Antibacterial Activity of T22, a Specific Peptidic Ligand of the Tumoral Marker CXCR4

Antiviral and antibacterial peptides: Mechanisms of action

Antimicrobial peptides (AMPs) present promising alternatives for addressing bacterial and viral multidrug resistance due to their distinctive properties. Understanding the mechanisms of these compounds is essential for achieving this objective. Therefore, this comprehensive review aims to highlight primary natural sources of AMPs and elucidate various aspects of the modes of action of antiviral and antibacterial peptides (ABPs). It emphasizes that antiviral peptides (AVPs) can disrupt the replication cycle of both enveloped and non-enveloped viruses at several stages, including pre-fusion, fusion, and post-entry into the host cell. Additionally, the review discusses the inhibitory effects of ABPs on bacterial growth, outlining their extracellular actions as well as their intracellular activities following membrane translocation. Factors such as structure, size, electric charge, environmental factors, degrading enzymes, and microbial resistance against AMPs can affect the function of AMPs.

Paradoxical cell targeting of calreticulin-empowered, protein-only nanoparticles

Surface-exposed calreticulin (CRT) serves as a crucial cell damage-associated molecular pattern for immunogenic apoptosis, by generating an "eat me" signal to macrophages. Aiming at precision immunotherapies we intended to artificially label tumoral cells in vivo with a recombinant CRT, in a targeted way. For that, we have constructed a CRT fusion protein intended to surface attach CXCR4+ cancer cells, to stimulate their immunological destruction. As a targeting ligand of the CRT construct and to drive its specific cell adhesion, we used the peptide V1, a derivative of the vMIP-II cytokine and an antagonist of CXCR4. The modular protein tends to self-assemble as regular 16 nm nanoparticles, assisted by ionic Zn. Through both in vivo and in vitro experiments, we have determined that CRT itself confers cell targeting capabilities to the construct overcoming those of V1, that are only moderate. In particular, CRT binds HeLa cells in absence of further internalization, by a route fully independent of CXCR4. Furthermore, by cytometry in THP-1 cells, we observed that the binding of the protein is preferential for dead cells over live cells, a fact that cannot be associated to a mere artefactual adsorption. These data are discussed in the context of the oligomerizing properties of CRT and the potential clinical applicability of proteins and protein materials functionalized with this novel cell surface ligand.

Is it possible to treat melanoma by intercepting the CXCR4/CXCL12 pathway?

Melanoma is a particularly aggressive type of skin cancer that can spread to distant organs, resulting in poor patient outcomes. C-X-C motif chemokine ligand 12 (CXCL12) interacts to the C-X-C chemokine receptor type 4 (CXCR4). This connection between CXCR4 and its companion ligand CXCL12 is important in melanoma metastasis and progression, encouraging cell proliferation, invasion, and survival via downstream signaling pathways. Furthermore, CXCR4 is implicated in the interaction between melanoma cells and the tumor microenvironment, which promotes malignant cell migration and immune evasion. Given the importance of the CXCR4/CXCL12 axis in melanoma, addressing this axis has the potential to prevent metastasis and improve patient outcomes. We present an overview of the CXCR4/CXCL12 axis in cancer progression and explain its role in the melanoma microenvironment in this paper. Furthermore, we investigate CXCR4's predictive usefulness as a possible biomarker for monitoring melanoma progression. Finally, we discuss the most recent research and clinical trials on CXCR4 inhibitors, emphasizing their efficacy and limits. We hope to improve the quality of life for melanoma patients by better understanding the role of CXCR4 and investigating novel therapeutic options.

Efficient Delivery of Antimicrobial Peptides in an Innovative, Slow-Release Pharmacological Formulation

Both nanostructure and multivalency enhance the biological activities of antimicrobial peptides (AMPs), whose mechanism of action is cooperative. In addition, the efficacy of a particular AMP should benefit from a steady concentration at the local place of action and, therefore, from a slow release after a dynamic repository. In the context of emerging multi-resistant bacterial infections and the urgent need for novel and effective antimicrobial drugs, we tested these concepts through the engineering of four AMPs into supramolecular complexes as pharmacological entities. For that purpose, GWH1, T22, Pt5, and PaD, produced as GFP or human nidogen-based His-tagged fusion proteins, were engineered as self-assembling oligomeric nanoparticles ranging from 10 to 70 nm and further packaged into nanoparticle-leaking submicron granules. Since these materials slowly release functional nanoparticles during their time-sustained unpacking, they are suitable for use as drug depots in vivo. In this context, a particular AMP version (GWH1-NIDO-H6) was selected for in vivo validation in a zebrafish model of a complex bacterial infection. The GWH1-NIDO-H6-secreting protein granules are protective in zebrafish against infection by the multi-resistant bacterium Stenotrophomonas maltophilia, proving the potential of innovative formulations based on nanostructured and slowly released recombinant AMPs in the fight against bacterial infections.

Targeting CXCR4 and CD47 Receptors: An Overview of New and Old Molecules for a Biological Personalized Anticancer Therapy

Biological therapy, with its multifaceted applications, has revolutionized the treatment of tumors, mainly due to its ability to exclusively target cancer cells and reduce the adverse effects on normal tissues. This review focuses on the therapies targeting the CXCR4 and CD47 receptors. We surveyed the results of early clinical trials testing compounds classified as nonpeptides, small peptides, CXCR4 antagonists or specific antibodies whose activity reduces or completely blocks the intracellular signaling pathways and cell proliferation. We then examined antibodies and fusion proteins against CD47, the receptor that acts as a “do not eat me” signal to phagocytes escaping immune surveillance. Despite these molecules being tested in early clinical trials, some drawbacks are emerging that impair their use in practice. Finally, we examined the ImmunoGenic Surrender mechanism that involves crosstalk and co-internalization of CXCR4 and CD47 upon engagement of CXCR4 by ligands or other molecules. The favorable effect of such compounds is dual as CD47 surface reduction impact on the immune response adds to the block of CXCR4 proliferative potential. These results suggest that a combination of different therapeutic approaches has more beneficial effects on patients’ survival and may pave the way for new accomplishments in personalized anticancer therapy.

Toxicity Profiling of Bacterial Inclusion Bodies in Human Caco-2 Cells

Bacterial inclusion bodies (IBs) are discrete macromolecular complexes that appear in recombinant prokaryotic cells under stress conditions. These structures are often discarded for biotechnological uses given the difficulty in recovering proteins of interest from them in a soluble form. However, recent approaches have revealed the potential of these protein clusters as biomaterials to promote cell growth and as protein depots for the release of recombinant proteins for biotechnological and biomedical applications. Although these kinds of natural supramolecular complexes have attracted great interest, no comprehensive study of their toxicity in cell cultures has been carried out. In this study, caco-2 cells were exposed to natural IBs, soluble protein-only nanoparticles (NPs), and non-assembled versions of the same protein for comparative purposes. Cytotoxicity, oxidative stress, and genotoxicity were analyzed for all these protein formats. Natural IBs and soluble protein formats demonstrated their safety in eukaryotic cells. No cytotoxicity, genotoxicity, or oxidative stress was detected in caco-2 cells exposed to the protein samples in any of the experimental conditions evaluated, which covered protein concentrations used in previous biological activity assays. These conditions evaluated the activity of protein samples obtained from three prokaryotic hosts [Escherichia coli and the endotoxin-free expression systems Lactococcus lactis and ClearColi® BL21 (DE3)]. Our results demonstrate that natural IBs and soluble protein nanoparticles are non-toxic materials for eukaryotic cells and that this may represent an interesting alternative to the classical unassembled format of recombinant proteins for certain applications in biotechnology and biomedicine.

Time-Prolonged Release of Tumor-Targeted Protein-MMAE Nanoconjugates from Implantable Hybrid Materials

The sustained release of small, tumor-targeted cytotoxic drugs is an unmet need in cancer therapies, which usually rely on punctual administration regimens of non-targeted drugs. Here, we have developed a novel concept of protein–drug nanoconjugates, which are packaged as slow-releasing chemically hybrid depots and sustain a prolonged secretion of the therapeutic agent. For this, we covalently attached hydrophobic molecules (including the antitumoral drug Monomethyl Auristatin E) to a protein targeting a tumoral cell surface marker abundant in several human neoplasias, namely the cytokine receptor CXCR4. By this, a controlled aggregation of the complex is achieved, resulting in mechanically stable protein–drug microparticles. These materials, which are mimetics of bacterial inclusion bodies and of mammalian secretory granules, allow the slow leakage of fully functional conjugates at the nanoscale, both in vitro and in vivo. Upon subcutaneous administration in a mouse model of human CXCR4⁺ lymphoma, the protein–drug depots release nanoconjugates for at least 10 days, which accumulate in the tumor with a potent antitumoral effect. The modification of scaffold cell-targeted proteins by hydrophobic drug conjugation is then shown as a novel transversal platform for the design of slow releasing protein–drug depots, with potential application in a broad spectrum of clinical settings.