Multifunctional Glycoconjugates for Recruiting Natural Antibodies against Cancer Cells

Invited for the cover of this issue is Olivier Renaudet and co-workers at the Université Grenoble Alpes and funded by the European Research Council (CoG “LEGO′” no. 647938). The image illustrates a synthetic chemist playing with supramolecular structures to kill cancer cells by using natural antibodies present in the blood stream. Read the full text of the article at 10.1002/chem.201903327

Impact of antigen density on recognition by monoclonal antibodies

Understanding antigen-antibody interactions is important to many emerging medical and bioanalytical applications. In particular, the levels of antigen expression at the cell surface may determine antibody-mediated cell death. This parameter has a clear effect on outcome in patients undergoing immunotherapy. In this context, CD20 which is expressed in the membrane of B cells has received significant attention as target for immunotherapy of leukemia and lymphoma using the monoclonal antibody rituximab. To systematically study the impact of CD20 density on antibody recognition, we designed self-assembled monolayers that display tunable CD20 epitope densities. For this purpose, we developed in situ click chemistry to functionalize SPR sensor chips. We find that the rituximab binding affinity depends sensitively and non-monotoneously on CD20 surface density. Strongest binding, with an equilibrium dissociation constant (KD = 32 nM) close to values previously reported from in vitro analysis with B cells (apparent KD between 5 and 19 nM), was obtained for an average inter-antigen spacing of 2 nm. This distance is required for improving rituximab recognition, and in agreement with the known requirement of CD20 to form clusters to elicit a biological response. More generally, this study offers an interesting outlook in the understanding of the necessity of epitope clusters for effective mAb recognition

PET imaging of αvβ3 integrin expression in tumours with 68Ga-labelled mono-, di- and tetrameric RGD peptides

Contains fulltext : 97195.pdf (publisher's version ) (Closed access)PURPOSE: Due to the restricted expression of alpha(v)beta(3) in tumours, alpha(v)beta(3) is considered a suitable receptor for tumour targeting. In this study the alpha(v)beta(3)-binding characteristics of (68)Ga-labelled monomeric, dimeric and tetrameric RGD peptides were determined and compared with their (111)In-labelled counterparts. METHODS: A monomeric (E-c(RGDfK)), a dimeric (E-[c(RGDfK)](2)) and a tetrameric (E{E[c(RGDfK)](2)}(2)) RGD peptide were synthesised, conjugated with DOTA and radiolabelled with (68)Ga. In vitro alpha(v)beta(3)-binding characteristics were determined in a competitive binding assay. In vivo alpha(v)beta(3)-targeting characteristics of the compounds were assessed in mice with subcutaneously growing SK-RC-52 xenografts. In addition, microPET images were acquired using a microPET/CT scanner. RESULTS: The IC(50) values for the Ga(III)-labelled DOTA-E-c(RGDfK), DOTA-E-[c(RGDfK)](2) and DOTA-E{E[c(RGDfK)](2)}(2) were 23.9 +/- 1.22, 8.99 +/- 1.20 and 1.74 +/- 1.18 nM, respectively, and were similar to those of the In(III)-labelled mono-, di- and tetrameric RGD peptides (26.6 +/- 1.15, 3.34 +/- 1.16 and 1.80 +/- 1.37 nM, respectively). At 2 h post-injection, tumour uptake of the (68)Ga-labelled mono-, di- and tetrameric RGD peptides (3.30 +/- 0.30, 5.24 +/- 0.27 and 7.11 +/- 0.67%ID/g, respectively) was comparable to that of their (111)In-labelled counterparts (2.70 +/- 0.29, 5.61 +/- 0.85 and 7.32 +/- 2.45%ID/g, respectively). PET scans were in line with the biodistribution data. On all PET scans, the tumour could be clearly visualised. CONCLUSION: The integrin affinity and the tumour uptake followed the order of DOTA-tetramer > DOTA-dimer > DOTA-monomer. The (68)Ga-labelled tetrameric RGD peptide has excellent characteristics for imaging of alpha(v)beta(3) expression with PET

Molecular imaging of angiogenesis with SPECT

Single-photon emission computed tomography (SPECT) and position emission tomography (PET) are the two main imaging modalities in nuclear medicine. SPECT imaging is more widely available than PET imaging and the radionuclides used for SPECT are easier to prepare and usually have a longer half-life than those used for PET. In addition, SPECT is a less expensive technique than PET. Commonly used gamma emitters are: 99mTc (Emax 141 keV, T1/2 6.02 h), 123I (Emax 529 keV, T1/2 13.0 h) and 111In (Emax 245 keV, T1/2 67.2 h). Compared to clinical SPECT, PET has a higher spatial resolution and the possibility to more accurately estimate the in vivo concentration of a tracer. In preclinical imaging, the situation is quite different. The resolution of microSPECT cameras (<0.5 mm) is higher than that of microPET cameras (>1.5 mm). In this report, studies on new radiolabelled tracers for SPECT imaging of angiogenesis in tumours are reviewed

Ratiometric luminescence detection of copper(I) by a resonant system comprising two antenna/lanthanide pairs

International audienceSelective and sensitive detection of Cu(I) is an ongoing challenge due to its important role in biological systems, for example. Herein, we describe a photoluminescent molecular chemosensor integrating two lanthanide ions (Tb$^{3+}$ and Eu$^{3+}$) and respective tryptophan and naphthalene antennas onto a polypeptide backbone. The latter was structurally inspired from copper-regulating biomacromolecules in Gram-negative bacteria and was found to bind Cu$^+$ effectively under pseudobiological conditions (log K$_{Cu}$$^+$ = 9.7 ± 0.2). Ion regulated modulation of lanthanide luminescence in terms of intensity and long, millisecond lifetime offers perspectives in terms of ratiometric and time-gated detection of Cu$^+$. The role of the bound ion in determining the photophysical properties is discussed with the aid of additional model compounds

Controlled surface density of RGD ligands for cell adhesion: evidence for ligand specificity by using QCM-D

International audienc

Development of a selective cell capture and release assay: impact of clustered RGD ligands

There is a growing interest in isolating tumor cells from biological samples. Considering that circulating tumor cells can be rare in blood, it appears challenging to capture these cells onto a surface with high selectivity and sensitivity. In the present paper, we describe the design of functionalized surfaces aimed at selectively capturing tumor cells by using an RGD peptide ligand with either a tetrameric or a monomeric presentation. β-Cyclodextrin-coated self-assembled monolayers were used as platforms for the binding of RGD ligands endowed with a redox ferrocene cluster. The dissociation of the inclusion complex on the surface accounts for the release of the captured cells upon the electrochemical oxidation of ferrocene. For this purpose, we determined suitable RGD densities for both monovalent and tetravalent ligand presentations. The results indicate that the clustered RGD architecture efficiently improves selective cell capture at a very low RGD surface density (∼10 RGD per μm2) compared to the monovalent presentation (∼1000 RGD per μm2)

Multimeric Presentation of RGD Peptidomimetics Enhances Integrin Binding and Tumor Cell Uptake

The use of multimeric ligands is considered as a promising strategy to improve tumor targeting for diagnosis and therapy. Herein, tetrameric RGD peptidomimetics were designed to target \u3b1v\u3b23 integrin-expressing tumor cells. These compounds were prepared via an oxime chemoselective assembly of cyclo(DKPRGD) ligands and a cyclodecapeptide scaffold that allows a tetrameric presentation. The resulting tetrameric RGD peptidomimetics were shown to improve \u3b1v\u3b23 integrin binding compared to the monomeric form. Interestingly, these compounds were also able to enhance tumor cell endocytosis in the same way as tetrameric RGD peptides. Altogether, the results show the potential of the tetrameric cyclo(DKP-RGD) ligands for in vivo imaging and drug delivery

Vectorization of photoreactive Ru(II) complexes into cancer cells

info:eu-repo/semantics/nonPublishe