Thrombospondin-1 in drug activity and tumor response to therapies.

Thrombospondins (TSPs) have numerous different roles in cancer, regulating the behavior of cancer cells and non-neoplastic cells, and defining the responses of tumor cells to environmental changes, thorough their ability to orchestrate cellular and molecular interactions in the tumor microenvironment (TME). As a result of these activities, TSPs can also control drug delivery and activity, tumor response and resistance to therapies, with different outcomes depending on the nature of TSP-interacting cell types, receptors, and ligands, in a highly context-dependent manner. This review, focusing primarily on TSP-1, discusses the effects of TSPs on tumor response to chemotherapy, antiangiogenic, low-dose metronomic chemotherapy, immunotherapy, and radiotherapy, by analyzing TSP activity on different cell compartments - tumor cells, vascular endothelial cells and immune cells. We review evidence of the value of TSPs, specifically TSP-1 and TSP-2, as biomarkers of prognosis and tumor response to therapy. Finally, we examine possible approaches to develop TSP-based compounds as therapeutic tools to potentiate the efficacy of anticancer therapy.

Identification of a novel extracellular inhibitor of FGF2/FGFR signaling axis by combined virtual screening and NMR spectroscopy approach.

The aberrant activation of the fibroblast growth factor 2 (FGF2)/fibroblast growth factor receptor (FGFR) signalling pathway drives severe pathologies, including cancer development and angiogenesis-driven pathologies. The perturbation of the FGF2/FGFR axis via extracellular allosteric small inhibitors is a promising strategy for developing FGFR inhibitors with improved safety and efficacy for cancer treatment. We have previously investigated the role of new extracellular inhibitors, such as rosmarinic acid (RA), which bind the FGFR-D2 domain and directly compete with FGF2 for the same binding site, enabling the disruption of the functional FGF2/FGFR interaction. To select ligands for the previously identified FGF2/FGFR RA binding site, NMR data-driven virtual screening has been performed on an in-house library of non-commercial small molecules and metabolites. A novel drug-like compound, a resorcinol derivative named RBA4 has been identified. NMR interaction studies demonstrate that RBA4 binds the FGF2/FGFR complex, in agreement with docking prediction. Residue-level NMR perturbations analysis highlights that the mode of action of RBA4 is similar to RA in terms of its ability to target the FGF2/FGFR-D2 complex, inducing perturbations on both proteins and triggering complex dissociation. Biological assays proved that RBA4 inhibited FGF2 proliferative activity at a level comparable to the previously reported natural product, RA. Identification of RBA4 chemical groups involved in direct interactions represents a starting point for further optimization of drug-like extracellular inhibitors with improved activity.

Controlled extracellular proteolysis of thrombospondins.

Limited proteolysis of thrombospondins is a powerful mechanism to ensure dynamic tuning of their activities in the extracellular space. Thrombospondins are multifunctional matricellular proteins composed of multiple domains, each with a specific pattern of interactions with cell receptors, matrix components and soluble factors (growth factors, cytokines and proteases), thus with different effects on cell behavior and responses to changes in the microenvironment. Therefore, the proteolytic degradation of thrombospondins has multiple functional consequences, reflecting the local release of active fragments and isolated domains, exposure or disruption of active sequences, altered protein location, and changes in the composition and function of TSP-based pericellular interaction networks. In this review current data from the literature and databases is employed to provide an overview of cleavage of mammalian thrombospondins by different proteases. The roles of the fragments generated in specific pathological settings, with particular focus on cancer and the tumor microenvironment, are discussed.

Inhibition of FGFR Signaling by Targeting FGF/FGFR Extracellular Interactions: Towards the Comprehension of the Molecular Mechanism through NMR Approaches.

NMR-based approaches play a pivotal role in providing insight into molecular recognition mechanisms, affording the required atomic-level description and enabling the identification of promising inhibitors of protein-protein interactions. The aberrant activation of the fibroblast growth factor 2 (FGF2)/fibroblast growth factor receptor (FGFR) signaling pathway drives several pathologies, including cancer development, metastasis formation, resistance to therapy, angiogenesis-driven pathologies, vascular diseases, and viral infections. Most FGFR inhibitors targeting the intracellular ATP binding pocket of FGFR have adverse effects, such as limited specificity and relevant toxicity. A viable alternative is represented by targeting the FGF/FGFR extracellular interactions. We previously identified a few small-molecule inhibitors acting extracellularly, targeting FGFR or FGF. We have now built a small library of natural and synthetic molecules that potentially act as inhibitors of FGF2/FGFR interactions to improve our understanding of the molecular mechanisms of inhibitory activity. Here, we provide a comparative analysis of the interaction mode of small molecules with the FGF2/FGFR complex and the single protein domains. DOSY and residue-level NMR analysis afforded insights into the capability of the potential inhibitors to destabilize complex formation, highlighting different mechanisms of inhibition of FGF2-induced cell proliferation.

Longitudinal evaluation of Wnt inhibitors and comparison with others serum osteoimmunological biomarkers in osteolytic bone metastasis.

Bone and the immune system are closely linked: bone regulates the hematopoietic stem cells, which are precursors of immune cells, and several immunoregulatory cytokines influence the differentiation of bone cells, thus defining the osteoimmunological system. Cytokines and growth factors produced by immune and bone cells promote tumors in bone, supporting the vicious cycle of bone metastasis. Therefore osteoimmunological molecules linking the immune and bone systems could have diagnostic and prognostic potential for bone metastases. The osteoimmunologic Wnt pathway has been recently described as an important pathway with a vital role in bone carcinogenesis and metastatic progression. We examined the Wnt inhibitor DKK-1, sclerostin and several other osteoimmunological biomarkers involved in bone metastatic progression: RANKL, OPG, OPN, matrix metalloproteinase MMP-3 and the Receptor of Advanced Glycosylated End-products sRAGE. OPN and sclerostin proved good biomarkers of metastatic bone progression; the RANKL/OPG ratio was a good indicator of bone erosion in the metastatic process, while sRAGE had a protective role against metastatic progression in bone. These results serve to define a panel of new osteoimmunological biomarkers that could be useful in assessing the progress of osteolytic bone metastases.