Browsing by Issue Date, starting with "2015-09-16"
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- Investigating the role of Annexin A2 in Epidermal Growth Factor (EGF) induced signalling in cancerPublication . Tanjeko, Ajime Tom; Madureira, Patricia AlexandraReactive oxygen species (ROS) are produced as a consequence of cellular metabolism and can also be produced by the cell in response to growth factor/growth factor receptor stimulation to function as second messengers in major signalling pathways. Recently, increasing evidence has revealed that the ROS, H2O2 is an important second messenger in cellular signal transduction, because of its high diffusion and ability to selectively target reactive cysteine residues in proteins. Currently, H2O2-mediated signalling has been implicated in several fundamental physiological processes such as cell proliferation, differentiation, migration and apoptosis. EGF/EGFR is one of the most mutated GF/GFR associations in cancer thanks to its role in tumorigenesis. The binding of EGF to EGFR induces downstream events leading to intracellular production of H2O2 for signalling. Cancer cells characteristically exhibit increased ROS levels compared to normal counterparts that gives them a proliferative advantage and promotes cancer progression. To balance the advantage of low ROS levels (nanomolar concentration for proliferative signalling pathways) against its damaging effect (as a specific oxidant at high concentrations), cancer cells induce the cellular antioxidant response. Our laboratory identified a novel redox regulatory protein, annexin A2 (ANXA2) and showed that its antioxidant function plays a crucial role in supporting tumour growth and chemoresistance. As a logical follow up to this research we investigated the role played by ANXA2 in oncogenic signalling pathways induced by EGF. Here, the activation of signalling pathways in pre-established MDA MB 231 breast cancer cell lines with knockdown for ANXA2 and respective control cells was investigated by western blotting upon treatment of these cells with 50 ng/ml of EGF at different time points. Biotinylated Iodoacetamide (BIAM) assays were done to assess the oxidation of reactive Cys residues in redox sensitive proteins upon treatment with EGF. Intracellular ROS levels and cell proliferation were also analysed in ANXA2 depleted versus control cancer cells upon treatment with EGF. Our results show that ANXA2 depletion in MDA MB 231 cancer cells leads to enhanced activation of the pro-survival and pro-proliferative PI3K/Akt signalling pathway, enhanced ROS production and increased proliferation rate upon EGF treatment compared to control cells. EGF treatment also led to oxidation/inhibition of the main regulator of the PI3K/Akt pathway, PTEN. Interestingly, we observed upregulation of PRDX II (a redox regulatory protein) in ANXA2 depleted MDA MB 231 cells. Taken together, our results demonstrate that ANXA2 plays a redox regulatory role in EGF induced ROSmediated PI3K/Akt signalling and that ANXA2 knockdown cells might be upregulating PRDX II to compensate for the loss of the ANXA2 redox regulatory protein.
- Lymphotoxin-beta receptor and RANK signaling in TEL-JAK2-induced T-cell leukemiaPublication . Fernandes, Mónica Alexandra Teotónio; Santos, Nuno Rodrigues dosT-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematopoietic malignancy that arises from the combination of genetic and epigenetic alterations in thymic T-cell precursors and extracellular signals provided by the microenvironment. It was previously found that RelB expression in non-hematopoietic stromal cells promoted T-cell leukemogenesis in the EμSRalpha-TEL-JAK2 transgenic (TJ2-Tg) mouse model. In thymic stromal cells, RelB is a transcription mediator of lymphotoxin-beta receptor (LTβR). Lymphotoxin-mediated activation of LTβR has been implicated in physiological crosstalk between T cells and lymphoid organ stromal cells, but also pathological processes, including carcinogenesis. Since its role in T-ALL has remained elusive, we aimed to determine whether LTβR signaling is activated and playing a role in TEL-JAK2-induced leukemogenesis. In TJ2-Tg thymic lymphomas, activation of LTα1β2-LTβR signaling axis was supported by LTβRencoding gene expression, while the genes encoding its cognate ligand, lymphotoxin (LT)-α and LTβ, were found to be expressed by leukemic T cells, in an NF-κB-dependent manner. LTα1β2 protein was detected at the surface of TJ2-Tg leukemic cells only upon ex vivo culture or mitogenic stimulation. Moreover, we found that cell-surface LTα1β2 is downmodulated in vivo, indicating ongoing signaling. Further supporting a role for lymphotoxin signaling, LTβR genetic deficiency delayed TEL-JAK2-induced leukemia onset, but the tumor load in lymphoid organs and leukemia cell surface phenotype were comparable in end-stage disease. In accordance, the detection of reduced proportions of malignant thymocytes in TJ2-Tg;Ltbr-/- mice with no signs of disease implicated LTβR in early stages of leukemia development. Together, these data indicate that T-ALL-derived lymphotoxin activates LTβR signaling in thymic stromal cells, promoting leukemogenesis. Importantly, lymphotoxin-encoding genes were expressed in T-ALL patient samples, indicating that these may be also involved in human disease. Thus, future studies should provide a better understanding on how cellular crosstalk mediated by the lymphotoxin-LTβR axis supports T-ALL and assess the utility of blocking LTβR signaling as a novel therapeutic approach.