Hypoxia imaging with 18F-FAZA PET/CT predicts radiotherapy response in esophageal adenocarcinoma xenografts

Advances in the Imaging of Esophageal and Gastroesophageal Junction Malignancies

Accurate imaging is key for the diagnosis and treatment of esophageal and gastroesophageal junction cancers . Current imaging modalities, such as computed tomography (CT) and 18F-FDG (2-deoxy-2-[18F]fluoro-D-glucose) positron emission tomography (PET)/CT, have limitations in accurately staging these cancers. MRI shows promise for T staging and residual disease assessment. Novel PET tracers, like FAPI, FLT, and hypoxia markers, offer potential improvements in diagnostic accuracy. 18F-FDG PET/MRI combines metabolic and anatomic information, enhancing disease evaluation. Radiomics and artificial intelligence hold promise for early detection, treatment planning, and response assessment. Theranostic nanoparticles and personalized medicine approaches offer new avenues for cancer therapy.

Concomitant [18F]F-FAZA and [18F]F-FDG Imaging of Gynecological Cancer Xenografts: Insight into Tumor Hypoxia

BACKGROUND/AIM

Herein we assessed the feasibility of imaging protocols using both hypoxia-specific [18F]F-FAZA and [18F]F-FDG in bypassing the limitations derived from the non-specific findings of [18F]F-FDG PET imaging of tumor-related hypoxia.

MATERIALS AND METHODS

CoCl2-generated hypoxia was induced in multidrug resistant (Pgp+) or sensitive (Pgp-) human ovarian (Pgp- A2780, Pgp+ A2780AD), and cervix carcinoma (Pgp- KB-3-1, Pgp+ KB-V-1) cell lines to establish corresponding tumor-bearing mouse models. Prior to [18F]F-FDG/[18F]F-FAZA-based MiniPET imaging, in vitro [18F]F-FDG uptake measurements and western blotting were used to verify the presence of hypoxia.

RESULTS

Elevated GLUT-1, and hexokinase enzyme-II expression driven by CoCl2-induced activation of hypoxia-inducible factor-1α explains enhanced cellular [18F]F-FDG accumulation. No difference was observed in the [18F]F-FAZA accretion of Pgp+ and Pgp- tumors. Tumor-to-muscle ratios for [18F]F-FAZA measured at 110-120 min postinjection (6.2±0.1) provided the best contrasted images for the delineation of PET-oxic and PET-hypoxic intratumor regions. Although all tumors exhibited heterogenous uptake of both radiopharmaceuticals, greater differences for [18F]F-FAZA between the tracer avid and non-accumulating regions indicate its superiority over [18F]F-FDG. Spatial correlation between [18F]F-FGD and [18F]F-FAZA scans confirms that hypoxia mostly occurs in regions with highly active glucose metabolism.

CONCLUSION

The addition of [18F]F-FAZA PET to [18F]F-FGD imaging may add clinical value in determining hypoxic sub-regions.

Advances in PET imaging of cancer

Molecular imaging has experienced enormous advancements in the areas of imaging technology, imaging probe and contrast development, and data quality, as well as machine learning-based data analysis. Positron emission tomography (PET) and its combination with computed tomography (CT) or magnetic resonance imaging (MRI) as a multimodality PET-CT or PET-MRI system offer a wealth of molecular, functional and morphological data with a single patient scan. Despite the recent technical advances and the availability of dozens of disease-specific contrast and imaging probes, only a few parameters, such as tumour size or the mean tracer uptake, are used for the evaluation of images in clinical practice. Multiparametric in vivo imaging data not only are highly quantitative but also can provide invaluable information about pathophysiology, receptor expression, metabolism, or morphological and functional features of tumours, such as pH, oxygenation or tissue density, as well as pharmacodynamic properties of drugs, to measure drug response with a contrast agent. It can further quantitatively map and spatially resolve the intertumoural and intratumoural heterogeneity, providing insights into tumour vulnerabilities for target-specific therapeutic interventions. Failure to exploit and integrate the full potential of such powerful imaging data may lead to a lost opportunity in which patients do not receive the best possible care. With the desire to implement personalized medicine in the cancer clinic, the full comprehensive diagnostic power of multiplexed imaging should be utilized.

Hypoxia-Responsive Aggregation of Gold Nanoparticles for Near-Infrared-II Photoacoustic Imaging-Guided Enhanced Radiotherapy

By directly harming cancer cells, radiotherapy (RT) is a crucial therapeutic approach for the treatment of cancers. However, the efficacy of RT is reduced by the limited accumulation and short retention time of the radiosensitizer in the tumor. Herein, we developed hypoxia-triggered in situ aggregation of nanogapped gold nanospheres (AuNNP@PAA/NIC NPs) within the tumor, resulting in second near-infrared window (NIR-II) photoacoustic (PA) imaging and enhanced radiosensitization. AuNNP@PAA/NIC NPs demonstrated increased accumulation and retention in hypoxic tumors, mainly due to the hypoxia-triggered aggregation. After aggregation of AuNNP@PAA/NIC NPs, the absorption of the system extended from visible light to NIR-II light owing to the plasmon coupling effects between adjacent nanoparticles. Compared to the normoxic tumor, the PA intensity at 1200 nm in the hypoxic tumor increased from 0.42 to 1.88 at 24 h postintravenous injection of AuNNP@PAA/NIC NPs, leading to an increase of 4.5 times. This indicated that the hypoxic microenvironment in the tumor successfully triggered the in situ aggregation of AuNNP@PAA/NIC NPs. The in vivo radiotherapeutic effect demonstrated that this hypoxia-triggered in situ aggregation of radiosensitizers significantly enhanced radiosensitization and thus resulted in superior cancer radiotherapeutic outcomes.

Personalized Oncology by In Vivo Chemical Imaging: Photoacoustic Mapping of Tumor Oxygen Predicts Radiotherapy Efficacy

We hereby apply the approach of photoacoustic chemical imaging, performing an in vivo chemical analysis that is spatially resolved (200 μm) and in real time, to predict a given tumor's response to therapy. Using triple negative breast cancer as a model, we took photoacoustic images of tumors' oxygen distributions in patient-derived xenografts (PDXs) in mice using biocompatible, oxygen-sensitive tumor-targeted chemical contrast nanoelements (nanosonophores), which function as contrast agents for photoacoustic imaging. Following radiation therapy, we established a quantitatively significant correlation between the spatial distribution of the initial oxygen levels in the tumor and its spatial distribution of the therapy's efficacy: the lower the local oxygen, the lower the local radiation therapy efficacy. We thus provide a simple, noninvasive, and inexpensive method to both predict the efficacy of radiation therapy for a given tumor and identify treatment-resistant regions within the tumor's microenvironment.

Prognostic Value of Serum Transferrin Level before Radiotherapy on Radio-Sensitivity and Survival in Patients with Nasopharyngeal Carcinoma

Purpose: To investigate the prognostic value of serum transferrin (TRF) level before intensity-modulated radiation therapy (IMRT) on radio-sensitivity and overall survival (OS) in patients with nasopharyngeal carcinoma (NPC). Methods: From October 2012 to October 2016, a total of 348 patients with NPC in the First Affiliated Hospital of Fujian Medical University were retrospectively analyzed in our study. The concentration of serum TRF was detected by the method of enzyme-linked immunosorbent assay (ELISA). In the whole group, 46 patients received IMRT, and 302 patients received IMRT plus chemotherapy. The radio-sensitive tumor was defined when the local tumor lesions disappeared completely in the nasopharyngeal MRI scan and no tumor residues were found under the electronic nasopharyngoscope one month after the end of radiotherapy. Results: The serum TRF level before IMRT was (1.34–3.89) g/L, with a median of 2.16 g/L and a mean of (2.20 ± 0.42) g/L. In the whole group, 242 cases (69.5%) were radiosensitive, and 106 cases (30.5%) were insensitive. The number of radiosensitive patients in the group of HTRF (transferrin > 2.16 g/L) and LTRF (transferrin ≤ 2.16 g/L) before radiotherapy was 129 (74.6%) and 113 (64.6%), respectively. The difference in radio-sensitivity between the two groups was statistically significant (χ2 = 4.103, p = 0.043). Logistic regression analysis showed that the level of TRF before radiotherapy (OR = 1.702; 95% CI 1.044~2.775; p = 0.033) was an independent factor for radio-sensitivity. The log-rank test showed that patients in the LTRF group achieved a significantly worse OS (χ2 = 5.388, p = 0.02) than those in the HTRF group. Cox regression analysis showed that baseline TRF level (HR = 1.706; 95% CI 1.065~2.731; p = 0.026) was an independent prognostic factor for overall survival. Conclusions: The low level of TRF before IMRT is a risk factor for radio-sensitivity and a prognostic factor for poor OS in NPC patients. It may be a promising marker to predict radio-sensitivity and OS in NPC patients who accept IMRT.

The Therapeutic Potential of Imidazole or Quinone-Based Compounds as Radiosensitisers in Combination with Radiotherapy for the Treatment of Head and Neck Squamous Cell Carcinoma

Simple Summary

Patients with curable head and neck cancers are usually treated with a combination of chemotherapy and radiotherapy, but they experience significant, severe side effects, which greatly affect their quality of life. Some of these patients still experience disease relapse after an intensive course of treatment due to tumours that are resistant to radiotherapy and chemotherapy because of hypoxia (lack of oxygen). In addition, some patients are not suitable for and/or are not able to have combined chemotherapy with radiotherapy due to their age or other physical conditions. Certain small-molecule drugs, which are used to treat various infections including malaria, have been shown to reduce hypoxia and thus make radiotherapy more effective. Therefore, their combination with radiotherapy could have less toxicities compared with the combination of chemotherapy with radiotherapy. Here, we discuss the promising results from preclinical work and clinical trials of these agents, and their potential use in the clinic, to reduce hypoxia and to sensitise radiotherapy. These agents could potentially be used for patients who are not suitable for combined chemotherapy and radiotherapy; they may also be used to reduce the dose of radiotherapy if able to enhance radiotherapy effect at lower dose in order to reduce toxicities while maintaining the treatment efficacy in a more personalised manner.

Abstract

The addition of platinum chemotherapy to primary radiotherapy (chemoradiation) improves survival outcomes for patients with head and neck squamous cell carcinoma (HNSCC), but it carries a high incidence of acute and long-term treatment-related complications, resulting in a poor quality of life. In addition, patients with significant co-morbidities, or older patients, cannot tolerate or do not benefit from concurrent chemoradiation. These patients are often treated with radiotherapy alone resulting in poor locoregional control and worse survival outcomes. Thus, there is an urgent need to assess other less toxic treatment modalities, which could become an alternative to chemoradiation in HNSCC. Currently, there are several promising anti-cancer drugs available, but there has been very limited success so far in replacing concurrent chemoradiation due to their low efficacy or increased toxicities. However, there is new hope that a treatment strategy that incorporates agents that act as radiosensitisers to improve the efficacy of conventional radiotherapy could be an alternative to more toxic chemotherapeutic agents. Recently, imidazole-based or quinone-based anti-malarial compounds have drawn considerable attention as potential radiosensitisers in several cancers. Here, we will discuss the possibility of using these compounds as radiosensitisers, which could be assessed as safe and effective alternatives to chemotherapy, particularly for patients with HNSCC that are not suitable for concurrent chemotherapy due to their age or co-morbidities or in metastatic settings. In addition, these agents could also be tested to assess their efficacy in combination with immunotherapy in recurrent and metastatic settings or in combination with radiotherapy and immunotherapy in curative settings.

State-of-the-art imaging in oesophago-gastric cancer

Radiological investigations are essential in the management of oesophageal and gastro-oesophageal junction cancers. The current multimodal combination of CT, 18F-fluorodeoxyglucose positron emission tomography combined with CT (PET/CT) and endoscopic ultrasound (EUS) has limitations, which hinders the prognostic and predictive information that can be used to guide optimum treatment decisions. Therefore, the development of improved imaging techniques is vital to improve patient management. This review describes the current evidence for state-of-the-art imaging techniques in oesophago-gastric cancer including high resolution MRI, diffusion-weighted MRI, dynamic contrast-enhanced MRI, whole-body MRI, perfusion CT, novel PET tracers, and integrated PET/MRI. These novel imaging techniques may help clinicians improve the diagnosis, staging, treatment planning, and response assessment of oesophago-gastric cancer.

Novel Tracers and Radionuclides in PET Imaging

The use of PET imaging agents in oncology, cardiovascular disease, and neurodegenerative disease shows the power of this technique in evaluating the molecular and biological characteristics of numerous diseases. These agents provide crucial information for designing therapeutic strategies for individual patients. Novel PET tracers are in continual development and many have potential use in clinical and research settings. This article discusses the potential applications of tracers in diagnostics, the biological characteristics of diseases, the ability to provide prognostic indicators, and using this information to guide treatment strategies including monitoring treatment efficacy in real time to improve outcomes and survival.

The tumour immune microenvironment in oesophageal cancer

Oesophageal cancer (OC) is an inflammation-associated malignancy linked to gastro-oesophageal reflux disease, obesity and tobacco use. Knowledge of the microenvironment of oesophageal tumours is relevant to our understanding of the development of OC and its biology, and has major implications for understanding the response to standard therapies and immunotherapies, as well as for uncovering novel targets. In this context, we discuss what is known about the TME in OC from tumour initiation to development and progression, and how this is relevant to therapy sensitivity and resistance in the two major types of OC. We provide an immunological characterisation of the OC TME and discuss its prognostic implications with specific comparison with the Immunoscore and immune-hot, -cold, altered-immunosuppressed and -altered-excluded models. Targeted therapeutics for the TME under pre-clinical and clinical investigation in OCs are also summarised. A deeper understanding of the TME will enable the development of combination approaches to concurrently target the tumour cells and TME delivering precision medicine to OC patients.

Hypoxia and its impact on the tumour microenvironment of gastroesophageal cancers

The malfeasant role of the hypoxic tumour microenvironment (TME) in cancer progression was recognized decades ago but the exact mechanisms that augment the hallmarks of cancer and promote treatment resistance continue to be elucidated. Gastroesophageal cancers (GOCs) represent a major burden of worldwide disease, responsible for the deaths of over 1 million people annually. Disentangling the impact of hypoxia in GOCs enables a better overall understanding of the disease pathogenesis while shining a light on novel therapeutic strategies and facilitating precision treatment approaches with the ultimate goal of improving outcomes for patients with these diseases. This review discusses the underlying principles and processes of the hypoxic response and the effect of hypoxia in promoting the hallmarks of cancer in the context of GOCs. We focus on its bidirectional influence on inflammation and how it drives angiogenesis, innate and adaptive immune evasion, metastasis, and the reprogramming of cellular bioenergetics. The contribution of the hypoxic GOC TME to treatment resistance is examined and a brief overview of the pharmacodynamics of hypoxia-targeted therapeutics is given. The principal methods that are used in measuring hypoxia and how they may enhance prognostication or provide rationale for individually tailored management in the case of tumours with significant hypoxic regions are also discussed.

In vivo noninvasive preclinical tumor hypoxia imaging methods: a review

Tumors exhibit areas of decreased oxygenation due to malformed blood vessels. This low oxygen concentration decreases the effectiveness of radiation therapy, and the resulting poor perfusion can prevent drugs from reaching areas of the tumor. Tumor hypoxia is associated with poorer prognosis and disease progression, and is therefore of interest to preclinical researchers. Although there are multiple different ways to measure tumor hypoxia and related factors, there is no standard for quantifying spatial and temporal tumor hypoxia distributions in preclinical research or in the clinic. This review compares imaging methods utilized for the purpose of assessing spatio-temporal patterns of hypoxia in the preclinical setting. Imaging methods provide varying levels of spatial and temporal resolution regarding different aspects of hypoxia, and with varying advantages and disadvantages. The choice of modality requires consideration of the specific experimental model, the nature of the required characterization and the availability of complementary modalities as well as immunohistochemistry.

Preclinical Applications of Multi-Platform Imaging in Animal Models of Cancer

In animal models of cancer, oncologic imaging has evolved from a simple assessment of tumor location and size to sophisticated multimodality exploration of molecular, physiologic, genetic, immunologic, and biochemical events at microscopic to macroscopic levels, performed noninvasively and sometimes in real time. Here, we briefly review animal imaging technology and molecular imaging probes together with selected applications from recent literature. Fast and sensitive optical imaging is primarily used to track luciferase-expressing tumor cells, image molecular targets with fluorescence probes, and to report on metabolic and physiologic phenotypes using smart switchable luminescent probes. MicroPET/single-photon emission CT have proven to be two of the most translational modalities for molecular and metabolic imaging of cancers: immuno-PET is a promising and rapidly evolving area of imaging research. Sophisticated MRI techniques provide high-resolution images of small metastases, tumor inflammation, perfusion, oxygenation, and acidity. Disseminated tumors to the bone and lung are easily detected by microCT, while ultrasound provides real-time visualization of tumor vasculature and perfusion. Recently available photoacoustic imaging provides real-time evaluation of vascular patency, oxygenation, and nanoparticle distributions. New hybrid instruments, such as PET-MRI, promise more convenient combination of the capabilities of each modality, enabling enhanced research efficacy and throughput.

A study of evaluating specific tissue oxygen saturation values of gastrointestinal tumors by removing adherent substances in oxygen saturation imaging

OBJECTIVES

Oxygen saturation (OS) imaging is a new method of endoscopic imaging that has clinical applications in oncology which can directly measure tissue oxygen saturation (Sto2) of the surface of gastrointestinal tract without any additional drugs or devices. This imaging technology is expected to contribute to research into cancer biology which leads to clinical benefit such as prediction to efficacy of chemotherapy or radiotherapy. However, adherent substances on tumors such as blood and white coating, pose a challenge for accurate measurements of the StO2 values in tumors. The aim of this study was to develop algorithms for discriminating between the tumors and their adherent substances, and to investigate whether it is possible to evaluate the tumor specific StO2 values excluding adherent substances during OS imaging.

METHODS

We plotted areas of tumors and their adherent substances using white-light images of 50 upper digestive tumors: blood (68 plots); reddish tumor (83 plots); white coating (89 plots); and whitish tumor (79 plots). Scatter diagrams and discriminating algorithms using spectrum signal intensity values were constructed and verified using validation datasets. StO2 values were compared between the tumors and tumor adherent substances using OS images of gastrointestinal tumors.

RESULTS

The discriminating algorithms and their accuracy rates (AR) were as follows: blood vs. reddish tumor: Y> - 4.90X+7.13 (AR: 95.9%) and white coating vs. whitish tumor: Y< -0.52X+0.17 (AR: 96.0%). The StO2 values (median, [range]) were as follows: blood, 79.3% [37.8%-100.0%]; reddish tumor, 74.5% [62.0%-86.9%]; white coating, 73.8% [42.1%-100.0%]; and whitish tumor, 65.7% [53.0%-76.3%].

CONCLUSIONS

OS imaging is strongly influenced by adherent substances for evaluating the specific StO2 value of tumors; therefore, it is important to eliminate the information of adherent substances for clinical application of OS imaging.

Self-Reporting and Splitting Nanopomegranates Potentiate Deep Tissue Cancer Radiotherapy via Elevated Diffusion and Transcytosis

The efficacy of nanoradiosensitizers in cancer therapy has been primarily impeded by their limited accessibility to radioresistant cancer cells residing deep inside tumor tissues. The failure to report tumor response to radiotherapy generally delays adjustment of the treatment schedule and sets up another substantial obstacle to clinical success. Here, we develop a nanopomegranate (RNP) platform that not only visualizes the cancer radiosensitivities but also potentiates deep tissue cancer radiotherapy via elevated passive diffusion and active transcytosis. The RNPs are engineered through the programmed self-assembly of a tumor environment-targeting polymeric matrix and modular building blocks of ultrasmall gold nanoparticles (Au₅). Once RNPs reach the tumors, the environmental acidity triggers the splitting and surface cationization of Au₅. The small dimension of Au₅ allows its passive diffusion, while positive surface charge enables its active transcytosis to cross the tumor interstitium. Meanwhile, the reporter element monitors the feedback of favorable radiotherapy responsiveness by detecting the activated apoptosis after radiation. The pivotal role of RNPs in improving and identifying radiotherapeutic outcomes is demonstrated in various tumor bearing mouse models with different radiosensitivities. In summary, our strategy offers a promising paradigm for deep tissue drug delivery as well as individualized precision radiotherapy.

Predicting response to radiotherapy in tumors with PET/CT: when and how?

Radiotherapy is one of the main methods for tumor treatment, with the improved radiotherapy delivery technique to combat cancer, there is a growing interest for finding effective and feasible ways to predict tumor radiosensitivity. Based on a series of changes in metabolism, microvessel density, hypoxic microenvironment, and cytokines of tumors after radiotherapy, a variety of radiosensitivity detection methods have been studied. Among the detection methods, positron emission tomography-computed tomography (PET/CT) is a feasible tool for response evaluation following definitive radiotherapy for cancers with a high negative predictive value. The prognostic or predictive value of PET/CT is currently being studied widely. However, there are many unresolved issues, such as the optimal probe of PET/CT for radiosensitivity prediction, the selection of the most useful PET/CT parameters and their optimal cut-offs such as total lesion glycolysis (TLG), metabolic tumor volume (MTV) and standardized uptake value (SUV), and the optimal timing of PET/CT pre-treatment, during or following RT. Different radiosensitivity of tumors, modes of radiotherapy action and fraction scheduling may complicate the appropriate choice. In this study, we will discuss the diverse methods for evaluating radiosensitivity, and will also focus on the selection of the optimal probe, timing, cut-offs and parameters of PET/CT for evaluating the radiotherapy response.

Rational design of fluorescent probes for targeted in vivo nitroreductase visualization

Three fluorescent probes were made by conjugation of para-, ortho-, and meta-nitrobenzene to the BODIPY core via a thiolether bond. It revealed that the linkage and nitro substituent position significantly influence the capability of NTR detection.

In Vivo Ester Hydrolysis as a New Approach in Development of Positron Emission Tomography Tracers for Imaging Hypoxia

Hypoxia is an important biochemical and physiological condition associated with uncontrolled growth of tumor. Measurement of hypoxia in tumor tissue may be useful in characterization of tumor progression and monitoring drug treatment. [¹⁸F]FMISO is the most widely employed radiotracer for imaging of hypoxic tissue with positron emission tomography (PET). However, it showed relatively low uptake in hypoxic tissues, which led to low target-to-background contrast in PET images. To overcome these shortcomings, two novel 2-fluoroproprioic acid esters, nitroimidazole derivatives 2-fluoropropionic acid 2-(2-nitro-imidazol-1-yl)-ethyl ester (FNPFT, [¹⁹F]5) and 2-fluoropropionic acid 2-(2-methyl-5-nitro-imidazol-1-yl)-ethyl ester (FMNPFT, [¹⁹F]8), were prepared and tested. Radiolabeling of [¹⁸F]5 and [¹⁸F]8 was accomplished in 45 min (radiochemical purity >95%, the decay-corrected radiochemical yield of [¹⁸F]5 was 11 ± 2%, and that of [¹⁸F]8 was 13 ± 2%, n = 5). In vitro cell uptake studies using EMT-6 tumor cells showed that both radiotracers [¹⁸F]5 and [¹⁸F]8 displayed significantly higher uptake in hypoxic cells than those under normoxic condition, while 2-[¹⁸F]fluoropropionic acid (2-[¹⁸F]FPA) displayed no difference. Biodistribution studies in mice bearing EMT-6 tumor showed that [¹⁸F]5, [¹⁸F]8, and 2-[¹⁸F]FPA displayed similar tumor and major organ uptakes. Tumor uptake values for all three agents were higher than those of [¹⁸F]FMISO, respectively ( P < 0.05). This is likely due to a rapid in vivo hydrolysis of [¹⁸F]5 and [¹⁸F]8 to their metabolite, 2-[¹⁸F]FPA. Micro PET imaging studies in the same EMT-6 implanted mice tumor model also demonstrated that both [¹⁸F]5 and [¹⁸F]8 displayed similar tumor uptake comparable to that of 2-[¹⁸F]FPA. In conclusion, two new fluorine-18 labeled nitroimidazole derivatives, [¹⁸F]5 and [¹⁸F]8, showed good tumor uptakes in mice bearing EMT-6 tumor. However, in vivo biodistribution results suggested that they were more likely reflect the predominance of in vivo produced metabolite, 2-[¹⁸F]FPA, which may not be related to tumor hypoxic condition.

FOXM1c promotes oesophageal cancer metastasis by transcriptionally regulating IRF1 expression

Objectives

We aimed to elucidate the role and molecular mechanisms of FOXM1 in regulating metastasis in oesophageal squamous cell carcinoma (ESCC) as well as its clinical implications.

Materials and methods

The expression levels of four isoforms of FOXM1 were analysed by real‐time PCR. Next, genetically modification using overexpression and RNAi systems and transwell were employed to examine FOXM1c function in invasion and migration. Dual luciferase and ChIP assays were performed to decipher the underlying mechanism for transcriptional regulation. The expression levels of FOXM1 and IRF1 were determined by immunohistochemistry staining in ESCC specimens.

Results

The FOXM1c was predominantly overexpressed in ESCC cell lines compared to the other FOXM1 isoforms. Ectopic expression of FOXM1c promoted invasion and migration of ESCC cells lines, whereas downregulation of FOXM1c inhibited these processes. Moreover, FOXM1c expression was positively correlated with IRF1 expression in ESCC cell lines and tumour specimens. IRF1 is, at least in part, responsible for FOXM1c‐mediated invasion and migration. Mechanistically, we identified IRF1 as a transcriptional target of FOXM1c and found a FOXM1c‐binding site in the IRF1 promoter region. Furthermore, high expression levels of both FOXM1c and IRF1 were positively associated with low survival rate and predicted a poor prognosis of oesophageal cancer patients.

Conclusion

FOXM1c promotes the metastasis by transcriptionally targeting IRF1 and may serve as a potential prognostic predictor for oesophageal cancer.

Synthesis of [18F]FAZA Using Nosyl and Iodo Precursors for Nucleophilic Radiofluorination

BACKGROUND

1-α-D-(5-Deoxy-5-[18F]fluoroarabinofuranosyl)-2-nitroimidazole ([18F]FAZA) is manufactured by nucleophilic radiofluorination of 1-α-D-(2',3'-di-O-acetyl-5'-O-toluenesulfonylarabinofuranosyl)- 2-nitroimidazole (DiAcTosAZA) and alkaline deprotection to afford [18F]FAZA. High yields (>60%) under optimized conditions frequently revert to low yields (<20%) in large scale, automated syntheses. Competing side reactions and concomitant complex reaction mixtures contribute to substantial loss of product during HPLC clean-up.

OBJECTIVE

To develop alternative precursors for facile routine clinical manufacture of [18F]FAZA that are compatible with current equipment and automated procedures.

METHODS

Two new precursors, 1-α-D-(2',3'-di-O-acetyl-5'-O-(4-nitrobenzene)sulfonyl-arabinofuranosyl)-2- nitroimidazole (DiAcNosAZA) and 1-α-D-(2',3'-di-O-acetyl-5'-iodo-arabinofuranosyl)-2-nitroimidazole (DiAcIAZA), were synthesized from commercially-available 1-α-D-arabinofuranosyl-2-nitroimidazole (AZA). A commercial automated synthesis unit (ASU) was used to condition F-18 for anhydrous radiofluorination, and to radiofluorinate DiAcNosAZA and DiAcIAZA using the local standardized protocol to manufacture [18F]FAZA from AcTosAZA.

RESULTS

DiAcNosAZA was synthesized via two pathways, in recovered yields of 29% and 40%, respectively. The nosylation of 1-α-D-(2',3'-di-O-acetyl-arabinofuranosyl)-2-nitroimidazole (DiAcAZA) featured a strong competing reaction that afforded 1-α-D-(2',3'-di-O-acetyl-5'-chloro-arabinofuranosyl)-2- nitroimidazole (DiAcClAZA) in 55% yield. Radiofluorination yields were better from DiAcNosAZA and DiAcIAZA than from DiAcTosAZA, and the presence of fewer side products afforded higher purity [18F]FAZA preparations. Several radioactive and non-radioactive by products of radiofluorination were assigned tentative chemical structures based on co-chromatography with authentic reference compounds.

CONCLUSION

DiAcClAZA, a major side-product in the preparation of DiAcNosAZA, and its deprotected analogue (ClAZA), are unproven hypoxic tissue radiosensitizers. DiAcNosAZA and DiAcIAZA provided good radiofluorination yields in comparison to AcTosAZA and could become preferred [18F]FAZA precursors if the cleaner reactions can be exploited to bypass HPLC purification.

How to Modulate Tumor Hypoxia for Preclinical In Vivo Imaging Research

Tumor hypoxia is related with tumor aggressiveness, chemo- and radiotherapy resistance, and thus a poor clinical outcome. Therefore, over the past decades, every effort has been made to develop strategies to battle the negative prognostic influence of tumor hypoxia. For appropriate patient selection and follow-up, noninvasive imaging biomarkers such as positron emission tomography (PET) radiolabeled ligands are unprecedentedly needed. Importantly, before being able to implement these new therapies and potential biomarkers into the clinical setting, preclinical in vivo validation in adequate animal models is indispensable. In this review, we provide an overview of the different attempts that have been made to create differential hypoxic in vivo cancer models with a particular focus on their applicability in PET imaging studies.