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- Eriksson, Oskar, 1984-
(författare)
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Studies on Tissue Factor with Focus on Cell Signaling and Cancer
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis have explored the functions of the protein Tissue Factor (TF), which together with its ligand coagulation factor VII/VIIa (FVII/FVIIa) forms a proteolytic complex that functions in initiation of blood coagulation and activation of cell signaling.In paper I, the mechanisms behind the observation that TF/FVIIa signaling protects cells from apoptosis were further investigated. Using cell culture models, we found that antiapoptotic signaling by TF/FVIIa requires signaling by the Insulin-like growth factor I receptor (IGF-1R), as synthetic IGF-1R inhibitors and IGF1-R siRNA knock-down abolished the antiapoptotic effect of FVIIa. Furthermore, the IGF-1R translocated to the cell nucleus after FVIIa stimulation, implying a role in regulation of gene expression.Papers II and III describe the discovery that the Eph tyrosine kinase receptors EphB2 and EphA2 are proteolytically cleaved directly by TF/FVIIa. By using mass spectrometry and N-terminal Edman sequencing, the exact cleavage site was identified after a conserved arginine residue in the EphA2/EphB2 ligand binding domains, in agreement with the cleavage preferences of FVIIa. TF and EphA2/EphB2 co-localized in cancer cell lines and FVIIa potentiated ligand-dependent Eph signaling by increasing cytoskeletal remodeling and cell repulsion, demonstrating a novel proteolytical event that modulates Eph receptor signaling.In paper IV, expression of TF was investigated in colorectal cancer in both the stromal and tumor cell compartments by immunohistochemistry using an anti-TF-antibody developed and validated by the Human Protein Atlas project. In normal large intestine, TF was strongly expressed in the innermost pericryptal sheath cell layer lining the epithelium, in a cell population distinct from intestinal pericryptal myofibroblasts. We evaluated TF expression in two colorectal cancer materials, and found that TF was variably present in both the stromal and tumor cell compartments. TF expressed by pericryptal sheath cells was progressively lost after the adenoma-to-carcinoma transition and was a strong predictor of survival in rectal but not colon cancer patients independently of disease stage, histological tumor grade and age.In summary, this thesis demonstrates novel signaling mechanisms for the TF/FVIIa complex, and provides evidence of a hitherto unknown role of TF expressed by a specific population of stromal cells in colorectal cancer.
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