| 1. |
- Balogh, Istvan, et al.
(författare)
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Analysis of Gas6 in Human Platelets and Plasma.
- 2005
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - 1524-4636. ; 25:6, s. 1280-1286
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Tidskriftsartikel (refereegranskat)abstract
- Objective - Gas6 is a member of the vitamin K-dependent protein family. Gas6- deficient mice were found to be resistant to thrombosis because of defective platelet function. Mouse Gas6 was demonstrated to be present in platelets and found to be involved in platelet aggregation. The aim of this study was to investigate the presence of Gas6 in human platelets and plasma and determine its role in platelet function. Methods and Results - The presence of Gas6 in human platelets and plasma was analyzed using sensitive immunologic methods. Mass spectrometry and ELISA were used to identify and quantify Gas6 in plasma. Gas6 was demonstrated to be present in human plasma, at a concentration determined to be 13 to 23 ng/mL (0.16 to 0.28 nM). Furthermore, plasma Gas6 levels were found to be lower in patients administered with warfarin. However, Gas6 was undetectable in human platelets. Conclusions - This is the first report to identify and quantify Gas6 in human plasma. However, Gas6 protein was not detected in human platelets, suggesting that any potential platelet-specific function could be because of Gas6 from the circulation. These findings open up new directions regarding the role of Gas6 in normal and pathophysiological situations such as inflammation, autoimmune disease, thrombosis and arteriosclerosis.
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| 2. |
- Carter, Jessica A., et al.
(författare)
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CpG dinucleotide-specific hypermethylation of the TNS3 gene promoter in human renal cell carcinoma
- 2013
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Ingår i: Epigenetics. - : Informa UK Limited. - 1559-2294 .- 1559-2308. ; 8:7, s. 739-747
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Tidskriftsartikel (refereegranskat)abstract
- Tensin3 is a cytoskeletal regulatory protein that inhibits cell motility. Downregulation of the gene encoding Tensin3 (TNS3) in human renal cell carcinoma (RCC) may contribute to cancer cell metastatic behavior. We speculated that epigenetic mechanisms, e.g., gene promoter hypermethylation, might account for TNS3 downregulation. In this study, we identified and validated a TNS3 gene promoter containing a CpG island, and quantified the methylation level within this region in RCC. Using a luciferase reporter assay we demonstrated a functional minimal promoter activity for a 500-bp sequence within the TNS3 CpG island. Pyrosequencing enabled quantitative determination of DNA methylation of each CpG dinucleotide (a total of 43) in the TNS3 gene promoter. Across the entire analyzed CpG stretch, RCC DNA showed a higher methylation level than both non-tumor kidney DNA and normal control DNA. Out of all the CpGs analyzed, two CpG dinucleotides, specifically position 2 and 8, showed the most pronounced increases in methylation levels in tumor samples. Furthermore, CpG-specific higher methylation levels were correlated with lower TNS3 gene expression levels in RCC samples. In addition, pharmacological demethylation treatment of cultured kidney cells caused a 3-fold upregulation of Tensin3 expression. In conclusion, these results reveal a differential methylation pattern in the TNS3 promoter occurring in human RCC, suggesting an epigenetic mechanism for aberrant Tensin downregulation in human kidney cancer.
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| 3. |
- Gustafsson, Anna, et al.
(författare)
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Differential expression of Axl and Gas6 in renal cell carcinoma reflecting tumor advancement and survival
- 2009
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Ingår i: Clinical Cancer Research. - : American association for cancer research. - 1078-0432 .- 1557-3265. ; 15:14, s. 4742-4749
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Overexpression of the receptor tyrosine kinase Axl is implicated in several cancers. Therefore, we conducted this study to determine the expression of Axl and its ligand Gas6 in various renal cell carcinoma (RCC) types and in oncocytoma. EXPERIMENTAL DESIGN: Real-time quantitative reverse transcription-PCR was used to quantify tumor mRNA levels for Axl and Gas6 in a cohort (n = 221) of RCC patients. Serum levels of soluble sAxl and Gas6 proteins were measured using specific ELISA assays (n = 282). The presence of Axl protein in tumor tissue was evaluated by immunohistochemistry (n = 294). Results were correlated to tumor-associated variables, clinical biochemical tests, and patient survival. RESULTS: Tumor Axl mRNA levels correlated independently to survival when assessed against tumor stage and grade. In the study group, the median cancer-specific survival of all RCC patients during 307 months of follow-up was 55 months (confidence interval, +/-40.4). The 25% of patients with lowest tumor Axl mRNA levels had significantly better survival than the rest (P = 0.0005), with 70% of the patients still alive at the end of follow-up. In contrast, in patients with medium-high Axl mRNA, only 25% were alive at the end of follow-up. Tumor Gas6 mRNA levels correlated to survival, tumor-associated variables, and disease severity as did serum levels of soluble sAxl and Gas6 protein. However, no correlation between Axl protein in tumor tissue and survival was found. CONCLUSIONS: Axl and Gas6 expression in RCC are associated with tumor advancement and patient survival. In particular, low tumor Axl mRNA levels independently correlated with improved survival.
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| 4. |
- Hafizi, Sassan, et al.
(författare)
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C1-TEN is a negative regulator of the Akt/PKB signal transduction pathway and inhibits cell survival, proliferation, and migration
- 2005
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Ingår i: FASEB Journal. - : Wiley. - 1530-6860 .- 0892-6638. ; 19:8, s. 971-971
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Tidskriftsartikel (refereegranskat)abstract
- We have previously identified C1 domain-containing phosphatase and TENsin homologue (C1-TEN) as being an intracellular binding partner for Axl receptor tyrosine kinase (RTK). C1-TEN is a tensin-related protein that houses an N-terminal region with predicted structural similarity to PTEN. Here, we report our observations on the effects of ectopic expression of C1-TEN in HEK293 cells, which resulted in profound molecular and phenotypic changes. Stable expression of C1-TEN altered cellular morphology, with less cell spreading and weaker filamentous actin staining. Cells overexpressing C1-TEN were inhibited greatly in their proliferation and migration rates as compared with mock-transfected cells. Furthermore, serum starvation-induced apoptosis caused a twofold increase in caspase 3 activity in C1-TEN-overexpressing cells vs. mock cells. In addition, C1-TEN-overexpressing cells showed a markedly reduced phosphorylation of Akt/PKB kinase and its substrate GSK3, as well as reduced Akt enzymatic activity. No such effects on JNK were observed. Also, serum-stimulated activation of Akt was delayed in C1-TEN-overexpressing cells, while no difference in profile of ERK activation was observed. Furthermore, cells expressing a C1-TEN mutant where the putative phosphatase active site cysteine at position 231 was substituted for a serine displayed full restoration of both cell proliferation and Akt activation. In conclusion, C1-TEN appears to be a novel intracellular phosphatase that negatively regulates the Akt/PKB signaling cascade, and is similar to its relative PTEN in this respect. However, the particular domain organization of C1-TEN may enable it to regulate RTK and other signaling complexes that are linked to Akt/PKB signaling in a unique manner.
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| 5. |
- Hafizi, Sassan, et al.
(författare)
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Differential effects of rapamycin, cyclosporine A, and FK506 on human coronary artery smooth muscle cell proliferation and signalling
- 2004
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Ingår i: Vascular Pharmacology. - : Elsevier BV. - 1537-1891. ; 41:4-5, s. 167-176
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Tidskriftsartikel (refereegranskat)abstract
- Background: Immunosuppressive agents are at the forefront of preventing organ rejection after transplantation. However, their effects on vascular smooth muscle cell-mediated intimal hyperplasia that occurs in post-transplant coronary artery disease are less well known. Methods and results: We investigated the in vitro effects of three immunosuppressive agents cyclosporine A (CsA), FK506 (tacrolimus), and rapamycin (sirolimus, Rapa) on cultured human coronary artery smooth muscle cells (cSMC). CsA inhibited both platelet-derived growth factor (PDGF)-stimulated DNA synthesis and serum-induced proliferation at high concentrations (greater than or equal to 1000 ng/ ml). The growth-inhibitory effect of CsA was not altered by anti-TGF-beta neutralising antibodies nor was autocrine TGF-beta release detected in CsA-treated culture medium. At inhibitory doses, CsA inhibited ERK kinase activation by PDGF, although cytotoxicity was also apparent. Most notably, CsA visibly prevented PDGF-induced altered cell morphology. Rapa was a highly potent and effective inhibitor of cSMC proliferation (reduction in DNA synthesis by >50% from 0.01 ng/ml), acting through inhibition of 70kDa S6 kinase (p70(S6k)). FK506 (1-1000 ng/ml) did not affect cSMC proliferation alone, although a greater than or equal to250-fold excess of FK506 over Rapa completely reversed the inhibitory effect of Rapa, confirming that these two agents share a common intracellular receptor, the FK506-binding protein (FKBP). Conclusion: Rapa is a powerful inhibitor of cSMC proliferation, while CsA slighly inhibits cSMC proliferation, although only at higher concentrations that may be toxic. These results indicate that therapeutic immunosuppression with Rapa may be additionally useful in prevention or delay of posttransplant coronary artery disease. (C) 2004 Elsevier Inc. All rights reserved.
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| 6. |
- Hafizi, Sassan, et al.
(författare)
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Differential response of human cardiac fibroblasts to angiotensin I and angiotensin II
- 2004
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Ingår i: Peptides. - : Elsevier BV. - 1873-5169 .- 0196-9781. ; 25:6, s. 1031-1033
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Tidskriftsartikel (refereegranskat)abstract
- The vasoactive peptide angiotensin II (Ang II) has been implicated as a mediator of myocardial fibrosis. We carried out a comparative investigation of the effects of Ang II and its precursor Ang I on collagen metabolism and proliferation in cultured human cardiac fibroblasts. Cardiac fibroblasts responded to both Ang I and Ang II with concentration-dependent increases in collagen synthesis but no proliferation. The stimulatory effect of Ang II was abolished by the AT, receptor antagonist losartan but not the AT(2) receptor antagonist PD123319. The response to Ang I was not affected by either antagonist, nor by the angiotensin-converting enzyme (ACE) inhibitor captopril. In conclusion, Both Ang I and Ang II stimulate collagen synthesis of human cardiac fibroblasts, the effect of Ang II occurring via the AT, receptor whilst Ang I appears to exert a direct effect through non-Ang II-dependent mechanisms. These results suggest distinct roles for angiotensin peptides in the development of cardiac fibrosis. (C) 2004 Elsevier Inc. All rights reserved.
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| 7. |
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| 8. |
- Hafizi, Sassan, et al.
(författare)
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Gas6 and protein S. Vitamin K-dependent ligands for the Axl receptor tyrosine kinase subfamily.
- 2006
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Ingår i: The FEBS Journal. - : Wiley. - 1742-464X. ; 273:23, s. 5231-5244
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Forskningsöversikt (refereegranskat)abstract
- Gas6 and protein S are two homologous secreted proteins that depend on vitamin K for their execution of a range of biological functions. A discrete subset of these functions is mediated through their binding to and activation of the receptor tyrosine kinases Axl, Sky and Mer. Furthermore, a hallmark of the Gas6-Axl system is the unique ability of Gas6 and protein S to tether their non receptor-binding regions to the negatively charged membranes of apoptotic cells. Numerous studies have shown the Gas6-Axl system to regulate cell survival, proliferation, migration, adhesion and phagocytosis. Consequently, altered activity/expression of its components has been detected in a variety of pathologies such as cancer and vascular, autoimmune and kidney disorders. Moreover, Axl overactivation can equally occur without ligand binding, which has implications for tumorigenesis. Further knowledge of this exquisite ligand-receptor system and the circumstances of its activation should provide the basis for development of novel therapies for the above diseases.
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| 9. |
- Hafizi, Sassan, et al.
(författare)
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Individual domains of Tensin2 exhibit distinct subcellular localisations and migratory effects.
- 2010
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Ingår i: International Journal of Biochemistry and Cell Biology. - : Elsevier BV. - 1878-5875 .- 1357-2725. ; 42, s. 52-61
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Tidskriftsartikel (refereegranskat)abstract
- Tensins are large intracellular proteins believed to link the extracellular matrix to the cytoskeleton via integrins. Tensins are multidomain proteins consisting of homologous C1, PTPase, C2, SH2 and PTB domains. Full-length Tensin proteins can undergo cleavage inside cells, thus yielding domains in isolation that may have discrete subcellular localisations and downstream effects. We expressed different isoforms of Tensin2 and their individual domains as recombinant green fluorescent protein (GFP)-fusion constructs in DU145 human prostate cancer cells. Under fluorescence confocal microscopy, the isolated domains of Tensin2 all displayed discrete distributions throughout the cytoplasm and the nucleus. In particular, partial constructs containing the C1 domain localised preferentially to the nucleus, including the isolated C1 domain and the PTPase domain. In contrast, all three full-length isoforms of Tensin2 were present exclusively in discrete punctate bodies throughout the cytoplasm. This punctate staining showed colocalisation with the tumour suppressor protein DLC-1 as well as with actin (phalloidin). Furthermore, DU145 cells transiently expressing partial Tensin2 constructs containing the PTB domain showed an increased haptotactic migration. In addition, stimulation of renal carcinoma cells stably expressing Tensin2 by the survival factor Gas6 caused phosphorylation of its receptor Axl, but no effect on Tensin2, which was already maximally phosphorylated at time 0. In conclusion, our results indicate that differential proteolytic cleavage of Tensin2 can liberate domains with discrete localisations and functions, which has implications for the role of Tensins in cancer cell survival and motility.
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| 10. |
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