First Evaluation of Radioiodinated Flavonoids as Necrosis-Avid Agents and Application in Early Assessment of Tumor Necrosis.

A rapid and accurate identification of necrotic tissues is of great importance to define disease severity, predict prognosis, and monitor responses to therapies. To seek necrosis-avid agents with clinically translational potential, we first evaluated the necrosis avidity of flavonoids in rodent models of muscular, myocardial, and tumoral necrosis. In this study, the necrosis avidity of eight radioiodinated 5,7-dihydroxyflavones was tested by ex vivo gamma counting, histochemical staining, and autoradiography in mouse models of ethanol-induced muscular necrosis. The necrosis avidity of a lead tracer, 131I-5, was further assessed in rat models of myocardial infarction and reperfusion. Therapy response was evaluated by 131I-5 single photon emission computed tomography/computed tomography imaging 24 h after combretastatin A-4 disodium phosphate (CA4P) therapy on rats bearing W256 breast carcinomas. The necrosis avidity mechanism for the tracers was studied by in vitro DNA binding experiments of 12 5,7-dihydroxyflavones and in vivo blocking experiments of 131I-5. In the results, all 131I-5,7-dihydroxyflavones showed intense uptake to necrotic muscles, and 131I-5 emerged as the most potential tracer among them. 131I-5 obtained a necrotic-viable myocardium ratio of 5.0 ± 0.9 in post-mortem biodistribution on reperfused myocardial infarction models and achieved necrosis imaging on CA4P-treated W256 tumors 4 h after tracer injection. DNA binding studies suggested that necrosis avidity was related to DNA binding to a certain extent. The uptake of 131I-5 in necrotic muscle was markedly blocked by excessive ethidium bromide and cold 5 with a 51.95% and 64.29% decline at 1 h after coinjection, respectively. In conclusion, flavonoids are necrosis-avid agents. Furthermore, 131I-5 can serve as a promising necrosis-avid diagnostic tracer for the rapid imaging of necrotic tissues, supporting the further molecular design of radiotracer based on 5.

Radioiodinated hypericin disulfonic acid sodium salts as a DNA-binding probe for early imaging of necrotic myocardium.

Necrotic myocardium imaging can provide great indicators of salvaged myocardial areas for clinical guidances to patients with myocardial infarction (MI). One of the key challenges in necrotic myocardium imaging however, is lack of ideal necrotic imaging tracers for exactly and timely depicting the necrotic myocardium. 131I-hypericin (131I-Hyp) is a promising tracer in exact necrotic myocardium delineation. However, it can't clearly image necrotic myocardium until 9h post injection (p.i.) for the high background signals in blood and lung due to the strong lipophilicity. Herein, an optimized 131I-hypericin-2,5-disulfonic acid sodium salts (131I-Shyp) probe was synthesized for better pharmacokinetic and biodistribution properties to necrosis imaging. And the related mechanisms of necrotic avidity ability of 131I-Hyp and 131I-Shyp were also explored. In the results, 131I-Shyp still showed selectively high accumulation in both necrotic cells and tissues. Biodistribution data revealed the decreased uptake of 131I-Shyp in normal organs (lung, spleen and heart) and blood (as shown in pharmacokinetics studies). 131I-Shyp presented quicker and clearer imaging for necrotic myocardium at 4h p.i. compared with 131I-Hyp, suggesting that improved hydrophilicity of 131I-Shyp may be conducive to its better pharmacokinetic and biodistribution properties to imaging. Additionally, DNA competitive binding assays and blocking experiments indicated that E-DNA is the possible target of Shyp and Hyp for their necrosis avidity. 131I-Shyp may serve as a potential E-DNA targeted probe for necrotic myocardium imaging with molecular specificity for clinical use.

Novel 18F-Labeled 1-Hydroxyanthraquinone Derivatives for Necrotic Myocardium Imaging.

Rapid detection and precise evaluation of myocardial viability is necessary to aid in clinical decision making whether to recommend revascularization for patients with myocardial infarction (MI). Three novel 18F-labeled 1-hydroxyanthraquinone derivatives were synthesized, characterized, and evaluated as potential necrosis avid imaging agents for assessment of myocardial viability. Among these tracers, [18F]FA3OP emerged as the most promising compound with best stability and highest targetability. Clear PET images of [18F]FA3OP were obtained in rat model of myocardial infarction and reperfusion at 1 h after injection. In addition, the possible mechanisms of [18F]FA3OP for necrotic myocardium were discussed. The results showed [19F]FA3OP may bind DNA to achieve targetability to necrotic myocardium by intercalation. In summary, [18F]FA3OP was a more promising "hot spot imaging" tracer for rapid visualization of necrotic myocardium.

Effects of skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones.

Necrosis avid agents (NAAs) can be used for diagnose of necrosis-related diseases, evaluation of therapeutic responses and targeted therapeutics of tumor. In order to probe into the effects of molecular skeleton structure on necrosis targeting and clearance properties of radioiodinated dianthrones, four dianthrone compounds with the same substituents but different skeletal structures, namely Hypericin (Hyp), protohypericin (ProHyp), emodin dianthrone mesomer (ED-1) and emodin dianthrone raceme (ED-2) were synthesized and radioiodinated. Then radioiodinated dianthrones were evaluated in vitro for their necrosis avidity in A549 lung cancer cells untreated and treated with H2O2. Their biodistribution and pharmacokinetic properties were determined in rat models of induced necrosis. In vitro cell assay revealed that destruction of rigid skeleton structure dramatically reduced their necrosis targeting ability. Animal studies demonstrated that destruction of rigid skeleton structure dramatically reduced the necrotic tissue uptake and speed up the clearance from the most normal tissues for the studied compounds. Among these (131)I-dianthrones, (131)I-Hyp exhibited the highest uptake and persistent retention in necrotic tissues. Hepatic infarction could be clearly visualized by SPECT/CT using (131)I-Hyp as an imaging probe. The results suggest that the skeleton structure of Hyp is the lead structure for further structure optimization of this class of NAAs.

Synthesis and Evaluation of 131I-Skyrin as a Necrosis Avid Agent for Potential Targeted Radionuclide Therapy of Solid Tumors.

An innovative anticancer approach targeted to necrotic tissues, which serves as a noncancerous and generic anchor, may present a breakthrough. Necrosis avid agents with a flat conjugate aromatic structure selectively accumulate in necrotic tissues, but they easily form aggregates that undesirably distribute to normal tissues. In this study, skyrin, a dianthraquinone compound with smaller and distorted π-cores and thus decreased aggregates as compared with hypericin (Hyp), was designed to target necrosis for tumor therapy. Aggregation studies of skyrin by UV/vis spectroscopy showed a smaller self-association constant with skyrin than with Hyp. Skyrin was labeled by iodine-131 with a radiochemical purity of 98% and exhibited good stability in rat serum for 72 h. In vitro cell uptake studies showed significant difference in the uptake of 131I-skyrin by necrotic cells compared to normal cells (P < 0.05). Compared in rats with liver and muscle necrosis, radiobiodistribution, whole-body autoradiography, and SPECT/CT studies revealed higher accumulation of 131I-skyrin in necrotic liver and muscle (p < 0.05), but lower uptake in normal organs, relative to that of 131I-Hyp. In mice bearing H22 tumor xenografts treated with combretastatin A4 disodium phosphate, the highest uptake of 131I-skyrin was found in necrotic tumor. In conclusion, 131I-skyrin appears a promising agent with reduced accumulation in nontarget organs for targeted radionuclide therapy of solid tumors.

Tumor necrosis targeted radiotherapy of non-small cell lung cancer using radioiodinated protohypericin in a mouse model.

Lung cancer is the leading cause of cancer-related death. About 80% of lung cancers are non-small cell lung cancers (NSCLC). Radiotherapy is widely used in treatment of NSCLC. However, the outcome of NSCLC remains unsatisfactory. In this study, a vascular disrupting agent (VDA) combretastatin-A4-phosphate (CA4P) was used to provide massive necrosis targets. (131)I labeled necrosis-avid agent protohypericin ((131)I-prohy) was explored for therapy of NSCLC using tumor necrosis targeted radiotherapy (TNTR). Gamma counting, autoradiography, fluorescence microscopy and histopathology were used for biodistribution analysis. Magnetic resonance imaging (MRI) was used to monitor tumor volume, ratios of necrosis and tumor doubling time (DT). The biodistribution data revealed 131I-prohy was delivered efficiently to tumors. Tracer uptake peaked at 24 h in necrotic tumor of (131)I-prohy with and without combined CA4P (3.87 ± 0.38 and 2.96 ± 0.34%ID/g). (131)I-prohy + CA4P enhanced the uptake of (131)I-prohy in necrotic tumor compared to (131)I-prohy alone. The TNTR combined with CA4P prolonged survival of tumor bearing mice relative to vehicle control group, CA4P control group and (131)I-prohy control group with median survival of 35, 20, 22 and 27 days respectively. In conclusion, TNTR appeared to be effective for the treatment of NSCLC.

Necrosis targeted radiotherapy with iodine-131-labeled hypericin to improve anticancer efficacy of vascular disrupting treatment in rabbit VX2 tumor models.

A viable rim of tumor cells surrounding central necrosis always exists and leads to tumor recurrence after vascular disrupting treatment (VDT). A novel necrosis targeted radiotherapy (NTRT) using iodine-131-labeled hypericin (131I-Hyp) was specifically designed to treat viable tumor rim and improve tumor control after VDT in rabbit models of multifocal VX2 tumors. NTRT was administered 24 hours after VDT. Tumor growth was significantly slowed down by NTRT with a smaller tumor volume and a prolonged tumor doubling time (14.4 vs. 5.7 days), as followed by in vivo magnetic resonance imaging over 12 days. The viable tumor rims were well inhibited in NTRT group compared with single VDT control group, as showed on tumor cross sections at day 12 (1 vs. 3.7 in area). High targetability of 131I-Hyp to tumor necrosis was demonstrated by in vivo SPECT as high uptake in tumor regions lasting over 9 days with 4.26 to 98 times higher radioactivity for necrosis versus the viable tumor and other organs by gamma counting, and with ratios of 7.7-11.7 and 10.5-13.7 for necrosis over peri-tumor tissue by autoradiography and fluorescence microscopy, respectively. In conclusion, NTRT improved the anticancer efficacy of VDT in rabbits with VX2 tumors.

Evaluation of a metalloporphyrin (THPPMnCl) for necrosis-affinity in rat models of necrosis.

The combination of an (13I)I-labeled necrosis-targeting agent (NTA) with a vascular disrupting agent is a novel and potentially powerful technique for tumor necrosis treatment (TNT). The purpose of this study was to evaluate a NTA candidate, THPPMnCl, using (131)I isotope for tracing its biodistribution and necrosis affinity. (131)I-THPPMnCl was intravenously injected in rat models with liver, muscle, and tumor necrosis and myocardial infarction (MI), followed by investigations with macroscopic autoradiography, triphenyltetrazolium chloride (TTC) histochemical staining, fluorescence microscopy and H&E stained histology for up to 9 days. (131)I-THPPMnCl displayed a long-term affinity for all types of necrosis and accumulation in the mononuclear phagocytic system especially in the liver. Autoradiograms and TTC staining showed a good targetability of (131)I-THPPMnCl for MI. These findings indicate the potential of THPPMnCl for non-invasive imaging assessment of necrosis, such as in MI. However, (13I)I-THPPMnCl is unlikely suitable for TNT due to its long-term retention in normal tissues.

Biliary and duodenal drainage for reducing the radiotoxic risk of antineoplastic 131I-hypericin in rat models.

Necrosis targeting radiopharmaceutical (131)I-hypericin ((131)I-Hyp) has been studied for the therapy of solid malignancies. However, serious side effects may be caused by its unwanted radioactivity after being metabolized by the liver and excreted via bile in the digestive tract. Thus the aim of this study was to investigate two kinds of bile draining for reducing them. Thirty-eight normal rats were intravenously injected with (131)I-Hyp, 24 of which were subjected to the common bile duct (CBD) drainage for gamma counting of collected bile and tissues during 1-6, 7-12, 13-18, and 19-24 h (n = 6 each group), 12 of which were divided into two groups (n = 6 each group) for comparison of the drainage efficiency between CBD catheterization and duodenum intubation by collecting their bile at the first 4 h. Afterwards the 12 rats together with the last two rats which were not drained were scanned via single-photon emission computerized tomography/computed tomography (SPECT/CT) to check the differences. The images showed that almost no intestinal radioactivity can be found in those 12 drained rats while discernible radioactivity in the two undrained rats. The results also indicated that the most of the radioactivity was excreted from the bile within the first 12 h, accounting to 92% within 24 h. The radioactive metabolites in the small and large intestines peaked at 12 h and 18 h, respectively. No differences were found in those two ways of drainages. Thus bile drainage is highly recommended for the patients who were treated by (131)I-Hyp if human being and rats have a similar excretion pattern. This strategy can be clinically achieved by using a nasobiliary or nasoduodenal drainage catheter.

Radiopharmaceutical evaluation of (131)I-protohypericin as a necrosis avid compound.

Hypericin is a necrosis avid agent useful for nuclear imaging and tumor therapy. Protohypericin, with a similar structure to hypericin except poorer planarity, is the precursor of hypericin. In this study, we aimed to investigate the impact of this structural difference on self-assembly, and evaluate the necrosis affinity and metabolism in the rat model of reperfused hepatic infarction. Protohypericin appeared less aggregative in solution compared with hypericin by fluorescence analysis. Biodistribution data of (131)I-protohypericin showed the percentage of injected dose per gram of tissues (%ID/g) increased with time and reached to the maximum of 7.03 at 24 h in necrotic liver by gamma counting. The maximum ratio of target/non-target tissues was 11.7-fold in necrotic liver at 72 h. Pharmacokinetic parameters revealed that the half-life of (131)I-protohypericin was 14.9 h, enabling a long blood circulation and constant retention in necrotic regions. SPECT-CT, autoradiography, and histological staining showed high uptake of (131)I-protohypericin in necrotic tissues. These results suggest that (131)I-protohypericin is a promising necrosis avid compound with a weaker aggregation tendency compared with hypericin and it may have a broad application in imaging and oncotherapy.

Trapping effect on a small molecular drug with vascular-disrupting agent CA4P in rodent H22 hepatic tumor model: in vivo magnetic resonance imaging and postmortem inductively coupled plasma atomic emission spectroscopy.

The aim of the present study is to verify the trapping effect of combretastatin A-4-phosphate (CA4P) on small molecular drugs in rodent tumors. Mice with H22 hepatocarcinoma were randomized into groups A and B. Magnetic resonance imaging (MRI) of T1WI, T2WI, and DWI was performed as baseline. Mice in group A were injected with Gd-DTPA and PBS. Mice in group B were injected with Gd-DTPA and CA4P. All mice undergo CE-T1WI at 0 h, 3 h, 6 h, 12 h, and 24 h. Enhancing efficacy of the two groups on CE-T1WI was compared with the signal-to-noise ratio (SNR) calculated. Concentrations of gadolinium measured by ICP-AES in the tumor were compared between groups. On the early CE-T1WI, tumors were equally enhanced in both groups. On the delayed CE-T1WI, the enhancing effect of group A was weaker than that of group B. The SNR and the concentration of gadolinium within the tumor of group A were lower than that of group B at 6 h, 12 h, and 24 h after administration. This study indicates that CA4P could improve the retention of Gd-DTPA in the tumor and MRI allowed dynamically monitoring trapping effects of CA4P on local retention of Gd-DTPA as a small molecular drug.

Evaluation of hypericin: effect of aggregation on targeting biodistribution.

Hypericin (Hy) has shown great promise as a necrosis-avid agent in cancer imaging and therapy. Given the highly hydrophobic and π-conjugated planarity characteristics, Hy tends to form aggregates. To investigate the effect of aggregation on targeting biodistribution, nonaggregated formulation (Non-Ag), aggregated formulation with overconcentrated Hy in dimethyl sulfoxide (Ag-DMSO) solution, and aggregated formulation in water solution (Ag-water) were selected by fluorescence measurement. They were labeled with ¹³¹I and evaluated for the necrosis affinity in rat model of reperfused hepatic infarction by gamma counting and autoradiography. The radioactivity ratio of necrotic liver/normal liver was 17.1, 7.9, and 6.4 for Non-Ag, Ag-DMSO, and Ag-water, respectively. The accumulation of two aggregated formulations (Ag-DMSO and Ag-water) in organs of mononuclear phagocyte system (MPS) was 2.62 ± 0.22 and 3.96 ± 0.30 %ID/g in the lung, and 1.44 ± 0.29 and 1.51 ± 0.23 %ID/g in the spleen, respectively. The biodistribution detected by autoradiography showed the same trend as by gamma counting. In conclusion, the Non-Ag showed better targeting biodistribution and less accumulation in MPS organs than aggregated formulations of Hy. The two aggregated formulations showed significantly lower and higher accumulation in targeting organ and MPS organs, respectively.

PD806: a novel oral vascular disrupting agent shows antitumor and antivascular effects in vitro and in vivo.

The aim of this study was to investigate the antitumor and antivascular effects of PD806, a new oral prodrug of AVE8063 in vitro and in vivo. The cytotoxicity of PD806 was determined against H22, Walker 256, A549, MCF-7, and BEL-7402 cells using MTT assays. Plasma pharmacokinetic analysis of AVE8063 generated in rats after a single oral administration of PD806 was carried out using the high-performance liquid chromatography method. H22 tumor-bearing mice models were used to show the antitumor activity. Antivascular responses were monitored by in vivo MRI and immunohistochemistry (CD31) in W256 tumor-bearing rats. A blood test and histopathology were performed to evaluate the toxicity of PD806. PD806 showed cytotoxicity against five types of tumor cell lines with the IC50 values in the micromolar concentration. A pharmacokinetic study indicated that PD806 converted into the active form, AVE8063, which showed a half-life of 5.24±0.70 h in rats. Daily oral administration of PD806 inhibited the growth of subcutaneously implanted H22 tumors in a dose-dependent manner. The tumor volume in the 300 mg/kg PD806 group was obviously smaller than that of the vehicle control group from day 6 onward (P<0.05), with inhibition rates of 62% on day 30. PD806 in the three-dose group significantly prolonged the survival of the H22 tumor-bearing mice (P<0.05). At 24 h after PD806 (150 and 200 mg/kg) was administered orally, tumor vascular shutdown was found on CE-T1WI with the presence of extended necrosis and tumor residue at the periphery. The enhancement ratio decreased significantly from 1.00±0.00 at baseline to 0.26±0.08 and 0.17±0.06, respectively (P<0.01). The necrosis ratio measured from CE-T1WI increased significantly from 34% in average at baseline to 52.96 and 60.30%, respectively (P<0.05). Immunohistochemical staining of tumor sections showed a marked reduction in CD31 staining vessels, with microvessel density reduced significantly to 8.71±1.76 and 3.33±1.04, respectively, compared with the vehicle control group (P<0.01). The results of hematology and histopathology showed that PD806 exerted no obvious toxicity during the treatment period. In conclusion, our results indicate that PD806 is an effective and safe vascular disrupting agent.

Radiopharmaceutical study on Iodine-131-labelled hypericin in a canine model of hepatic RFA-induced coagulative necrosis.

PURPOSE: Hypericin (HYP) has been found avid to necrosis in small animal studies. We sought to evaluate the tissue distribution of (131)I-HYP in a large animal model and to explore the theranostic utilities of (131)I-HYP after radiofrequency ablation (RFA). MATERIALS AND METHODS: This animal experiment was approved by the institutional ethics committee. Twenty-five male dogs were enrolled and subjected to transabdominal hepatic RFA. (131)I-HYP was prepared by an electrophilic substitution method and intravenously administered at 0.5 mCi/kg. Systemic and regional distributions of (131)I-HYP were monitored dynamically by single-photon emission computed tomography/computed tomography (SPECT-CT), gamma counting, autoradiography, and fluorescent and light microscopy at different time points up to 14 days. Experimental data were quantified and statistically analysed. RESULTS: Most of the tissues and organs retained (131)I-HYP only transiently. (131)I-HYP was mainly metabolised in the liver and excreted into the bile. (131)I-HYP gradually accumulated in the RFA-induced necrosis with a peak concentration occurring within 2 days and lasting over 2 weeks as visualised by in vivo SPECT-CT and ex vivo autoradiography and fluorescent microscopy, and quantified by radioactivity and fluorescence measurements. Accumulation of (131)I-HYP was low in both the necrosis centre and normal liver tissue. CONCLUSION: (131)I-HYP showed persistent high affinity to hepatic thermo-coagulative necrosis, but only a transient uptake by normal liver in dogs. Necrosis caused by RFA could be indicated by (131)I-HYP on nuclear imaging, which suggests a supplementary measure for tumour detection and therapy.

Necrosis targeted combinational theragnostic approach using radioiodinated Sennidin A in rodent tumor models.

Residual cancer cells and subsequent tumor relapse is an obstacle for curative cancer treatment. Tumor necrosis therapy (TNT) has recently been developed to cause residual tumor regression or destruction. Here, we exploited the avidity of the sennidin A (SA) tracer and radioiodinated SA (¹³¹I-SA) to necrotic tumors in order to further empower TNT. We showed high uptake and prolonged retention of SA in necrotic tumors and a quick clearance in other non-targeted tissues including the liver. On SPECT-CT images, tumor mass appeared persistently as a hotspot. Based on the prominent targetability of ¹³¹I-SA to the tumor necrosis, we designed a combinational theragnostic modality. The vascular disrupting agent (VDA) combretastatin A4 phosphate (CA4P) was used to cause massive tumor necrosis, which formed the target of ¹³¹I-SA that subsequently killed the residual tumor cells by cross-fire irradiation of beta particles. Consequently, ¹³¹I-SA combined with CA4P significantly inhibited tumor growth, extended tumor doubling time and prolonged mean animal survival. In conclusion, ¹³¹I-SA in combination with necrosis inducing drugs/therapies may generate synergetic tumoricidal effects on solid malignancies by means of primary debulking and secondary cleansing process.

Hypericin as a marker for determination of myocardial viability in a rat model of myocardial infarction.

The aim of this study was to investigate the necrosis-avid agent hypericin as a potential indicator for determination of myocardial infarction (MI). Male Sprague-Dawley rats (n = 30) weighing 350 ± 20 g were subjected to acute reperfused MI. Animals were divided into four groups (n = 6), in which hypericin was intravenously injected at 0, 1, 2 and 5 mg kg(-1) respectively. One day after injection, rats were euthanized with their hearts excised for qualitative and quantitative studies by means of microscopic fluorescence examination to decide the dosage of hypericin. Another group was injected with hypericin at the decided dose and evaluated by fluorescence macroscopy in colocalization with triphenyltetrazoliumchloride (TTC) and histomorphology. Infarct-to-normal contrast ratio and relative infarct size were quantified. Hypericin-induced red fluorescence was significantly brighter in necrotic than in viable myocardium as proven by a six times higher mean fluorescence density. Mean MI area was 35.66 ± 22.88% by hypericin fluorescence and 32.73 ± 21.98% by TTC staining (R(2) = 0.9803). Global MI-volume was 34.56 ± 21.07% by hypericin and 35.11 ± 20.47% by TTC staining (R(2) = 0.9933). The results confirm that hypericin specifically labeled necrosis, and enhanced the imaging contrast between the infarcted and normal myocardium, suggesting its potential applications for the assessment of myocardial viability.

Improvement of solubility and targetability of radioiodinated hypericin by using sodium cholate based solvent in rat models of necrosis.

Hypericin (Hyp) is newly recognized as a necrosis avid agent, but its poor solubility imposes a great hindrance in clinical application. The aim of this paper was to explore sodium cholate (NaCh) as a potential solvent for Hyp and assess the targetability of (131)I-Hyp in rat necrosis models. Hyp solubility in NaCh solutions was evaluated by equilibrium solubility measurement. Biodistribution of (131)I-Hyp in NaCh solutions and mixed organic solvents was investigated in rat models of liver and muscle necrosis examined with MRI and SPECT/CT in vivo. In addition, pharmacokinetics of (131)I-Hyp in NaCh solutions was studied in healthy rats. Results showed NaCh could improve Hyp solubility and (131)I-Hyp incubated in NaCh solutions/rat plasma was stable up to 120 h. On SPECT/CT images at 24 h post injection, liver infarction location appeared as hot spots. Liver necrosis-to-liver ratios were 12.2, 10.0, 9.6 and 8.2 in 60, 15, 2 mmol/L of NaCh solutions and organic solvents, and muscle necrosis-to-liver ratios were 11.1, 10.1, 7.7 and 7.4, respectively. Pharmacokinetics study revealed t(1/2)z (11.93, 8.96 h, p > 0.05) and AUC (0-∞) (421.21, 553.34 MBq/L h, p < 0.05) of (131)I-Hyp in 2, 60 mmol/L of NaCh solutions, respectively. In conclusion, NaCh was an effective cosolvent, and the necrosis avidity of NaCh-dissolved (131)I-Hyp/Hyp was demonstrated.

Radioiodinated hypericin: its biodistribution, necrosis avidity and therapeutic efficacy are influenced by formulation.

PURPOSE: To study whether formulation influences biodistribution, necrosis avidity and tumoricidal effects of the radioiodinated hypericin, a necrosis avid agent for a dual-targeting anticancer radiotherapy. METHODS: Iodine-123- and 131-labeled hypericin ((123)I-Hyp and (131)I-Hyp) were prepared with Iodogen as oxidant, and formulated in dimethyl sulfoxide (DMSO)/PEG400 (polyethylene glycol 400)/water (25/60/15, v/v/v) or DMSO/saline (20:80, v/v). The formulations with excessive Hyp were optically characterized. Biodistribution, necrosis avidity and tumoricidal effects were studied in rats (n = 42) without and with reperfused liver infarction and implanted rhabdomyosarcomas (R1). To induce tumor necrosis, R1-rats were pre-treated with a vascular disrupting agent. Magnetic resonance imaging, tissue-gamma counting, autoradiography and histology were used. RESULTS: The two formulations differed significantly in fluorescence and precipitation. (123)I-Hyp/Hyp in DMSO/PEG400/water exhibited high uptake in necrosis but lower concentration in the lung, spleen and liver (p < 0.01). Tumor volumes of 0.9 ± 0.3 cm(3) with high radioactivity (3.1 ± 0.3% ID/g) were detected 6 days post-treatment. By contrast, (131)I-Hyp/Hypin DMSO/saline showed low uptake in necrosis but high retention in the spleen and liver (p < 0.01). Tumor volumes reached 2.6 ± 0.7 cm(3) with low tracer accumulation (0.1 ± 0.04%ID/g). CONCLUSIONS: The formulation of radioiodinated hypericin/hypericin appears crucial for its physical property, biodistribution, necrosis avidity and tumoricidal effects.

Dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging noninvasive evaluation of vascular disrupting treatment on rabbit liver tumors.

Evaluation of vascular disrupting treatment (VDT) is generally based on tumor size and enhancement on conventional magnetic resonance imaging (MRI) which, unfortunately, may be limited in providing satisfactory information. The purpose of the study is to evaluate consecutive changes of 20 rabbit VX2 liver tumors after VDT by dynamic contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI) at a 3.0 T MR unit. Twenty four hours after intravenous injection of Combretastatin A-4-phosphate (CA4P) at 20 mg/kg, DCE-MRI derived Maximum Slope of Increase (MSI) and Positive Enhancement Integral (PEI) decreased sharply due to sudden shutting down of tumor feeding vessels. DWI derived Apparent Diffusion Coefficient (ADC) in tumor periphery decreased because of ischemic cell edema. On day 4, an increase of MSI was probably caused by the recovery of blood supply. A remarkable increase of ADC represented a large scale of necrosis among tumors. On day 8, the blood perfusion further decreased and the extent of necrosis further increased, reflected by lower MSI and PEI values and higher ADC value. On day 12, a second decrease of ADC was noticed because the re-growth of periphery tumor. The experimental data indicate that the therapeutic effects of VDT may be noninvasively monitored with DCE-MRI (reflecting tumor blood perfusion) and DWI (reflecting the changes of histology), which provide powerful measures for assessment of anticancer treatments.

Necrosis affinity evaluation of 131I-hypericin in a rat model of induced necrosis.

Cancers are often with spontaneous or therapeutic necrosis that could be utilized as a generic target for developing new treatments. The purpose of this study was to investigate the biodistribution and pharmacokinetics of radioiodinated hypericin (Hyp), a naturally occurring compound, after intravenous (i.v.) injection in a rat model of liver and muscle necrosis (n = 42), and evaluate its necrosis affinity. Hyp was labeled with (131)I with labeling efficiency >99%. After incubating in solution/rat plasma for 8 days, radiochemical purity of (131)I-Hyp remained 98.1 and 97.1%, respectively, indicating good in vitro stability. SPECT-CT images at 24 h after i.v. injection of (131)I-Hyp in rats with induced liver and muscle necrosis showed obvious tracer absorption in necrotic tissues. Biodistribution studies revealed that the percentage of the injected dose per gram of tissue (%ID/g) evolved from 1.9 %ID/g at 6 h, through a maximum 3.0 %ID/g at 12 h, to 1.0 %ID/g at 192 h in necrotic liver. Pharmacokinetics studies revealed that the terminal elimination half-life, total body clearance and area under the curve of (131)I-Hyp were 32.7 h, 9.2 L/h/kg and 1.6 MBq/L*h, respectively. These results demonstrated that (131)I-Hyp features a long blood circulation in animals and persistent retention in necrotic tissues. Therefore, (131)I-labeled Hyp could be a broad-spectrum anti-tumor agent with a cost much cheaper relative to the biological agents such as monoclonal antibodies.