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

Multimodal Theranostic Nanoparticles for Necrosis Targeting, Fluorescence/SPECT Imaging, and Radiotherapy of Residual Tumors after Hepatocellular Carcinoma Ablation

Thermal ablation has been commonly used as an effective treatment for hepatocellular carcinoma; however, peri-necrotic tumor residues after ablation play a significant role in tumor recurrence and poor prognosis. Therefore, developing agents that can effectively target and eliminate residual tumors is critically needed. Necrosis targeting strategies have potential implications for evaluating tumor necrosis areas and treating the surrounding residual tumors. To address this issue, we have developed a biodegradable nanoparticle with necrosis avidity that is compatible with fluorescence imaging, single photon emission computed tomography (SPECT) imaging, and necrosis targeted radiotherapy. The nanoparticles were synthesized using iodine-131-labeled hypericin (131I-Hyp) as the core and amphiphilic copolymer poly(ethylene glycol)-block-poly(ε-caprolactone) (PEG-PCL) as the shell. The developed nanoparticle, PNP@(131I-Hyp), has a uniform spherical morphology with a size of 33.07 ± 3.94 and 45.93 ± 0.58 nm determined by cryogenic transmission electron microscopy (cryo-TEM) and dynamic light-scattering analysis (polydispersity index = 0.19 ± 0.01), respectively, and having a good stability and blood compatibility in vitro. In mouse subcutaneous ablated-residual tumor models, fluorescence and SPECT imaging demonstrated that PNP@(131I-Hyp) prominently accumulated in the tumor and was retained for as long as 168 h following intravenous injection. Moreover, ex vivo analyses showed that PNP@(131I-Hyp) mainly gathered in the necrotic zones of subcutaneous tumors and inhibited residual tumors by radiotherapy. In addition, histological examination of harvested organs and hematological analysis demonstrated that intravenous injection of 5 mCi/kg nanoparticles caused no gross abnormalities. This multifunctional nanoparticle, therefore, has necrosis imaging and targeted therapeutic effects on residual tumors after thermal ablation of hepatocellular carcinoma, showing potential for clinical application.

Hypericin: A natural anthraquinone as promising therapeutic agent

BACKGROUND

Hypericin is a prominent secondary metabolite mainly existing in genus Hypericum. It has become a research focus for a quiet long time owing to its extensively pharmacological activities especially the anti-cancer, anti-bacterial, anti-viral and neuroprotective effects. This review concentrated on summarizing and analyzing the existing studies of hypericin in a comprehensive perspective.

METHODS

The literature with desired information about hypericin published after 2010 was gained from electronic databases including PubMed, SciFinder, Science Direct, Web of Science, China National Knowledge Infrastructure databases and Wan Fang DATA.

RESULTS

According to extensive preclinical and clinical studies conducted on the hypericin, an organized and comprehensive summary of the natural and artificial sources, strategies for improving the bioactivities, pharmacological activities, drug combination of hypericin was presented to explore the future therapeutic potential of this active compound.

CONCLUSIONS

Overall, this review offered a theoretical guidance for the follow-up research of hypericin. However, the pharmacological mechanisms, pharmacokinetics and structure activity relationship of hypericin should be further studied in future research.

Preparation and validation of cyclodextrin-based excipients for radioiodinated hypericin applied in a targeted cancer radiotherapy

BACKGROUND

Iodine-131 labeled hypericin (¹³¹I-Hyp) has been utilized as a necrosis-avid theragnostic tracer in a dual targeting pan-anticancer strategy called OncoCiDia. Widespread use of previously-tested solvent dimethyl sulfoxide (DMSO) is limited by safety concerns. To tackle this, the present study was designed to explore a clinically feasible excipient for the formulation of the hydrophobic ¹³¹I-Hyp for intravenous administration.

METHOD

Solubility of Hyp in serial solutions of already-approved hydroxypropyl-β-cyclodextrin (HP-β-CD) was evaluated by UVspectrophotometry and 50% HP-β-CD was chosen for further experiments. Two novel HP-β-CD-based formulations of ¹³¹I-Hyp were compared with previous DMSO-based formulation, with regards to necrosis-targetability and biodistribution, by magnetic resonance imaging, single-photon emission computed tomography (SPECT), gamma counting, autoradiography, fluorescence microscopy and histopathology.

RESULTS

Hyp solubility was enhanced with increasing HP-β-CD concentrations. The radiochemical purity of ¹³¹I-Hyp was higher than 90% in all formulations. The necrosis-targetability of ¹³¹I-Hyp in the novel formulations was confirmed in vivo by SPECT and in vitro by autoradiography, fluorescence microscopy and histopathology. The plasma clearance of radioactivity was faster in the novel formulations.

CONCLUSION

The novel ¹³¹I-Hyp formulations with HP-β-CD could be a suitable pharmaceutical excipient for ¹³¹I-Hyp for intravenous administration.

A novel multimodal nanoplatform for targeting tumor necrosis

Peri-necrotic tumor regions have been found to be a source of cancer stem cells (CSC), important in tumor recurrence. Necrotic and peri-necrotic tumor zones have poor vascular supply, limiting effective exposure to systemically administered therapeutics. Therefore, there is a critical need to develop agents that can effectively target these relatively protected tumor areas. We have developed a multi-property nanoplatform with necrosis avidity, fluorescence imaging and X-ray tracking capabilities to evaluate its feasibility for therapeutic drug delivery. The developed nanoparticle consists of three elements: poly(ethylene glycol)-block-poly(ε-caprolactone) as the biodegradable carrier; hypericin as a natural compound with fluorescence and necrosis avidity; and gold nanoparticles for X-ray tracking. This reproducible nanoparticle has a hydrodynamic size of 103.9 ± 1.7 nm with a uniform spherical morphology (polydispersity index = 0.12). The nanoparticle shows safety with systemic administration and a stable 30 day profile. Intravenous nanoparticle injection into a subcutaneous tumor-bearing mouse and intra-arterial nanoparticle injection into rabbits bearing VX2 orthotopic liver tumors resulted in fluorescence and X-ray attenuation within the tumors. In addition, ex vivo and histological analysis confirmed the accumulation of hypericin and gold in areas of necrosis and peri-necrosis. This nanoplatform, therefore, has the potential to enhance putative therapeutic drug delivery to necrotic and peri-necrotic areas, and may also have an application for monitoring early response to anti-tumor therapies.

Au-Hyp-NP developed by encapsulation of gold and hypericin into PEG-PCL nanoplatform for fluorescence and X-ray tracking with tumor necrosis targeting.

Discovery of necrosis avidity of rhein and its applications in necrosis imaging

Necrosis-avid agents possess exploitable theragnostic utilities including evaluation of tissue viability, monitoring of therapeutic efficacy as well as diagnosis and treatment of necrosis-related disorders. Rhein (4,5-dihydroxyl-2-carboxylic-9,10-dihydrodiketoanthracene), a naturally occurring monomeric anthraquinone compound extensively found in medicinal herbs, was recently demonstrated to have a newly discovered necrosis-avid trait and to show promising application in necrosis imaging. In this overview, we present the discovering process of rhein as a new necrosis-avid agent as well as its potential imaging applications in visualisation of myocardial necrosis and early evaluation of tumour response to therapy. Moreover, the molecular mechanism exploration of necrosis avidity behind rhein are also presented. The discovery of necrosis avidity with rhein and the development of rhein-based molecular probes may further expand the scope of necrosis-avid compounds and highlight the potential utility of necrosis-avid molecular probes in necrosis imaging.

Biodegradable Hypericin-Containing Nanoparticles for Necrosis Targeting and Fluorescence Imaging

Necrosis targeting and imaging has significant implications for evaluating tumor growth, therapeutic response, and delivery of therapeutics to perinecrotic tumor zones. Hypericin is a hydrophobic molecule with high necrosis affinity and fluorescence imaging properties. To date, the safe and effective delivery of hypericin to areas of necrosis in vivo remains a challenge because of its incompatible biophysical properties. To address this issue, we have developed a biodegradable nanoparticle (Hyp-NP) for delivery of hypericin to tumors for necrosis targeting and fluorescence imaging. The nanoparticle was developed using methoxy poly(ethylene glycol)-b-poly(ε-caprolactone) and hypericin by a modified solvent evaporation technique. The size of Hyp-NP was 19.0 ± 1.8 nm from cryo-TEM and 37.3 ± 0.7 nm from dynamic light-scattering analysis with a polydispersity index of 0.15 ± 0.01. The encapsulation efficiency of hypericin was 95.05% w/w by UV-vis absorption. After storage for 30 days, 91.4% hypericin was retained in Hyp-NP with nearly no change in hydrodynamic size, representing nanoparticle stability. In an ovarian cancer cell line, Hyp-NP demonstrated cellular internalization with intracellular cytoplasmic localization and preserved fluorescence and necrosis affinity. In a mouse subcutaneous tumor model, tumor accumulation was noted at 8 h postinjection, with near-complete clearance at 96 h postinjection. Hyp-NP was shown to be tightly localized within necrotic tumor zones. Histological analysis of harvested organs demonstrated no gross abnormalities, and in vitro, no hemolysis was observed. This proof-of-concept study demonstrates the potential clinical applications of Hyp-NP for necrosis targeting.

A Model In Vitro Study Using Hypericin: Tumor-Versus Necrosis-Targeting Property and Possible Mechanisms

Hypericin (Hyp) had been explored as a tumor-seeking agent for years; however, more recent studies showed its necrosis-avidity rather than cancer-seeking property. To further look into this discrepancy, we conducted an in vitro study on Hyp retention in vital and dead cancerous HepG2 and normal LO2 cell lines by measuring the fluorescence intensity and concentration of Hyp in cells. To question the DNA binding theory for its necrosis-avidity, the subcellular distribution of Hyp was also investigated to explore the possible mechanisms of the necrosis avidity. The fluorescence intensity and concentration are significantly higher in dead cells than those in vital cells, and this difference did not differ between HepG2 and LO2 cell lines. Hyp was taken up in vital cells in the early phase and excreted within hours, whereas it was retained in dead cells for more than two days. Confocal microscopy showed that Hyp selectively accumulated in lysosomes rather than cell membrane or nuclei. Hyp showed a necrosis-avid property rather than cancer-targetability. The long-lasting retention of Hyp in dead cells may be associated with halted energy metabolism and/or binding with certain degraded cellular substrates. Necrosis-avidity of Hyp was confirmed, which may be associated with halted energy metabolism in dead LO2 or HepG2 cells.

Rhein-based necrosis-avid MRI contrast agents for early evaluation of tumor response to microwave ablation therapy

PURPOSE

Early evaluation of tumor response to thermal ablation therapy can help identify untreated tumor cells and then perform repeated treatment as soon as possible. The purpose of this work was to explore the potential of rhein-based necrosis-avid contrast agents (NACAs) for early evaluation of tumor response to microwave ablation (MWA).

METHODS

3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay was performed to test the cytotoxicity of rhein-based NACAs against HepG2 cells. Rat models of liver MWA were used for investigating the effectiveness of rhein-based NACAs in imaging the MWA lesion, the optimal time period for post-MWA MRI examination, and the metabolic behaviors of ⁶⁸ Ga-labeled rhein-based NACAs. Rat models of orthotopic liver W256 tumor MWA were used for investigating the time window of rhein-based NACAs for imaging the MWA lesion, the effectiveness of these NACAs in distinguishing the residual tumor and the MWA lesion, and their feasibility in early evaluating the tumor response to MWA.

RESULTS

Gadolinium 2,2',2''-(10-(2-((4-(4,5-Dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2-carboxamido)butyl)amino)-2-oxoethyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triyl)triacetic acid (GdL₂ ) showed low cytotoxicity and high quality in imaging the MWA region. The optimal time period for post-MWA MRI examination using GdL₂ was 2 to 24 h after the treatment. During 2.5 to 3.5 h postinjection, GdL₂ can better visualize the MWA lesion in comparison with gadolinium 2-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl]acetic acid (Gd-DOTA), and the residual tumor would not be enhanced. The tumor response to MWA as evaluated by using GdL₂ -enhanced MRI was consistent with histological examination.

CONCLUSION

GdL₂ appears to be a promising NACA for the tumor response assessment after thermal ablation therapies.

Prognostic value of enhancement rate by enhanced ultrasound in hepatitis B virus-positive hepatocellular carcinoma undergoing radiofrequency ablation

AIM

To assess the prognostic significance of enhancement rate (ER) measured by contrast-enhanced ultrasonography (CEUS) in patients with hepatocellular carcinoma (HCC) undergoing radiofrequency ablation (RFA).

MATERIALS AND METHODS

A total of 253 patients with single primary HCC undergoing preoperative CEUS and RFA were enrolled in this study. The ER were evaluated though pretreatment CEUS. After a mean follow-up of 36.8 ± 10.2 months, the correlation of ER measured by CEUS and survival after RFA was analyzed by univariate and multivariate analysis. The optimal cutoff ER value to predict survival was determined using receiver-operating characteristic analysis.

RESULTS

Mean follow-up period for all 253 patients was 36.8 ± 10.2 months, 31.2% of patients had died at endpoint. The optimal cutoff ER value predicting survival was 2.2 dB/s. Univariate analysis demonstrated that patients with a high ER level had poorer OS (62.8 months vs 48.8 months, P = 0.02) and recurrence-free survival (RFS = 60.2 months vs 47.4 months, P = 0.03) than patients with a low ER level. ER measured by CEUS also been confirmed as independent risk factor for overall survival (hazard ratio [HR], 1.87; 95% confidence interval [95% CI], 1.21-7.25; P < 0.01) and RFS (HR, 1.67; 95% CI, 1.08-6.21; P < 0.01) in multivariate analysis enrolling gender, BMI, tumor size, antiviral therapy, HBV DNA, histological differentiation, Child-Pugh score and tumor node metastasis (TNM) stage.

CONCLUSIONS

ER measured by CEUS was a significant predictive factor for survival after RFA for HCC.

Avenues to molecular imaging of dying cells: Focus on cancer

Successful treatment of cancer patients requires balancing of the dose, timing, and type of therapeutic regimen. Detection of increased cell death may serve as a predictor of the eventual therapeutic success. Imaging of cell death may thus lead to early identification of treatment responders and nonresponders, and to “patient‐tailored therapy.” Cell death in organs and tissues of the human body can be visualized, using positron emission tomography or single‐photon emission computed tomography, although unsolved problems remain concerning target selection, tracer pharmacokinetics, target‐to‐nontarget ratio, and spatial and temporal resolution of the scans. Phosphatidylserine exposure by dying cells has been the most extensively studied imaging target. However, visualization of this process with radiolabeled Annexin A5 has not become routine in the clinical setting. Classification of death modes is no longer based only on cell morphology but also on biochemistry, and apoptosis is no longer found to be the preponderant mechanism of cell death after antitumor therapy, as was earlier believed. These conceptual changes have affected radiochemical efforts. Novel probes targeting changes in membrane permeability, cytoplasmic pH, mitochondrial membrane potential, or caspase activation have recently been explored. In this review, we discuss molecular changes in tumors which can be targeted to visualize cell death and we propose promising biomarkers for future exploration.

Biodistribution and tolerance of intravenous iodine-131-labelled hypericin in healthy dogs

Hypericin (Hyp) is a necrosis-avid compound that can be efficiently labelled with radioiodine for both diagnostic and therapeutic purposes. Before ¹³¹ I-Hyp can be considered as a clinically useful drug in a combination therapy for canine cancer patients, evaluation of its toxicity is necessary. The aim of this study was to investigate the biodistribution and tolerance of a single dose administration of ¹³¹ I-Hyp. Three healthy dogs were included. ¹³¹ I-Hyp at a dose of 0.2 mg/kg and an activity of 185 MBq was intravenously injected. The effects on physical, haematological and biochemical parameters were characterized and the biodistribution and elimination pattern, the effective half-life and dose rate were assessed. Drug-related adverse events were limited to mild gastrointestinal signs, resolving within 48 hours. No significant differences were found in blood haematology and serum biochemistry before and after treatment. Following administration, highest percentage of injected dose (%ID ± SD) was found in the liver (5.5 ± 0.33), the lungs (4.17 ± 0.14) and the heart (3.11 ± 0.78). After 24 hours, highest %ID was found in colon (4.25 ± 1.45) and liver (3.45 ± 0.60). Clearance from all organs was effective within 7 days. Effective half-life was established at 80 hours, and the dose rate fell below <20 μSv/h at 1 m within 1 day. The current study reveals that single dose treatment with ¹³¹ I-Hyp at the described dose is well tolerated by healthy dogs and supports the use of radioiodinated hypericin in a combination therapy for canine cancer patients.

Potential of Radiofrequency Ablation in Combination with Immunotherapy in the Treatment of Hepatocellular Carcinoma

Radiofrequency ablation (RFA) is an important treatment option for patients with early hepatocellular carcinoma (HCC). RFA offers a reliable, reproducible modality to effectively treat hepatic lesions with minimal collateral damage to the surrounding hepatic parenchyma. In addition to traditional open operative techniques, RFA can be performed percutaneously or laparoscopically to minimize the physiologic insult to the patient. Due to the concomitant hepatic damage and dysfunction that often is present in patients with HCC these factors make RFA a frequently utilized therapeutic option. However, RFA is most efficacious in treating smaller tumors (≤ 2 cm), particularly when an ablation margin of ≥ 4-5 mm can be obtained. RFA has diminishing utility in larger tumors, resulting in reduced three and five year overall survival rates when compared to surgical resection. Multimodal approaches to include RFA with other standard and investigational approaches have become a subject of recent interest. RFA capably produces cellular destruction causing liberation of a substantial amount of antigens, many of which are tumor-specific providing a favorable environment for immune recognition. We propose that utilizing an immunotherapeutic approach in conjunction with RFA is the next logical step in the treatment of HCC. In this review, we summarize how RFA modulates antitumor immunity and works in concert with immunotherapy in the treatment of HCC. The information provided is expected to help the future design of novel RFA-integrated immunotherapies which are able to generate durable and powerful antitumor immune response to achieve optimal tumor control.