A critical role of thrombin/PAR-1 in ADP-induced platelet secretion and the second wave of aggregation

BACKGROUND

The stable or second wave of platelet aggregation often observed in ADP-stimulated platelet-rich plasma (PRP) with an artificially lowered extracellular calcium level has been attributed to enhanced thromboxane A2 (TXA2 ) generation and inhibition of ectonucleotidase activity. However, the role of thrombin in ADP-induced platelet secretion and the second wave of aggregation is unknown.

OBJECTIVES AND METHODS

We employed aggregometry, flow cytometry, immunoblotting and ELISA to determine whether and how thrombin participates in ADP-induced platelet secretion and the second wave of aggregation.

RESULTS

ADP induces a phosphoinositide 3-kinase (PI3K) pathway-dependent thrombin generation, presumably resulting from the cleavage of αII b β3 -associated prothrombin. Generated thrombin subsequently activates protease-activated receptor-1 (PAR-1) and mediates dense granule secretion and the second wave of platelet aggregation in ADP-stimulated citrated PRP. Thus, ADP-induced dense granule secretion and the second wave of platelet aggregation in PRP were similarly and non-additively blocked by thrombin inhibitor hirudin, PAR-1 antagonist SCH-79797 or PI3K inhibitor wortmannin. Moreover, ADP stimulation caused the dissociation of prothrombin from αII b β3 and an increased plasma thrombin level; both were prevented by wortmannin. Furthermore, the wortmannin-inhibited second wave of platelet aggregation by ADP was restored by a subaggregation concentration of PAR-1 activating peptide SFLLRN. Blocking TXA2 production with indomethacin or restoring extracellular calcium to physiological concentration did not influence this thrombin/PAR-1 dependence.

CONCLUSIONS

A PI3K-dependent thrombin generation and the resultant PAR-1 activation serve as an indispensable mechanism to relay the platelet activation process induced by ADP.

Forward error correction supported 150 Gbit/s error-free wavelength conversion based on cross phase modulation in silicon

We build a forward error correction (FEC) module and implement it in an optical signal processing experiment. The experiment consists of two cascaded nonlinear optical signal processes, 160 Gbit/s all optical wavelength conversion based on the cross phase modulation (XPM) in a silicon nanowire and subsequent 160 Gbit/s-to-10 Gbit/s demultiplexing in a highly nonlinear fiber (HNLF). The XPM based all optical wavelength conversion in silicon is achieved by off-center filtering the red shifted sideband on the CW probe. We thoroughly demonstrate and verify that the FEC code operates correctly after the optical signal processing, yielding truly error-free 150 Gbit/s (excl. overhead) optically signal processed data after the two cascaded nonlinear processes.

Ultracold fermi gases with resonant dipole-dipole interaction

The superfluid phases in resonant dipolar Fermi gases are investigated by the standard mean-field theory. In contrast to the crossover from Bose-Einstein condensation (BEC) to Bardeen-Cooper-Schrieffer superfluid in Fermi gases with isotropic interactions, resonant dipolar interaction leads to two completely different BEC phases of the tight-binding Fermi molecules on both sides of the resonance, which are characterized by two order parameters with distinct internal symmetries. We point out that, near the resonances, the two competitive phases can coexist, and an emergent relative phase between the two order parameters spontaneously breaks time-reversal symmetry, which could be observed in momentum resolved rf spectroscopy.

Structure and growth of quasi-one-dimensional YSi2 nanophases on Si(100)

Quasi-one-dimensional YSi(2) nanostructures are formed via self-assembly on the Si(100) surface. These epitaxial nanowires are metastable and their formation strongly depends on the growth parameters. Here, we explore the various stages of yttrium silicide formation over a range of metal coverages and growth temperatures, and establish a rudimentary phase diagram for these novel and often coexisting nanophases. We identify, in addition to previously identified stoichiometric wires, several new nanowire systems. These nanowires exhibit a variety of surface reconstructions, which sometimes coexist on a single wire. From a comparison of scanning tunneling microscopy images, tunneling spectra, and first-principles density functional theory calculations, we determine that these surface reconstructions arise from local orderings of yttrium vacancies. Nanowires often agglomerate into nanowire bundles, the thinnest of which are formed from single wire pairs. The calculations show that such bundles are energetically favored compared to well-separated single wires. Thicker bundles are formed at slightly higher temperature. They extend over several microns, forming a robust network of conducting wires that could possibly be employed in nanodevice applications.

Abstract P3-04-08: Expression of hormone-responsive genes in benign breast tissue varies with menstrual cycle phase and menopausal status

Background: The expression of many genes is known to be regulated by ambient hormone levels. In a preliminary study of random fine-needle aspirate (rFNA) samples from benign breast tissue, we found several genes that were highly correlated with the serum levels of progesterone (P4) and estradiol (E2). We now present data to further validate these genes as markers of menstrual cycle phase (MCP) and menopausal status (MPS) in benign breast tissue which may allow retrospective classification of archived breast samples with respect to MCP and MPS at the time of sampling.

Methods: 240 rFNA samples from healthy women with recorded hormonal data at the time of sampling were analyzed. We divided these subjects by menstrual cycle phase (MCP) and menopausal status (MPS): 41 early follicular: (low circulating E2 and P4); 48 mid-cycle (high E2 and low P4); 31 luteal (moderate E2 and high P4). 120 post-menopausal (low E2 and low P4). 100 ng of RNA from rFNA samples of the breast was reverse transcribed. Amplicons of interest were linearly amplified to 14 cycles for 35 genes related to hormone responsiveness. qPCR reactions were carried out using the TaqMan OpenArray (Applied Biosystems). For each gene of interest, expression levels were normalized to the average expression of GAPDH. Gene expression difference between groups were conducted using the Mann-Whitney Test. P-values from gene expression difference were adjusted via the Benjamini-Hochberg (1995) approach.

Results: The mean value of TNFSF11 expression level was 13.19 fold higher in luteal phase subjects than in post-menopausal subjects (p = 0.0003) where there was also the biggest difference of serum P4 level between groups. The expression of DIO2 and MYBPC1 was also significantly higher in luteal phase group than in the post-menopausal group (p = 0.005, p = 0.02, respectively). These 3 genes also demonstrated a higher expression pattern in luteal phase than mid-cycle and follicular phase but analysis is still ongoing. All comparisons between these groups will be presented at the meeting.

Conclusion: The expression levels of TNFSF11, DIO2 and MYBPC1 vary with MCP and MPS. These hormone-responsive genes are candidate MCP classifiers which could be applied to archived breast samples to assess whether biomarkers of breast cancer risk are stable across the menstrual cycle, since MCP and MPS variation is likely an important source of biological noise in studies of archived breast biopsy material.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-04-08.

Abstract P2-05-21: Molecular subtypes of invasive breast cancers show differential expression of the proliferation marker Aurora Kinase A (AURKA)

Background: Invasive breast cancer (IBC) has been classified into four major subtypes based on gene expression profiling. The luminal A subtype (LA) has the best prognosis, when compared to luminal B (LB), HER2+, and basal-like (Basal). Ki67 by gene expression or immunohistochemistry (IHC) is commonly used as a proliferation index. The function of Ki67 in proliferation remains unknown. AURKA (STK15) is known to play an important role in mitosis, and is a component of the 21-gene recurrence score of the Oncotype Dx. With multiple platforms of molecular data available from hundreds of IBC tissues in The Cancer Genome Atlas project (TCGA), we sought to study the association of AURKA with different IBC subtypes and explore its use as a proliferation marker in IBCs.

Methods: Gene expression (Agilent, log2 transformed), relative DNA copy number (CN, Affymetrix SNP 6.0), and exome sequence mutation (Illumina) data for 459 IBC cases were downloaded from the TCGA data portal. PAM50 classification results of all samples were obtained from the TCGA breast cancer AWG group and included 203 LA, 113 LB, 51 HER2+, 84 Basal-like, and 8 Normal-like which were not used in this study due to the low numbers. Kruskal-Wallis tests were used to evaluate the differences among four subtypes on AURKA expression and CN, followed by Wilcoxon Mann-Whitney test with Bonferroni adjustment for pairwise analyses. Pearson's Correlation Coefficient was used for correlation analyses. All statistical analyses were performed using SAS and R, and two-sided, p values <.05 were considered statistically significant.

Results: There was a significant difference among IBC subtypes, in gene expression as well as in CN (p values < 0.0001). AURKA mRNA levels were significantly lower in LA (mean±SD, −2.61±0.63) compared to LB (−1.45±0.78), HER2+ (−1.38±0.61), and Basal (−1.26±0.62) subtypes (p values all < 0.0001). No significant difference was detected between other subtype pairs. In CN analysis, Basal (0.09±0.22) was lower than HER2+ (0.32±0.308, p < 0.0002) and LB (0.33±0.41, p < 0.0001), and LA (0.14±0.28) is lower than HER2 (p < 0.0016) and LB (p < 0.0001), but no other significant CN difference between the subtypes were found. The means and SDs are provided for reference only. No correlation of p53 mutation status and AURKA expression were observed. However, AURKA gene expression level is correlated with MKI67 gene expression (R = 0.69, p < 2.2e−16), and its correlation with PAM50 proliferation score is even higher (R = 0.80, p < 2.2e−16).

Discussion: Using the TCGA data we observed that the mean gene expression level of AURKA is significantly lower in LA than the other IBC subtypes, by more than 50% (note the log2 transformation). This differential expression is not completely due to CN changes (especially for the Basal subtype). There is a strong association with other tumor cell proliferation markers such as the MKI67 gene and the PAM50 proliferation score. We are using computational and laboratorial studies to better understand the role of AURKA in the etiology of invasive breast cancers.

The views expressed in this article are those of the author and do not reflect the official policy of the Department of Defense, or U.S. Government.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P2-05-21.

Abstract P5-01-07: Fibroadenomatoid changes are more prevalent in middle-aged women and have a positive association with invasive breast cancer

Background: The role of benign breast diseases (BBDs) in the development of invasive breast cancers (IBCs) has been studied for many years. Some BBDs have been studied comprehensively (e.g., fibrocystic changes (FCC)) while less is known about other BBDs (e.g., fiboadenomatoid changes (FAC)). FAC has been considered by some researchers as a precursor of fibroadenoma (FA). Conclusions from different studies vary, partially due to different interpretation methods and diagnostic criteria when multiple hospitals and pathologists were involved. In this study, we used subjects in the Clinical Breast Care Project (CBCP) from a military medical center where pathology slides were reviewed by a single breast pathologist to study FAC, FA, and FCC in comparison to the published literature.

Methods: Subjects were enrolled in the study following IRB-approved, HIPAA-compliant protocols. All the clinicopathologic data are available from the CBCP data warehouse (DW4TR). In the CBCP, FCC is composed of 4 components: stromal fibrosis, cysts, apocrine metaplasia, and sclerosing adenosis. Two modeling studies were performed. i) For the BBDs and IBC association study, two groups of subjects were identified: 1136 subjects diagnosed with “Benign” or “Atypical” diseases, and 619 cases diagnosed with IBCs. A logistic regression model was developed for the prediction of IBCs by the 3 BBDs and 2 well-established risk factors (RF): age (younger, <=40; middle-aged, 41–60; older, >60) and race (Caucasian, African American, Asian, and other). ii) For the RF association study with the BBDs, 6 additional RFs reported to be associated with these BBDs were identified from the literature: current use of oral contraceptives, number of live births, education, body mass index, hormonal replacement therapy, and IBC family history. These 8 RFs were used to develop a logistic regression model for each of the BBDs. The analyses were performed in SAS.

Results: In the first study, age and race were confirmed as RFs for IBCs. FAC was positively associated with IBC (OR = 3.04, 95%CI=2.06 to 4.50). FA was negatively associated with IBC, and the level of the association was stronger in women without FCC (OR = 0.15, 95%CI=0.08 to 0.28), compared to women with FCC (OR = 0.40, 95%CI=0.24 to 0.65). FCC was not significantly associated with IBC. Results from the second study indicated that, age was significantly associated with FAC (p = 0.015), specifically the middle-aged women were more likely to have FAC compared to younger women (OR = 2.03, 95%CI=1.23 to 3.34), while the older women were at a non-significantly increased risk. Trends of association with FAC were also noted for the number of live birth (p = 0.095), ethnicity (p = 0.096), and current oral contraceptive pill use (p = 0.077). The FCC model results were in general consistent with the literature, and we also confirmed that age was negatively associated with the diagnosis of FA.

Discussion: Our study was consistent with FCC findings in the literature. We observed that FAC was positively associated with IBC, whereas FA was negatively associated. Also, FAC occurred more often in middle-aged women while FAs occurrence was higher in younger women. Our results suggest that FAC and FA may be two different diseases.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-01-07.

RFLP analysis of the progeny from Oryza alta Swallen x Oryza sativa L

RFLP analyses were carried out in the progeny from a cross of two phylogenetically distant rice species, wild rice Oryza alta Swallen (CCDD, 2n = 48) and cultivated rice O. sativa L. (AA, 2n = 24). The sterile plants gave heterozygous RFLP patterns at most of the loci detected. They looked more like their wild rice parent, with 36 chromosomes in their root-tip cells and pollen mother cells. In two partially fertile plants, however, most of the markers that were used showed RFLP patterns similar to the cultivated parent, O. sativa. By cytological study, it was found that nearly one-third of the chromosomes had been eliminated in the partially fertile plants. Their seeds have short awns, which is a characteristic of their wild parent, O. alta. An introgression occurred in one of the partially fertile plants, which led to the discussion about a nonconventional mechanism in wide hybridization for transference of wild rice chromosome segments to cultivated rice chromosomes.

RPTPζ/phosphacan is abnormally glycosylated in a model of muscle-eye-brain disease lacking functional POMGnT1

Congenital muscular dystrophies (CMDs) with associated brain abnormalities are a group of disorders characterized by muscular dystrophy and brain and eye abnormalities that are frequently caused by mutations in known or putative glycotransferases involved in protein O-mannosyl glycosylation. Previous work identified α-dystroglycan as the major substrate for O-mannosylation and its altered glycosylation the major cause of these disorders. However, work from several labs indicated that other proteins in the brain are also O-mannosylated and therefore could contribute to CMD pathology in patients with mutations in the protein O-mannosylation pathway, however few of these proteins have been identified and fully characterized in CMDs. In this study we identify receptor protein tyrosine phosphatase ζ (RPTPζ) and its secreted variant, phosphacan, as another potentially important substrate for protein O-mannosylation in the brain. Using a mouse model of muscle-eye-brain disease lacking functional protein O-mannose β-1,2-N-acetylglucosaminyltransferase (POMGnT1), we show that RPTPζ/phosphacan is shifted to a lower molecular weight and distinct carbohydrate epitopes normally detected on the protein are either absent or substantially reduced, including Human Natural Killer-1 (HNK-1) reactivity. The spatial and temporal expression patterns of these O-mannosylated forms of RPTPζ/phosphacan and its hypoglycosylation and loss of HNK-1 glycan epitopes in POMGnT1 knockouts are suggestive of a role in the neural phenotypes observed in patients and animal models of CMDs.