Improved therapeutic outcomes of thermal ablation on rat orthotopic liver allograft sarcoma models by radioiodinated hypericin induced necrosis targeted radiotherapy

Sequential Administrations of a Vascular-Disrupting Agent, High-Intensity Focused Ultrasound, and a Radioactively labeled Necrosis Avid Compound for Eradicating Solid Malignancies

Radical treatment of malignant solid tumors should aim to be less traumatic, precise, and effective. OncoCiDia, as a noninvasive, sequential dual-targeting, small-molecule, broad spectrum anticancer theranostic approach, may fulfill these requirements of solid cancer (Onco) treatment with both tumoricidal (Ci) and diagnostic (Dia) effects. However, it is unlikely to cure patients with cancer, especially those with large and irregular tumors and with tumors residing in certain organs, such as the brain and pancreas, because of insufficient necrosis generation. To amplify ablative efficacy, this shortcoming could be overcome by combining high-intensity focused ultrasound (HIFU) with the use of a vascular-disrupting agent (VDA) and a radioactively labeled necrosis avid compound (NAC), such as ¹³¹I-Hypericin (¹³¹I-Hyp), which are the first and second targeting drugs used in OncoCiDia. This study proposes the combined use of OncoCiDia and HIFU (Onco-HIFU-CiDia) as a synergistic treatment for malignant tumors to achieve a curative multimodality and multidrug regimen for patients with solid cancers, in accordance with the current trend of cancer patient care.

Application and Importance of Theranostics in the Diagnosis and Treatment of Cancer

The number of cancer cases worldwide in terms of morbidity and mortality is a serious concern, despite the presence of therapeutic interventions and supportive care. Limitations in the current available diagnosis methods and treatments methods may contribute to the increase in cancer mortality. Theranostics, is a novel approach that has opened avenues for the simultaneous precise diagnosis and treatment for cancer patients. Although still in the early development stage, theranostic agents such as quantum dots, radioisotopes, liposomes and plasmonic nanobubbles can be bound to anticancer drugs, cancer cell markers and imaging agents, with the support of available imaging techniques, provide the potential to facilitate diagnosis, treatment and management of cancer patients. Herein, we discuss the potential benefits of several theranostic tools for the management of cancer. Specifically, quantum dots, radio-labelled isotopes, liposomes and plasmonic nanobubbles coupled with targeting agents and/or anticancer molecules and imaging agents as theranostic agents are deliberated upon in this review. Overall, the use of theranostic agents shows promise in cancer management. Nevertheless, intensive research is required to realize these expectations.

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.

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.

Imaging Cell Death: Focus on Early Evaluation of Tumor Response to Therapy

Cell death plays a prominent role in the treatment of cancer, because most anticancer therapies act by the induction of cell death including apoptosis, necrosis, and other pathways of cell death. Imaging cell death helps to identify treatment responders from nonresponders and thus enables patient-tailored therapy, which will increase the likelihood of treatment response and ultimately lead to improved patient survival. By taking advantage of molecular probes that specifically target the biomarkers/biochemical processes of cell death, cell death imaging can be successfully achieved. In recent years, with the increased understanding of the molecular mechanism of cell death, a variety of well-defined biomarkers/biochemical processes of cell death have been identified. By targeting these established cell death biomarkers/biochemical processes, a set of molecular imaging probes have been developed and evaluated for early monitoring treatment response in tumors. In this review, we mainly present the recent advances in identifying useful biomarkers/biochemical processes for both apoptosis and necrosis imaging and in developing molecular imaging probes targeting these biomarkers/biochemical processes, with a focus on their application in early evaluation of tumor response to therapy.

Updated developments on molecular imaging and therapeutic strategies directed against necrosis

Cell death plays important roles in living organisms and is a hallmark of numerous disorders such as cardiovascular diseases, sepsis and acute pancreatitis. Moreover, cell death also plays a pivotal role in the treatment of certain diseases, for example, cancer. Noninvasive visualization of cell death contributes to gained insight into diseases, development of individualized treatment plans, evaluation of treatment responses, and prediction of patient prognosis. On the other hand, cell death can also be targeted for the treatment of diseases. Although there are many ways for a cell to die, only apoptosis and necrosis have been extensively studied in terms of cell death related theranostics. This review mainly focuses on molecular imaging and therapeutic strategies directed against necrosis. Necrosis shares common morphological characteristics including the rupture of cell membrane integrity and release of cellular contents, which provide potential biomarkers for visualization of necrosis and necrosis targeted therapy. In the present review, we summarize the updated joint efforts to develop molecular imaging probes and therapeutic strategies targeting the biomarkers exposed by necrotic cells. Moreover, we also discuss the challenges in developing necrosis imaging probes and propose several biomarkers of necrosis that deserve to be explored in future imaging and therapy research.

18F-Deoxyglucose (18F-FDG) Positron Emission Tomography/Computed Tomography (PET/CT) Monitoring of Dynamic Growth Characteristics of Walker-256 Tumor Models in 3 Different Locations in Rats

BACKGROUND We explored the ideal method of establishing subcutaneous, breast, and liver tumor models using the same Walker-256 cells, and investigated the dynamic growth characteristics using ¹⁸F-deoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT), which provides basic information for choosing an experimental animal model. MATERIAL AND METHODS We established tumor models in 3 locations (subcutaneous, breast, and liver) in W256 Sprague-Dawley rats. ¹⁸F-FDG PET/CT imaging was performed from 6 days to 18 days after injecting the cells subcutaneously. Tumor volume of interest (VOI), maximum standard uptake value (SUVmax), and average standard uptake value (SUVavg) were obtained from the image. The difference of the growth characteristics in tumor volume and SUVs among the 3 groups were compared. Histopathology of the tumors was also analyzed. RESULTS The tumors in subcutaneous location grew fastest, followed by tumors located in the breast, and tumors in the liver grew slowest. Significant differences in tumor VOI (p=0.01) were observed. ¹⁸F-FDG uptake of the subcutaneous and breast tumors increased until day 10 and then decreased subsequently. ¹⁸F-FDG uptake of the liver tumor reached a peak at day 10, and necrosis peaked at day 12. The histopathology analysis results indicated that the necrosis was mainly located in the center of tumors while the viable tissues were located on the periphery. Similarly, CD 31 and Ki-67 were mainly expressed on the tumor periphery. CONCLUSIONS Subcutaneous, breast, and liver tumor models were easy to establish using Walker-256 cells. They showed fast growth and high uptake of ¹⁸F-FDG. These kinds of tumor models were optimal in evaluating anti-tumor efficacy by ¹⁸F-FDG PET/CT, but it may be essential to determine the best time-points at which to use it.