Leukocyte- and platelet-derived microparticles correlate with thrombus weight and tissue factor activity in an experimental mouse model of venous thrombosis.

Microparticles (MP) are lipid vesicles from platelets, leukocytes and endothelial cells that are involved in early thrombogenesis. We evaluated a detailed time-course analysis of MPs on thrombogenesis and the associated tissue factor (TF) activity in wild-type, in gene-deleted for E- and P-selectins and with high levels of P-selectin expression after the initiation of venous thrombosis in mice. Inferior vena cava (IVC) ligation was performed on C57BL/6 mice (n = 191, 59 = wild-type [WT], 55 = gene-deleted for E- and P - selectins [knock-outs, EPKO] and 77 = elevated levels of soluble P-selectin, named Delta Cytoplasmic Tail (DeltaCT). Animals were euthanised at various time points to assess MP production, origin and thrombus weight. MPs were re-injected into separate mice at concentrations of 80,000 and 160,000 units, as well as from different ages. In addition, MPs from thrombosed animals were pooled and TF activity quantitated using a chromogenic assay. Thrombus weight correlated negatively with MPs derived from leukocytes, and positively with MPs derived from platelets for WT animals (p < 0.05), while MPs from platelets presented a positive correlation to thrombus weight in the WT and EPKO groups (p < 0.01). Total MPs correlated negatively with thrombus weight in the DeltaCT group (p < 0.05). MP re-injections led to greater thrombus weight, while older MP reinjections tended to form larger thrombus than younger. Finally, TF bearing MPs showed a significant correlation to MP concentrations (R = 0.99). In conclusion, MPs appear to be an important element in venous thrombogenesis.

Prophylactic P-selectin inhibition with PSI-421 promotes resolution of venous thrombosis without anticoagulation.

P-selectin inhibition has been evaluated as a therapeutic for prevention and treatment of venous thrombosis. In this study, a novel oral small-molecule inhibitor of P-selectin, PSI-421, was evaluated in a baboon model of stasis induced deep vein thrombosis (DVT). Experimental groups included i) primates receiving a single oral dose of 1 mg/kg PSI-421 two days prior and continued six days after thrombosis (n = 3); ii) primates receiving a single daily subcutaneous dose of 0.57 mg/kg enoxaparin sodium two days prior and continued six days post thrombosis (n = 3); and iii) primates receiving no treatment (n = 3). PSI-421 treated primates had greater percent vein reopening and less vein wall inflammation than the enoxaparin and controls at day 6. Microparticle tissue factor activity (MPTFA) was significantly lower in the animals receiving PSI-421 immediately after thrombosis (T+6 hours day 0) suggesting lower potential for thrombogenesis in these animals. PSI-421 also reduced soluble P-selectin levels versus controls at T+6 hours day 0, day 2 and 6. Experimental animals in any group showed no adverse effects on coagulation. This study is the first to demonstrate a reduction in MPTFA associated with vein reopening and reduced vein inflammation due to oral P-selectin inhibition in a baboon model of DVT.

Resolution of venous thrombosis using a novel oral small-molecule inhibitor of P-selectin (PSI-697) without anticoagulation.

P-selectin inhibition has been shown to decrease thrombogenesis in multiple animal species. In this study, we show that a novel oral small-molecule inhibitor of P-selectin, PSI-697, promotes thrombus resolution and decreases inflammation in a baboon model of venous thrombosis. Experimental groups consisted of the following: 1) primates receiving a single oral dose of PSI-697 (30 mg/kg) daily starting three days pre-iliac vein balloon occlusion, and continued for six days; 2) primates receiving a single treatment dose of a low-molecular-weight-heparin (LMWH) (1.5 mg/kg) daily starting one day pre-iliac balloon occlusion, and continued for six days; and 3) primates receiving a single oral dose of a vehicle control daily starting three days pre-iliac vein balloon occlusion, and continued for six days. Animals receiving PSI-697, although thrombosed after balloon deflation, demonstrated greater than 80% vein lumen opening over time, with no opening (0%) for vehicle control (p < 0.01). LMWH opening evident after balloon deflation slightly deteriorated over time compared to PSI-697. PSI-697 therapy also significantly decreased vein wall inflammation determined by magnetic resonance venography (MRV). Importantly, this beneficial opening occurred without measured anticoagulation. Animals receiving PSI-697 demonstrated significantly increased plasma D-dimer levels versus LMWH and control animals six hours post thrombus induction (p < 0.01). This study is the first to demonstrate the effectiveness of oral P-selectin inhibition to modify venous thrombogenesis, increase vein lumen opening, and decrease inflammation in a large animal model.

Allelic loss and tumor pathology in head and neck squamous cell carcinoma.

Allelic loss is a common occurrence in head and neck tumors and has been shown to be an independent predictor of prognosis; however, the relationship between allelic loss and tumor pathology is not well-known. We studied 139 patients who were newly diagnosed with squamous cell cancer of the head and neck to determine whether tumor pathology was correlated with allelic loss at one or more of eight different regions on chromosomes 3p, 5q, 8p, 9p, 10p, 18q, and 21q. At each chromosomal region, loss of heterozygosity at any one of three or four highly polymorphic microsatellite markers that spanned the region in question was considered evidence for allelic loss. A pathologist scored all tumors for seven tumor pathology and host interface parameters. Mean allelic loss across all eight regions was associated with mitotic index (P =.034) and inflammatory response (P =.005). For allelic loss at specific chromosomal regions, the most statistically significant trends were between overall tumor grade and 3p14.2-p13 (P =.014), mitotic index and 3p24.3-p14.3 (P =.026), 9p24.2-p21 (P =.004) and 18q12.3-q23 (P =.009), inflammatory response and 3p14.2-p13 (P =.008) and 9p24.2-p21 (P =.001), desmoplastic response and 9p24.2-p21 (P =.009), and pattern of invasion and 21q21-q22.2 (P =.015). Our results suggest that genes involved in tumor suppression and oncogenesis can potentially be classified based on specific pathologic events in head and neck squamous cell carcinogenesis that they modify.