Anti-Monomeric C-Reactive Protein Antibody Ameliorates Arthritis and Nephritis in Mice.

Conformation-specific Ags are ideal targets for mAb-based immunotherapy. Here, we demonstrate that the monomeric form of C-reactive protein (mCRP) is a specific therapeutic target for arthritis and nephritis in a murine model. Screening of >1800 anti-mCRP mAb clones identified 3C as a clone recognizing the monomeric, but not polymeric, form of CRP. The anti-mCRP mAb suppressed leukocyte infiltration in thioglycollate-induced peritonitis, attenuated rheumatoid arthritis symptoms in collagen Ab-induced arthritis model mice, and attenuated lupus nephritis symptoms in MRL/Mp-lpr/lpr lupus-prone model mice. These data suggest that the anti-mCRP mAb 3C has therapeutic potential against rheumatoid arthritis and lupus nephritis.

Stromal cell-derived factor-1 (CXCL12) activates integrins by direct binding to an allosteric ligand-binding site (site 2) of integrins without CXCR4.

Leukocyte arrest on the endothelial cell surface during leukocyte extravasation is induced by rapid integrin activation by chemokines. We recently reported that fractalkine induces integrin activation without its receptor CX3CR1 through binding to the allosteric site (site 2) of integrins. Peptides from site 2 bound to fractalkine and suppressed integrin activation by fractalkine. We hypothesized that this is not limited to membrane-bound fractalkine. We studied whether stromal cell-derived factor-1 (SDF1), another chemokine that plays a critical role in leukocyte arrest, activates integrins through binding to site 2. We describe here that (1) SDF1 activated soluble integrin αvß3 in cell-free conditions, suggesting that SDF1 can activate αvß3 without CXCR4; (2) site 2 peptide bound to SDF1, suggesting that SDF1 binds to site 2; (3) SDF1 activated integrins αvß3, α4ß1, and α5ß1 on CHO cells (CXCR4-negative) and site 2 peptide suppressed the activation; (4) A CXCR4 antagonist AMD3100 did not affect the site 2-mediated integrin activation by SDF1; (5) Cell-surface integrins were fully activated in 1 min (much faster than activation of soluble αvß3) and the activation lasted at least for 1 h. We propose that the binding of SDF1 to cell-surface proteoglycan facilitates the allosteric activation process; (6) Mutations in the predicted site 2-binding site in SDF1 suppressed integrin activation. These results suggest that SDF1 (e.g. presented on proteoglycans) can rapidly activate integrins in an allosteric manner by binding to site 2 in the absence of CXCR4. The allosteric integrin activation by SDF1 is a novel target for drug discovery.

Direct binding to integrins and loss of disulfide linkage in interleukin-1ß (IL-1ß) are involved in the agonistic action of IL-1ß.

There is a strong link between integrins and interleukin-1ß (IL-1ß), but the specifics of the role of integrins in IL-1ß signaling are unclear. We describe that IL-1ß specifically bound to integrins αvß3 and α5ß1. The E128K mutation in the IL1R-binding site enhanced integrin binding. We studied whether direct integrin binding is involved in IL-1ß signaling. We compared sequences of IL-1ß and IL-1 receptor antagonist (IL1RN), which is an IL-1ß homologue but has no agonistic activity. Several surface-exposed Lys residues are present in IL-1ß, but not in IL1RN. A disulfide linkage is present in IL1RN, but is not in IL-1ß because of natural C117F mutation. Substitution of the Lys residues to Glu markedly reduced integrin binding of E128K IL-1ß, suggesting that the Lys residues mediate integrin binding. The Lys mutations reduced, but did not completely abrogate, agonistic action of IL-1ß. We studied whether the disulfide linkage plays a role in agonistic action of IL-1ß. Reintroduction of the disulfide linkage by the F117C mutation did not affect agonistic activity of WT IL-1ß, but effectively reduced the remaining agonistic activity of the Lys mutants. Also, deletion of the disulfide linkage in IL1RN by the C116F mutation did not make it agonistic. We propose that the direct binding to IL-1ß to integrins is primarily important for agonistic IL-1ß signaling, and that the disulfide linkage indirectly affects signaling by blocking conformational changes induced by weak integrin binding to the Lys mutants. The integrin-IL-1ß interaction is a potential target for drug discovery.

Secreted Phospholipase A2 Type IIA (sPLA2-IIA) Activates Integrins in an Allosteric Manner.

Secreted phospholipase A2 type IIA (sPLA2-IIA) is a well-established pro-inflammatory protein and has been a major target for drug discovery. However, the mechanism of its signaling action has not been fully understood. We previously found that sPLA2-IIA binds to integrins αvß3 and α4ß1 in human and that this interaction plays a role in sPLA2-IIA's signaling action. Our recent studies found that sPLA2-IIA activates integrins in an allosteric manner through direct binding to a newly identified binding site of integrins (site 2), which is distinct from the classical RGD-binding site (site 1). The sPLA2-IIA-induced integrin activation may be related to the signaling action of sPLA2-IIA. Since sPLA2-IIA is present in normal human tears in addition to rheumatoid synovial fluid at high concentrations the sPLA2-IIA-mediated integrin activation on leukocytes may be involved in immune responses in normal and pathological conditions.

Proinflammatory secreted phospholipase A2 type IIA (sPLA-IIA) induces integrin activation through direct binding to a newly identified binding site (site 2) in integrins αvß3, α4ß1, and α5ß1.

Integrins are activated by signaling from inside the cell (inside-out signaling) through global conformational changes of integrins. We recently discovered that fractalkine activates integrins in the absence of CX3CR1 through the direct binding of fractalkine to a ligand-binding site in the integrin headpiece (site 2) that is distinct from the classical RGD-binding site (site 1). We propose that fractalkine binding to the newly identified site 2 induces activation of site 1 though conformational changes (in an allosteric mechanism). We reasoned that site 2-mediated activation of integrins is not limited to fractalkine. Human secreted phospholipase A2 type IIA (sPLA2-IIA), a proinflammatory protein, binds to integrins αvß3 and α4ß1 (site 1), and this interaction initiates a signaling pathway that leads to cell proliferation and inflammation. Human sPLA2-IIA does not bind to M-type receptor very well. Here we describe that sPLA2-IIA directly activated purified soluble integrin αvß3 and transmembrane αvß3 on the cell surface. This activation did not require catalytic activity or M-type receptor. Docking simulation predicted that sPLA2-IIA binds to site 2 in the closed-headpiece of αvß3. A peptide from site 2 of integrin ß1 specifically bound to sPLA2-IIA and suppressed sPLA2-IIA-induced integrin activation. This suggests that sPLA2-IIA activates αvß3 through binding to site 2. sPLA2-IIA also activated integrins α4ß1 and α5ß1 in a site 2-mediated manner. We recently identified small compounds that bind to sPLA2-IIA and suppress integrin-sPLA2-IIA interaction (e.g. compound 21 (Cmpd21)). Cmpd21 effectively suppressed sPLA2-IIA-induced integrin activation. These results define a novel mechanism of proinflammatory action of sPLA2-IIA through integrin activation.

Peripheral neuropathies during biologic therapies.

Peripheral neuropathies should be recognized as the adverse effects of biological agents, especially anti-TNF agents. However, no solid clinical databases for biological agent-associated peripheral neuropathies (BAPN) have been established in Japan. Here we report two cases of peripheral neuropathy associated with anti-TNF agents. One was peroneal motor neuropathy. The other case was chronic inflammatory demyelinating polyradiculoneuropathy. In addition, we summarize the previous reports on BAPN and discuss their prevalence rate, pathogenesis and management.

Insulin-like growth factor (IGF) signaling requires αvß3-IGF1-IGF type 1 receptor (IGF1R) ternary complex formation in anchorage independence, and the complex formation does not require IGF1R and Src activation.

Integrin αvß3 plays a role in insulin-like growth factor 1 (IGF1) signaling (integrin-IGF1 receptor (IGF1R) cross-talk) in non-transformed cells in anchorage-dependent conditions. We reported previously that IGF1 directly binds to αvß3 and induces αvß3-IGF1-IGF1R ternary complex formation in these conditions. The integrin-binding defective IGF1 mutant (R36E/R37E) is defective in inducing ternary complex formation and IGF signaling, whereas it still binds to IGF1R. We studied if IGF1 can induce signaling in anchorage-independent conditions in transformed Chinese hamster ovary cells that express αvß3 (ß3-CHO) cells. Here we describe that IGF1 signals were more clearly detectable in anchorage-independent conditions (polyHEMA-coated plates) than in anchorage-dependent conditions. This suggests that IGF signaling is masked by signals from cell-matrix interaction in anchorage-dependent conditions. IGF signaling required αvß3 expression, and R36E/R37E was defective in inducing signals in polyHEMA-coated plates. These results suggest that αvß3-IGF1 interaction, not αvß3-extracellular matrix interaction, is essential for IGF signaling. Inhibitors of IGF1R, Src, AKT, and ERK1/2 did not suppress αvß3-IGF-IGF1R ternary complex formation, suggesting that activation of these kinases are not required for ternary complex formation. Also, mutations of the ß3 cytoplasmic tail (Y747F and Y759F) that block ß3 tyrosine phosphorylation did not affect IGF1R phosphorylation or AKT activation. We propose a model in which IGF1 binding to IGF1R induces recruitment of integrin αvß3 to the IGF-IGF1R complex and then ß3 and IGF1R are phosphorylated. It is likely that αvß3 should be together with the IGF1-IGF1R complex for triggering IGF signaling.

An integrin binding-defective mutant of insulin-like growth factor-1 (R36E/R37E IGF1) acts as a dominant-negative antagonist of the IGF1 receptor (IGF1R) and suppresses tumorigenesis but still binds to IGF1R.

Insulin-like growth factor-1 (IGF1) is a major therapeutic target for cancer. We recently reported that IGF1 directly binds to integrins (αvß3 and α6ß4) and induces ternary complex formation (integrin-IGF1-IGF1 receptor (IGF1R)) and that the integrin binding-defective mutant of IGF1 (R36E/R37E) is defective in signaling and ternary complex formation. These findings predict that R36E/R37E competes with WT IGF1 for binding to IGF1R and inhibits IGF signaling. Here, we described that excess R36E/R37E suppressed cell viability increased by WT IGF1 in vitro in non-transformed cells. We studied the effect of R36E/R37E on viability and tumorigenesis in cancer cell lines. We did not detect an effect of WT IGF1 or R36E/R37E in cancer cells under anchorage-dependent conditions. However, under anchorage-independent conditions, WT IGF1 enhanced cell viability and induced signals, whereas R36E/R37E did not. Notably, excess R36E/R37E suppressed cell viability and signaling induced by WT IGF1 under anchorage-independent conditions. Using cancer cells stably expressing WT IGF1 or R36E/R37E, we determined that R36E/R37E suppressed tumorigenesis in vivo, whereas WT IGF1 markedly enhanced it. R36E/R37E suppressed the binding of WT IGF1 to the cell surface and the subsequent ternary complex formation induced by WT IGF1. R36E/R37E suppressed activation of IGF1R by insulin. WT IGF1, but not R36E/R37E, induced ternary complex formation with the IGF1R/insulin receptor hybrid. These findings suggest that 1) IGF1 induces signals under anchorage-independent conditions and that 2) R36E/R37E acts as a dominant-negative inhibitor of IGF1R (IGF1 decoy). Our results are consistent with a model in which ternary complex formation is critical for IGF signaling.

Integrins αvß3 and α4ß1 act as coreceptors for fractalkine, and the integrin-binding defective mutant of fractalkine is an antagonist of CX3CR1.

The membrane-bound chemokine fractalkine (FKN, CX3CL1) on endothelial cells plays a role in leukocyte trafficking. The chemokine domain (FKN-CD) is sufficient for inducing FKN signaling (e.g., integrin activation), and FKN-CD binds to its receptor CX3CR1 on leukocytes. Whereas previous studies suggest that FKN-CD does not directly bind to integrins, our docking simulation studies predicted that FKN-CD directly interacts with integrin α(v)ß(3). Consistent with this prediction, we demonstrated that FKN-CD directly bound to α(v)ß(3) and α(4)ß(1) at a very high affinity (K(D) of 3.0 × 10(-10) M to α(v)ß(3) in 1 mM Mn(2+)). Also, membrane-bound FKN bound to integrins α(v)ß(3) and α(4)ß(1), suggesting that the FKN-CD/integrin interaction is biologically relevant. The binding site for FKN-CD in α(v)ß(3) was similar to those for other known α(v)ß(3) ligands. Wild-type FKN-CD induced coprecipitation of integrins and CX3CR1 in U937 cells, suggesting that FKN-CD induces ternary complex formation (CX3CR1, FKN-CD, and integrin). Based on the docking model, we generated an integrin-binding defective FKN-CD mutant (the K36E/R37E mutant). K36E/R37E was defective in ternary complex formation and integrin activation, whereas K36E/R37E still bound to CX3CR1. These results suggest that FKN-CD binding to CX3CR1 is not sufficient for FKN signaling, and that FKN-CD binding to integrins as coreceptors and the resulting ternary complex formation are required for FKN signaling. Notably, excess K36E/R37E suppressed integrin activation induced by wild-type FKN-CD and effectively suppressed leukocyte infiltration in thioglycollate-induced peritonitis. These findings suggest that K36E/R37E acts as a dominant-negative CX3CR1 antagonist and that FKN-CD/integrin interaction is a novel therapeutic target in inflammatory diseases.

The heparin-binding domain of VEGF165 directly binds to integrin αvß3 and VEGFR2/KDR D1: a potential mechanism of negative regulation of VEGF165 signaling by αvß3.

VEGF-A is a key cytokine in tumor angiogenesis and a major therapeutic target for cancer. VEGF165 is the predominant isoform of VEGF-A, and it is the most potent angiogenesis stimulant. VEGFR2/KDR domains 2 and 3 (D2D3) bind to the N-terminal domain (NTD, residues 1-110) of VEGF165. Since removal of the heparin-binding domain (HBD, residues 111-165) markedly reduced the mitogenic activity of the growth factor, it has been proposed that the HBD plays a critical role in the mitogenicity of VEGF165. Here, we report that αvß3 specifically bound to the isolated VEGF165 HBD but not to VEGF165 NTD. Based on docking simulation and mutagenesis, we identified several critical amino acid residues within the VEGF165 HBD required for αvß3 binding, i.e., Arg123, Arg124, Lys125, Lys140, Arg145, and Arg149. We discovered that VEGF165 HBD binds to the KDR domain 1 (D1) and identified that Arg123 and Arg124 are critical for KDR D1 binding by mutagenesis, indicating that the KDR D1-binding and αvß3-binding sites overlap in the HBD. Full-length VEGF165 mutant (R123A/R124A/K125A/K140A/R145A/R149A) defective in αvß3 and KDR D1 binding failed to induce ERK1/2 phosphorylation, integrin ß3 phosphorylation, and KDR phosphorylation and did not support proliferation of endothelial cells, although the mutation did not affect the KDR D2D3 interaction with VEGF165. Since ß3-knockout mice are known to show enhanced VEGF165 signaling, we propose that the binding of KDR D1 to the VEGF165 HBD and KDR D2D3 binding to the VEGF165 NTD are critically involved in the potent mitogenicity of VEGF165. We propose that binding competition between KDR and αvß3 to the VEGF165 HBD endows integrin αvß3 with regulatory properties to act as a negative regulator of VEGF165 signaling.

A Case of Atypical Hemolytic Uremic Syndrome Triggered by Acute Pancreatitis in a Patient with a Membrane Cofactor Protein (CD46) Genetic Variant.

Atypical hemolytic uremic syndrome (aHUS) is a type of HUS. We herein report a case of aHUS triggered by pancreatitis in a patient with a heterozygous variant of membrane cofactor protein (MCP; P165S), a complement-related gene. Plasma exchange therapy and hemodialysis improved thrombocytopenia and anemia without leading to end-stage kidney disease. This MCP heterozygous variant was insufficient to cause aHUS on its own. Pancreatitis, in addition to a genetic background with a MCP heterozygous variant, led to the manifestation of aHUS. This case supports the "multiple hit theory" that several factors are required for the manifestation of aHUS.

Cross-talk between integrin α6ß4 and insulin-like growth factor-1 receptor (IGF1R) through direct α6ß4 binding to IGF1 and subsequent α6ß4-IGF1-IGF1R ternary complex formation in anchorage-independent conditions.

Integrin αvß3 plays a role in insulin-like growth factor-1 (IGF1) signaling (integrin-IGF1 receptor (IGF1R) cross-talk). The specifics of the cross-talk are, however, unclear. In a current model, "ligand occupancy" of αvß3 (i.e. the binding of extracellular matrix proteins) enhances signaling induced by IGF1 binding to IGF1R. We recently reported that IGF1 directly binds to αvß3 and induces αvß3-IGF1-IGF1R ternary complex formation. Consistently, the integrin binding-defective IGF1 mutant (R36E/R37E) is defective in inducing ternary complex formation and IGF signaling, but it still binds to IGF1R. Like αvß3, integrin α6ß4 is overexpressed in many cancers and is implicated in cancer progression. Here, we discovered that α6ß4 directly bound to IGF1, but not to R36E/R37E. Grafting the ß4 sequence WPNSDP (residues 167-172), which corresponds to the specificity loop of ß3, to integrin ß1 markedly enhanced IGF1 binding to ß1, suggesting that the WPNSDP sequence is involved in IGF1 recognition. WT IGF1 induced α6ß4-IGF1-IGF1R ternary complex formation, whereas R36E/R37E did not. When cells were attached to matrix, exogenous IGF1 or α6ß4 expression had little or no effect on intracellular signaling. When cell-matrix adhesion was reduced (in poly(2-hydroxyethyl methacrylate-coated plates), IGF1 induced intracellular signaling and enhanced cell survival in an α6ß4-dependent manner. Also IGF1 enhanced colony formation in soft agar in an α6ß4-dependent manner. These results suggest that IGF binding to α6ß4 plays a major role in IGF signaling in anchorage-independent conditions, which mimic the in vivo environment, and is a novel therapeutic target.

Identification of inhibitors against interaction between pro-inflammatory sPLA2-IIA protein and integrin αvß3.

Increased concentrations of secreted phospholipase A2 type IIA (sPLA2-IIA), have been found in the synovial fluid of patients with rheumatoid arthritis. It has been shown that sPLA2-IIA specifically binds to integrin αvß3, and initiates a signaling pathway that leads to cell proliferation and inflammation. Therefore, the interaction between integrin and sPLA2-IIA could be a potential therapeutic target for the treatment of proliferation or inflammation-related diseases. Two one-bead-one-compound peptide libraries were constructed and screened, and seven target hits were identified. Herein we report the identification, synthesis, and biological testing of two pyrazolylthiazole-tethered peptide hits and their analogs. Biological assays showed that these compounds were able to suppress the sPLA2-IIA-integrin interaction and sPLA2-IIA-induced migration of monocytic cells and that the blockade of the sPLA2-IIA-integrin binding was specific to sPLA2-IIA and not to the integrin.

Virtual Screening of Protein Data Bank via Docking Simulation Identified the Role of Integrins in Growth Factor Signaling, the Allosteric Activation of Integrins, and P-Selectin as a New Integrin Ligand.

Integrins were originally identified as receptors for extracellular matrix (ECM) and cell-surface molecules (e.g., VCAM-1 and ICAM-1). Later, we discovered that many soluble growth factors/cytokines bind to integrins and play a critical role in growth factor/cytokine signaling (growth factor-integrin crosstalk). We performed a virtual screening of protein data bank (PDB) using docking simulations with the integrin headpiece as a target. We showed that several growth factors (e.g., FGF1 and IGF1) induce a integrin-growth factor-cognate receptor ternary complex on the surface. Growth factor/cytokine mutants defective in integrin binding were defective in signaling functions and act as antagonists of growth factor signaling. Unexpectedly, several growth factor/cytokines activated integrins by binding to the allosteric site (site 2) in the integrin headpiece, which is distinct from the classical ligand (RGD)-binding site (site 1). Since 25-hydroxycholesterol, a major inflammatory mediator, binds to site 2, activates integrins, and induces inflammatory signaling (e.g., IL-6 and TNFα secretion), it has been proposed that site 2 is involved in inflammatory signaling. We showed that several inflammatory factors (CX3CL1, CXCL12, CCL5, sPLA2-IIA, and P-selectin) bind to site 2 and activate integrins. We propose that site 2 is involved in the pro-inflammatory action of these proteins and a potential therapeutic target. It has been well-established that platelet integrin αIIbß3 is activated by signals from the inside of platelets induced by platelet agonists (inside-out signaling). In addition to the canonical inside-out signaling, we showed that αIIbß3 can be allosterically activated by inflammatory cytokines/chemokines that are stored in platelet granules (e.g., CCL5, CXCL12) in the absence of inside-out signaling (e.g., soluble integrins in cell-free conditions). Thus, the allosteric activation may be involved in αIIbß3 activation, platelet aggregation, and thrombosis. Inhibitory chemokine PF4 (CXCL4) binds to site 2 but did not activate integrins, Unexpectedly, we found that PF4/anti-PF4 complex was able to activate integrins, indicating that the anti-PF4 antibody changed the phenotype of PF4 from inhibitory to inflammatory. Since autoantibodies to PF4 are detected in vaccine-induced thrombocytopenic thrombosis (VIPP) and autoimmune diseases (e.g., SLE, and rheumatoid arthritis), we propose that this phenomenon is related to the pathogenesis of these diseases. P-selectin is known to bind exclusively to glycans (e.g., sLex) and involved in cell-cell interaction by binding to PSGL-1 (CD62P glycoprotein ligand-1). Unexpectedly, through docking simulation, we discovered that the P-selectin C-type lectin domain functions as an integrin ligand. It is interesting that no one has studied whether P-selectin binds to integrins in the last few decades. The integrin-binding site and glycan-binding site were close but distinct. Also, P-selectin lectin domain bound to site 2 and allosterically activated integrins.

The heparin-binding domain of VEGF165 directly binds to integrin αvß3 and plays a critical role in signaling.

VEGF-A is a key cytokine in tumor angiogenesis and a major therapeutic target for cancer. VEGF165 is the predominant isoform and is the most potent angiogenesis stimulant. VEGFR2/KDR domains 2 and 3 (D2D3) bind to the N-terminal domain (NTD, residues 1-110) of VEGF165. Since removal of the heparin-binding domain (HBD, residues 111-165) markedly reduced the mitogenic activity of VEGF165, it has been proposed that the HBD plays a critical role in the mitogenicity of VEGF165. Integrin αvß3 has been shown to bind to VEGF165, but the role of integrin αvß3 in VEGF165 signaling are unclear. Here we describe that αvß3 specifically bound to the isolated HBD, but not to the NTD. We identified several critical amino acid residues in HBD for integrin binding (Arg-123, Arg-124, Lys-125, Lys-140, Arg-145, and Arg-149) by docking simulation and mutagenesis, and generated full-length VEGF165 that is defective in integrin binding by including mutations in the HBD. The full-length VEGF165 mutant defective in integrin binding (R123A/R124A/K125A/K140A/R145A/R149A) was defective in ERK1/2 phosphorylation, integrin ß3 phosphorylation, and KDR phosphorylation, although the mutation did not affect KDR binding to VEGF165. We propose a model in which VEGF165 induces KDR (through NTD)-VEGF165 (through HBD)-integrin αvß3 ternary complex formation on the cell surface and this process is critically involved in potent mitogenicity of VEGF165.

Pro-Inflammatory Chemokines CCL5, CXCL12, and CX3CL1 Bind to and Activate Platelet Integrin αIIbß3 in an Allosteric Manner.

Activation of platelet integrin αIIbß3, a key event for hemostasis and thrombus formation, is known to be mediated exclusively by inside-out signaling. We showed that inflammatory chemokines CX3CL1 and CXCL12 in previous studies, and CCL5 in this study, bound to the allosteric binding site (site 2) of vascular integrin αvß3, in addition to the classical ligand binding site (site 1), and allosterically activated integrins independent of inside-out signaling. Since αIIbß3 is exposed to inflammatory chemokines at increased concentrations during inflammation (e.g., cytokine/chemokine storm) and platelet activation, we hypothesized that these chemokines bind to and activate αIIbß3 in an allosteric activation mechanism. We found that these chemokines bound to αIIbß3. Notably, they activated soluble αIIbß3 in 1 mM Ca2+ by binding to site 2. They activated cell-surface αIIbß3 on CHO cells, which lack machinery for inside-out signaling or chemokine receptors, quickly (<1 min) and at low concentrations (1-10 ng/mL) compared to activation of soluble αIIbß3, probably because chemokines bind to cell surface proteoglycans. Furthermore, activation of αIIbß3 by the chemokines was several times more potent than 1 mM Mn2+. We propose that CCL5 and CXCL12 (stored in platelet granules) may allosterically activate αIIbß3 upon platelet activation and trigger platelet aggregation. Transmembrane CX3CL1 on activated endothelial cells may mediate platelet-endothelial interaction by binding to and activating αIIbß3. Additionally, these chemokines in circulation over-produced during inflammation may trigger αIIbß3 activation, which is a possible missing link between inflammation and thrombosis.

Differential expression of PD­L1 and PD­L2 is associated with the tumor microenvironment of TILs and M2 TAMs and tumor differentiation in non­small cell lung cancer.

To improve the treatment strategy of immune­checkpoint inhibitors for non­small cell lung cancer (NSCLC), a comprehensive analysis of programmed death­ligand (PD­L)1 and PD­L2 expression is clinically important. The expression of PD­L1 and PD­L2 on both tumor cells (TCs) and tumor­infiltrating immune cells (ICs) was investigated, with respect to tumor­infiltrating lymphocytes (TILs) and M2 tumor­associated macrophages (TAMs), which are key components of the tumor microenvironment, in 175 patients with resected NSCLC. The TIL and M2 TAM densities were associated with the expression of PD­L1 on the two TCs (both P<0.0001) and ICs (both P<0.0001). The TIL and M2 TAM densities were also associated with the expression of PD­L2 on both TCs (P=0.0494 and P=0.0452, respectively) and ICs (P=0.0048 and P=0.0125, respectively). However, there was no correlation between the percentage of PD­L1­positive TCs and the percentage of PD­L2­positive TCs (r=0.019; P=0.8049). Meanwhile, tumor differentiation was significantly associated with the PD­L1 expression on TCs and ICs (P=0.0002 and P<0.0001, respectively). By contrast, tumor differentiation was inversely associated with the PD­L2 expression on both TCs and ICs (P=0.0260 and P=0.0326, respectively). In conclusion, the combined evaluation of PD­L1 and PD­L2 expression could be clinically important in the treatment strategy of immune­checkpoint inhibitors in patients with NSCLC. In particular, the evaluation of PD­L2 expression may be necessary for patients with PD­L1­negative NSCLC.