Increasing evidence suggests that platelets play a predominant role in colon and breast cancer metastasis but the underlying molecular mechanisms remain elusive. Glycoprotein VI (GPVI) is a platelet-specific receptor for collagen and fibrin that triggers platelet activation through immunoreceptor tyrosine-based activation motif (ITAM)-signaling and thereby regulates diverse functions including platelet adhesion, aggregation and procoagulant activity. GPVI has been proposed as a safe antithrombotic target as its inhibition is protective in models of arterial thrombosis with only minor effects on hemostasis. Here, we demonstrate that genetic deficiency of platelet GPVI in mice decreases experimental and spontaneous metastasis of colon and breast cancer cells. Similar results were obtained with mice lacking the spleen-tyrosine kinase Syk in platelets, an essential component of the ITAM-signaling cascade. In vitro and in vivo analyses show that mouse, as well as human GPVI, supports platelet adhesion to colon and breast cancer cells. Using a CRISPR/Cas9-based gene knock-out approach, we identified Galectin-3 as the major counter-receptor of GPVI on tumor cells. In vivo studies demonstrated that the interplay between platelet GPVI and tumor cell-expressed Galectin-3 utilizes ITAM-signaling components in platelets and favors the extravasation of tumor cells. Finally, we showed that JAQ1 F(ab)2-mediated inhibition of GPVI efficiently impairs platelet-tumor cell interaction and tumor metastasis. Our study reveals a new mechanism by which platelets promote the metastasis of colon and breast cancer cells and suggests that GPVI represents a promising target for antimetastatic therapies.

A series of (E)-11-isonitrosostrychnine oxime ethers, 2-aminostrychnine, (strychnine-2-yl)propionamide, 18-oxostrychnine, and N-propylstrychnine bromide were synthesized and evaluated pharmacologically at human α1 and α1β glycine receptors in a functional fluorescence-based and a whole-cell patch-clamp assay and in [H]strychnine binding studies. 2-Aminostrychnine and the methyl, allyl, and propargyl oxime ethers were the most potent α1 and α1β antagonists in the series, displaying IC values similar to those of strychnine at the two receptors. Docking experiments to the strychnine binding site of the crystal structure of the α3 glycine receptor indicated the same orientation of the strychnine core for all analogues. For the most potent oxime ethers, the ether substituent was accommodated in a lipophilic receptor binding pocket. The findings identify the oxime hydroxy group as a suitable attachment point for linking two strychnine pharmacophores by a polymethylene spacer and are, therefore, important for the design of bivalent ligands targeting glycine receptors.

ABSTRACT.The non-covalent coating of carbon-based nanomaterials, such as carbon nanotubes, has important applications in nanotechnology and nanomedicine. The molecular modeling of this process can clarify its mechanism and provide a tool for the design of novel materials. In this paper, the coating mechanism of single-walled carbon nanotubes (SWCNT) in aqueous solutions by 1,2 -dimethoxyethane oxide (DME), 1,2 -dimethoxypropane oxide (DMP), polyethylene oxide (PEO), polypropylene oxide (PPO) pentamers, and L64 triblock copolymer chains have been studied using molecular dynamics (MD) simulations. The results suggest a preferential binding to the SWCNT surface of the DMP molecules with respect to DME mainly driven by their difference in hydrophobicy. For the longer pentamers, it depends by the chain conformation. PPO isomers with radius of gyration larger than PEO pentamers bind more tightly than those with more compact conformation. In the case, of the L64 triblock copolymer, the coating of the SWCNT surface produce a shell of PPO blocks with the PEO chains protruding into bulk water as expected from the so-called non-wrapping binding mechanism of SWCNT. In addition, polymer coating, qualitative agreement with experimental evidences on the poor capability of the L64 to disperse SWCNT, do not prevent the formation of CNT aggregates.

The processes of CNTs bundle formation and insertion/rearrangement inside lipid bilayers, as models of cellular membranes, is described and analyzed in details using simulations on the microsecond scale. Molecular Dynamics simulations employing hybrid particle-field models (MD-SCF) show that during the insertion process lipid molecules coat bundles surfaces The distortions of bilayers are more pronounced for systems undergoing to insertion of bundles made of longer CNTs. Interestingly, in this case, for the insertion of bundles in perpendicular orientation, it has been possible to observe, for the first time, a transient poration of the bilayer and a subsequent water percolation through it.