Preliminary evaluation of alpha-emitting radioembolization in animal models of hepatocellular carcinoma.

Hepatocellular carcinoma is the most common primary liver cancer and the fifth most frequently diagnosed cancer worldwide. Most patients with advanced disease are offered non-surgical palliative treatment options. This work explores the first alpha-particle emitting radioembolization for the treatment and monitoring of hepatic tumors. Furthermore, this works demonstrates the first in vivo simultaneous multiple-radionuclide SPECT-images of the complex decay chain of an [225Ac]Ac-labeled agent using a clinical SPECT system to monitor the temporal distribution. A DOTA chelator was modified with a lipophilic moiety and radiolabeled with the α-particle emitter Actinium-225. The resulting agent, [225Ac]Ac-DOTA-TDA, was emulsified in ethiodized oil and evaluated in vivo in mouse model and the VX2 rabbit technical model of liver cancer. SPECT imaging was performed to monitor distribution of the TAT agent and the free daughters. The [225Ac]Ac-DOTA-TDA emulsion was shown to retain within the HEP2G tumors and VX2 tumor, with minimal uptake within normal tissue. In the mouse model, significant improvements in overall survival were observed. SPECT-imaging was able to distinguish between the Actinium-225 agent (Francium-221) and the loss of the longer lived daughter, Bismuth-213. An α-particle emitting TARE agent is capable of targeting liver tumors with minimal accumulation in normal tissue, providing a potential therapeutic agent for the treatment of hepatocellular carcinoma as well as a variety of hepatic tumors. In addition, SPECT-imaging presented here supports the further development of imaging methodology and protocols that can be incorporated into the clinic to monitor Actinium-225-labeled agents.

Activatable UCL/CT/MR-enhanced in vivo imaging-guided radiotherapy and photothermal therapy.

Although sophisticated radiotherapy (RT) technology has been widely applied in clinical oncotherapy, unsatisfactory therapeutic effects due to hypoxic tumor microenvironments and complications are still prevalent. Herein, copper sulphide nanoparticles (CuS NPs) wrapped on the surface of upconversion nanoparticles (UCNPs) via manganese dioxide (MnO2) coatings were synthesized for O2 self-supplementing and enhanced combinational RT/photothermal therapy (PTT). In our design, the nanoplatforms can be rapidly enriched at tumor sites by the enhanced permeability and retention (EPR) effect and respond to the tumor microenvironment. The surface MnO2 coatings can interact with over-expressed H2O2 in tumors and cause an abundant generation of oxygen for hypoxic improvement, leading to an enhanced RT. More importantly, by irradiation with near-infrared light, the scattered CuS NPs can convert light energy into heat to destroy tumor cells and reinforce the therapeutic effects of RT. Furthermore, these NPs also displayed excellent performances in upconversion fluorescence imaging (UCL), computerized tomographic (CT) scanning and magnetic resonance imaging (MRI), demonstrating a potential imaging-guided cancer therapy system.

The anti-angiogenic agent lenvatinib induces tumor vessel normalization and enhances radiosensitivity in hepatocellular tumors.

The evaluation of angiogenesis inhibitors requires the analysis of the precise structure and function of tumor vessels. The anti-angiogenic agents lenvatinib and sorafenib are multi-target tyrosine kinase inhibitors that have been approved for the treatment of hepatocellular carcinoma (HCC). However, the different effects on tumor vasculature between lenvatinib and sorafenib are not well understood. In this study, we analyzed the effects of both drugs on vascular structure and function, including vascular normalization, and investigated whether the normalization had a positive effect on a combination therapy with the drugs and radiation using micro X-ray computed tomography with gold nanoparticles as a contrast agent, as well as immunohistochemical analysis and interstitial fluid pressure (IFP) measurement. In mice subcutaneously transplanted with mouse HCC cells, treatment with lenvatinib or sorafenib for 14 days inhibited tumor growth and reduced the tumor vessel volume density. However, analysis of integrated data on vessel density, rates of pericyte-covering and perfused vessels, tumor hypoxia, and IFP measured 4 days after drug treatment showed that treatment with 3 mg/kg of lenvatinib significantly reduced the microvessel density and normalized tumor vessels compared to treatment with 50 mg/kg of sorafenib. These results showed that lenvatinib induced vascular normalization and improved the intratumoral microenvironment in HCC tumors earlier and more effectively than sorafenib. Moreover, such changes increased the radiosensitivity of tumors and enhanced the effect of lenvatinib and radiation combination therapy, suggesting that this combination therapy is a powerful potential application against HCC.

Relationship between locomotor activity rhythm and corticosterone levels during HCC development, progression, and treatment in a mouse model.

Cancer-related fatigue (CRF) and stress are common symptoms in cancer patients and represent early side effects of cancer treatment which affect the life quality of the patients. CRF may partly depend on disruption of the circadian rhythm. Locomotor activity and corticosterone rhythms are two important circadian outputs which can be used to analyze possible effects on the circadian function during cancer development and treatment. The present study analyzes the relationship between locomotor activity rhythm, corticosterone levels, hepatocellular carcinoma (HCC) development, and radiotherapy treatment in a mouse model. HCC was induced in mice by single injection of diethylnitrosamine (DEN) and chronic treatment of phenobarbital in drinking water. Another group received chronic phenobarbital treatment only. Tumor bearing animals were divided randomly into four groups irradiated at four different Zeitgeber time points. Spontaneous locomotor activity was recorded continuously; serum corticosterone levels and p-ERK immunoreaction in the suprachiasmatic nucleus (SCN) were investigated. Phenobarbital treated mice showed damped corticosterone levels and a less stable 24 hours activity rhythm as well as an increase in activity during the light phase, reminiscent of sleep disruption. The tumor mice showed an increase in corticosterone level during the inactive phase and decreased activity during the dark phase, reminiscent of CRF. After irradiation, corticosterone levels were further increased and locomotor activity rhythms were disrupted. Lowest corticosterone levels were observed after irradiation during the early light phase; thus, this time might be the best to apply radiotherapy in order to minimize side effects.

Correlation and Agreement of Yttrium-90 Positron Emission Tomography/Computed Tomography with Ex Vivo Radioembolization Microsphere Deposition in the Rabbit VX2 Liver Tumor Model.

PURPOSE: To demonstrate a stronger correlation and agreement of yttrium-90 (90Y) positron emission tomography (PET)/computed tomography (CT) measurements with explant liver tumor dosing compared with the standard model (SM) for radioembolization. MATERIALS AND METHODS: Hepatic VX2 tumors were implanted into New Zealand white rabbits, with growth confirmed by 7 T magnetic resonance imaging. Seventeen VX2 rabbits provided 33 analyzed tumors. Treatment volumes were calculated from manually drawn volumes of interest (VOI) with three-dimensional surface renderings. Radioembolization was performed with glass 90Y microspheres. PET/CT imaging was completed with scatter and attenuation correction. Three-dimensional ellipsoid VOI were drawn to encompass tumors on fused images. Tumors and livers were then explanted for inductively coupled plasma (ICP)-optical emission spectroscopy (OES) analysis of microsphere content. 90Y PET/CT and SM measurements were compared with reference standard ICP-OES measurements of tumor dosing with Pearson correlation and Bland-Altman analyses for agreement testing with and without adjustment for tumor necrosis. RESULTS: The median infused activity was 33.3 MBq (range, 5.9-152.9). Tumor dose was significantly correlated with 90Y PET/CT measurements (r = 0.903, P < .001) and SM estimates (r = 0.607, P < .001). Bland-Altman analyses showed that the SM tended to underestimate the tumor dosing by a mean of -8.5 Gy (CI, -26.3-9.3), and the degree of underestimation increased to a mean of -18.3 Gy (CI, -38.5-1.9) after the adjustment for tumor necrosis. CONCLUSIONS: 90Y PET/CT estimates were strongly correlated and had better agreement with reference measurements of tumor dosing than SM estimates.

MicroRNA-1271-5p inhibits cell proliferation and enhances radiosensitivity by targeting CDK1 in hepatocellular carcinoma.

This study aims to determine whether miR-1271-5p inhibits cell proliferation and enhances the radiosensitivity by targeting cyclin-dependent kinase 1 (CDK1) in hepatocellular carcinoma (HCC). Its expression levels in the HCC cell lines were significantly lower than those in normal human liver cell line. Bioinformatics analysis indicated CDK1 was a potential target of miR-1271-5p. Dual-Luciferase Reporter Assay confirmed that CDK1 is a direct target gene of miR-1271-5p. With overexpression of miR-1271-5p in SMMC-7721 and HuH-7 cells, cell proliferation was decreased, radiosensitivity was enhanced, cell cycle distribution was altered and the growth of transplanted tumours in nude mice was significantly reduced. miR-1271-5p overexpression enhanced radiosensitivity, which could be reduced by CDK1 overexpression. Overall, our findings suggested that miR-1271-5p inhibits cell proliferation and enhances the radiosensitivity of HCC cell lines by targeting CDK1.

Reevaluation of CBE value of BPA for hepatocytes.

The compound biological effectiveness (CBE) value of boronophenylalanine (BPA) for hepatocytes was experimentally determined for the purpose of boron neutron capture therapy (BNCT) for liver tumors. In this study, the critical reevaluation of previous value was performed. In previous experimental studies, the contribution of ß component of dose was ignored in the response curve to X-ray. X-ray dose cell survival curves were estimated by combining the α/ß values obtained in the ordinary micronucleus (MN) assay with the curve of MN-negative cell fraction (MN(-)F) to dose. This curve was compared to the boron neutron capture reaction (BNCR) dose curve. As a result, the CBE value was 4 at doses close to 0 Gy, decreasing to about 1.0 at doses close to 4.5 Gy. The new value is smaller than the previous value 4.2. This indicates that the bioequivalent dose to normal liver is lower than previously expected. Therefore, higher doses can be given to the tumor.

Early Diffusion-Weighted Imaging and Proton Magnetic Resonance Spectroscopy Features of Liver Transplanted Tumors Treated with Radiation in Rabbits: Correlation with Histopathology.

In this study, we sought to determine how diffusion-weighted imaging (DWI) and proton magnetic resonance spectroscopy (1H-MRS) features are associated with histopathological results, and explored the cellular mechanisms of DWI and 1H-MRS in early radiosensitivity of transplanted liver tumors. VX2 tumors were implanted into the hind leg muscles of 60 New Zealand White Rabbits. All rabbits were randomly divided into ten subgroups according to treatment: irradiated or nonirradiated and according to different times postirradiation. Magnetic resonance scanning was then performed one day before irradiation and on days 1, 3, 5 and 7 postirradiation. Differences in tumor volume, apparent diffusion coefficient (ADC) value, choline/creatine ratio and lipid/creatine ratio, and their associations with histopathological findings, were assessed. Tumor volumes in the irradiated groups were smaller than control values, while ADC values increased gradually with time postirradiation; choline/creatine ratios were reduced while lipid/creatine ratios were larger compared to control values. Bax protein levels after irradiation increased with time. Interestingly, the ADC value and Bax-positive grade showed the same increasing trend (r = 0.900, P < 0.001). Additionally, choline/creatine and lipid/creatine ratios were respectively significantly associated with Bax-positive grade. Furthermore, significant associations of tumor volume with ADC value, choline/creatine ratio and lipid/creatine ratio were observed. These findings demonstrated that ADC value, choline/creatine ratio and lipid/creatine ratio, indicators of early radiosensitivity, are related to cell apoptosis.

Hypoxia-targeted 131I therapy of hepatocellular cancer after systemic mesenchymal stem cell-mediated sodium iodide symporter gene delivery.

Adoptively transferred mesenchymal stem cells (MSCs) home to solid tumors. Biologic features within the tumor environment can be used to selectively activate transgenes in engineered MSCs after tumor invasion. One of the characteristic features of solid tumors is hypoxia. We evaluated a hypoxia-based imaging and therapy strategy to target expression of the sodium iodide symporter (NIS) gene to experimental hepatocellular carcinoma (HCC) delivered by MSCs.MSCs engineered to express transgenes driven by a hypoxia-responsive promoter showed robust transgene induction under hypoxia as demonstrated by mCherry expression in tumor cell spheroid models, or radioiodide uptake using NIS. Subcutaneous and orthotopic HCC xenograft mouse models revealed significant levels of perchlorate-sensitive NIS-mediated tumoral radioiodide accumulation by tumor-recruited MSCs using 123I-scintigraphy or 124I-positron emission tomography. Functional NIS expression was further confirmed by ex vivo 123I-biodistribution analysis. Administration of a therapeutic dose of 131I in mice treated with NIS-transfected MSCs resulted in delayed tumor growth and reduced tumor perfusion, as shown by contrast-enhanced sonography, and significantly prolonged survival of mice bearing orthotopic HCC tumors. Interestingly, radioiodide uptake into subcutaneous tumors was not sufficient to induce therapeutic effects. Our results demonstrate the potential of using tumor hypoxia-based approaches to drive radioiodide therapy in non-thyroidal tumors.

(125)I-labeled anti-bFGF monoclonal antibody inhibits growth of hepatocellular carcinoma.

AIM: To investigate the inhibitory efficacy of (125)I-labeled anti-basic fibroblast growth factor (bFGF) monoclonal antibody (mAb) in hepatocellular carcinoma (HCC). METHODS: bFGF mAb was prepared by using the 1G9B9 hybridoma cell line with hybridization technology and extracted from ascites fluid through a Protein G Sepharose affinity column. After labeling with (125)I through the chloramine-T method, bFGF mAb was further purified by a Sephadex G-25 column. Gamma radiation counter GC-1200 detected radioactivity of (125)I-bFGF mAb. The murine H22 HCC xenograft model was established and randomized to interventions with control (phosphate-buffered saline), (125)I-bFGF mAb, (125)I plus bFGF mAb, bFGF mAb, or (125)I. The ratios of tumor inhibition were then calculated. Expression of bFGF, fibroblast growth factor receptor (FGFR), platelet-derived growth factor, and vascular endothelial growth factor (VEGF) mRNA was determined by quantitative reverse transcriptase real-time polymerase chain reaction. RESULTS: The purified bFGF mAb solution was 8.145 mg/mL with a titer of 1:2560000 and was stored at -20 °C. After coupling, (125)I-bFGF mAb was used at a 1: 1280000 dilution, stored at 4 °C, and its specific radioactivity was 37 MBq/mg. The corresponding tumor weight in the control, (125)I, bFGF mAb, (125)I plus bFGF mAb, and (125)I-bFGF mAb groups was 1.88 ± 0.25, 1.625 ± 0.21, 1.5 ± 0.18, 1.41 ± 0.16, and 0.98 ± 0.11 g, respectively. The tumor inhibition ratio in the (125)I, bFGF mAb, (125)I plus bFGF mAb, and (125)I-bFGF mAb groups was 13.6%, 20.2%, 25.1%, and 47.9%, respectively. Growth of HCC xenografts was inhibited significantly more in the (125)I-bFGF mAb group than in the other groups (P < 0.05). Expression of bFGF and FGFR mRNA in the (125)I-bFGF mAb group was significantly decreased in comparison with other groups (P < 0.05). Groups under interventions revealed increased expression of VEGF mRNA (except for (125)I group) compared with the control group. CONCLUSION: (125)I-bFGF mAb inhibits growth of HCC xenografts. The coupling effect of (125)I-bFGF mAb is more effective than the concomitant use of (125)I and bFGF mAb.

Brachytherapy Using Elastin-Like Polypeptides with (131)I Inhibit Tumor Growth in Rabbits with VX2 Liver Tumor.

BACKGROUND: Brachytherapy is a targeted type of radiotherapy utilized in the treatment of cancers. Elastin-like polypeptides are a unique class of genetically engineered peptide polymers that have several attractive properties for brachytherapy. AIMS: To explore the feasibility and application of brachytherapy for VX2 liver tumor using elastin-like polypeptides with (131)I so as to provide reliable experimental evidence for a new promising treatment of liver cancer. METHODS: Elastin-like polypeptide as carrier was labeled with (131)I using the iodogen method. Ten eligible rabbits with VX2 liver tumor were randomly divided into the treatment group (n = 5) and control group (n = 5). The treatment group received brachytherapy using elastin-like polypeptide with (131)I, and in the control group, elastin-like polypeptide was injected into the VX2 liver tumor as a control. Periodic biochemical and imaging surveillances were required to assess treatment efficacy. RESULTS: The stability of elastin-like polypeptide with (131)I in vitro was maintained at over 96.8 % for 96 h. Biochemistry and imaging indicated brachytherapy using elastin-like polypeptide with (131)I for liver tumor can improve liver function and inhibit tumor growth (P < 0.05). CONCLUSIONS: Elastin-like polypeptide can be an ideal carrier of (131)I and have high labeling efficiency, radiochemical purity and stability. Brachytherapy using elastin-like polypeptide with (131)I for liver tumor is a useful therapy that possesses high antitumor efficacy advantages.

Radiation Inhibits Interleukin-12 Production via Inhibition of C-Rel through the Interleukin-6/ Signal Transducer and Activator of Transcription 3 Signaling Pathway in Dendritic Cells.

Radiotherapy (RT) is a potent anti-tumor modality. However, unwanted effects including increased recurrence and metastasis that involve factors such as cytokines, which induce complex molecular mechanisms, have also been reported. In a previous study, we showed that interleukin (IL)-12 and radiotherapy combination treatment suppressed tumor growth and metastasis in a hepatoma mouse model. In this study, we investigated the mechanism underlying the IL-12 anti-tumor effect during radiotherapy. In tumor-bearing mice, irradiation decreased IL-12 expression in the tumors and spleens. However, a number of dendritic cells infiltrated into the tumors in which IL-12 expression did not decrease. To further study the underlying detailed mechanism for this decrease in IL-12, LPS-stimulated bone marrow-derived dendritic cells (BMDCs) were irradiated, and then IL-12- and IL-6-associated molecules were examined in irradiated tumors and BMDCs. Irradiation resulted in IL-12 suppression and IL-6 increase. IL-6 and signal transducer and activator of transcription 3 (STAT3) inhibitors restored the irradiation-induced IL-12 decrease via suppression of C-Rel activation. Taken together, our study suggests that irradiation-induced IL-6 can decrease IL-12 production through the inhibition of C-Rel phosphorylation by the IL-6/STAT3 signaling pathway.

Polychromatic visible and infrared light (480-3400 nm) downregulates the growth of hepatoma MH22a in mice.

We studied the effect of polychromatic visible (380-750 nm) (VIS) and combined with the visible infrared (480-3400 nm) (VIS-IR) radiation on the growth of hepatoma in mice. In the first series of experiments on C3HA mice with subcutaneously transplanted syngeneic hepatoma MH22a it was shown 1.5-4 times inhibition of tumor volume after irradiation of tumor-bearing mice with VIS-infrared light at a dose 4.8 J/ cm2. Mice irradiation at doses of 9.6 J/cm2 and 38.4 J/cm2 had no effect on the rate of tumor growth. Exposition to VIS and IR-light in all doses we used an increase of the surviveness of animals in the 1.5 and 2 times respectively was observed. In a second series of experiments we investigated the effect VIS-IR radiation on tumor cells in vitro with subsequent inoculation to intact mice. After implantation in mice irradiated cells at a dose of 4.8 J/cm2 9.6 J/cm2 inhibition of tumor growth during the first 25 days at 3-12 times as compared to control and increased survival in mice 1.5-2 respectively was observed. The main results of this study consists in the fact that none of the doses used VIS and a IR-radiation has not been shown to stimulate tumor growth both in irradiated mice with tumors, and the irradiation of MH22a hepatoma cells under in vitro conditions prior to transplantation of intact mice. Furthermore it was detected dose range VIS-IR light (4.8-9.6 Joules/cm2) when the rate of growth of hepatoma MH22a decreased and increased surviveness of animals.

Autoradiographic and histopathological studies of boric acid-mediated BNCT in hepatic VX2 tumor-bearing rabbits: Specific boron retention and damage in tumor and tumor vessels.

Hepatoma is a malignant tumor that responds poorly to conventional therapies. Boron neutron capture therapy (BNCT) may provide a better way for hepatoma therapy. In this research, (10)B-enriched boric acid (BA, 99% (10)B) was used as the boron drug. A multifocal hepatic VX2 tumor-bearing rabbit model was used to study the mechanisms of BA-mediated BNCT. Autoradiography demonstrated that BA was selectively targeted to tumors and tumor vessels. Histopathological examination revealed the radiation damage to tumor-bearing liver was concentrated in the tumor regions during BNCT treatment. The selective killing of tumor cells and the destruction of the blood vessels in tumor masses may be responsible for the success of BA-mediated BNCT for liver tumors.

Biological effects of irradiating hepatocellular carcinoma cells by internal exposure with 125I-labeled 5-iodo-2'-deoxyuridine-chitosan drug loading nanoparticles.

In this study, the authors evaluate the biological effects of irradiation of hepatocellular carcinoma cells by internal exposure with (125)I-labeled 5-iodo-2'-deoxyuridine ((125)I-UdR)-chitosan drug loading nanoparticles ((125)I-UdR-CS-DLN). The authors observed that accumulation of nanoparticles was significantly (p<0.05) higher in hepatocellular carcinoma cells HepG2 than normal liver cells HL-7702 after treated with (125)I-UdR-CS-DLN for 30 minutes. Survival of HepG2 cells was significantly lower at (125)I-UdR-CS-DLN doses higher than 37 kBq/mL (more significant in the G1 phase and G2/M phase) than the HL-7702 cells. In addition, (125)I-UdR-CS-DLN induced a higher level of DNA double-strand breaks than (125)I-UdR, and HepG2 cells exhibited a lower level of DNA repair when compared with HL-7702 cells. In vivo animal experiments, TUNEL staining, after targeted treatment, showed that (125)I-UdR-CS-DLN induced significant cell apoptosis in rabbit hepatocellular tumors in situ than (125)I-UdR infusion at the same dose. In conclusion, hepatocellular carcinoma cells were significantly irradiated with (125)I-UdR-CS-DLN compared with (125)I-UdR, and (125)I-UdR-CS-DLN irradiation enhanced DNA damage, induced liver cancer cell apoptosis, and prevented DNA damage repair. However, evaluating the extent of damage and organ sparing in vivo should also be considered.

Preparation and therapeutic evaluation of (188)Re-thermogelling emulsion in rat model of hepatocellular carcinoma.

Radiolabeled Lipiodol(®) (Guerbet, Villepinte, France) is routinely used in hepatoma therapy. The temperature-sensitive hydrogel polyethylene glycol-b-poly-DL-lactic acid-co-glycolic acid-b-polyethylene glycol triblock copolymer is used as an embolic agent and sustained drug release system. This study attempted to combine the polyethylene glycol-b-poly-DL-lactic acid-co-glycolic acid-b-polyethylene glycol hydrogel and radio-labeled Lipiodol to form a new radio-thermogelling emulsion, rhenium-188-N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride-Lipiodol/hydrogel ((188)Re-ELH). The therapeutic potential of (188)Re-ELH was evaluated in a rodent hepatoma model. Rhenium-188 chelated with N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride was extracted with Lipiodol to obtain rhenium-188-N,N'-1,2-ethanediylbis-L-cysteine diethyl-ester dihydrochloride-Lipiodol ((188)Re-EL), which was blended with the hydrogel in equal volumes to develop (188)Re-ELH. The (188)Re-ELH phase stability was evaluated at different temperatures. Biodistribution patterns and micro-single-photon emission computed tomography/computed tomography images in Sprague Dawley rats implanted with the rat hepatoma cell line N1-S1 were observed after in situ tumoral injection of ~3.7 MBq (188)Re-ELH. The therapeutic potential of (188)Re-EL (48.58±3.86 MBq/0.1 mL, n=12) was evaluated in a 2-month survival study using the same animal model. The therapeutic effects of (188)Re-ELH (25.52±4.64 MBq/0.1 mL, n=12) were evaluated and compared with those of (188)Re-EL. The responses were assessed by changes in tumor size and survival rates. The (188)Re-ELH emulsion was stable in the gel form at 25°C-35°C for >52 hours. Biodistribution data and micro-single-photon emission computed tomography/computed tomography images of the (188)Re-ELH group indicated that most activity was selectively observed in hepatomas. Long-term (188)Re-ELH studies have demonstrated protracted reductions in tumor volumes and positive effects on the survival rates (75%) of N1-S1 hepatoma-bearing rats. Conversely, the 2-month survival rate was 13% in the control sham group. Therapeutic responses differed significantly between the two groups (P<0.005). Thus, the hydrogel enhanced the injection stability of (188)Re-EL in an animal hepatoma model. Given the synergistic results, direct (188)Re-ELH intratumoral injection is a potential therapeutic alternative for hepatoma treatment.

[(111)In-DTPA]octreotide tumor uptake in GEPNET liver metastases after intra-arterial administration: an overview of preclinical and clinical observations and implications for tumor radiation dose after peptide radionuclide therapy.

AIMS: With the aim to improve peptide receptor radionuclide therapy effects in patients with gastroenteropancreatic neuroendocrine tumor (GEPNET) liver metastases we explored the effect of intra-arterial (IA) administration of [(111)In-DTPA]octreotide ((111)In-DTPAOC) on tumor uptake in an animal model and in a patient study. METHODS: Preclinical study: After administering (111)In-DTPAOC intra-venously (IV) or IA, biodistribution studies were performed in rats with a hepatic somatostatin receptor subtype 2 (sst2)-positive tumor. Clinical study: 3 patients with neuroendocrine liver metastases were injected twice with (111)In-DTPAOC. The first injection was given IV, and 2 weeks later, the second was injected IA (hepatic artery). Planar images of the abdomen were made up to 72 hours after injection. Blood samples were taken and urine was collected. Pharmacokinetic modeling was performed on the IV and IA data of the same patient. Based on this model, additional (177)Lu dosimetry calculations for IV and IA administrations were performed. RESULTS: The preclinical study showed a two-fold higher (111)In-DTPAOC tumor uptake after IA administration than after IV injection. Patient data showed a large variability in radioactivity increment in liver metastases after IA administration compared with IV administration. Renal radioactivity was not significantly lower after IA administration; (177)Lu dosimetry simulations in 1 patient using a maximum kidney radiation dose of 23 Gy showed IA administration resulted in a mean increase in tumor radiation dose of 2.9-fold. CONCLUSION: Preclinical and clinical data both indicate that IA administration of radiolabeled somatostatin analogs via the hepatic artery can significantly increase radionuclide uptake in GEPNET, sst2-positive, liver metastases up to 72 hours postinjection, although the effect of IA administration can differ between patients.

Relationship between diffusion-weighted imaging and Bcl-2 expression in rabbit models of hepatic VX2 tumors after radiotherapy.

The paper aims to study diffusion-weighted imaging (DWI) and Bcl-2 gene expression in hepatic VX2 tumors after three-dimensional conformal radiotherapy (3D-CRT), we successfully developed 40 rabbit models with hepatic VX2 tumors. 3D-CRT was performed on 28 rabbit hepatic VX2 tumors, which were then randomly and evenly divided into four groups. The remaining 12 controls did not receive radiotherapy. Conventional and DWI was performed at 1, 5, 10, and 15 days following radiation therapy. We measured apparent diffusion coefficients (ADCs) in both a region of interest (ROI) of the VX2 tumor tissue and normal liver tissue and then calculated the ratio between them. RT-PCR was performed to detect the expression of the anti-apoptotic gene Bcl-2. On days 5 and 10, the ADC ratios of the radiotherapy groups were 1.322+-0.270 and 0.964+-0.341, respectively. On days 5, 10, and 15, Bcl-2 gene expression in the radiotherapy group was 0.563+-0.284, 0.421+-0.242, and 0.314+-0.152, respectively. For all three days, the gene expression values from the radiotherapy group were significantly lower than that in the control group (P less than 0.01). Statistical analysis revealed that ADC ratio and Bcl-2 gene expression were significantly negatively correlated (r=-0.493, P less than 0.01). Our results demonstrated that DWI sequence can reflect molecular changes at different time points for hepatic VX2 tumors following radiotherapy.

Hepatocytes determine the hypoxic microenvironment and radiosensitivity of colorectal cancer cells through production of nitric oxide that targets mitochondrial respiration.

PURPOSE: To determine whether host hepatocytes may reverse hypoxic radioresistance through nitric oxide (NO)-induced oxygen sparing, in a model relevant to colorectal cancer (CRC) liver metastases. METHODS AND MATERIALS: Hepatocytes and a panel of CRC cells were incubated in a tissue-mimetic coculture system with diffusion-limited oxygenation, and oxygen levels were monitored by an oxygen-sensing fluorescence probe. To activate endogenous NO production, cocultures were exposed to a cytokine mixture, and the expression of inducible nitric oxide synthase was analyzed by reverse transcription-polymerase chain reaction, Western blotting, and NO/nitrite production. The mitochondrial targets of NO were examined by enzymatic activity. To assess hypoxic radioresponse, cocultures were irradiated and reseeded for colonies. RESULTS: Resting hepatocytes consumed 10-40 times more oxygen than mouse CT26 and human DLD-1, HT29, HCT116, and SW480 CRC cells, and thus seemed to be the major effectors of hypoxic conditioning. As a result, hepatocytes caused uniform radioprotection of tumor cells at a 1:1 ratio. Conversely, NO-producing hepatocytes radiosensitized all CRC cell lines more than 1.5-fold, similar to the effect of selective mitochondrial inhibitors. The radiosensitizing effect was associated with a respiratory self-arrest of hepatocytes at the level of aconitase and complex II, which resulted in profound reoxygenation of tumor cells through oxygen sparing. Nitric oxide-producing hepatocytes were at least 10 times more active than NO-producing macrophages to reverse hypoxia-induced radioresistance. CONCLUSIONS: Hepatocytes were the major determinants of the hypoxic microenvironment and radioresponse of CRC cells in our model of metabolic hypoxia. We provide evidence that reoxygenation and radiosensitization of hypoxic CRC cells can be achieved through oxygen sparing induced by endogenous NO production in host hepatocytes.

Tumor reoxygenation following administration of Mitogen-Activated Protein Kinase inhibitors: a rationale for combination with radiation therapy.

BACKGROUND AND PURPOSE: The relevance of Mitogen Activated Protein Kinase (MAPK) inhibitors as co-treatments for radiation therapy is investigated, with special focus on a potential link between the MAPK pathway and tumor hypoxia, which is a critical determinant for response to therapy. MATERIALS AND METHODS: The effects of two MAPK inhibitors, Sorafenib and PD0325901, were monitored daily using in vivo EPR (Electron Paramagnetic Resonance) oximetry in FSaII and TLT tumor models in order to identify a window of reoxygenation, during which tumor blood flow, oxygen consumption and radiation sensitivity were assessed. RESULTS: Reoxygenation was shown after two days of treatments with Sorafenib or PD0325901 in two tumor models, which was further successfully exploited with Sorafenib for improving the radiation response of FSaII tumors by a factor of 1.5. The increase in tumor oxygenation was shown to be the result of two major factors: (i) an increase in blood flow for Sorafenib, that might be linked to its anti-angiogenic effect (vascular normalization), and (ii) a decrease in oxygen consumption for Sorafenib and PD0325901, due to an alteration of the mitochondrial activity. CONCLUSION: We evidenced tumor reoxygenation in vivo following MAPK inhibition and suggest a rationale for the combination of radiation therapy with Sorafenib.