Valrubicin-loaded immunoliposomes for specific vesicle-mediated cell death in the treatment of hematological cancers

We created valrubicin-loaded immunoliposomes (Val-ILs) using the antitumor prodrug valrubicin, a hydrophobic analog of daunorubicin. Being lipophilic, valrubicin readily incorporated Val-lLs that were loaded with specific antibodies. Val-ILs injected intravenously rapidly reached the bone marrow and spleen, indicating their potential to effectively target cancer cells in these areas. Following the transplantation of human pediatric B-cell acute lymphoblastic leukemia (B-ALL), T-cell acute lymphoblastic leukemia (T-ALL), or acute myeloid leukemia (AML) in immunodeficient NSG mice, we generated patient-derived xenograft (PDX) models, which were treated with Val-ILs loaded with antibodies to target CD19, CD7 or CD33. Only a small amount of valrubicin incorporated into Val-ILs was needed to induce leukemia cell death in vivo, suggesting that this approach could be used to efficiently treat acute leukemia cells. We also demonstrated that Val-ILs could reduce the risk of contamination of CD34+ hematopoietic stem cells by acute leukemia cells during autologous peripheral blood stem cell transplantation, which is a significant advantage for clinical applications. Using EL4 lymphoma cells on immunocompetent C57BL/6 mice, we also highlighted the potential of Val-ILs to target immunosuppressive cell populations in the spleen, which could be valuable in impairing cancer cell expansion, particularly in lymphoma cases. The most efficient Val-ILs were found to be those loaded with CD11b or CD223 antibodies, which, respectively, target the myeloid-derived suppressor cells (MDSC) or the lymphocyte-activation gene 3 (LAG-3 or CD223) on T4 lymphocytes. This study provides a promising preclinical demonstration of the effectiveness and ease of preparation of Val-ILs as a novel nanoparticle technology. In the context of hematological cancers, Val-ILs have the potential to be used as a precise and effective therapy based on targeted vesicle-mediated cell death.

Development of an Immuno-SPECT/Fluorescent Bimodal Tracer Targeting Human or Murine PD-L1 on Preclinical Models

Detection of biomarkers to diagnose, treat, and predict the efficacy of cancer therapies is a major clinical challenge. Currently, biomarkers such as PD-L1 are commonly detected from biopsies, but this approach does not take into account the spatiotemporal heterogeneity of their expression in tumors. A solution consists in conjugating monoclonal antibodies (mAbs) targeting these biomarkers with multimodal imaging probes. In this study, a bimodal [111In]-DOTA-aza-BODIPY probe emitting in the near-infrared (NIR) was grafted onto mAbs targeting murine or human PD-L1 either in a site-specific or random manner. In vitro, these bimodal mAbs showed a good stability and affinity for PD-L1. In vivo, they targeted specifically PD-L1 and were detected by both fluorescence and SPECT imaging. A significant benefit of site-specific conjugation on glycans was observed compared to random conjugation on lysine. The potential of this bimodal agent was also highlighted, thanks to a proof of concept of fluorescence-guided surgery in a human PD-L1+ tumor model.

Cherenkov Radiation induced photodynamic therapy - repurposing older photosensitizers, and radionuclides

CONTEXT

Old-generation photosensitizers are minimally used in current photodynamic therapy (PDT) because they absorb in the UV/blue/green region of the spectrum where biological tissues are generally highly absorbing. The UV/blue light of Cherenkov Radiation (CR) from nuclear disintegration of beta-emitter radionuclides shows promise as an internal light source to activate these photosensitizers within tissue. Outline of the study: 1) radionuclide choice and Cherenkov Radiation, 2) Photosensitizer choice, synthesis and radiolabeling, 3) CR-induced fluorescence, 4) Verification of ROS formation, 5) CR-induced PDT with either free eosine and free CR emitter, or with radiolabelled eosin.

RESULTS

Cherenkov Radiation Energy Transfer (CRET) from therapeutic radionuclides (90Y) and PET imaging radionuclides (18F, 68Ga) to eosin was shown by spectrofluorimetry and in vitro, and was shown to result in a PDT process. The feasibility of CR-induced PDT (CR-PDT) was demonstrated in vitro on B16F10 murine melanoma cells mixing free eosin (λabs = 524 nm, ΦΔ 0.67) with free CR-emitter [18F]-FDG under their respective intrinsic toxicity levels (0.5 mM/8 MBq) and by trapping singlet oxygen with diphenylisobenzofuran (DPBF). An eosin-DOTAGA-chelate conjugate 1 was synthesized and radiometallated with CR-emitter [68Ga] allowed to reach 25 % cell toxicity at 0.125 mM/2 MBq, i.e. below the toxicity threshold of each component measured on controls. Incubation time was carefully examined, especially for CR emitters, in light of its toxicity, and its CR-emitting yield expected to be 3 times as much for 68Ga than 18F (considering their β particle energy) per radionuclide decay, while its half-life is about twice as small.

PERSPECTIVE

This study showed that in complete darkness, as it is at depth in tissues, PDT could proceed relying on CR emission from radionuclides only. Interestingly, this study also repurposed PET imaging radionuclides, such as 68Ga, to trigger a therapeutic event (PDT), albeit in a modest extent. Moreover, although it remains modest, such a PDT approach may be used to achieve additional tumoricidal effect to RIT treatment, where radionuclides, such as 90Y, are strong CR emitters, i.e. very potent light source for photosensitizer activation.

SPECT Imaging of Lysyl Oxidase-like 2 in a Model of Idiopathic Pulmonary Fibrosis

Noninvasive imaging of idiopathic pulmonary fibrosis (IPF) remains a challenge. The aim of this study was to develop an antibody-based radiotracer targeting Lysyl Oxidase-like 2 (LOXL2), an enzyme involved in the fibrogenesis process, for SPECT/CT imaging of pulmonary fibrosis. The bifunctional chelator DOTAGA-PEG₄-NH₂ was chemoenzymatically conjugated to the murine antibody AB0023 using microbial transglutaminase, resulting in a degree of labeling (number of chelators per antibody) of 2.3. Biolayer interferometry confirmed that the binding affinity of DOTAGA-AB0023 to LOXL2 was preserved with a dissociation constant of 2.45 ± 0.04 nM. DOTAGA-AB0023 was then labeled with ¹¹¹In and in vivo experiments were carried out in a mice model of progressive pulmonary fibrosis induced by intratracheal administration of bleomycin. [¹¹¹In]In-DOTAGA-AB0023 was injected in three groups of mice (control, fibrotic, and treated with nintedanib). SPECT/CT images were recorded over 4 days p.i. and an ex vivo biodistribution study was performed by gamma counting. A significant accumulation of the tracer in the lungs of the fibrotic mice was observed at D18 post-bleomycin. Interestingly, the tracer uptake was found selectively upregulated in fibrotic lesions observed on CT scans. Images of mice that received the antifibrotic drug nintedanib from D8 up to D18 showed a decrease in [¹¹¹In]In-DOTAGA-AB0023 lung uptake associated with a decrease in pulmonary fibrosis measured by CT scan. In conclusion, we report the first radioimmunotracer targeting the protein LOXL2 for nuclear imaging of IPF. The tracer showed promising results in a preclinical model of bleomycin-induced pulmonary fibrosis, with high lung uptake in fibrotic areas, and accounted for the antifibrotic activity of nintedanib.

Oleanolic Acid Glycosides from Scabiosa caucasica and Scabiosa ochroleuca: Structural Analysis and Cytotoxicity

In the field of research on medicinal plants from the Armenian flora, the phytochemical study of two Scabiosa L. species, S. caucasica M. Bieb. and S. ochroleuca L. (Caprifoliaceae), has led to the isolation of five previously undescribed oleanolic acid glycosides from an aqueous-ethanolic extract of the roots: 3-O-α-L-rhamnopyranosyl-(1→3)-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid, 3-O-β-D-xylopyranosyl-(1→2)-[α-L-rhamnopyranosyl-(1→4)]-β-D-xylopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester, 3-O-α-L-rhamnopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-glucopyranosyl-(1→4)-β-D-xylopyranosyl-(1→3)-α-L-rhamnopyranosyl-(1→2)-α-L-arabinopyranosyloleanolic acid 28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranosyl ester. Their full structural elucidation required extensive 1D and 2D NMR experiments, as well as mass spectrometry analysis. For the biological activity of the bidesmosidic saponins and the monodesmosidic saponin, their cytotoxicity on a mouse colon cancer cell line (MC-38) was evaluated.

Abstract 2767: Simultaneous 18F-FDG PET/MR imaging for metastases identification in a disseminated human preclinical melanoma model

Melanoma is a skin cancer at high risk of metastatic progression, hence associated with poorer prognosis. Imaging represents an essential tool to assess tumor stage, but also to monitor disease progression and therapy response. However, a single imaging technique cannot efficiently detect and characterize all metastases. Therefore, we evaluated the potential of simultaneous 18F-FDG PET/MR imaging in preclinical models of disseminated melanoma at different stages. Female Nude and SDRG rats were intravenously injected with CMEL 5 cells, originating from brain metastases of a human melanoma. On day (D) 60, 70, and 80 post-injection, Nude rats were imaged using brain T2-weighted (T2w) 7T MRI and whole-body simultaneous 18F-FDG (10-15 MBq) PET/MR. Furthermore, whole-body and brain T2w MR images were acquired using a 4.7T MRI on D20 and D34 post-injection in SDRG rats. Visual detection and quantitative analysis of lesions were performed on MRI or PET/MR images, and results were confronted with necropsy (melanin pigmented lesions) and gamma counting data. From D60 post-CMEL-5 cell injection, all Nude animals exhibited metastases in one to four different locations. Moreover, most of metastases locations found in clinical setting were detected in our experimental model using simultaneous 18F-FDG PET/MR imaging, even allowing the observation of brain lesions on T2w MR images. MRI further allowed precise contouring of each organ of interest to effectively identify bone, lung, adrenal and spleen metastases with enhanced 18F-FDG uptake. Additionally, PET image quantification in adrenals was consistent with gamma counting results. As anticipated, small lesions below PET spatial resolution limit (i.e. <1 mm) were not detected by imaging. SDRG rats displayed a faster and more homogenous tumor spread in brain, lungs and liver on MR images, while more metastases were seen during autopsy (additional spreading to pancreas, adrenals, reproductive system, bones, lymph nodes and skin). The experimental model of disseminated CMEL-5 melanoma in Nude rats demonstrates its ability to mimic the human pathology. Hence, it appears to be a promising tool to monitor therapy response and potentially recognize progression from pseudo-progression. Simultaneous PET/MR imaging has shown to be more effective than stand-alone techniques in detecting melanoma dissemination, except for brain and small lesions for which the PET data are altered by partial volume effect. Thus, by complementing previously acquired MR images from the novel SDRG rat model with simultaneously acquired PET images, we could also provide insights on this promising metastatic model.

Citation Format: Alexandra Oudot, Peggy Provent, Alan Courteau, Nicolas Hoffmann, Melanie Guillemin, Jordan Longin, Sarah Belderbos, Bertrand Collin, Marc Hillairet de Boisferon, Alexandre Cochet, Cyril Berthet. Simultaneous 18F-FDG PET/MR imaging for metastases identification in a disseminated human preclinical melanoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2767.

IL-1RAP, a Key Therapeutic Target in Cancer

Cancer is a major cause of death worldwide and especially in high- and upper-middle-income countries. Despite recent progress in cancer therapies, such as chimeric antigen receptor T (CAR-T) cells or antibody-drug conjugate (ADC), new targets expressed by the tumor cells need to be identified in order to selectively drive these innovative therapies to tumors. In this context, IL-1RAP recently showed great potential to become one of these new targets for cancer therapy. IL-1RAP is highly involved in the inflammation process through the interleukins 1, 33, and 36 (IL-1, IL-33, IL-36) signaling pathways. Inflammation is now recognized as a hallmark of carcinogenesis, suggesting that IL-1RAP could play a role in cancer development and progression. Furthermore, IL-1RAP was found overexpressed on tumor cells from several hematological and solid cancers, thus confirming its potential involvement in carcinogenesis. This review will first describe the structure and genetics of IL-1RAP as well as its role in tumor development. Finally, a focus will be made on the therapies based on IL-1RAP targeting, which are now under preclinical or clinical development.

Superparamagnetic Iron Oxide Nanoparticles for Immunotherapy of Cancers through Macrophages and Magnetic Hyperthermia

Cancer immunotherapy has tremendous promise, but it has yet to be clinically applied in a wider variety of tumor situations. Many therapeutic combinations are envisaged to improve their effectiveness. In this way, strategies capable of inducing immunogenic cell death (e.g., doxorubicin, radiotherapy, hyperthermia) and the reprogramming of the immunosuppressive tumor microenvironment (TME) (e.g., M2-to-M1-like macrophages repolarization of tumor-associated macrophages (TAMs)) are particularly appealing to enhance the efficacy of approved immunotherapies (e.g., immune checkpoint inhibitors, ICIs). Due to their modular construction and versatility, iron oxide-based nanomedicines such as superparamagnetic iron oxide nanoparticles (SPIONs) can combine these different approaches in a single agent. SPIONs have already shown their safety and biocompatibility and possess both drug-delivery (e.g., chemotherapy, ICIs) and magnetic capabilities (e.g., magnetic hyperthermia (MHT), magnetic resonance imaging). In this review, we will discuss the multiple applications of SPIONs in cancer immunotherapy, focusing on their theranostic properties to target TAMs and to generate MHT. The first section of this review will briefly describe immune targets for NPs. The following sections will deal with the overall properties of SPIONs (including MHT). The last section is dedicated to the SPION-induced immune response through its effects on TAMs and MHT.

Development of Anti-LRRC15 Small Fragments for Imaging Purposes Using a Phage-Display ScFv Approach

The human leucine-rich repeat-containing protein 15 (LRRC15) is a membrane protein identified as a marker of CAF (cancer-associated fibroblast) cells whose overexpression is positively correlated with cancer grade and outcome. Nuclear molecular imaging (i.e., SPECT and PET) to track LRRC15 expression could be very useful in guiding further therapeutic strategies. In this study, we developed an ScFv mouse phage-display library to obtain small fragment antibodies against human LRRC15 for molecular imaging purposes. Mice were immunized with recombinant human LRRC15 (hLRRC15), and lymph node cells were harvested for ScFv (single-chain variable fragment) phage-display analysis. The built library was used for panning on cell lines with constitutive or induced expression after transfection. The choice of best candidates was performed by screening various other cell lines, using flow cytometry. The selected candidates were reformatted into Cys-ScFv or Cys-diabody by addition of cysteine, and cloned in mammalian expression vectors to obtain batches of small fragments that were further used in site-specific radiolabeling tests. The obtained library was 1.2 × 107 cfu/µg with an insertion rate >95%. The two panning rounds performed on cells permittedenrichment of 2 × 10−3. Screening with flow cytometry allowed us to identify 28 specific hLRRC15 candidates. Among these, two also recognized murine LRCC15 and were reformatted into Cys-ScFv and Cys-diabody. They were expressed transiently in a mammalian system to obtain 1.0 to 4.5 mg of Cys fragments ready for bioconjugation and radiolabeling. Thus, in this paper, we demonstrate the relevance of the phage-display ScFv library approach for the fast-track development of small antibodies for imaging and/or immunotherapy purposes.

Abstract 1296: MEK inhibition overcomes chemoimmunotherapy resistance by inducing CXCL10 in cancer cells

Chemotherapy with anti PD-1/PD-L1 mAb has become the standard of care for patients with metastatic non-small cell lung cancer (NSCLC). Using lung tumor models, where pemetrexed-platinum chemotherapy (PEM/CDDP) remains unable to synergize with immune checkpoint inhibitors (ICI), we linked failure of this treatment with its inability to induce CXCL10 expression and CD8+ T cell recruitment. Using drug screening, we showed that combining a MEK inhibitor (MEKi) with PEM/CDDP triggers CXCL10 secretion by cancer cells and CD8+ T cell recruitment, and restores ICI efficacy. PEM/CDDP plus MEKi promotes optineurin (OPTN)-dependent mitophagy, resulting in CXCL10 production in a mitochondrial DNA and TLR9-dependent manner. TLR9 or autophagy/mitophagy processes genetic inactivation of abort the antitumor efficacy of PEM/CDDP plus MEKi/anti PD-L1 therapy. In human NSCLC, high OPTN, TLR9 and CXCL10 expression is associated with better response to ICI. Our results underline the role of TLR9 and OPTN-dependent mitophagy in enhancing chemoimmunotherapy efficacy.

Citation Format: Emeric Limagne, Lisa Nuttin, Marion Thibaudin, Elise Jacquin, Romain Aucagne, Marjorie Bon, Elise Ballot, Solène Revy, Robby Barnestein, Caroline Truntzer, Valentin Derangère, Jean-David Fumet, Rébé Cédric, Pierre-Simon Bellaye, Coureche-Guillaume Kaderbhai, Aodrenn Spill, Bertrand Collin, Mary Callanan, Aurélie Lagrange, Laure Favier, Bruno Coudert, Laurent Arnould, Sylvain Ladoire, Bertrand Routy, Philippe Joubert, François Ghiringhelli. MEK inhibition overcomes chemoimmunotherapy resistance by inducing CXCL10 in cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1296.

MEK inhibition overcomes chemoimmunotherapy resistance by inducing CXCL10 in cancer cells

Chemotherapy with anti PD-1/PD-L1 antibodies has become the standard of care for patients with metastatic non-small cell lung cancer (mNSCLC). Using lung tumor models, where pemetrexed and cisplatin (PEM/CDDP) chemotherapy remains unable to synergize with immune checkpoint inhibitors (ICIs), we linked the failure of this treatment with its inability to induce CXCL10 expression and CD8⁺ T cell recruitment. Using drug screening, we showed that combining a MEK inhibitor (MEKi) with PEM/CDDP triggers CXCL10 secretion by cancer cells and CD8⁺ T cell recruitment, sensitizing it to ICIs. PEM/CDDP plus a MEKi promotes optineurin (OPTN)-dependent mitophagy, resulting in CXCL10 production in a mitochondrial DNA- and TLR9-dependent manner. TLR9 or autophagy/mitophagy inhibition abolishes the anti-tumor efficacy of PEM/CDDP plus MEKi/anti-PD-L1 therapy. In human NSCLCs, high OPTN, TLR9, and CXCL10 expression is associated with a better response to ICIs. Our results underline the role of TLR9- and OPTN-dependent mitophagy in enhancing chemoimmunotherapy efficacy.

Measurement of hypoxia in the lung in idiopathic pulmonary fibrosis: a matter of control

We read with great interest the paper by Porteret al. [1] published in the October 2021 issue of the European Respiratory Journal. The authors’ aim was to explore the potential benefit of the hypoxia tracer [¹⁸F]fluoromisonidazole ([¹⁸F]F-MISO) in idiopathic pulmonary fibrosis (IPF). Given the lack of non-invasive imaging tools for the diagnosis and/or the follow-up of patients with IPF, this study appears to be an essential first step towards the personalised management of IPF patients through imaging biomarkers for early/active fibrosis. In vivo molecular imaging, in particular positron emission tomography (PET), has become a crucial tool in preclinical research, clinical trials and medical practice, especially in the field of oncology. In lung fibrosis, recent advances have been made with the aim of developing molecular imaging tools in preclinical models, a necessary step toward clinical certification [2]. Among tracers validated at the preclinical level, imaging probes targeting collagen (⁶⁸Ga-CBP8 [3]), integrins ([¹⁸F]FB-A20FMDV2 [4]) and glucose metabolism ([¹⁸F]FDG [5]) have been successfully evaluated in clinical trials and may ultimately improve IPF management.

Despite the discouraging results provided by Porter and co-workers, we believe that there is room for improvements, mainly by using better controls, which may ultimately lead to more promising outcomes for the use of hypoxia-focused imaging in IPF patientshttps://bit.ly/30Ku2AV

The GRP94 Inhibitor PU-WS13 Decreases M2-like Macrophages in Murine TNBC Tumors: A Pharmaco-Imaging Study with 99mTc-Tilmanocept SPECT

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancers and is not eligible for hormone and anti-HER2 therapies. Identifying therapeutic targets and associated biomarkers in TNBC is a clinical challenge to improve patients' outcome and management. High infiltration of CD206⁺ M2-like macrophages in the tumor microenvironment (TME) indicates poor prognosis and survival in TNBC patients. As we previously showed that membrane expression of GRP94, an endoplasmic reticulum chaperone, was associated with the anti-inflammatory profile of human PBMC-derived M2 macrophages, we hypothesized that intra-tumoral CD206⁺ M2 macrophages expressing GRP94 may represent innovative targets in TNBC for theranostic purposes. We demonstrate in a preclinical model of 4T1 breast tumor-bearing BALB/c mice that (i) CD206-expressing M2-like macrophages in the TME of TNBC can be specifically detected and quantified using in vivo SPECT imaging with ^99mTc-Tilmanocept, and (ii) the inhibition of GRP94 with the chemical inhibitor PU-WS13 induces a decrease in CD206-expressing M2-like macrophages in TME. This result correlated with reduced tumor growth and collagen content, as well as an increase in CD8⁺ cells in the TME. ^99mTc-Tilmanocept SPECT imaging might represent an innovative non-invasive strategy to quantify CD206⁺ tumor-associated macrophages as a biomarker of anti-GRP94 therapy efficacy and TNBC tumor aggressiveness.

Steroidal glycosides from the Vietnamese cultivar Cordyline fruticosa "Fairchild red"

A phytochemical study of Cordyline fruticosa "Fairchild red" (Asparagaceae) from Vietnam, led to the isolation of fourteen steroidal glycosides, including twelve previously undescribed along with two known ones. Ten compounds were obtained by successive solid/liquid chromatographic methods from an aqueous-ethanolic extract of the roots, and four from the aerial parts. Their structures were elucidated mainly by spectroscopic analysis 2D NMR and mass spectroscopy (ESI-MS), as spirostanol glycosides, 5α-spirost-25(27)-ene-1β,3β,4α-triol 1-O-β-D-fucopyranoside, 5α-spirost-(25)27-ene-1β,3β,4α-triol 1-O-β-D-xylopyranoside, 5α-spirost-(25)27-ene-1β,3β,4α-triol 1-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-fucopyranoside, 5α-spirost-(25)27-ene-1β,3β,4α-triol 1-O-α-L-rhamnopyranosyl-(1 → 2)-(4-O-sulfo)-β-D-fucopyranoside, 5α-spirost-25(27)-ene-1β,3β-diol 1-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-fucopyranoside, and 5α-spirost-25(27)-ene-1β,3β-diol 1-O-α-L-rhamnopyranosyl-(1 → 2)-α-L-arabinopyranoside. Furostanol glycosides were also isolated as 26-O-β-D-glucopyranosyl-5α-furost-(25)27-ene-1β,3β,4α,22α,26-pentol 1-O-β-D-fucopyranoside, 26-O-β-D-glucopyranosyl-22α-methoxy-5α-furost-(25)27-ene-1β,3β,4α,26-tetrol 1-O-β-D-fucopyranoside, 26-O-β-D-glucopyranosyl-5α-furost-(25)27-ene-1β,3β,22α,26-tetrol 1-O-β-D-glucopyranoside, 26-O-β-D-glucopyranosyl-5α-furost-(25)27-ene-1β,3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-glucopyranoside, 26-O-β-D-glucopyranosyl-5α-furost-(25)27-ene-1β,3β,22α,26-tetrol 1-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-fucopyranoside, and 26-O-β-D-glucopyranosyl-22α-methoxy-5α-furost-(25)27-ene-1β,3β,26-triol 1-O-α-L-rhamnopyranosyl-(1 → 2)-β-D-fucopyranoside. All the isolated compounds were further evaluated for their cytotoxicity against 4T1 cell line, from a mouse mammary gland tissue, using MTS method.

[123I]MIBG is a better early marker of anthracycline cardiotoxicity than [18F]FDG: a preclinical SPECT/CT and simultaneous PET/MR study

Background

During anthracycline treatment of cancer, there is a lack for biomarkers of cardiotoxicity besides the cardiac dysfunction. The objective of the present study was to compare [¹⁸F]FDG and [¹²³I]MIBG (metaiodobenzylguanidine) in a longitudinal study in a doxorubicin-induced cardiotoxicity rat model.

Methods

Male Wistar Han rats were intravenously administered 3 times at 10 days’ interval with saline or doxorubicin (5 mg/kg). [¹²³I]MIBG SPECT/CT (single photon emission computed tomography-computed tomography) and simultaneous [¹⁸F]FDG PET (positron emission tomography)/7 Tesla cardiac MR (magnetic resonance) imaging acquisitions were performed at 24 h interval before first doxorubicin / saline injection and every 2 weeks during 6 weeks. At 6 weeks, the heart tissue was collected for histomorphometry measurements.

Results

At week 4, left ventricle (LV) end-diastolic volume was significantly reduced in the doxorubicin group. At week 6, the decreased LV end-diastolic volume was maintained, and LV end-systolic volume was increased resulting in a significant reduction of LV ejection fraction (47 ± 6% vs. 70 ± 3%). At weeks 4 and 6, but not at week 2, myocardial [¹⁸F]FDG uptake was decreased compared with the control group (respectively, 4.2 ± 0.5%ID/g and 9.2 ± 0.8%ID/g at week 6). Moreover, [¹⁸F]FDG cardiac uptake correlated with cardiac function impairment. In contrast, from week 2, a significant decrease of myocardial [¹²³I]MIBG heart to mediastinum ratio was detected in the doxorubicin group and was maintained at weeks 4 and 6 with a 45.6% decrease at week 6.

Conclusion

This longitudinal study precises that after doxorubicin treatment, cardiac [¹²³I]MIBG uptake is significantly reduced as early as 2 weeks followed by the decrease of the LV end-diastolic volume and [¹⁸F]FDG uptake at 4 weeks and finally by the increase of LV end-systolic volume and decrease of LV ejection fraction at 6 weeks. Cardiac innervation imaging should thus be considered as an early key feature of anthracycline cardiac toxicity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00835-1.

GARP: A Key Target to Evaluate Tumor Immunosuppressive Microenvironment

Simple Summary

Tumors are not only composed of cancer cells but also of various infiltrating cells constituting the tumor microenvironment (TME); all these cells produce growth factors which contribute to tumor progression and invasiveness. Among them, transforming growth factor-β1 (TGF-β1) has been shown to be a potent immunosuppressive cytokine favoring cell proliferation and invasion and to be associated with resistance to anticancer treatments. Glycoprotein-A repetition predominant (GARP) plays a critical role in the activation of TGF-β1 and has been shown to be expressed at the membrane of cancer cells and also of regulatory T cells and platelets in the TME. An increased GARP expression has been shown in a variety of cancers. The objective of this review is to highlight GARP’s expression and function in cancer and to evaluate its potential as a predictive and therapeutic follow-up biomarker that could be assessed, in real time, by molecular imaging.

Abstract

Glycoprotein-A repetitions predominant (GARP) is the docking receptor for latent transforming growth factor (LTGF-β) and promotes its activation. In cancer, increased GARP expression has been found in many types of cancer. GARP is expressed by regulatory T cells and platelets in the tumor microenvironment (TME) and can be also expressed by tumor cells themselves. Thus, GARP can be widely present in tumors in which it plays a major role in the production of active TGF-β, contributing to immune evasion and cancer progression via the GARP-TGF-β pathway. The objective of this review is to highlight GARP expression and function in cancer and to evaluate the potential of membrane GARP as a predictive and therapeutic follow-up biomarker that could be assessed, in real time, by molecular imaging. Moreover, as GARP can be secreted, a focus will also be made on soluble GARP as a circulating biomarker.

Development of an Easily Bioconjugatable Water-Soluble Single-Photon Emission-Computed Tomography/Optical Imaging Bimodal Imaging Probe Based on the aza-BODIPY Fluorophore

A water-soluble fluorescent aza-BODIPY platform (Wazaby) was prepared and functionalized by a polyazamacrocycle agent and a bioconjugable arm. The resulting fluorescent derivative was characterized and bioconjugated onto a trastuzumab monoclonal antibody as a vector. After bioconjugation, the imaging agent appeared to be stable in serum (>72 h at 37 °C) and specifically labeled HER-2-positive breast tumors slices. The bioconjugate was radiolabeled with [¹¹¹In] indium and studied in vivo. The developed monomolecular multimodal imaging probe (MOMIP) is water-soluble and chemically and photochemically stable, emits in the near infrared (NIR) region (734 nm in aqueous media), and displays a good quantum yield of fluorescence (around 15%). Single-photon emission-computed tomography and fluorescence imaging have been performed in nude mice bearing HER2-overexpressing HCC1954 human breast cancer xenografts and have evidenced the good tumor targeting of the [¹¹¹In] In bimodal agent. Finally, the proof of concept of using it as a new tool for fluorescence-guided surgery has been shown.

Positron Emission Tomography Imaging of Neurotensin Receptor-Positive Tumors with 68Ga-Labeled Antagonists: The Chelate Makes the Difference Again

Neurotensin receptor 1 (NTS₁) is involved in the development and progression of numerous cancers, which makes it an interesting target for the development of diagnostic and therapeutic agents. A small molecule NTS₁ antagonist, named [¹⁷⁷Lu]Lu-IPN01087, is currently evaluated in phase I/II clinical trials for the targeted therapy of neurotensin receptor-positive cancers. In this study, we synthesized seven compounds based on the structure of NTS₁ antagonists, bearing different chelating agents, and radiolabeled them with gallium-68 for PET imaging. These compounds were evaluated in vitro and in vivo in mice bearing a HT-29 xenograft. The compound [⁶⁸Ga]Ga-bisNODAGA-16 showed a promising biodistribution profile with mainly signal in tumor (4.917 ± 0.776%ID/g, 2 h post-injection). Its rapid clearance from healthy tissues led to high tumor-to-organ ratios, resulting in highly contrasted PET images. These results were confirmed on subcutaneous xenografts of AsPC-1 tumor cells, a model of NTS₁-positive human pancreatic adenocarcinoma.

Near-infrared emitting fluorescent homobimetallic gold(I) complexes displaying promising in vitro and in vivo therapeutic properties

Three near-infrared (NIR-I) optical theranostic systems were synthesized, characterized and studied in vitro and in vivo. These original homo-bimetallic gold(I)-based aza-BODIPY complexes proved to be trackable through near-infrared optical imaging in cells and in mice. They display anti-proliferative properties in micromolar range against human and murine cancer cell lines (4T1, MDA-MB-231, CT26, and SW480). Moreover, the injection of the most promising theranostic agent in CT26 tumor-bearing BALB/c mice induced a significant anti-cancer activity.

Nanofitins targeting heat shock protein 110: An innovative immunotherapeutic modality in cancer

The presence of an inactivating heat shock protein 110 (HSP110) mutation in colorectal cancers has been correlated with an excellent prognosis and with the ability of HSP110 to favor the formation of tolerogenic (M2-like) macrophages. These clinical and experimental results suggest a potentially powerful new strategy against colorectal cancer: the inhibition of HSP110. In this work, as an alternative to neutralizing antibodies, Nanofitins (scaffold ~7 kDa proteins) targeting HSP110 were isolated from the screening of a synthetic Nanofitin library, and their capacity to bind (immunoprecipitation, biolayer interferometry) and to inhibit HSP110 was analyzed in vitro and in vivo. Three Nanofitins were found to inhibit HSP110 chaperone activity. Interestingly, they share a high degree of homology in their variable domain and target the peptide-binding domain of HSP110. In vitro, they inhibited the ability of HSP110 to favor M2-like macrophages. The Nanofitin with the highest affinity, A-C2, was studied in the CT26 colorectal cancer mice model. Our PET/scan experiments demonstrate that A-C2 may be localized within the tumor area, in accordance with the reported HSP110 abundance in the tumor microenvironment. A-C2 treatment reduced tumor growth and was associated with an increase in immune cells infiltrating the tumor and particularly cytotoxic macrophages. These results were confirmed in a chicken chorioallantoic membrane tumor model. Finally, we showed the complementarity between A-C2 and an anti-PD-L1 strategy in the in vivo and in ovo tumor models. Overall, Nanofitins appear to be promising new immunotherapeutic lead compounds.

[18F]FMISO PET/CT imaging of hypoxia as a non-invasive biomarker of disease progression and therapy efficacy in a preclinical model of pulmonary fibrosis: comparison with the [18F]FDG PET/CT approach

Purpose

Idiopathic pulmonary fibrosis (IPF) is a progressive disease with poor outcome and limited therapeutic options. Imaging of IPF is limited to high-resolution computed tomography (HRCT) which is often not sufficient for a definite diagnosis and has a limited impact on therapeutic decision and patient management. Hypoxia of the lung is a significant feature of IPF but its role on disease progression remains elusive. Thus, the aim of our study was to evaluate hypoxia imaging with [¹⁸F]FMISO as a predictive biomarker of disease progression and therapy efficacy in preclinical models of lung fibrosis in comparison with [¹⁸F]FDG.

Methods

Eight-week-old C57/BL6 mice received an intratracheal administration of bleomycin (BLM) at day (D) 0 to initiate lung fibrosis. Mice received pirfenidone (300 mg/kg) or nintedanib (60 mg/kg) by daily gavage from D9 to D23. Mice underwent successive PET/CT imaging at several stages of the disease (baseline, D8/D9, D15/D16, D22/D23) with [¹⁸F]FDG and [¹⁸F]FMISO. Histological determination of the lung expression of HIF-1α and GLUT-1 was performed at D23.

Results

We demonstrate that mean lung density on CT as well as [¹⁸F]FDG and [¹⁸F]FMISO uptakes are upregulated in established lung fibrosis (1.4-, 2.6- and 3.2-fold increase respectively). At early stages, lung areas with [¹⁸F]FMISO uptake are still appearing normal on CT scans and correspond to areas which will deteriorate towards fibrotic lesions at later timepoints. Nintedanib and pirfenidone dramatically and rapidly decreased mean lung density on CT as well as [¹⁸F]FDG and [¹⁸F]FMISO lung uptakes (pirfenidone: 1.2-, 2.9- and 2.6-fold decrease; nintedanib: 1.2-, 2.3- and 2.5-fold decrease respectively). Early [¹⁸F]FMISO lung uptake was correlated with aggressive disease progression and better nintedanib efficacy.

Conclusion

[¹⁸F]FMISO PET imaging is a promising tool to early detect and monitor lung fibrosis progression and therapy efficacy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-021-05209-2.

The HSP GRP94 interacts with macrophage intracellular complement C3 and impacts M2 profile during ER stress

The role of GRP94, an endoplasmic reticulum (ER) stress protein with both pro- and anti-inflammatory functions, has not been investigated in macrophages during ER stress, whereas ER stress has been reported in many diseases involving macrophages. In this work, we studied GRP94 in M1/LPS + IFNγ and M2/IL-4 primary macrophages derived from human monocytes (isolated from buffy coats), in basal and ER stress conditions induced by thapsigargin (Tg), an inducer of ER calcium depletion and tunicamycin (Tm), an inhibitor of N-glycosylation. We found that GRP94 was expressed on the membrane of M2 but not M1 macrophages. In M2, Tg, but not Tm, while decreased GRP94 content in the membrane, it induced its secretion. This correlated with the induction of a pro-inflammatory profile, which was dependent on the UPR IRE1α arm activation and on a functional GRP94. As we previously reported that GRP94 associated with complement C3 at the extracellular level, we analyzed C3 and confirmed GRP94-C3 interaction in our experimental model. Further, Tg increased this interaction and, in these conditions, C3b and cathepsin L were detected in the extracellular medium where GRP94 co-immunoprecipitated with C3 and C3b. Finally, we showed that the C3b inactivated fragment, iC3b, only present on non-stressed M2, depended on functional GRP94, making both GRP94 and iC3b potential markers of M2 cells. In conclusion, our results show that GRP94 is co-secreted with C3 under ER stress conditions which may facilitate its cleavage by cathepsin L, thus contributing to the pro-inflammatory profile observed in stressed M2 macrophages.

Lipoproteins LDL versus HDL as nanocarriers to target either cancer cells or macrophages

In this work, we have explored natural unmodified low- and high-density lipoproteins (LDL and HDL, respectively) as selective delivery vectors in colorectal cancer therapy. We show in vitro in cultured cells and in vivo (NanoSPECT/CT) in the CT-26 mice colorectal cancer model that LDLs are mainly taken up by cancer cells, while HDLs are preferentially taken up by macrophages. We loaded LDLs with cisplatin and HDLs with the heat shock protein-70 inhibitor AC1LINNC, turning them into a pair of “Trojan horses” delivering drugs selectively to their target cells as demonstrated in vitro in human colorectal cancer cells and macrophages, and in vivo. Coupling of the drugs to lipoproteins and stability was assessed by mass spectometry and raman spectrometry analysis. Cisplatin vectorized in LDLs led to better tumor growth suppression with strongly reduced adverse effects such as renal or liver toxicity. AC1LINNC vectorized into HDLs induced a strong oxidative burst in macrophages and innate anticancer immune response. Cumulative antitumor effect was observed for both drug-loaded lipoproteins. Altogether, our data show that lipoproteins from patient blood can be used as natural nanocarriers allowing cell-specific targeting, paving the way toward more efficient, safer, and personalized use of chemotherapeutic and immunotherapeutic drugs in cancer.

Dual Cherenkov Radiation-Induced Near-Infrared Luminescence Imaging and Photodynamic Therapy toward Tumor Resection

Cherenkov radiation (CR), the blue light seen in nuclear reactors, is emitted by some radiopharmaceuticals. This study showed that (1) a portion of CR could be transferred in the region of the optical spectrum, where biological tissues are most transparent: as a result, upon radiance amplification in the near-infrared window, the detection of light could occur twice deeper in tissues than during classical Cherenkov luminescence imaging and (2) Cherenkov-photodynamic therapy (CR-PDT) on cells could be achieved under conditions mimicking unlimited depth using the CR-embarked light source, which is unlike standard PDT, where light penetration depth is limited in biological tissues. Both results are of utmost importance for simultaneous applications in tumor resection and post-resection treatment of remaining unresected margins, thanks to a molecular construct designed to raise its light collection efficiency (i.e., CR energy transfer) by conjugation with multiple CR-absorbing (water-soluble) antenna followed by intramolecular-FRET/TBET energy transfers.

Experimental evaluation of survival of Vibrio parahaemolyticus in fertilized cold-water sediment

AIMS

This experimental study focuses on survival and consistence of Vibrio parahaemolyticus in cold-water sediments and how increasing temperature and nutritional availability can affect growth.

METHODS AND RESULTS

A pathogenic strain of V. parahaemolyticus was inoculated in seawater microcosms containing bottom sediment. Gradually, during 14 days, the temperature was upregulated from 8 to 21°C. Culturable V. parahaemolyticus was only found in the sediment but declined over time and did not recover even after another 2 days at 37°C. Numbers of culturable bacteria matched the amount found by q-PCR indicating that they did not enter a dormant state, contrary to those in the water layer. After adding decaying phytoplankton as fertilizer to the microcosms of 8 and 21°C for 7 and 14 days, the culturability of the bacteria increased significantly in the sediments at both temperatures and durations of exposure.

CONCLUSION

The study showed that V. parahaemolyticus can stay viable in cold-water sediment and growth was stimulated by fertilizers rather than by temperature.

SIGNIFICANCE AND IMPACT OF THE STUDY

Vibrio parahaemolyticus is a common cause of seafood-borne gastroenteritis and is today recognized in connection to increasing ocean temperature. The results indicate that this pathogen should be considered a risk in well-fertilized environments, such as aquacultures, even during cold periods.

Cleaved Caspase-3 Transcriptionally Regulates Angiogenesis-Promoting Chemotherapy Resistance

Caspases are well known for their role in apoptosis. Recently, nonapoptotic roles of caspases have been identified, however, these noncanonical roles are not well documented and the mechanisms involved are not fully understood. Here, we studied the role of cleaved caspase-3 using human- and mouse-proficient caspase-3 cancer cell lines and human-deficient caspase-3 cancer cells. Cleaved caspase-3 functioned as a transcription factor and directly bound to DNA. A DNA-binding domain was identified in the small subunit of caspase-3 and an active conformation was essential for caspase-3 transcriptional activity. Caspase-3 DNA binding enhanced angiogenesis by upregulating the expression of proangiogenic genes and by activating pathways that promoted endothelial cell activation. Some proapoptotic genes were downregulated in caspase-3-proficient cells. Inhibiting caspase-3 increased the efficacy of chemotherapy and decreased spontaneous tumor development. These data highlight a novel nonapoptotic role of caspase-3 and suggest that cleaved caspase-3 could be a new therapeutic target in cancer. SIGNIFICANCE: These findings report a noncanonical function of caspase-3 by demonstrating its ability to transcriptionally regulate the VEGFR pathway.

Superparamagnetic Nanoparticle Delivery to the Cochlea Through Round Window by External Magnetic Field: Feasibility and Toxicity

Introduction. The objective of this study was to evaluate the feasibility and toxicity of superparamagnetic iron oxide nanoparticles (SPIONs) administered into the cochlea through the round window (RW) by an external magnetic field. Materials and Methods. In 5 Wistar rats, the left RW was punctured. SPIONs suspended in hyaluronic gel (5 mg/mL) were applied in the RW niche and covered by a muscle graft. The nanoparticles were mobilized using a rare earth magnet (0.54 T) held in 4 consecutive positions around the head. The right ear served as control. Hearing function was monitored by auditory brainstem responses (4-32 kHz tone bursts). Results. The auditory thresholds remained unchanged 1 month after the administration. The histological study of the cochleae showed that SPIONs were driven into the scala tympani in the basal turn, the second turn, and the apex. Conclusion. Superparamagnetic nanoparticles can be driven inside the cochlea toward the apex with a preserved hearing up to 1 month in rats.

Abstract 4082: Preclinical assessment of external or targeted radiotherapy in combination with immunotherapies and co-development of companion imaging diagnostic

Immunotherapies have proven to be highly efficient for cancer treatments and combination with either internal vectorized or external radiotherapies can enhance this efficacy through notably increasing tumor immune infiltrate. The clinical evaluation of such combination therapies requires expertise and exquisite processes in multiple fields, immunotherapy, radiotherapy and nuclear medicine. Similarly, this applies into preclinical settings for assessing proof of concept of novel combinations. Herein, we will present our preclinical evaluation process to combine external or internal (i.e. lutetium-177 radiolabeled molecule) radiotherapy with immunotherapies that include radiochemistry, target expression in tissue by autoradiography, in vitro binding evaluation, in vivo tolerance and activity based on single or fractionated treatment doses. The targeted radiotherapy (TRT) is a systemic target-based approach combining a high-affinity receptor-binding ligand radiolabeled with a high-energy beta-emitting radionuclide whereas external 3D image guided radiotherapy targets the shape of the tumors very precisely. Combination studies with immunotherapies in preclinical setting require the selection of appropriate and relevant syngenic or humanized mouse models, driven by target expression, radioresistance (i.e hypoxia), and tumor immune infiltrate (lymphocyte CD8, macrophage etc.). In addition, the therapeutic evaluation should take into consideration the tolerance related to ionizing radiations, the scheduling of treatment (cumulated dose, fractionation), antitumor immune response and monitoring of immune checkpoint target expression. As nuclear imaging is a powerful tool to monitor and predict in vivo target expression and treatment efficacy, TRT is systematically developed in parallel of a PET or SPECT companion diagnostic to visualize and quantify the target expression prior to the treatment with a therapeutic radiolabeled drug. It necessitates the development of radiolabeling processes for either therapeutic or diagnostic purposes and is then performed concomitantly using appropriate bioconjugation strategies suited for theranostic pairs of radionuclides .We will present our recent results that highlight the importance to optimize the external radiotherapy schedule to improve the efficacy and synergistic effect of the association radiotherapy/immunotherapy such as anti-PDL1. Similarly, it is of high interest to combine 177Lu-labeled molecule with immune checkpoint inhibitors in various solid tumors. Transversal skills are mandatory to perform such models and experiments, all being conducted in a dedicated facility for external 3D image guided radiotherapy (SARRP), radiochemistry (hot cells, 177Lu, 68Ga, 64Cu, 89Zr, 111In) and pharmaco-imaging (PET, SPECT, MRI, CT, and optical).

Citation Format: Olivier Raguin, Céline Mirjolet, Claire Bernhard, Peggy Provent, Bertrand Collin, Franck Denat, Fabrice Viviani, Alexandre Cochet, Cyril Berthet. Preclinical assessment of external or targeted radiotherapy in combination with immunotherapies and co-development of companion imaging diagnostic [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4082.

Modular Assembly of Multimodal Imaging Agents through an Inverse Electron Demand Diels-Alder Reaction

The combination of two imaging probes on the same biomolecule gives access to targeted bimodal imaging agents that can provide more accurate diagnosis, complementary information, or that may be used in different applications, such as nuclear imaging and fluorescence guided surgery. In this study, we demonstrate that dichlorotetrazine, a small, commercially available compound, can be used as a modular platform to easily assemble various imaging probes. Doubly labeled tetrazines can then be conjugated to a protein through a biorthogonal IEDDA reaction. A series of difunctionalized tetrazine compounds containing various chelating agents and fluorescent dyes was synthesized. As a proof of concept, one of these bimodal probes was conjugated to trastuzumab, previously modified with a constrained alkyne group, and the resulting dual-labeled antibody was evaluated in a mouse model, bearing a HER2-positive tumor. A significant uptake into tumor tissues was observed in vivo, by both SPECT-CT and fluorescence imaging, and confirmed ex vivo in biodistribution studies.

A Promising Family of Fluorescent Water-Soluble aza-BODIPY Dyes for in Vivo Molecular Imaging

A new family of water-soluble and bioconjugatable aza-BODIPY fluorophores was designed and synthesized using a boron- functionalization strategy. These dissymmetric bis-ammonium aza-BODIPY dyes present optimal properties for a fluorescent probe; i.e., they are highly water-soluble, very stable in physiological medium; they do not aggregate in PBS, possess high quantum yield; and finally, they can be easily bioconjugated to antibodies. Preliminary in vitro and in vivo studies were performed for one of these fluorophores to image PD-L1 (Programmed Death-Ligand 1), highlighting the high potential of these new probes for future in vivo optical imaging studies.

Functionalization of theranostic AGuIX® nanoparticles for PET/MRI/optical imaging

A novel trifunctional imaging probe containing a chelator of radiometal for PET, a NIR heptamethine cyanine dye, and a bioconjugatable handle, has been grafted onto AGuIX® nanoparticles via a Michael addition reaction. The resulting functionalized nanoparticles have been fully characterized, radiolabelled with ⁶⁴Cu, and evaluated in a mice TSA tumor model using multimodal (PET/MRI/optical) imaging.

The controlled dual functionalization of AGuIX® nanoparticles afforded trimodal imaging (PET/MRI/fluorescence) theranostic agents.

Cherenkov luminescence imaging is a fast and relevant preclinical tool to assess tumour hypoxia in vivo

PURPOSE

Molecular imaging techniques visualise biomarkers for both drug development and personalised medicine. In this field, Cherenkov luminescence imaging (CLI) seems to be very attractive by allowing imaging with clinical PET radiotracers with high-throughput capabilities. In this context, we developed a fast CLI method to detect tumour hypoxia with ¹⁸F-fluoromisonidazole (FMISO) for drug development purposes.

METHODS

Colon cancer model was induced in mice by subcutaneous injection of 1 × 10⁶ CT-26 cells. FMISO was injected, and simultaneous PET-blood oxygen level dependent (BOLD)-MRI followed by CLI were performed along with immunohistochemistry staining with pimonidazole.

RESULTS

There was a significant correlation between FMISO PET and CLI tumour uptakes, consistent with the BOLD-MRI mapping. Tumour-to-background ratio was significantly higher for CLI compared with PET and MRI. Immunohistochemistry confirmed tumour hypoxia. The imaging workflow with CLI was about eight times faster than the PET-MRI procedure.

CONCLUSION

CLI is a fast and relevant tool to assess tumour hypoxia. This approach could be particularly interesting for hypoxia-targeting drug development.

Radiolabeled F(ab')2-cetuximab for theranostic purposes in colorectal and skin tumor-bearing mice models

PURPOSE

This study aimed to investigate theranostic strategies in colorectal and skin cancer based on fragments of cetuximab, an anti-EGFR mAb, labeled with radionuclide with imaging and therapeutic properties, ¹¹¹In and ¹⁷⁷Lu, respectively.

METHODS

We designed F(ab')₂-fragments of cetuximab radiolabeled with ¹¹¹In and ¹⁷⁷Lu. ¹¹¹In-F(ab')₂-cetuximab tumor targeting and biodistribution were evaluated by SPECT in BalbC nude mice bearing primary colorectal tumors. The efficacy of ¹¹¹In-F(ab')₂-cetuximab to assess therapy efficacy was performed on BalbC nude mice bearing colorectal tumors receiving 17-DMAG, an HSP90 inhibitor. Therapeutic efficacy of the radioimmunotherapy based on ¹⁷⁷Lu-F(ab')₂-cetuximab was evaluated in SWISS nude mice bearing A431 tumors.

RESULTS

Radiolabeling procedure did not change F(ab')₂-cetuximab and cetuximab immunoreactivity nor affinity for HER1 in vitro. ¹¹¹In-DOTAGA-F(ab')₂-cetuximab exhibited a peak tumor uptake at 24 h post-injection and showed a high tumor specificity determined by a significant decrease in tumor uptake after the addition of an excess of unlabeled-DOTAGA-F(ab')₂-cetuximab. SPECT imaging of ¹¹¹In-DOTAGA-F(ab')₂-cetuximab allowed an accurate evaluation of tumor growth and successfully predicted the decrease in tumor growth induced by 17-DMAG. Finally, ¹⁷⁷Lu-DOTAGA-F(ab')₂-cetuximab radioimmunotherapy showed a significant reduction of tumor growth at 4 and 8 MBq doses.

CONCLUSIONS

¹¹¹In-DOTAGA-F(ab')₂-cetuximab is a reliable and stable tool for specific in vivo tumor targeting and is suitable for therapy efficacy assessment. ¹⁷⁷Lu-DOTAGA-F(ab')₂-cetuximab is an interesting theranostic tool allowing therapy and imaging.

Abstract P5-01-03: HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer

Introduction: HER2 is positive in approximately 20-30% of all breast cancer and is associated with poor prognosis, higher mortality and higher metastatic incidence. Current diagnosis of HER2 expression relies on invasive methods requiring tissue biopsy which can lead to variable results due to inter/intra-metastatic and intratumoral heterogeneity in breast cancers. It has been recently demonstrated that HER2 molecular imaging based on pertuzumab, an antibody targeting HER2, could represent a more accurate non-invasive method to assess HER2 expression and evaluate its spatial and temporal heterogeneity. Aim: In the present study, we aimed at developing radiolabeled pertuzumab Fab fragments for HER2 imaging. Tumor uptake of radiolabeled Fab was evaluated in an animal model of HER2 breast cancer by SPECT-CT, and the impact of trastuzumab on HER2 imaging was assessed. The objective of this study was to validate the feasibility of HER2 imaging with a pertuzumab-derived probe and to evaluate the possible translation of such a probe for clinical use in patients treated or not with anti-HER2 therapy. Methods: Fab fragments of pertuzumab have been generated by papain digestion and bioconjugated with the bifunctional chelating agent DOTAGA for incorporation of Indium 111 to generate an HER2-specific probe for SPECT (111In-DOTAGA-pertuzumab-Fab). The functionality of both radiolabeled Fab and whole pertuzumab was evaluated by in vitro assays using HER2-overexpressing human breast cancer cell line (HCC1954). Tumor uptake of pertuzumab-Fab and whole pertuzumab (111In-DOTAGA-Pertuzumab) has been evaluated in Balb/c nude mice bearing BT-474 tumors with or without pre-treatment with trastuzumab for 24h. Results: In the current study we demonstrate that Fab fragments of pertuzumab keep similar HER2 binding properties than whole pertuzumab and can therefore be a suitable HER2-targeted probe. In vivo, 111In-DOTAGA-pertuzumab-Fab showed better pharmacokinetics than whole pertuzumab with faster tumor uptake and blood clearance allowing faster imaging with better tumor/blood ratio. In addition, tumor uptake of 111In-DOTAGA-pertuzumab-Fab is not modified by pre-treatment with trastuzumab. Conclusion: We assume that radiolabeled pertuzumab-Fab should be of great interest if the intention to treat is based on anti-HER2 monoclonal antibodies-based therapies rather than small molecules (e.g. lapatinib). Interestingly, pertuzumab has been shown to be also beneficial in combination with trastuzumab and chemotherapy in non-metastatic patients through its approval for the neoadjuvant treatment and very recently in the APHINITY clinical trial aiming for an approval in the adjuvant treatment of early breast cancer. These data suggest that pertuzumab will be extensively used in various HER-2 positive breast cancers underlining the interest to perform molecular imaging of HER2 expression as a predictive biomarker of efficacy.

Citation Format: Oudot A, Bellaye P-S, Vrigneaud J-M, Raguin O, Bernhard C, Dumont L, Brunotte F, Savina A, Bouquet F, Fumoleau P, Collin B. HER2 imaging by SPECT-CT using 111In radiolabeled pertuzumab-fab DOTAGA-conjugate: A proof of concept study in a preclinical model of breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-01-03.

Docetaxel-titanate nanotubes enhance radiosensitivity in an androgen-independent prostate cancer model

Around 40% of high-risk prostate cancer patients who undergo radiotherapy (RT) will experience biochemical failure. Chemotherapy, such as docetaxel (DTX), can enhance the efficacy of RT. Multidrug resistance mechanisms often limit drug efficacy by decreasing intracellular concentrations of drugs in tumor cells. It is, therefore, of interest to develop nanocarriers of DTX to maintain the drug inside cancer cells and thus improve treatment efficacy. The purpose of this study was to investigate the use of titanate nanotubes (TiONts) to develop a TiONts-DTX nanocarrier and to evaluate its radiosensitizing in vivo efficacy in a prostate cancer model. In vitro cytotoxic activity of TiONts-DTX was evaluated using an MTS assay. The biodistribution of TiONts-DTX was analyzed in vivo by single-photon emission computed tomography. The benefit of TiONts-DTX associated with RT was evaluated in vivo. Eight groups with seven mice in each were used to evaluate the efficacy of the nanohybrid combined with RT: control with buffer IT injection ± RT, free DXL ± RT, TiONts ± RT and TiONts-DXL ± RT. Mouse behavior, health status and tumor volume were monitored twice a week until the tumor volume reached a maximum of 2,000 mm³. More than 70% of nanohybrids were localized inside the tumor 96 h after administration. Tumor growth was significantly slowed by TiONts-DTX associated with RT, compared with free DTX in the same conditions (P=0.013). These results suggest that TiONts-DTX improved RT efficacy and might enhance local control in high-risk localized prostate cancer.

Redshifted Cherenkov Radiation for in vivo Imaging: Coupling Cherenkov Radiation Energy Transfer to multiple Förster Resonance Energy Transfers

Cherenkov Radiation (CR), this blue glow seen in nuclear reactors, is an optical light originating from energetic β-emitter radionuclides. CR emitter ⁹⁰Y triggers a cascade of energy transfers in the presence of a mixed population of fluorophores (which each other match their respective absorption and emission maxima): Cherenkov Radiation Energy Transfer (CRET) first, followed by multiple Förster Resonance Energy transfers (FRET): CRET ratios were calculated to give a rough estimate of the transfer efficiency. While CR is blue-weighted (300–500 nm), such cascades of Energy Transfers allowed to get a) fluorescence emission up to 710 nm, which is beyond the main CR window and within the near-infrared (NIR) window where biological tissues are most transparent, b) to amplify this emission and boost the radiance on that window: EMT6-tumor bearing mice injected with both a radionuclide and a mixture of fluorophores having a good spectral overlap, were shown to have nearly a two-fold radiance boost (measured on a NIR window centered on the emission wavelength of the last fluorophore in the Energy Transfer cascade) compared to a tumor injected with the radionuclide only. Some CR embarked light source could be converted into a near-infrared radiation, where biological tissues are most transparent.

MANOTA: a promising bifunctional chelating agent for copper-64 immunoPET

A comparison of four bifunctional chelating agents showed superior behaviour of a new NOTA derivative for ⁶⁴Cu labelling of antibody fragments.

Near-Infrared-Emitting BODIPY-trisDOTA(111) In as a Monomolecular Multifunctional Imaging Probe: From Synthesis to In Vivo Investigations

A new generation of monomolecular imaging probes (MOMIP) based on a distyryl-BODIPY (BODIPY=boron-dipyrromethene) coupled with three DOTA macrocycles has been prepared (DOTA=1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). The MOMIP presents good fluorescence properties and is very stable in serum. The bimodal probe was conjugated to trastuzumab, and an optical in vivo study showed high accumulation of the imaging agent at the tumor site. (111) In radiometallation of the bioconjugate was performed in high radiochemical yield, highlighting the potential of this new BODIPY-chelators derivative as a bimodal imaging probe.

Minor changes in the macrocyclic ligands but major consequences on the efficiency of gold nanoparticles designed for radiosensitization

Many studies have been devoted to adapting the design of gold nanoparticles to efficiently exploit their promising capability to enhance the effects of radiotherapy. In particular, the addition of magnetic resonance imaging modality constitutes an attractive strategy for enhancing the selectivity of radiotherapy since it allows the determination of the most suited delay between the injection of nanoparticles and irradiation. This requires the functionalization of the gold core by an organic shell composed of thiolated gadolinium chelates. The risk of nephrogenic systemic fibrosis induced by the release of gadolinium ions should encourage the use of macrocyclic chelators which form highly stable and inert complexes with gadolinium ions. In this context, three types of gold nanoparticles (Au@DTDOTA, Au@TADOTA and Au@TADOTAGA) combining MRI, nuclear imaging and radiosensitization have been developed with different macrocyclic ligands anchored onto the gold cores. Despite similarities in size and organic shell composition, the distribution of gadolinium chelate-coated gold nanoparticles (Au@TADOTA-Gd and Au@TADOTAGA-Gd) in the tumor zone is clearly different. As a result, the intravenous injection of Au@TADOTAGA-Gd prior to the irradiation of 9L gliosarcoma bearing rats leads to the highest increase in lifespan whereas the radiophysical effects of Au@TADOTAGA-Gd and Au@TADOTA-Gd are very similar.