumor cell spheroids alone. Similar increase in galectin-1 was observed in tumor tissue originating from the tumor-endothelial cell spheroids in vivo and radiation exposure further induced galectin-1 in these tumors. The overall results suggest feasibility of using a clinical or subclinical radiation dose to increase expression of the galectin-1 receptor on the tumor microvasculature to promote delivery of therapeutics via the anginex peptide. This approach may reduce systemic toxicity, overcome drug resistance, and improve the therapeutic efficacy of conventional chemo/radiation strategies.

Microbeam radiation therapy alters vascular architecture and tumor oxygenation and is enhanced by a galectin-1 targeted anti-angiogenic peptide.

In this study, we sought to determine the therapeutic potential of variably sized (50 µm or 500 µm wide, 14 mm tall) parallel microbeam radiation therapy (MRT) alone and in combination with a novel anti-angiogenic peptide, anginex, in mouse mammary carcinomas (4T1)--a moderately hypoxic and radioresistant tumor with propensity to metastasize. The fraction of total tumor volume that was directly irradiated was approximately 25% in each case, but the distance between segments irradiated by the planar microbeams (width of valley dose region) varied by an order of magnitude from 150-1500 µm corresponding to 200 µm and 2000 µm center-to-center inter-microbeam distances, respectively. We found that MRT administered in 50 µm beams at 150 Gy was most effective in delaying tumor growth. Furthermore, tumor growth delay induced by 50 µm beams at 150 Gy was virtually indistinguishable from the 500 µm beams at 150 Gy. Fifty-micrometer beams at the lower peak dose of 75 Gy induced growth delay intermediate between 150 Gy and untreated tumors, while 500 µm beams at 75 Gy were unable to alter tumor growth compared to untreated tumors. However, the addition of anginex treatment increased the relative tumor growth delay after 500 µm beams at 75 Gy most substantially out of the conditions tested. Anginex treatment of animals whose tumors received the 50 µm beams at 150 Gy also led to an improvement in growth delay from that induced by the comparable MRT alone. Immunohistochemical staining for CD31 (endothelial cells) and αSMA (smooth muscle pericyte-associated blood vessels as a measure of vessel normalization) indicated that vessel density was significantly decreased in all irradiated groups and pericyte staining was significantly increased in the irradiated groups on day 14 after irradiation. The addition of anginex treatment further decreased the mean vascular density in all combination treatment groups and further increased the amount of pericyte staining in these tumors. Finally, evidence of tumor hypoxia was found to decrease in tumors analyzed at 1-14 days after MRT in the groups receiving 150 Gy peak dose, but not 75 Gy peak dose. Our results suggest that tumor vascular damage induced by MRT at these potentially clinically acceptable peak entrance doses may provoke vascular normalization and may be exploited to improve tumor control using agents targeting angiogenesis.

Conductive thermal ablation of 4T1 murine breast carcinoma reduces severe hypoxia in surviving tumour.

PURPOSE: The purpose of this study was to quantify hypoxia changes in viable tumour volumes after thermal ablation of a murine breast carcinoma. METHODS: Murine breast 4T1 tumours were grown in the rear leg of BALB/c mice to an average diameter of 10-12 mm. Tumours were treated with conductive interstitial thermal therapy (CITT) at a peak temperature of 80-90°C for 10 min. The animals were euthanised 72 h later, and the tumours were removed for immunohistochemical staining with pimonidazole - a marker of partial pressure of oxygen. The levels of pimonidazole staining intensity were used to quantify changes in hypoxia gradients in terms of strong, medium and weak positive pixel fractions. RESULTS: The pimonidazole staining ratio of viable control tumour tissue to viable tissue in tumours that were ablated was 0.7 for weak staining, 2.7 for medium staining and 8.0 (p < 0.03) for strong pimonidazole staining. CONCLUSION: This shift of pimonidazole staining toward lower intensity pixels in the remaining tumour indicates that tumour ablation with CITT may increase radiosensitivity of the remaining tumour tissue and presents a rationale for combination therapy.

Vascular disrupting agent arsenic trioxide enhances thermoradiotherapy of solid tumors.

Our previous studies demonstrated arsenic trioxide- (ATO-) induced selective tumor vascular disruption and augmentation of thermal or radiotherapy effect against solid tumors. These results suggested that a trimodality approach of radiation, ATO, and local hyperthermia may have potent therapeutic efficacy against solid tumors. Here, we report the antitumor effect of hypofractionated radiation followed by ATO administration and local 42.5 °C hyperthermia and the effects of cisplatin and thermoradiotherapy. We found that the therapeutic efficacy of ATO-based thermoradiotherapy was equal or greater than that of cisplatin-based thermoradiotherapy, and marked evidence of in vivo apoptosis and tumor necrosis were observed in ATO-treated tumors. We conclude that ATO-based thermoradiotherapy is a powerful means to control tumor growth by using vascular disruption to augment the effects of thermal and radiation therapy.

Tumor-Endothelial Cell Three-dimensional Spheroids: New Aspects to Enhance Radiation and Drug Therapeutics.

Classic cancer research for several decades has focused on understanding the biology of tumor cells in vitro. However, extending these findings to in vivo settings has been impeded owing to limited insights on the impact of microenvironment on tumor cells. We hypothesized that tumor cell biology and treatment response would be more informative when done in the presence of stromal components, like endothelial cells, which exist in the tumor microenvironment. To that end, we have developed a system to grow three-dimensional cultures of GFP-4T1 mouse mammary tumor and 2H11 murine endothelial cells in hanging drops of medium in vitro. The presence of 2H11 endothelial cells in these three-dimensional cocultures was found to sensitize 4T1-GFP tumor cells to chemotherapy (Taxol) and, at the same time, protect cells from ionizing radiation. These spheroidal cultures can also be implanted into the dorsal skinfold window chamber of mice for fluorescence imaging of vascularization and disease progression/treatment response. We observed rapid neovascularization of the tumor-endothelial spheroids in comparison to tumor spheroids grown in nude mice. Molecular analysis revealed pronounced up-regulation of several proangiogenic factors in the tumor tissue derived from the tumor-endothelial spheroids compared with tumor-only spheroids. Furthermore, the rate of tumor growth from tumor-endothelial spheroids in mice was faster than the tumor cell-only spheroids, resulting in greater metastasis to the lung. This three-dimensional coculture model presents an improved way to investigate more pertinent aspects of the therapeutic potential for radiation and/or chemotherapy alone and in combination with antiangiogenic agents.

Repression of multiple myeloma growth and preservation of bone with combined radiotherapy and anti-angiogenic agent.

The effects of ionizing radiation, with or without the anti-angiogenic agent anginex (Ax), on multiple myeloma growth were tested in a SCID-rab mouse model. Mice carrying human multiple myeloma cell-containing pre-implanted bone grafts were treated weekly with various regimens for 8 weeks. Rapid multiple myeloma growth, assessed by bioluminescence intensity (IVIS), human lambda Ig light chain level in serum (ELISA), and the volume of bone grafts (caliper), was observed in untreated mice. Tumor burden in mice receiving combined therapy was reduced to 59% (by caliper), 43% (by ELISA), and 2% (by IVIS) of baseline values after 8 weeks of treatment. Ax or radiation alone slowed but did not stop tumor growth. Four weeks after the withdrawal of the treatments, tumor burden remained minimal in mice given Ax + radiation but increased noticeably in the other three groups. Multiple myeloma suppression by Ax + radiation was accompanied by a marked decrease in the number and activity of osteoclasts in bone grafts assessed by histology. Bone graft integrity was preserved by Ax + radiation but was lost in the other three groups, as assessed by microCT imaging and radiography. These results suggest that radiotherapy, when primed by anti-angiogenic agents, may be a potent therapy for focal multiple myeloma.

Prevention and mitigation of acute death of mice after abdominal irradiation by the antioxidant N-acetyl-cysteine (NAC).

Gastrointestinal (GI) injury is a major cause of acute death after total-body exposure to large doses of ionizing radiation, but the cellular and molecular explanations for GI death remain dubious. To address this issue, we developed a murine abdominal irradiation model. Mice were irradiated with a single dose of X rays to the abdomen, treated with daily s.c. injection of N-acetyl-l-cysteine (NAC) or vehicle for 7 days starting either 4 h before or 2 h after irradiation, and monitored for up to 30 days. Separately, mice from each group were assayed 6 days after irradiation for bone marrow reactive oxygen species (ROS), ex vivo colony formation of bone marrow stromal cells, and histological changes in the duodenum. Irradiation of the abdomen caused dose-dependent weight loss and mortality. Radiation-induced acute death was preceded not only by a massive loss of duodenal villi but also, surprisingly, abscopal suppression of stromal cells and elevation of ROS in the nonirradiated bone marrow. NAC diminished these radiation-induced changes and improved 10- and 30-day survival rates to >50% compared with <5% in vehicle-treated controls. Our data establish a central role for abscopal stimulation of bone marrow ROS in acute death in mice after abdominal irradiation.