EGFR/FOXO3a/BIM signaling pathway determines chemosensitivity of BMP4-differentiated glioma stem cells to temozolomide

Iwona Anna Ciechomska,Bartosz Wojtas,Bozena Kaminska,Bartlomiej Gielniewski,Jakub Mieczkowski

doi:10.1038/s12276-020-0479-9

Iwona Anna Ciechomska, Bartosz Wojtas + Show 3 more

Open Access

https://doi.org/10.1038/s12276-020-0479-9

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Abstract

Accumulating evidence suggests that glioma stem cells (GSCs), which are rare cells characterized by pluripotency and self-renewal ability, are responsible for glioblastoma (GBM) propagation, recurrence and resistance to therapies. Bone morphogenic proteins (BMPs) induce GSC differentiation, which leads to elimination of GSCs and sensitization of glioma to chemotherapeutics. Alterations in the epidermal growth factor receptor (EGFR) gene are detected in more than half of GBMs; however, the role of EGFR in the chemoresistance of GSCs remains unknown. Here, we examined whether EGFR signaling affects BMP4-induced differentiation of GSCs and their response to the alkylating drug temozolomide (TMZ). We show that BMP4 triggers the SMAD signaling cascade in GSCs independent of the EGFR level. BMP4 downregulated the levels of pluripotency markers (SOX2 and OLIG2) with a concomitant induction of an astrocytic marker (GFAP) and a neuronal marker (β-Tubulin III). However, GSCs with different EGFR levels responded differently to treatments. BMP4-induced differentiation did not enhance sensitivity to TMZ in EGFRlow GSCs, in contrast to EGFRhigh GSCs, which underwent apoptosis. We then identified differences in cell cycle regulation. In EGFRlow cells, BMP4-triggered G1 cell cycle arrest which was not detected in EGFRhigh cells. RNA-seq profiles further highlighted transcriptomic alterations and distinct processes characterizing EGFR-dependent responses in the course of BMP4-induced differentiation. We found that the control of BIM (the pro-apoptotic BCL-2 family protein) by the AKT/FOXO3a axis only operated in BMP4-differentiated EGFRhigh cells upon TMZ treatment.

Highlights

Glioblastoma (GBM; World Health Organization gradeIV glioma) originates from neural stem or progenitor cells, when they undergo oncogenic transformation
The level of pathway-specific phospho-SMAD1/5, but not phosphoSMAD3, was increased upon BMP4 stimulation (Fig. S1). This indicates that BMP4 induces canonical Bone morphogenic proteins (BMPs) signaling in all tested glioma stem cells (GSCs) and that different epidermal growth factor receptor (EGFR)
The fold changes of the expression of downregulated genes were more similar between cell types than the fold changes of upregulated genes. These results suggest that BMP4 differentiation causes broader expression changes in EGFRlow spheres, and downregulated processes in EGFRlow and EGFRhigh cells are more similar than the upregulated ones

Summary

Introduction

Glioblastoma (GBM; World Health Organization gradeIV glioma) originates from neural stem or progenitor cells, when they undergo oncogenic transformation. GBMs are highly heterogeneous tumors containing cells with distinct functional phenotypes and different molecular abnormalities[9]. Primary GBMs are either mono- or polygenomic tumors (64 versus 36%, respectively) and express glioma stem cell markers, including CD133, CD15, A2B5, and CD4410. The presence of glioma stem cells (GSCs) or tumor initiating cells confers intrinsic GBM heterogeneity[11]. GSCs have a great impact on glioma progression and treatment response, as the failure of current therapies to eliminate GSCs is considered to be a major factor contributing to inevitable GBM recurrence. Therapeutics targeting GSCs are proposed as a promising treatment strategy. One such approach is to differentiate GSCs to reduce their intrinsic resistance[12,13,14]

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