Integrin alpha9 emerges as a key therapeutic target to reduce metastasis in rhabdomyosarcoma and neuroblastoma.

The majority of current cancer therapies are aimed at reducing tumour growth, but there is lack of viable pharmacological options to reduce the formation of metastasis. This is a paradox, since more than 90% of cancer deaths are attributable to metastatic progression. Integrin alpha9 (ITGA9) has been previously described as playing an essential role in metastasis; however, little is known about the mechanism that links this protein to this process, being one of the less studied integrins. We have now deciphered the importance of ITGA9 in metastasis and provide evidence demonstrating its essentiality for metastatic dissemination in rhabdomyosarcoma and neuroblastoma. However, the most translational advance of this study is to reveal, for the first time, the possibility of reducing metastasis by pharmacological inhibition of ITGA9 with a synthetic peptide simulating a key interaction domain of ADAM proteins, in experimental metastasis models, not only in childhood cancers but also in a breast cancer model.

Conformational ensemble of the TNF-derived peptide solnatide in solution.

Tumor necrosis factor (TNF) is a homotrimer that has two spatially distinct binding regions, three lectin-like domains (LLD) at the TIP of the protein and three basolaterally located receptor-binding sites, the latter of which are responsible for the inflammatory and cell death-inducing properties of the cytokine. Solnatide (a.k.a. TIP peptide, AP301) is a 17-mer cyclic peptide that mimics the LLD of human TNF which activates the amiloride-sensitive epithelial sodium channel (ENaC) and, as such, recapitulates the capacity of TNF to enhance alveolar fluid clearance, as demonstrated in numerous preclinical studies. TNF and solnatide interact with glycoproteins and these interactions are necessary for their trypanolytic and ENaC-activating activities. In view of the crucial role of ENaC in lung liquid clearance, solnatide is currently being evaluated as a novel therapeutic agent to treat pulmonary edema in patients with moderate-to-severe acute respiratory distress syndrome (ARDS), as well as severe COVID-19 patients with ARDS. To facilitate the description of the functional properties of solnatide in detail, as well as to further target-docking studies, we have analyzed its folding properties by NMR. In solution, solnatide populates a set of conformations characterized by a small hydrophobic core and two electrostatically charged poles. Using the structural information determined here and also that available for the ENaC protein, we propose a model to describe solnatide interaction with the C-terminal domain of the ENaCα subunit. This model may serve to guide future experiments to validate specific interactions with ENaCα and the design of new solnatide analogs with unexplored functionalities.

Structure-based design of a Cortistatin analogue with immunomodulatory activity in models of inflammatory bowel disease.

Ulcerative colitis and Crohn's disease are forms of inflammatory bowel disease whose incidence and prevalence are increasing worldwide. These diseases lead to chronic inflammation of the gastrointestinal tract as a result of an abnormal response of the immune system. Recent studies positioned Cortistatin, which shows low stability in plasma, as a candidate for IBD treatment. Here, using NMR structural information, we design five Cortistatin analogues adopting selected native Cortistatin conformations in solution. One of them, A5, preserves the anti-inflammatory and immunomodulatory activities of Cortistatin in vitro and in mouse models of the disease. Additionally, A5 displays an increased half-life in serum and a unique receptor binding profile, thereby overcoming the limitations of the native Cortistatin as a therapeutic agent. This study provides an efficient approach to the rational design of Cortistatin analogues and opens up new possibilities for the treatment of patients that fail to respond to other therapies.

Topical administration of somatostatin prevents retinal neurodegeneration in experimental diabetes.

Retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy (DR). Somatostatin (SST) is an endogenous neuroprotective peptide that is downregulated in the diabetic eye. The aim of the study was to test the usefulness of topical administration of SST in preventing retinal neurodegeneration. For this purpose, rats with streptozotocin-induced diabetes mellitus (STZ-DM) were treated with either SST eye drops or vehicle for 15 days. Nondiabetic rats treated with vehicle served as a control group. Functional abnormalities were assessed by electroretinography (ERG), and neurodegeneration was assessed by measuring glial activation and the apoptotic rate. In addition, proapoptotic (FasL, Bid, and activation of caspase-8 and caspase-3) and survival signaling pathways (BclxL) were examined. Intraretinal concentrations of glutamate and its main transporter glutamate/aspartate transporter (GLAST) were also determined. Treatment with SST eye drops prevented ERG abnormalities, glial activation, apoptosis, and the misbalance between proapoptotic and survival signaling detected in STZ-DM rats. In addition, SST eye drops inhibited glutamate accumulation in the retina and GLAST downregulation induced by diabetes mellitus. We conclude that topical administration of SST has a potent effect in preventing retinal neurodegeneration induced by diabetes mellitus. In addition, our findings open up a new preventive pharmacological strategy targeted to early stages of DR.

Acridine and quindoline oligomers linked through a 4-aminoproline backbone prefer G-quadruplex structures.

BACKGROUND: DNA-intercalating drugs are planar molecules with several fused aromatic rings that form stacks between DNA base pairs, reducing the opening and unwinding of the double helix. Recently, interest on intercalating agents has moved in the search for new ligands to G-quadruplex structures. METHODS: The DNA binding properties of 4-aminoproline oligomers functionalized with one, two or three units of acridine and/or quindoline have been analyzed by competitive dialysis. A NMR/molecular dynamics study was performed on G-quadruplex telomeric sequence and the 4-aminoproline dimer carrying two quindolines. A model of the complex with the telomeric DNA quadruplex is described. RESULTS AND CONCLUSIONS: A selectivity of quindoline 4-aminoproline oligomers for G-quadruplex and triplex structures was observed, especially for those quadruplex sequences found in telomeres and in the promoter regions of c-myc and bcl-2 oncogenes. In this model the quindoline dimer is stabilized by π-π stacking interactions between the aromatic rings of the ligand and the nucleobases of the telomeric sequence that are located above and below the molecule. GENERAL SIGNIFICANCE: The results of this work can be used for the design of new molecules with high affinity to telomeres which may have anticancer properties.

Lamellarin D bioconjugates II: Synthesis and cellular internalization of dendrimer and nuclear location signal derivatives.

The design and synthesis of Lamellarin D conjugates with a nuclear localization signal peptide and a poly(ethylene glycol)-based dendrimer are described. Conjugates 1-4 were obtained in 8-84% overall yields from the corresponding protected Lamellarin D. Conjugates 1 and 4 are 1.4- to 3.3-fold more cytotoxic than the parent compound against three human tumor cell lines (MDA-MB-231 breast, A-549 lung, and HT-29 colon). Besides, conjugates 3 and 4 showed a decrease in activity potency in BJ skin fibroblasts, a normal cell culture. Cellular internalization was analyzed, and a nuclear distribution pattern was observed for 4, which contains a nuclear localization signaling sequence.

Solid-phase combinatorial synthesis of a lysyl-tRNA synthetase (LysRS) inhibitory library.

The solid-phase combinatorial synthesis of a new library with potential inhibitory activity against the cytoplasmic lysyl-tRNA synthetase (LysRS) isoform of Trypanosoma brucei is described. The library has been specifically designed to mimic the lysyl adenylate complex. The design was carried out by dividing the complex into four modular parts. Proline derivatives (cis-gamma-amino-L-proline or trans-gamma-hydroxy-L-proline) were chosen as central scaffolds. After primary screening, three compounds of the library caused in vitro inhibition of the tRNA aminoacylation reaction in the low micromolar range.

Design, synthesis and antiproliferative properties of oligomers with chromophore units linked by amide backbones.

The preparation of oligomers made up of several chromophore units as compounds with potential fluorescent and antiproliferative properties is described. Specifically, chromophore units with protected-amino groups and one carboxylic group are described, together with methods to assemble these units using peptide chemistry. Some of these compounds have antiproliferative activity.

Solid-phase synthesis of oligomers carrying several chromophore units linked by phosphodiester backbones.

A method for the preparation of oligomers by linking chromophore units is described. Specifically, the synthesis of chromophore units having a protected-hydroxyl group and a phosphoramidite function is described, along with a method to link several units using solid-phase phosphite-triester protocols.

Solid-phase synthesis of sulfamate peptidomimetics.

A synthetic method for the preparation of sulfamate peptidomimetics is described. The methodology allows sulfamoylation in the solid phase using sulfamoyl chloride in DMA, followed by the acylation of the corresponding sulfamoylated product. Following this approach, several derivatives have been prepared starting from distinct alcohol sources, including alpha-, beta-, and gamma-hydroxyacids and phenols. The presence of protected amino functions on the building blocks opens the possibility of the addition of more diversity. This approach, which is compatible with Fmoc/Boc/Alloc protection, provides a useful and efficient tool for the preparation of new sulfamate peptidomimetics.

Cell-penetrating proline-rich peptidomimetics.

Cell-penetrating peptides (CPPs) offer potential as delivery agents for the cellular administration of drugs. However, the pharmacological utility of CPPs that are derived from natural amino acids is limited by their rapid metabolic degradation, low membrane permeability, and toxicity. Various peptidomimetics able to overcome these problems have been described, including peptides formed by D-amino acids and beta-peptides. This chapter summarizes the synthesis of gamma-proline-derived peptides and polyproline dendrimers for drug delivery applications, and includes descriptions of several modifications in the gamma-peptides (mimicking the side chains of the alpha-amino acids) or modulating the dendrimer surface. 5(6)-Carboxyfluorescein labeling of the aforementioned peptidomimetics for use in cell translocation studies is also described. Furthermore, different protocols for the study of the drug delivery capabilities of these compounds are reviewed, including enzymatic stability studies, cellular uptake measurements by plate fluorimetry and flow cytometry, confocal laser scanning microscopy, and cytotoxicity assays.

Cell-penetrating cis-gamma-amino-l-proline-derived peptides.

The synthesis of cis-gamma-amino-l-proline oligomers functionalized at the proline alpha-amine with several groups that mimic the side chains of natural amino acids, including alanine, leucine, and phenylalanine, is herein described. These gamma-peptides enter into different cell lines (COS-1 and HeLa) via an endocytic mechanism. The ability of these compounds to be taken up into cells was studied at 37 degrees C and 4 degrees C by plate fluorimetry, flow cytometry, and confocal microscopy. In addition to their capacity for cellular uptake, these unnatural short length oligomers offer advantages over the well-known penetrating TAT peptide, such as being less toxic than TAT and protease resistance.

A new class of foldamers based on cis-gamma-amino-L-proline.

A synthetic method for the preparation of conformationally constrained gamma-peptides derived from gamma-amino-L-proline is described. The methodology allows the independent buildup of the peptide backbone and the introduction of sequential variations by reactions with the alpha-amino group of gamma-aminoproline. Both alkyl- and acyl-substituted gamma-peptides have been prepared and studied by CD and NMR. Conformational restrictions due to the cyclic structure of the monomer give rise to long-range interactions that are indicative of secondary structures even in aqueous solution. Interresidue NOEs suggest a concatenation of turns that, in a permissive solvent, could give rise to an isolated hydrogen bond ribbon, flanked and protected by proline rings.