PDGF receptor alpha inhibition induces apoptosis in glioblastoma cancer stem cells refractory to anti-Notch and anti-EGFR treatment

Abstract

BackgroundCancer stem cells (CSC) represent a rare fraction of cancer cells characterized by resistance to chemotherapy and radiation, therefore nowadays there is great need to develop new targeted therapies for brain tumors and our study aim to target pivotal transmembrane receptors such as Notch, EGFR and PDGFR, which are already under investigation in clinical trials setting for the treatment of Glioblastoma Multiforme (GBM).MethodsMTS assay was performed to evaluate cells response to pharmacological treatments. Quantitative RT-PCR and Western blots were performed to state the expression of Notch1, EGFR and PDGFRα/β and the biological effects exerted by either single or combined targeted therapy in GBM CSC. GBM CSC invasive ability was tested in vitro in absence or presence of Notch and/or EGFR signaling inhibitors.ResultsIn this study, we investigated gene expression and function of Notch1, EGFR and PDGFR to determine their role among GBM tumor core- (c-CSC) vs. peritumor tissue-derived cancer stem cells (p-CSC) of six cases of GBM. Notch inhibition significantly impaired cell growth of c-CSC compared to p-CSC pools, with no effects observed in cell cycle distribution, apoptosis and cell invasion assays. Instead, anti-EGFR therapy induced cell cycle arrest, sometimes associated with apoptosis and reduction of cell invasiveness in GBM CSC. In two cases, c-CSC pools were more sensitive to simultaneous anti-Notch and anti-EGFR treatment than either therapy alone compared to p-CSC, which were mostly resistant to treatment. We reported the overexpression of PDGFRα and its up-regulation following anti-EGFR therapy in GBM p-CSC compared to c-CSC. RNA interference of PDGFRα significantly reduced cell proliferation rate of p-CSC, while its pharmacological inhibition with Crenolanib impaired survival of both CSC pools, whose effects in combination with EGFR inhibition were maximized.ConclusionsWe have used different drugs combination to identify the more effective therapeutic targets for GBM CSC, particularly against GBM peritumor tissue-derived CSC, which are mostly resistant to treatments. Overall, our results provide the rationale for simultaneous targeting of EGFR and PDGFR, which would be beneficial in the treatment of GBM.Electronic supplementary materialThe online version of this article (doi:10.1186/1476-4598-13-247) contains supplementary material, which is available to authorized users.

Analysis of angiogenesis related factors in glioblastoma, peritumoral tissue and their derived cancer stem cells

“…The Boyden chamber assay demonstrated a greater capability of GCSCs with respect to PCSCs to stimulate the migration of ECs, under this condition, although not all samples of CSCs showed the same amplitude of response (Figure 4A). These results demonstrated the great variability of effects induced by both GCSCs and PCSCs that can be probably blamed on intrinsic differences among patients, as previously reported by others [22]. In addition, these data were supported by the analysis of VEGF mRNA, which was found to be expressed at a higher level in HUVECs co-cultured with GCSCs (Figure 4B), suggesting a potential direct effect of GCSCs, rather than PCSCs, on EC-induced VEGF release.…”

Adaptive Chromatin Remodeling Drives Glioblastoma Stem Cell Plasticity and Drug Tolerance

“…Yet in the context of drug treatment, this promotion of a slow-cycling state may have the untoward consequence of conferring resistance. The Notch-dependency of the refractory GSC state may thus portend opportunities for combination therapy, some of which are now being explored in pre-clinical and early clinical studies (Cenciarelli et al, 2014; Xu et al, 2016; Yahyanejad et al, 2016) .…”

The interference of Notch1 target Hes1 affects cell growth, differentiation and invasiveness of glioblastoma stem cells through modulation of multiple oncogenic targets

“…RTKs activation through binding to specific ligands induces its auto-phosphorylation and activation of MAP kinase, PI3K/Akt, Jak/Stat3 signaling [17–20]. …”