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Understanding tumour resistance: Receptors and signalling pathways that can lead the race against tumour angiogenesis

Final Report Summary - ALTANGIOTARGET (Understanding tumour resistance: Receptors and signalling pathways that can lead the race against tumour angiogenesis)

Glioblastoma (GBM) represents >50% of gliomas and 16% of primary brain tumours. Based on the latest classification by the WHO, median survival of patients with GBM, depending on the treatment regime, ranges between 9.9 and 15 months. As aetiology of this aggressive tumour is unknown in most cases, identification of “players-targets” is the holy grail of research in the field.
Blood supply in GBM is a complex, key process that involves many different steps, including vascular co-option, angiogenesis, vasculogenesis and vascular mimicry, and is orchestrated by numerous factors and their receptors. Among these factors, one of the most important pro-angiogenic pathways, which has already found its way to the clinic, is that of the vascular endothelial growth factor A (VEGF-A) and its main receptor VEGF receptor 2 (VEGFR2). VEGF-A is over-expressed in GBMs and has been correlated with prognosis. Drugs targeting VEGF-A, such as bevacizumab, have been long tried in GBM therapy in combination with the standard regimen of radiotherapy and chemotherapy, but has failed to improve overall survival in newly diagnosed GBM patients or patients with progressive GBM. Intensive research up to date has highlighted the need to identify alternative druggable targets for inhibition of angiogenesis and/or tumor progression in GBM.
Receptor protein tyrosine phosphatase beta/zeta (RPTP beta/zeta) and its ligand pleiotrophin (PTN) are expressed in a plethora of tumours and have been the centre of attention for the host lab. Both PTN and RPTP beta/zeta are overexpressed in GBMs and have been suggested as important players in GBM growth and angiogenesis. More recently, the host lab has identified RPTP beta/zeta as a receptor that also mediates VEGF-A165-induced endothelial cell proliferation through up-regulation of cell surface nucleolin (NCL). NCL is over-expressed on the plasma membrane of tumour and activated endothelial cells, mediates both PTN and VEGF-A angiogenic effects, such as proliferation and migration induction, and has been in the recent research interests of the host lab.
ALTangioTARGET is structured around the following objectives:
A. Identification of the degree of interaction of VEGF with RPTP beta/zeta in GBM cell lines and evaluation of its significance in migration, angiogenesis and apoptosis in vitro, as well as angiogenesis and tumour growth in vivo.
B. Determination of the cross-talk between RPTP beta/zeta and other VEGF receptors/co-receptors and of their signalling pathways that subsequently activate nuclear factor of activated T cells (NFAT) and/or activator protein 1 (AP-1) pathways and eventually play part in VEGF-induced cell migration, angiogenesis and inhibition of apoptosis.
Objective A was divided into six work packages (WP) and objective B into three WP.
The findings are summarised as follows:
1. Establishment of the expression of the VEGF receptors and co-receptors of interest in five GBM cell lines,
2. Identification of VEGF-RPTP beta/zeta interaction in GBM cell lines,
3. Establishment of protocols for the down-regulation of RPTP beta/zeta in GBM cell lines and elucidation of the role of RPTP beta/zeta down-regulation in VEGF-induced GBM cell migration,
4. Optimization of immunohistochemistry parameters for the development of a reproducible protocol for in situ PLA in tissues,
5. Data on possible VEGF-A regions that affect interaction with RPTP beta/zeta,
6. Data on the effects of VEGF-A derived peptides on basal and VEGF-A-induced angiogenic actions in vitro and in vivo,
7. Refinement of the expression and activation of NFAT in human endothelial and GBM cells under basal and VEGF-A-stimulated conditions,
8. Investigation of the role of RPTP beta/zeta in VEGF-induced signalling related to AP-1 activation.
With the conclusion of the expected publication, ALTangioTARGET will contribute to new knowledge that will guide future efforts towards designing novel therapeutic approaches for GBM.
The fellow gained invaluable experience in numerous in vitro and in vivo techniques and familiarised herself with the relevant literature and with a multidisciplinary research approach, which at the same time gave her the opportunity to collaborate with numerous research groups. She also participated in career development workshops and applied for permanent positions in academia. She improved transferable skills, such as communication and presentation, and extended her experience in teaching and supervising at both undergraduate and graduate level. The fellow and host lab planned and managed to fulfil the majority of the desired dissemination activities, among which the new website and the facebook page of the research group (http://molphangio.upatras.gr/ https://www.facebook.com/Laboratory-of-Molecular-Pharmacology-Angiogenesis-group-809259629172069/) during a two year course of a smooth and uneventful project in terms of management.