3D Coculture between Cancer Cells and Macrophages: From Conception to Experimentation

A tumor is a complex cluster with many types of cells in the microenvironment that help it grow. Macrophages, immune cells whose main role is to maintain body homeostasis, represent in the majority of cancers the most important cell population. In this context, they are called tumor-associated macrophages (TAMs) because of their phenotype, which contributes to tumor growth. In order to limit the use of animals, there is a real demand for the creation of in vitro models able to represent more specifically the complexity of the tumor microenvironment (TME) in order to characterize it and evaluate new treatments. However, the two-dimensional (2D) culture, which has been used for a long time, has shown many limitations, especially in terms of tumor representation. The three-dimensional (3D) models, developed over the last 20 years, have made it possible to get closer to what happens in vivo in terms of phenotypic and functional characteristics. Due to their architectural similarity to in vivo tissues, they provide a more physiologically relevant in vitro system. Most recently, it is the development of 3D coculture models in which two or three cell lines are cultured together that has allowed a better representation of TME with cell-cell interactions. Unfortunately, there is no clear direction for the design of these models at this time. In this Review on the coculture between cancer cells and TAMs, an in-depth analysis is performed to answer multiple questions on the conception of these models: Which models to use, and with which material and cancer lineage? Which monocyte or macrophage lines should be added to the coculture? And how can these models be exploited?

Homologation of the Alkyl Side Chain of Antimitotic Phenyl 4-(2-Oxo-3-alkylimidazolidin-1-yl)benzenesulfonate Prodrugs Selectively Targeting CYP1A1-Expressing Breast Cancers Improves Their Stability in Rodent Liver Microsomes

Phenyl 4-(2-oxo-3-alkylimidazolidin-1-yl)benzenesulfonates (PAIB-SOs) are a new family of antimitotic prodrugs bioactivated in breast cancer cells expressing CYP1A1. In this study, we report that the ¹⁴C-labeled prototypical PAIB-SO [¹⁴C]CEU-818 and its antimitotic counterpart [¹⁴C]CEU-602 are distributed in whole mouse body and they show a short half-life in mice. To circumvent this limitation, we evaluated the effect of the homologation of the alkyl side chain of the imidazolidin-2-one moiety of PAIB-SOs. Our studies evidence that PAIB-SOs bearing an n-pentyl side chain exhibit antiproliferative activity in the nanomolar-to-low-micromolar range and a high selectivity toward CYP1A1-positive breast cancer cells. Moreover, the most potent n-pentyl PAIB-SOs were significantly more stable toward rodent liver microsomes. In addition, PAIB-SOs 10 and 14 show significant antitumor activity and low toxicity in chorioallantoic membrane (CAM) assay. Our study confirms that homologation is a suitable approach to improve the rodent hepatic stability of PAIB-SOs.

Synthesis and In Vitro Comparison of DOTA, NODAGA and 15-5 Macrocycles as Chelators for the 64Cu-Labelling of Immunoconjugates

The development of ⁶⁴Cu-based immuno-PET radiotracers requires the use of copper-specific bifunctional chelators (BFCs) that contain functional groups allowing both convenient bioconjugation and stable copper complexes to limit in vivo bioreduction, transmetallation and/or transchelation. The excellent in vivo kinetic inertness of the pentaazamacrocyclic [⁶⁴Cu]Cu-15-5 complex prompted us to investigate its potential for the ⁶⁴Cu-labelling of monoclonal antibodies (mAbs), compared with the well-known NODAGA and DOTA chelators. To this end, three NODAGA, DOTA and 15-5-derived BFCs, containing a pendant azadibenzocyclooctyne moiety, were synthesised and a robust methodology was determined to form covalent bonds between them and azide-functionalised trastuzumab, an anti-HER2 mAb, using strain-promoted azide-alkyne cycloaddition. Unlike the DOTA derivative, the NODAGA- and 15-5-mAb conjugates were radiolabelled with ⁶⁴Cu, obtaining excellent radiochemical yields, under mild conditions. Although all the radioimmunoconjugates showed excellent stability in PBS or mouse serum, [⁶⁴Cu]Cu-15-5- and [⁶⁴Cu]Cu-NODAGA-trastuzumab presented higher resistance to transchelation when challenged by EDTA. Finally, the immunoreactive fraction of the radioimmunoconjugates (88-94%) was determined in HER-2 positive BT474 human breast cancer cells, confirming that the bioconjugation and radiolabelling processes implemented had no significant impact on antigen recognition.

Assessment of 99mTc-NTP 15-5 uptake on cartilage, a new proteoglycan tracer: Study protocol for a phase I trial (CARSPECT)

Background

^99mTc-NTP 15-5 is a SPECT radiotracer targeting proteoglycans (PG), components of the cartilaginous extracellular matrix. Imaging of PGs would be useful for the early detection of cartilage disorders (osteoarthritis, arthritis and chondrosarcoma, Aromatase Inhibitor associated arthralgia (AIA) in breast cancer), and the follow-up of patients under treatment. According to preclinical study results, ^99mTc-NTP 15-5, is a good candidate for a specific functional molecular imaging of joints. We intend to initiate a first in-human study to confirm and quantify ^99mTc-NTP 15-5 uptake in healthy joints.

Methods

As the clinical development of this radiotracer would be oriented toward the functional imaging of joint pathologies, we have chosen to include patients with healthy joints (unilateral osteoarthritis of the knee or breast cancer with indication of AI treatment). This phase I study will be an open-label, multicenter, dose-escalation trial of a radiopharmaceutical orientation to determine the recommended level of activity of ^99mTc-NTP 15-5 to obtain the best joint tracer contrasts on images, without dose limiting toxicity (DLT). The secondary objectives will include the study of the pharmacology, biodistribution (using planar whole body and SPECT-CT acquisitions), toxicity, and dosimetry of this radiotracer. The dose escalation with 3 activity levels (5, 10, and 15 MBq/kg), will be conditioned by the absence at the previous level of DLT and of a visualized tracer accumulation on more than 80% of healthy joints as observed on scintigraphy performed at ≤ 2 h post-injection.

Discussion

This first in-human phase I trial will be proof-of-concept of the relevance of ^99mTc-NTP 15-5 as a cartilage tracer, with the determination of the optimal methodology (dose and acquisition time) to obtain the best contrast to provide a functional image of joints with SPECT-CT.

Trial registration number

Clinicaltrials.gov: NCT04481230. Identifier in French National Agency for the Safety of Medicines and Health Products (ANSM): N°EudraCT 2020-000495-37.

Antibody-induced pain-like behavior and bone erosion: links to subclinical inflammation, osteoclast activity, and acid-sensing ion channel 3-dependent sensitization

ABSTRACT

Several bone conditions, eg, bone cancer, osteoporosis, and rheumatoid arthritis (RA), are associated with a risk of developing persistent pain. Increased osteoclast activity is often the hallmark of these bony pathologies and not only leads to bone remodeling but is also a source of pronociceptive factors that sensitize the bone-innervating nociceptors. Although historically bone loss in RA has been believed to be a consequence of inflammation, both bone erosion and pain can occur years before the symptom onset. Here, we have addressed the disconnection between inflammation, pain, and bone erosion by using a combination of 2 monoclonal antibodies isolated from B cells of patients with RA. We have found that mice injected with B02/B09 monoclonal antibodies (mAbs) developed a long-lasting mechanical hypersensitivity that was accompanied by bone erosion in the absence of joint edema or synovitis. Intriguingly, we have noted a lack of analgesic effect of naproxen and a moderate elevation of few inflammatory factors in the ankle joints suggesting that B02/B09-induced pain-like behavior does not depend on inflammatory processes. By contrast, we found that inhibiting osteoclast activity and acid-sensing ion channel 3 signaling prevented the development of B02/B09-mediated mechanical hypersensitivity. Moreover, we have identified secretory phospholipase A2 and lysophosphatidylcholine 16:0 as critical components of B02/B09-induced pain-like behavior and shown that treatment with a secretory phospholipase A2 inhibitor reversed B02/B09-induced mechanical hypersensitivity and bone erosion. Taken together, our study suggests a potential link between bone erosion and pain in a state of subclinical inflammation and offers a step forward in understanding the mechanisms of bone pain in diseases such as RA.

Phase I study of [131I] ICF01012, a targeted radionuclide therapy, in metastatic melanoma: MELRIV-1 protocol

Background

Benzamide-based radioligands targeting melanin were first developed for imaging melanoma and then for therapeutic purpose with targeted radionuclide therapy (TRT).

[¹³¹I]ICF01012 presents a highly favorable pharmacokinetics profile in vivo for therapy. Tumour growth reduction and increase survival have been established in preclinical models of melanoma. According the these preclinical results, we initiate a first-in-human study aimed to determine the recommended dose of [¹³¹I]ICF01012 to administer for the treatment of patients with pigmented metastatic melanoma.

Methods

The MELRIV-1 trial is an open-label, multicentric, dose-escalation phase I trial. The study is divided in 2 steps, a selection part with an IV injection of low activity of [¹³¹I]ICF01012 (185 MBq at D0) to select patients who might benefit from [¹³¹I]ICF01012 TRT in therapeutic part, i.e. patient presenting at least one tumour lesion with [¹³¹I]ICF01012 uptake and an acceptable personalized dosimetry to critical organs (liver, kidney, lung and retina). According to dose escalation scheme driven by a Continual Reassessment Method (CRM) design, a single therapeutic injection of 800 MBq/m², or 1600 MBq/m², or 2700 MBq/m² or 4000 MBq/m² of [¹³¹I]ICF01012 will be administered at D11 (± 4 days). The primary endpoint is the recommended therapeutic dose of [¹³¹I]ICF01012, with DLT defined as any grade 3-4 NCI-CT toxicity during the 6 weeks following therapeutic dose. Safety, pharmacokinetic, biodistribution (using planar whole body and SPECT-CT acquisitions), sensitivity / specificity of [¹³¹I]ICF01012, and therapeutic efficacy will be assessed as secondary objectives. Patients who received therapeutic injection will be followed until 3 months after TRT. Since 6 to 18 patients are needed for the therapeutic part, up to 36 patients will be enrolled in the selection part.

Discussion

This study is a first-in-human trial evaluating the [¹³¹I]ICF01012 TRT in metastatic malignant melanomas with a diagnostic dose of the [¹³¹I]ICF01012 to select the patients who may benefit from a therapeutic dose of [¹³¹I]ICF01012, with at least one tumor lesion with [¹³¹I]ICF01012 uptake and an acceptable AD to healthy organ.

Trial registration

Clinicaltrials.gov: NCT03784625. Registered on December 24, 2018.

Identifier in French National Agency for the Safety of Medicines and Health Products (ANSM): N°EudraCT 2016-002444-17.

Multicellular tumor spheroids of LNCaP-Luc prostate cancer cells as in vitro screening models for cytotoxic drugs

An increasing number of studies concerning solid cancers, including prostate cancer, are tending to demonstrate the predominant role of the interactions of tumor cells with their microenvironment, and underlining the relevance of therapeutic approaches co-targeting these two components. Artificial in vitro 3D culture models, such as spheroids, are therefore being designed to allow intercellular interactions between tumor cells and the matrix, under hypoxic conditions mimicking a microtumor. This project aims to develop and characterize a multicellular tumor spheroid (MCTS) model of human prostate cancer cells expressing PSMA, for in vitro drug screening. To this end, 1,000 cells/well were seeded in 100 µl of culture medium with 0.5% of methylcellulose in 96-well, non-adherent, V-shaped bottom plates. Bioluminescent imaging of the spheroids enabled the measurement of spheroid growth. From Day 7 of growth, immunofluorescence studies showed cellular proliferation (Ki-67), mainly located in the periphery of the spheroid section, associated with the formation of an apoptotic core (TUNEL). Scanning electron microscopy and fluorescent imaging (Lox-1 probe) showed the presence of an extracellular matrix and the installation of an oxygen gradient leading to the formation of a hypoxic area during growth. This hypoxia was correlated with increased VEGF excretion. Drug sensitivity was assessed on 2D and 3D cultures. The LNCaP-Luc spheroids are more resistant to docetaxel and TH-302, a hypoxia-activated prodrug, compared with cells grown in a monolayer. For docetaxel, this resistance increased with the spheroid growth stage, whereas the activity of TH-302 was potentiated by the hypoxic environment. In conclusion, the development of LNCaP-Luc cell MCTS provides a simple model mimicking a microtumor; it appears to be particularly well-suited to the validation of new therapeutic approaches targeting proliferation and the microenvironment.

A Convenient Route to New (Radio)Fluorinated and (Radio)Iodinated Cyclic Tyrosine Analogs

The use of radiolabeled non-natural amino acids can provide high contrast SPECT/PET metabolic imaging of solid tumors. Among them, radiohalogenated tyrosine analogs (i.e., [¹²³I]IMT, [¹⁸F]FET, [¹⁸F]FDOPA, [¹²³I]8-iodo-L-TIC(OH), etc.) are of particular interest. While radioiodinated derivatives, such as [¹²³I]IMT, are easily available via electrophilic aromatic substitutions, the production of radiofluorinated aryl tyrosine analogs was a long-standing challenge for radiochemists before the development of innovative radiofluorination processes using arylboronate, arylstannane or iodoniums salts as precursors. Surprisingly, despite these methodological advances, no radiofluorinated analogs have been reported for [¹²³I]8-iodo-L-TIC(OH), a very promising radiotracer for SPECT imaging of prostatic tumors. This work describes a convenient synthetic pathway to obtain new radioiodinated and radiofluorinated derivatives of TIC(OH), as well as their non-radiolabeled counterparts. Using organotin compounds as key intermediates, [¹²⁵I]5-iodo-L-TIC(OH), [¹²⁵I]6-iodo-L-TIC(OH) and [¹²⁵I]8-iodo-L-TIC(OH) were efficiently prepared with good radiochemical yield (RCY, 51–78%), high radiochemical purity (RCP, >98%), molar activity (Am, >1.5–2.9 GBq/µmol) and enantiomeric excess (e.e. >99%). The corresponding [¹⁸F]fluoro-L-TIC(OH) derivatives were also successfully obtained by radiofluorination of the organotin precursors in the presence of tetrakis(pyridine)copper(II) triflate and nucleophilic [¹⁸F]F⁻ with 19–28% RCY d.c., high RCP (>98.9%), Am (20–107 GBq/µmol) and e.e. (>99%).

Synthesis and in vitro preliminary evaluation of prostate-specific membrane antigen targeted upconversion nanoparticles as a first step towards radio/fluorescence-guided surgery of prostate cancer

Over the last decade, upconversion nanoparticles (UCNP) have been widely investigated in nanomedicine due to their high potential as imaging agents in the near-infrared (NIR) optical window of biological tissues. Here, we successfully develop active targeted UCNP as potential probes for dual NIR-NIR fluorescence and radioactive-guided surgery of prostate-specific membrane antigen (PSMA)(+) prostate cancers. We designed a one-pot thermolysis synthesis method to obtain oleic acid-coated spherical NaYF4:Yb,Tm@NaYF4 core/shell UCNP with narrow particle size distribution (30.0 ± 0.1 nm, as estimated by SAXS analysis) and efficient upconversion luminescence. Polyethylene glycol (PEG) ligands bearing different anchoring groups (phosphate, bis- and tetra-phosphonate-based) were synthesized and used to hydrophilize the UCNP. DLS studies led to the selection of a tetra-phosphonate PEG(2000) ligand affording water-dispersible UCNP with sustained colloidal stability in several aqueous media. PSMA-targeting ligands (i.e., glutamate-urea-lysine derivatives called KuEs) and fluorescent or radiolabelled prosthetic groups were grafted onto the UCNP surface by strain-promoted azide-alkyne cycloaddition (SPAAC). These UCNP, coated with 10 or 100% surface density of KuE ligands, did not induce cytotoxicity over 24 h incubation in LNCaP-Luc or PC3-Luc prostate cancer cell lines or in human fibroblasts for any of the concentrations evaluated. Competitive binding assays and flow cytometry demonstrated the excellent affinity of UCNP@KuE for PSMA-positive LNCaP-Luc cells compared with non-targeted UCNP@CO2H. Furthermore, the binding of UCNP@KuE to prostate tumour cells was positively correlated with the surface density of PSMA-targeting ligands and maintained after 125I-radiolabelling. Finally, a preliminary biodistribution study in LNCaP-Luc-bearing mice demonstrated the radiochemical stability of non-targeted [125I]UCNP paving the way for future in vivo assessments.

Simultaneous proteoglycans and hypoxia mapping of chondrosarcoma environment by frequency selective CEST MRI

PURPOSE

To evaluate the relevance of CEST frequency selectivity in simultaneous in vivo imaging of both of chondrosarcoma's phenotypic features, that are, its high proteoglycan concentration and its hypoxic core.

METHODS

Swarm rat chondrosarcomas were implanted subcutaneously in NMRI nude mice. When tumors were measurable (12-16 days postoperative), mice were submitted to GAG, guanidyl, and APT CEST imaging. Proteoglycans and hypoxia were assessed in parallel by nuclear imaging exploiting ^99m Tc-NTP 15-5 and ¹⁸ F-FMISO, respectively. Data were completed by ex vivo analysis of proteoglycans (histology and biochemical assay) and hypoxia (immunofluorescence).

RESULTS

Quantitative analysis of GAG CEST evidenced a significantly higher signal for tumor tissues than for muscles. These results were in agreement with nuclear imaging and ex vivo data. For imaging tumoral pH in vivo, the CEST ratio of APT/guanidyl was studied. This highlighted an important heterogeneity inside the tumor. The hypoxic status was confirmed by ¹⁸ F-FMISO PET imaging and ex vivo immunofluorescence.

CONCLUSION

CEST MRI simultaneously imaged both chondrosarcoma properties during a single experimental run and without the injection of any contrast agent. Both MR and nuclear imaging as well as ex vivo data were in agreement and showed that this chondrosarcoma animal model was rich in proteoglycans. However, even if tumors were lightly hypoxic at the stage studied, acidic areas were highlighted and mapped inside the tumor.

Internal dosimetry of [99m Tc]NTP15-5 radiotracer for cartilage imaging in preclinical and clinical models using the GATE Monte Carlo platform

PURPOSE

This study aims to perform dosimetry for [^99m Tc]NTP15-5 radiotracer used in imaging of articular cartilage in rabbits and humans. The radiotracer (covered by a world patent WO 01/00621 A1) has been proposed in the previous years for the study of cartilage in osteoarthritis diseases. A sensitive imaging approach is essential to quantify osteoarthritis progression and monitor response to new therapies. [^99m Tc]NTP15-5 binds to cartilage proteoglycans whose decreased content is associated to a loss of biomedical function of cartilage. We have implemented the whole dosimetry study concerning this new radiotracer for rabbits and humans using the GATE Monte Carlo platform.

MATERIALS AND METHODS

Absorbed doses to critical organs are determined using the MIRD formalism. Biodistribution data are obtained by organ sampling, measuring the activity in organs for three rabbits sacrificed at various times postadministration, and by SPECT/CT imaging at different times after injection. Most important sources are cartilages (in knees and intervertebral discs), due to localization together with the liver and kidneys due to excretion of the agent. S-values are calculated from rabbit's CT scan and human CT scan using the GATE v8.0 Monte Carlo platform. Cumulated activity in humans is extrapolated from animals using the %kg-dose/g method. Particular attention is given to dose calculation in bones, bone marrow and organs at risk.

RESULTS

The dosimetry performed in rabbits shows highest absorbed doses for liver and kidneys with respectively 22.5 and 43.8 µGy per MBq of injected activity. In humans, we found absorbed doses for a maximum injected activity of 15 MBq/kg, that is, 1050 MBq for an adult of 70 kgs of 9.03 mGy for kidneys and 4.16 mGy for knee cartilages. Effective dose is 2.69 µSv/MBq.

CONCLUSIONS

The dosimetry profile of [^99m Tc]NTP15-5 in the context of preclinical trials is of major importance in order to make sure that organs at risk are not overexposed. GATE provides all the capability needed to calculate dose profiles for internal dosimetry. The extrapolation of the dose for a human model is a first step towards clinical trials.

Optimization of IEDDA bioorthogonal system: Efficient process to improve trans-cyclooctene/tetrazine interaction

The antibody pretargeting approach for radioimmunotherapy (RIT) using inverse electron demand Diels-Alder cycloaddition (IEDDA) constitutes an emerging theranostic approach for solid cancers. However, IEDDA pretargeting has not reached clinical trial. The major limitation of the IEDDA strategy depends largely on trans-cyclooctene (TCO) stability. Indeed, TCO may isomerize into the more stable but unreactive cis-cyclooctene (CCO), leading to a drastic decrease of IEDDA efficiency. We have thus developed both efficient and reproducible synthetic pathways and analytical follow up for (PEGylated) TCO derivatives, providing high TCO isomeric purity for antibody modification. We have set up an original process to limit the isomerization of TCO to CCO before the mAbs' functionalization to allow high TCO/tetrazine cycloaddition.

Design, synthesis and evaluation of targeted hypoxia-activated prodrugs applied to chondrosarcoma chemotherapy

The tumor microenvironment in chondrosarcoma (CHS), a chemo- and radio-resistant cancer provides unique hallmarks for developing a chondrosarcoma targeted drug-delivery system. Tumor targeting could be achieved using a quaternary ammonium function (QA) as a ligand for aggrecan, the main high negative charged proteoglycan of the extracellular matrix of CHS, and a 2-nitroimidazole as trigger that enables hypoxia-responsive drug release. In a previous work, ICF05016 was identified as efficient proteoglycan-targeting hypoxia-activated prodrug in a human extraskeletal myxoid chondrosarcoma model in mice and a first study of the structure-activity relationship of the QA function and the alkyl linker length was conducted. Here, we report the second part of the study, namely the modification of the nitro-aromatic trigger and the position of the proteoglycan-targeting ligand at the aromatic ring as well as the nature of the alkylating mustard. Synthetic approaches have been established to functionalize the 2-nitroimidazole ring at the N-1 and C-4 positions with a terminal tertiary alkyl amine, and to perform the phosphorylation step namely through the use of an amine borane complex, leading to phosphoramide and isophosphoramide mustards and also to a phosphoramide mustard bearing four 2-chloroethyl chains. In a preliminary study using a reductive chemical activation, QA-conjugates, except the 4-nitrobenzyl one, were showed to undergo efficient cleavage with release of the corresponding mustard. However N,N,N-trimethylpropylaminium tethered to the N-1 or C-4 positions of the imidazole seemed to hamper the enzymatic reduction of the prodrugs and all tested compounds featured moderate selectivity toward hypoxic cells, likely not sufficient for application as hypoxia-activated prodrugs.

[18F]ML-10 PET imaging fails to assess early response to neoadjuvant chemotherapy in a preclinical model of triple negative breast cancer

PURPOSE

Pathological complete response to the neoadjuvant therapy (NAT) for triple negative breast cancer (TNBC) is predictive of prolonged patient survival. Methods for early evaluation of NAT efficiency are still needed, in order to rapidly adjust the therapeutic strategy in case of initial non-response. One option for this is molecular imaging of apoptosis induced by chemotherapy. Therefore, we investigated the capacity of [18F]ML-10 PET imaging, an apoptosis radiotracer, to detect tumor cell apoptosis and early predict the therapeutic response of human TNBC.

RESULTS

Initially, the induction of apoptosis by different therapies was quantified. We confirmed, in vitro, that paclitaxel or epirubicin, the fundamental cytotoxic drugs for breast cancer, induce apoptosis in TNBC cell lines. Exposure of TNBC models MDA-MB-231 and MDA-MB-468 to these drugs induced a significant increase (p < 0.01) of the apoptotic hallmarks: DNA fragmentation, membrane phospholipid scrambling, and PARP activation. Secondarily, apoptotic fraction was compared to the intracellular accumulation of the radiotracer. [18F]ML-10 accumulated in the apoptotic cells after 72 h of treatment by paclitaxel in vitro; this accumulation positively correlated with the apoptotic fraction. In vivo, [18F]ML-10 was rapidly cleared from the nontarget organs and mainly eliminated by the kidneys. Comparison of the in vivo [18F]FDG, [18F]FMISO, and [18F]ML-10 uptakes revealed that the tumor accumulation of [18F]ML-10 was directly related to the tumor hypoxia level. Finally, after the in vivo treatment of TNBC murine xenografts by paclitaxel, apoptosis was well induced, as demonstrated by the cleaved caspase-3 levels; however, no significant increase of [18F]ML-10 accumulation in the tumors was observed, either on day 3 or day 6 after the end of the treatment.

CONCLUSIONS

These results highlighted that PET imaging using [18F]ML-10 allows the visualization of apoptotic cells in TNBC models. Nevertheless, the increase of the chemotherapy-induced apoptotic response when using paclitaxel could not be assessed using this radiotracer in our mouse model.

Pretargeted radioimmunotherapy and SPECT imaging of peritoneal carcinomatosis using bioorthogonal click chemistry: probe selection and first proof-of-concept

Rationale: Pretargeted radioimmunotherapy (PRIT) based upon bioorthogonal click chemistry has been investigated for the first time in the context of peritoneal carcinomatosis using a CEA-targeting 35A7 mAb bearing trans-cyclooctene (TCO) moieties and several ¹⁷⁷Lu-labeled tetrazine (Tz) radioligands. Starting from three Tz probes containing PEG linkers of varying lengths between the DOTA and Tz groups (i.e. PEG_n = 3, 7, or 11, respectively, for Tz-1, Tz-2, and Tz-3), we selected [¹⁷⁷Lu]Lu-Tz-2 as the most appropriate for pretargeted SPECT imaging and demonstrated its efficacy in tumor growth control. Methods: An orthotopic model of peritoneal carcinomatosis (PC) was obtained following the intraperitoneal (i.p.) injection of A431-CEA-Luc cells in nude mice. Tumor growth was assessed using bioluminescence imaging. Anti-CEA 35A7 mAb was grafted with 2-3 TCO per immunoglobulin. Pretargeted SPECT imaging and biodistribution experiments were performed to quantify the activity concentrations of [¹⁷⁷Lu]Lu-Tz-1-3 in tumors and non-target organs to determine the optimal Tz probe for the PRIT of PC. Results: The pharmacokinetic profiles of [¹⁷⁷Lu]Lu-Tz-1-3 alone were determined using both SPECT imaging and biodistribution experiments. These data revealed that [¹⁷⁷Lu]Lu-Tz-1 was cleared via both the renal and hepatic systems, while [¹⁷⁷Lu]Lu-Tz-2 and [¹⁷⁷Lu]Lu-Tz-3 were predominantly excreted via the renal system. In addition, these results illuminated that the longer the PEG linker, the more rapidly the Tz radioligand was cleared from the peritoneal cavity. The absorbed radiation dose corresponding to pretargeting with 35A7-TCO followed 24 h later by [¹⁷⁷Lu]Lu-Tz-1-4 was higher for tumors following the administration of [¹⁷⁷Lu]Lu-Tz-2 (i.e. 0.59 Gy/MBq) compared to either [¹⁷⁷Lu]Lu-Tz-1 (i.e. 0.25 Gy/MBq) and [¹⁷⁷Lu]Lu-Tz-3 (i.e. 0.18 Gy/MBq). In a longitudinal PRIT study, we showed that the i.p. injection of 40 MBq of [¹⁷⁷Lu]Lu-Tz-2 24 hours after the systemic administration of 35A7-TCO significantly slowed tumor growth compared to control mice receiving only saline or 40 MBq of [¹⁷⁷Lu]Lu-Tz-2 alone. Ex vivo measurement of the peritoneal carcinomatosis index (PCI) confirmed that PRIT significantly reduced tumor growth (PCI = 15.5 ± 2.3 after PRIT vs 30.0 ± 2.3 and 30.8 ± 1.4 for the NaCl and [¹⁷⁷Lu]Lu-Tz-2 alone groups, respectively). Conclusion: Our results clearly demonstrate the impact of the length of PEG linkers upon the biodistribution profiles of ¹⁷⁷Lu-labeled Tz radioligands. Furthermore, we demonstrated for the first time the possibility of using bioorthogonal chemistry for both the pretargeted SPECT and PRIT of peritoneal carcinomatosis.

Targeted Radionuclide Therapy Decreases Melanoma Lung Invasion by Modifying Epithelial-Mesenchymal Transition-Like Mechanisms

Melanin-radiolabeled molecules for targeted radionuclide therapy (TRT) provide a promising approach for the treatment of pigmented melanoma. Among these radiolabeled molecules, the iodinated melanin-specific binding molecule ([¹³¹I]ICF01012) has shown a significant antitumor effect on metastatic melanoma preclinical models. We report herein that [¹³¹I]ICF01012 decreases the epithelial-mesenshymal transition-like (EMT-like) markers in both in vivo and in vitro three-dimensional (3D) melanoma spheroid models. [¹³¹I]ICF01012 spheroids irradiation resulted in reduced clonogenic capacity of all pigmented spheroids accompanied by increased protein expression levels of phosphorylated H2A.X, p53 and its downstream target p21. In addition, [¹³¹I]ICF01012 treatment leads to a significant increase of cell pigmentation as demonstrated in SK-MEL3 human xenograft model. We also showed that [¹³¹I]ICF01012 decreases the size and the number of melanoma lung colonies in the syngeneic murine B16BL6 in vivo model assessing its potentiality to kill circulating tumor cells. Taken together, these results indicate that [¹³¹I]ICF01012 reduces metastatic capacity of melanoma cells presumably through EMT-like reduction and cell differentiation induction.

Homoharringtonine, an approved anti-leukemia drug, suppresses triple negative breast cancer growth through a rapid reduction of anti-apoptotic protein abundance

Triple negative breast cancers (TNBC) without BRCA1/2 gene mutation or BRCAness are nowadays the breast malignancies most difficult to treat. Improvement of their treatment, for all phases of the disease, is an important unmet medical need. We analyzed the effect of homoharringtonine (HHT), a natural protein synthesis inhibitor approved for treatment of chronic myeloid leukemia, on four cell lines representing aggressive, BRCA1/2 non-mutated, TNBC genomic categories. We show that HHT inhibits in vitro growth of all cell lines for more than 80%, after 48-72 h exposure to 20-100 ng/mL, the concentrations achievable in human plasma after subcutaneous administration of the drug. HHT, at 100 ng/mL, strongly reduced levels of a major TNBC survival factor, anti-apoptotic protein Mcl-1, after only 2 h of exposure, in all cell lines except MDA-MB-231. Other anti-apoptotic proteins, Bcl-2, survivin and XIAP, were also strongly downregulated. Moreover, in vivo growth of the least sensitive cell line to HHT in vitro, MDA-MB-231, was inhibited for 36.5% in mice, by 1 mg/kg of the drug, given subcutaneously, bi-daily, over 7 days. These results demonstrate marked antineoplastic activity of homoharringtonine in TNBC, making further development of the drug in this disease highly warranted.

Abstract 5803: Homoharringtonine, a natural protein synthesis inhibitor, inhibits growth of triple negative breast cancer in vitro and in vivo

Introduction: Triple negative breast cancer (TNBC) is a heterogeneous disease for which new therapeutic approaches are urgently needed. Homoharringtonine (HHT) is a protein synthesis inhibitor clinically approved in chronic myeloid leukemia. Its multi-factor mechanism of action includes downregulation of short-lived cellular proteins like Mcl-1. As increased protein synthesis lies behind several hallmarks of cancer present in TNBC, we investigated the effect of HHT on TNBC in vitro and in vivo.

Methods: TNBC cell lines CAL-51, MDA-MB-231 and MDA-MB-468, representative of aggressive, BRCA1 non-mutated TNBC (Lehmann, J Clin Invest 2011) were used. HHT was provided by LeukePharma, Houston, TX, USA. Cell viability was assessed by sulphorhodamine B assay. Number of cells in different cell cycle phases or in apoptosis was determined by flow cytometry. Protein expression was evaluated by western blot. For in vivo experiments, xenografts of MDA-MB-231 were established in Swiss nu/nu mice, treated for 7 days by subcutaneous HHT (1 mg/kg, bi-daily), and analyzed on day 10. Evaluation of HHT on MDA-MB-468 and CAL-51 xenografts is ongoing.

Results: Already after 24h of exposure to 100 ng/ml HHT (mean plasma HHT concentration after 5 mg/m2/day in humans (Sentenac S et al, Blood 2003)), viability of CAL-51 and MDA-MB-468 cells was strongly reduced (10.4±1.0% and 19.2±2.2% of control, respectively). This inhibition level was obtained in MDA-MB-231 cells only after 72h (18.7±4.8%). After 48h in 100 ng/ml HHT, MDA-MB-231 and -468 cells accumulated in the S phase of the cell cycle, whereas the CAL-51 accumulated in the G1/0 phase. This was associated with an increase of apoptosis in CAL-51 (42.0±2.4% vs 9.2±1.3%, untreated vs treated cells, respectively) and in MDA-MB-468 (24.2±2.8% vs 12.2±3.6%) but not in MDA-MB-231 (9.0±2.2% vs 3.6±1.7%). Concordantly, 100 ng/ml of HHT induced, after only 2h, a marked decrease of the level of anti-apoptotic proteins Mcl-1, Bcl-2, survivin and XIAP in CAL-51 and MDA-MB-468 cells, which preceded by 2h the reduction of caspase-3 level. No change in expression of those proteins was observed in MDA-MB-231 during all 48h of exposure to HHT. On the other side, the quantity of phosphorylated S6 increased in MDA-MB-231 but decreased in CAL-51 and MDA-MB-468 already after 24h of incubation with 100 ng/ml HHT. In vivo, HHT reduced growth of MDA-MB-231 xenografts for 36.5% (tumor volume on day 10: 230.4±27.7% mm3 vs 146.2±15.5% mm3, untreated vs treated, respectively).

Conclusion: HHT exerts cytotoxic action on TNBC cell lines CAL-51 and MDA-MB-468 whereas its effect on MDA-MB-231 is dominantly cytostatic. Because of its capacity to rapidly reduce the levels of anti-apoptotic proteins, HHT is worth further studies as potential sensitizer of TNBC to chemo- and/or targeted therapy.

Citation Format: Mohamad Yakhni, Arnaud Briat, Elisabeth Miot-Noirault, Florent Cachin, Frederique Penault-Llorca, Nina Radosevic-Robin. Homoharringtonine, a natural protein synthesis inhibitor, inhibits growth of triple negative breast cancer in vitro and in vivo [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5803.

Evaluation of the Active Targeting of Melanin Granules after Intravenous Injection of Dendronized Nanoparticles

The biodistribution of dendronized iron oxides, NPs10@D1_DOTAGA and melanin-targeting NPs10@D1_ICF_DOTAGA, was studied in vivo using magnetic resonance imaging (MRI) and planar scintigraphy through [¹⁷⁷Lu]Lu-radiolabeling. MRI experiments showed high contrast power of both dendronized nanoparticles (DPs) and hepatobiliary and urinary excretions. Little tumor uptake could be highlighted after intravenous injection probably as a consequence of the negatively charged DOTAGA-derivatized shell, which reduces the diffusion across the cells' membrane. Planar scintigraphy images demonstrated a moderate specific tumor uptake of melanoma-targeted [¹⁷⁷Lu]Lu-NPs10@D1_ICF_DOTAGA at 2 h post-intravenous injection (pi), and the highest tumor uptake of the control probe [¹⁷⁷Lu]Lu-NPs10@D1_DOTAGA at 30 min pi, probably due to the enhanced permeability and retention effect. In addition, ex vivo confocal microscopy studies showed a high specific targeting of human melanoma samples impregnated with NPs10@D1_ICF_Alexa647_ DOTAGA.

Targeting DNA repair by coDbait enhances melanoma targeted radionuclide therapy

Radiolabelled melanin ligands offer an interesting strategy for the treatment of disseminated pigmented melanoma. One of these molecules, ICF01012 labelled with iodine 131, induced a significant slowing of melanoma growth. Here, we have explored the combination of [¹³¹I]ICF01012 with coDbait, a DNA repair inhibitor, to overcome melanoma radioresistance and increase targeted radionuclide therapy (TRT) efficacy. In human SK-Mel 3 melanoma xenograft, the addition of coDbait had a synergistic effect on tumor growth and median survival. The anti-tumor effect was additive in murine syngeneic B16Bl6 model whereas coDbait combination with [¹³¹I]ICF01012 did not increase TRT side effects in secondary pigmented tissues (e.g. hair follicles, eyes). Our results confirm that DNA lesions induced by TRT were not enhanced with coDbait association but, the presence of micronuclei and cell cycle blockade in tumor shows that coDbait acts by interrupting or delaying DNA repair. In this study, we demonstrate for the first time, the usefulness of DNA repair traps in the context of targeted radionuclide therapy.

Antibody PEGylation in bioorthogonal pretargeting with trans-cyclooctene/tetrazine cycloaddition: in vitro and in vivo evaluation in colorectal cancer models

Bioorthogonal chemistry represents a challenging approach in pretargeted radioimmunotherapy (PRIT). We focus here on mAb modifications by grafting an increase amount of trans-cyclooctene (TCO) derivatives (0 to 30 equivalents with respect to mAb) bearing different polyethylene glycol (PEG) linkers between mAb and TCO (i.e. PEG₀ (1), PEG₄ (2) and PEG₁₂ (3)) and assessing their functionality. We used colorectal xenograft (HT29/Ts29.2) and peritoneal carcinomatosis (A431-CEA-Luc/35A7) as tumor cells/mAbs models and fluorescent tetrazines (TZ). MALDI-TOF MS shows that grafting with 2,3 increases significantly the number of TCO per mAb compared with no PEG. In vitro immunofluorescence showed that Ts29.2 and 35A7 labeling intensity is correlated with the number of TCO when using 1,3 while signals reach a maximum at 10 equivalents when using 2. Under 10 equivalents conditions, the capacity of resulting mAbs-1–3 for antigen recognition is similar when reported per grafted TCO and comparable to mAbs without TCO. In vivo, on both models, pretargeting with mAbs-2,3 followed by TZ injection induced a fluorescent signal two times lower than with mAbs-1. These findings suggest that while PEG linkers allow a better accessibility for TCO grafting, it might decrease the number of reactive TCO. In conclusion, mAb-1 represents the best candidate for PRIT.

Tetraspanin 8 (TSPAN 8) as a potential target for radio-immunotherapy of colorectal cancer

Tetraspanin 8 (TSPAN8) overexpression is correlated with poor prognosis in human colorectal cancer (CRC). A murine mAb Ts29.2 specific for human TSPAN8 provided significant efficiency for immunotherapy in CRC pre-clinical models. We therefore evaluate the feasability of targeting TSPAN8 in CRC with radiolabeled Ts29.2. Staining of tissue micro-arrays with Ts29.2 revealed that TSPAN8 espression was restricted to a few human healthy tissues. DOTA-Ts29.2 was radiolabeled with 111In or 177Lu with radiochemical purities >95%, specific activity ranging from 300 to 600 MBq/mg, and radioimmunoreactive fractions >80%. The biodistribution of [111In]DOTA-Ts29.2 in nude mice bearing HT29 or SW480 CRC xenografts showed a high specificity of tumor localization with high tumor/blood ratios (HT29: 4.3; SW480-TSPAN8: 3.9 at 72h and 120h post injection respectively). Tumor-specific absorbed dose calculations for [177Lu]DOTA-Ts29.2 was 1.89 Gy/MBq, establishing the feasibility of using radioimmunotherapy of CRC with this radiolabeled antibody. A significant inhibition of tumor growth in HT29 tumor-bearing mice treated with [177Lu]DOTA-Ts29.2 was observed compared to control groups. Ex vivo experiments revealed specific DNA double strand breaks associated with cell apoptosis in [177Lu]DOTA-Ts29.2 treated tumors compared to controls. Overall, we provide a proof-of-concept for the use of [111In/177Lu]DOTA-Ts29.2 that specifically target in vivo aggressive TSPAN8-positive cells in CRC.

Linker structure-activity relationships in fluorodeoxyglucose chlorambucil conjugates for tumor-targeted chemotherapy

Nitrogen mustards, such as chlorambucil (CLB), can cause adverse side-effects due to ubiquitous distribution in non-target organs. To minimize this toxicity, strategies of tumor-targeting drug delivery have been developed, where a cytotoxic warhead is linked to a tumor-cell-specific small ligand. Malignant cells exhibit marked glucose avidity and an accelerated metabolism by aerobic glycolysis, known as the Warburg effect, and recognized as a hallmark of cancer. A targeting approach exploiting the Warburg effect by conjugation of CLB to 2-fluoro-2-deoxyglucose (FDG) was previously reported and identified two peracetylated glucoconjugates 2 and 3 with promising antitumor activities in vivo. These results prompted us to investigate the importance of the spacer in this tumor-targeting glucose-based conjugates. Here we report the chemical synthesis and an in vitro cytotoxicity evaluation, using a 5-member panel of human tumor cell lines and human fibroblasts, of 16 new CLB glucoconjugates in which the alkylating drug is attached to the C-1 position of FDG via different linkages. We studied the structure-activity relationships in the linker, and evidenced the positive impact of an aromatic linker on in vitro cytotoxicity: compound 51 proved to be the most active FDG-CLB glucoside, characterized by a bis-aromatic spacer tethered to CLB through an amide function.

Theranostic Approach for Metastatic Pigmented Melanoma Using ICF15002, a Multimodal Radiotracer for Both PET Imaging and Targeted Radionuclide Therapy

PURPOSE: This work reports, in melanoma models, the theranostic potential of ICF15002 as a single fluorinated and iodinated melanin-targeting compound. METHODS: Studies were conducted in the murine syngeneic B16BL6 model and in the A375 and SK-MEL-3 human xenografts. ICF15002 was radiolabeled with fluorine-18 for positron emission tomography (PET) imaging and biodistribution, with iodine-125 for metabolism study, and iodine-131 for targeted radionuclide therapy (TRT). TRT efficacy was assessed by tumor volume measurement, with mechanistics and dosimetry parameters being determined in the B16BL6 model. Intracellular localization of ICF15002 was characterized by secondary ion mass spectrometry (SIMS). RESULTS: PET imaging with [¹⁸F]ICF15002 evidenced tumoral uptake of 14.33 ± 2.11%ID/g and 4.87 ± 0.93%ID/g in pigmented B16BL6 and SK-MEL-3 models, respectively, at 1 hour post inoculation. No accumulation was observed in the unpigmented A375 melanoma. SIMS demonstrated colocalization of ICF15002 signal with melanin polymers in melanosomes of the B16BL6 tumors. TRT with two doses of 20 MBq [¹³¹I]ICF15002 delivered an absorbed dose of 102.3 Gy to B16BL6 tumors, leading to a significant tumor growth inhibition [doubling time (DT) of 2.9 ± 0.5 days in treated vs 1.8 ± 0.3 in controls] and a prolonged median survival (27 days vs 21 in controls). P53S15 phosphorylation and P21 induction were associated with a G2/M blockage, suggesting mitotic catastrophe. In the human SK-MEL-3 model, three doses of 25 MBq led also to a DT increase (26.5 ± 7.8 days vs 11.0 ± 3.8 in controls) and improved median survival (111 days vs 74 in controls). CONCLUSION: Results demonstrate that ICF15002 fulfills suitable properties for bimodal imaging/TRT management of patients with pigmented melanoma.

GPR40 mediates potential positive effects of a saturated fatty acid enriched diet on bone

SCOPE

The stimulation of the free fatty acid receptor G-protein coupled receptor (GPR) 40 by GW9508 prevents bone loss by inhibiting osteoclast activity, both in vitro and in vivo. Here, we questioned whether the stimulation of the GPR40 receptor by dietary fatty acids may lead to the same beneficial effect on bone.

METHODS AND RESULTS

We investigated (i) the impact of a fatty acid enriched diet (high-fat diet [HFD]) on bone health in C57/BL6 female mice depending on (ii) the estrogen status (ovariectomy) and (iii) the genotype (GPR40^+/+ or GPR40^-/- ). Bone mineral density (BMD), body composition, weight, inflammation and bone remodeling parameters were monitored. HFD decreased BMD in HFD-SH-GPR40^+/+ mice but OVX failed to further impact BMD in HFD-OVX-GPR40^+/+ mice, while additional bone loss was observed in HFD-OVX-GPR40^-/- animals. These data suggest that when stimulated by fatty acid enriched diets GPR40 contributes to counteract ovariectomy-induced bone alteration. The sparing effect is supported by the modulation of both the osteoprotegerin/receptor activator of nuclear factor kappa-B ligand (OPG/RANKL) ratio in blood stream and the expression level of inflammatory markers in adipose tissues. Bone preservation by GPR40 stimulation is dependent on the presence of long-chain saturated fatty acids.

CONCLUSION

GPR40 contributes to counter ovariectomy-induced bone loss in a context of saturated fatty acid enrichment.

Association of colorectal cancer with pathogenic Escherichia coli: Focus on mechanisms using optical imaging

AIM: To investigate the molecular or cellular mechanisms related to the infection of epithelial colonic mucosa by pks-positive Escherichia coli (E. coli) using optical imaging.

METHODS: We choose to evaluate the tumor metabolic activity using a fluorodeoxyglucose analogue as 2-deoxyglucosone fluorescent probes and to correlate it with tumoral volume (mm³). Inflammation measuring myeloperoxidase (MPO) activity and reactive oxygen species production was monitored by a bioluminescent (BLI) inflammation probe and related to histological examination and MPO levels by enzyme-linked immunosorbent assay (ELISA) on tumor specimens. The detection and quantitation of these two signals were validated on a xenograft model of human colon adenocarcinoma epithelial cells (HCT116) in nude mice infected with a pks-positive E. coli. The inflammatory BLI signal was validated intra-digestively in the colitis-CEABAC10 DSS models, which mimicked Crohn’s disease.

RESULTS: Using a 2-deoxyglucosone fluorescent probe, we observed a high and specific HCT116 tumor uptake in correlation with tumoral volume (P = 0.0036). Using the inflammation probe targeting MPO, we detected a rapid systemic elimination and a significant increase of the BLI signal in the pks-positive E. coli-infected HCT116 xenograft group (P < 0.005). ELISA confirmed that MPO levels were significantly higher (1556 ± 313.6 vs 234.6 ± 121.6 ng/mL P = 0.001) in xenografts infected with the pathogenic E. coli strain. Moreover, histological examination of tumor samples confirmed massive infiltration of pks-positive E. coli-infected HCT116 tumors by inflammatory cells compared to the uninfected group. These data showed that infection with the pathogenic E. coli strain enhanced inflammation and ROS production in tumors before tumor growth. Moreover, we demonstrated that the intra-digestive monitoring of inflammation is feasible in a reference colitis murine model (CEABAC10/DSS).

CONCLUSION: Using BLI and fluorescence optical imaging, we provided tools to better understand host-pathogen interactions at the early stage of disease, such as inflammatory bowel disease and colorectal cancer.

Melanoma-targeted delivery system (part 2): Synthesis, radioiodination and biological evaluation in B16F0 bearing mice

Here we report the synthesis and radiolabelling with iodine-125 of a melanoma-selective prodrug (17a*) and its parent drug IUdR. The in vivo and ex vivo biodistributions of [(125)I](17a*) and [(125)I]IUdR were evaluated in a model of melanoma B16F0-bearing mice. The pharmacokinetic profile of [(125)I](17a*) suggests rapid release of the active drug [(125)I]IUdR after i.v. administration of [(125)I](17a*). Preliminary metabolism studies in dedicated compartments (i.e. blood, urine and tumour) yielded results consistent with this hypothesis.

Pomegranate Peel Extract Prevents Bone Loss in a Preclinical Model of Osteoporosis and Stimulates Osteoblastic Differentiation in Vitro

The nutritional benefits of pomegranate have attracted great scientific interest. The pomegranate, including the pomegranate peel, has been used worldwide for many years as a fruit with medicinal activity, mostly antioxidant properties. Among chronic diseases, osteoporosis, which is associated with bone remodelling impairment leading to progressive bone loss, could eventually benefit from antioxidant compounds because of the involvement of oxidative stress in the pathogenesis of osteopenia. In this study, with in vivo and ex vivo experiments, we investigated whether the consumption of pomegranate peel extract (PGPE) could limit the process of osteopenia. We demonstrated that in ovariectomized (OVX) C57BL/6J mice, PGPE consumption was able to significantly prevent the decrease in bone mineral density (-31.9%; p < 0.001 vs. OVX mice) and bone microarchitecture impairment. Moreover, the exposure of RAW264.7 cells to serum harvested from mice that had been given a PGPE-enriched diet elicited reduced osteoclast differentiation and bone resorption, as shown by the inhibition of the major osteoclast markers. In addition, PGPE appeared to substantially stimulate osteoblastic MC3T3-E1 alkaline phosphatase (ALP) activity at day 7, mineralization at day 21 and the transcription level of osteogenic markers. PGPE may be effective in preventing the bone loss associated with ovariectomy in mice, and offers a promising alternative for the nutritional management of this disease.

99mTc-NTP 15-5 Imaging for Cartilage Involvement in Experimental Rheumatoid Arthritis: Comparison with Routinely Used Molecular Imaging Methods and Sensitivity to Chronic Nonsteroidal Antiinflammatory Drug Treatment

This study determined, using the intraarticular complete Freund adjuvant arthritis mice model, whether the radiotracer (99m)Tc-N-(triethylammonium)-3-propyl-[15]ane-N5 ((99m)Tc-NTP 15-5) targeting proteoglycans has a pathophysiologic validity for in vivo imaging of rheumatoid arthritis (RA) and its response to chronic nonsteroidal antiinflammatory drugs.

METHODS

We investigated the time course of cartilage remodeling by (99m)Tc-NTP 15-5 scintigraphy, bone damages by (99m)Tc-hydroxymethylene diphosphonate imaging, inflammation by (18)F-FDG PET, and joint proteoglycan content and pain behavior in animals, without and with meloxicam treatment. Paw circumference, thermal pain behavior, and histology as well as proteoglycan content of the whole joint were determined.

RESULTS

(99m)Tc-NTP 15-5 showed specific tracer accumulation within RA joints, with a significant increase in scintigraphic ratio observed in RA versus shams from day 3 to day 28. (18)F-FDG evidenced uptake in RA joints from day 15 to day 29. Animals treated with meloxicam (5 mg/kg) exhibited a dose-dependent decrease in both (99m)Tc-NTP 15-5 and (18)F-FDG uptake ratios versus saline-treated animals. (99m)Tc-hydroxymethylene diphosphonate bone scans were only positive at day 14 in RA versus shams, with a significant effect of meloxicam. An increase in proteoglycans of RA joint and thermal pain behavior were observed and were dose-dependently reduced by meloxicam.

CONCLUSION

These experimental results bring data in favor of the (99m)Tc-NTP 15-5 radiotracer for assessing, in vivo, cartilage remodeling in RA that could be used to monitor therapy.

Development and Preliminary Evaluation of TFIB, a New Bimodal Prosthetic Group for Bioactive Molecule Labeling

The new readily available prosthetic group, tetrafluorophenyl 4-fluoro-3-iodobenzoate (TFIB), designed for both molecular imaging and targeted radionuclide therapy purposes was radiolabeled either with fluorine or iodine radionuclides with excellent radiochemical yields and purities. These radiolabeled tags were conjugated to N,N-diethylethylenediamine to give melanin-targeting radiotracers [ (125) I]9 and [ (18) F]9, which were successfully evaluated by PET and gamma scintigraphic imaging in B16F0 pigmented melanoma-bearing C57BL/6J mice. Then, radiolabeled [ (125) I]/[ (18) F]TFIB was used to tag tumor-targeting peptides (i.e., PEG3[c(RGDyK)]2 and NDP-MSH targeting αvβ3 integrin and MC1R receptors, respectively) in mild conditions and with good radiochemical yields (47-83% d.c.) and purities (>99%). The resulting radiolabeled peptides were assessed both in vitro and by PET imaging in animal models.

Radiolabeled dendritic probes as tools for high in vivo tumor targeting: application to melanoma

A small-sized and bifunctional¹¹¹In-radiolabeled dendron shows highin vivotargeting efficiency towards an intracellular target in a murine melanoma model.

[¹²³I]ICF01012 melanoma imaging and [¹³¹I]ICF01012 dosimetry allow adapted internal targeted radiotherapy in preclinical melanoma models

BACKGROUND

Melanin-targeting radiotracers are interesting tools for imaging and treatment of pigmented melanoma metastases. However, variation of the pigment concentration may alter the efficiency of such targeting.

OBJECTIVES

A clear assessment of both tumor melanin status and dosimetry are therefore prerequisites for internal radiotherapy of disseminated melanoma.

MATERIALS & METHODS

The melanin tracer ICF01012 was labelled with iodine-123 for melanoma imaging in pigmented murine B16F0 and human SK-Mel 3 melanomas.

RESULTS

In vivo imaging showed that the uptake of [(123)I]ICF01012 to melanomas correlated significantly with melanin content. Schedule treatment of 3 × 25 MBq [(131)I]ICF01012 significantly reduced SK-Mel 3 tumor growth and significantly increased the median survival in treated mice. For this protocol, the calculated delivered dose was 53.2 Gy.

CONCLUSION

Radio-iodinated ICF01012 is a good candidate for both imaging and therapeutic purposes for patients with metastatic pigmented melanomas.

Synthesis and Biological Evaluation of New Quinoxaline Derivatives of ICF01012 as Melanoma-Targeting Probes

The aim of this study was the synthesis and pharmacokinetic selection of a best melanin-targeting ligand for addressing anticancer agents to pigmented melanoma. Seven quinoxaline carboxamide derivatives were synthesized and radiolabeled with iodine-125. Biodistribution studies of compounds [ (125) I]1a-g performed in melanoma-bearing mice tumor showed significant tumor uptake (range 2.43-5.68%ID/g) within 1 h after i.v. injection. Fast clearance of the radioactivity from the nontarget organs mainly via the urinary system gave high tumor-to-blood and tumor-to-muscle ratios. Given its favorable clearance and high tumor-melanoma uptake at 72 h, amide 1d was the most promising melanoma-targeting ligand in this series. Compound 1d will be used as building block for the design of new melanoma-selective drug delivery systems.

(123)I-BZA2 as a melanin-targeted radiotracer for the identification of melanoma metastases: results and perspectives of a multicenter phase III clinical trial

Our group has developed a new radiopharmaceutical, (123)I - N-(2-diethylaminoethyl)-2-iodobenzamide ((123)I-BZA2), a benzamide derivative able to bind to melanin pigment in melanoma cells. In a prospective and multicentric phase III clinical study, the value of (18)F-FDG PET/CT and (123)I-BZA2 scintigraphy was compared for melanoma staging.

METHODS

Patients with a past history of cutaneous or ocular melanoma were included from 8 hospitals. (18)F-FDG imaging was performed according to a standard PET protocol. Whole-body, static planar, and SPECT/CT (if available) images were acquired 4 h after injection of a 2 MBq/kg dose of (123)I-BZA2. (18)F-FDG and (123)I-BZA2 sensitivity and specificity for the diagnosis of melanoma metastasis were calculated and compared on both a lesion basis and a patient basis. True-positive and true-negative lesion status was determined after 6 mo of clinical follow-up or according to lesion biopsies (if available). Melanin content in biopsies was evaluated with the standard Fontana-Masson silver method and was correlated with (123)I-BZA2 uptake. Based on statistical analysis, the number of inclusions was estimated at 186.

RESULTS

In all, 87 patients were enrolled from 2008 to 2010. Of these, 45 (52%) had metastases. A total of 338 imaging abnormalities were analyzed; 86 lesions were considered metastases, and 20 of 25 lesion biopsies found melanoma metastases. In a patient-based analysis, the sensitivity of (18)F-FDG for diagnosis of melanoma metastases was higher than that of (123)I-BZA2, at 87% and 39%, respectively (P < 0.05). For specificity, (18)F-FDG and (123)I-BZA2 were not statistically different, at 78% and 94%, respectively. In a lesion-based analysis, the sensitivity of (18)F-FDG was statistically higher than that of (123)I-BZA2 (80% vs. 23%, P < 0.05). The specificity of (18)F-FDG was lower than that of (123)I-BZA2 (54% vs. 86%, P < 0.05). According to biopsy analysis, only 9 of 20 metastatic lesions (45%) were pigmented with high melanin content. (123)I-BZA2 imaging was positive for 6 of 8 melanin-positive lesions, fairly positive for 3 of 10 melanin-negative lesions, and negative for 7 of 10 melanin-negative lesions. The sensitivity and specificity of (123)I-BZA2 for the diagnosis of melanin-positive lesions were 75% and 70%, respectively. Because of a low (123)I-BZA2 sensitivity, this clinical trial was prematurely closed after 87 patients had been included.

CONCLUSION

This study confirms the value of (18)F-FDG PET/CT for melanoma staging and strengthens the high accuracy of (123)I-BZA2 for diagnosis of melanin-positive metastatic melanoma. Moreover, benzamide derivatives radiolabeled with therapeutic radionuclide may offer a new strategy for the treatment of metastatic melanoma patients harboring melanin-positive metastases.

Pomegranate seed oil prevents bone loss in a mice model of osteoporosis, through osteoblastic stimulation, osteoclastic inhibition and decreased inflammatory status

In the current context of longer life expectancy, the prevalence of osteoporosis is increasingly important. This is why development of new strategies of prevention is highly suitable. Pomegranate seed oil (PSO) and its major component, punicic acid (a conjugated linolenic acid), have potent anti-inflammatory and anti-oxidative properties both in vitro and in vivo, two processes strongly involved in osteoporosis establishment. In this study, we demonstrated that PSO consumption (5% of the diet) improved significantly bone mineral density (240.24±11.85 vs. 203.04±34.19 mg/cm(3)) and prevented trabecular microarchitecture impairment in ovariectomized (OVX) mice C57BL/6J, compared to OVX control animals. Those findings are associated with transcriptional changes in bone tissue, suggesting involvement of both osteoclastogenesis inhibition and osteoblastogenesis improvement. In addition, thanks to an ex vivo experiment, we provided evidence that serum from mice fed PSO (5% by gavage) had the ability to significantly down-regulate the expression of specific osteoclast differentiation markers and RANK-RANKL downstream signaling targets in osteoclast-like cells (RAW264.7) (RANK: negative 0.49-fold vs. control conditions). Moreover, in osteoblast-like cells (MC3T3-E1), it elicited significant increase in alkaline phosphatase activity (+159% at day 7), matrix mineralization (+271% on day 21) and transcriptional levels of major osteoblast lineage markers involving the Wnt/β-catenin signaling pathways. Our data also reveal that PSO inhibited pro-inflammatory factors expression while stimulating anti-inflammatory ones. These results demonstrate that PSO is highly relevant regarding osteoporosis. Indeed, it offers promising alternatives in the design of new strategies in nutritional management of age-related bone complications.

The polyphenol fisetin protects bone by repressing NF-κB and MKP-1-dependent signaling pathways in osteoclasts

Osteoporosis is a bone pathology leading to increase fractures risk and challenging quality of life. Since current treatments could exhibit deleterious side effects, the use of food compounds derived from plants represents a promising innovative alternative due to their potential therapeutic and preventive activities against human diseases. In this study, we investigated the ability of the polyphenol fisetin to counter osteoporosis and analyzed the cellular and molecular mechanisms involved. In vivo, fisetin consumption significantly prevented bone loss in estrogen deficiency and inflammation mice osteoporosis models. Indeed, bone mineral density, micro-architecture parameters and bone markers were positively modulated by fisetin. Consistent with in vivo results, we showed that fisetin represses RANKL-induced osteoclast differentiation and activity as demonstrated by an inhibition of multinucleated cells formation, TRAP activity and differentiation genes expression. The signaling pathways NF-κB, p38 MAPK, JNK and the key transcription factors c-Fos and NFATc1 expressions induced by RANKL, were negatively regulated by fisetin. We further showed that fisetin inhibits the constitutive proteasomal degradation of MKP-1, the phosphatase that deactivates p38 and JNK. Consistently, using shRNA stable cell lines, we demonstrated that impairment of MKP-1 decreases fisetin potency. Taken together, these results strongly support that fisetin should be further considered as a bone protective agent.