421P - Cross-talk between the notch and transforming growth factor-β (TGF-β) signaling pathways in glioma initiating cells (GICs)

Date 28 September 2014
Event ESMO 2014
Session Poster Display session
Topics Central Nervous System Malignancies
Translational Research
Presenter Davis Torrejon Castro
Citation Annals of Oncology (2014) 25 (suppl_4): iv137-iv145. 10.1093/annonc/mdu330
Authors D. Torrejon Castro1, R. Bonavia2, A. Chiollaz2, J. Seoane3
  • 1Medical Oncology, Vall d'Hebron University Hospital Institut d'Oncologia, ES-08035 - Barcelona/ES
  • 2Translational Research Program, Vall d'Hebron Institute of Oncology (VHIO), 08035 - Barcelona/ES
  • 3Gene Expression And Cancer Laboratory, Vall d'Hebron Institute of Oncology, Vall d'Hebron University Hospital, 08035 - Barcelona/ES

Abstract

Aim

Recently, a subpopulation of tumor cells with stem-like properties has been identified in gliomas (GICs). Previous studies have demonstrated an extremely important role of TGF-ß and Notch pathways in the biology of GICs. However, the molecular mechanisms responsible for the maintenance of the GICs induced by TGF-ß are still to discover. This study will focus on the interactions in both directions between the TGF-ß and Notch pathways. In normal stem cells Id family proteins, which can be induced by TGF-ß, are necessary to maintain high levels of expression of Hes, a major Notch target, and to maintain the undifferentiated state in the developing central nervous system. Therefore we need a detailed study of this signaling pathway in GICs, the molecular mechanisms responsible for the maintenance of this cell population and the connection with the TGF-ß pathway.

Methods

The cellular model used in our study consists in patient-derived cultures: fresh surgically isolated tumor tissue from glioblastoma patients undergoing surgery in the Vall d'Hebron Hospital was dissociated and cultured in selective serum-free culture medium supplemented with EGF and FGF. In these conditions cells form spherical cell structures, called gliomaspheres.

Results

The stimulation of gliomasphere cultures with TGF-ß induced transactivation of the Notch pathway, as observed by cleavage (activation) of Notch1 by western blot and by increase of Notch target genes (Hes1, Hey1). The induction of Notch targets was completely blocked by pretreatment with the gamma-secretase inhibitor. TGF-ß treatment also induced increased expression of the Notch ligand Jagged1. By blocking Jagged1 expression by RNA interference we were able to prevent TGF-ß induced activation of Notch1. The treatment of gliomasphere cultures with gamma-secretase inhibitor caused a strong decrease in the percentage of cells with high CD44 expression (CD44high), which are enriched in glioma initiating cells (GICs), similarly to what observed with the TGF-ß receptor I (TßRI) inhibitor. The combination of the two inhibitors produced a further decrease of CD44high cells.

Conclusions

We propose that a new combinatorial therapeutic to target both TGF-ß and Notch might be more effective in cases of partial or no response to therapies based on either drug alone.

Disclosure

All authors have declared no conflicts of interest.