Coordination of signalling networks and tumorigenic properties by ABL in glioblastoma cells

Fabienne Lamballe,Dominique Figarella-Branger,Nathalie Baeza,Sara Toscano,Flavio Maina,Françoise Helmbacher,Filippo Conti,Maria Arechederra

doi:10.18632/oncotarget.12546

Abstract

The cytoplasmic tyrosine kinase ABL exerts positive or negative effects in solid tumours according to the cellular context, thus functioning as a “switch modulator”. The therapeutic effects of drugs targeting a set of signals encompassing ABL have been explored in several solid tumours. However, the net contribution of ABL inhibition by these agents remains elusive as these drugs also act on other signalling components. Here, using glioblastoma (GBM) as a cellular paradigm, we report that ABL inhibition exacerbates mesenchymal features as highlighted by down-regulation of epithelial markers and up-regulation of mesenchymal markers. Cells with permanent ABL inhibition exhibit enhanced motility and invasive capabilities, while proliferation and tumorigenic properties are reduced. Intriguingly, permanent ABL inhibition also interferes with GBM neurosphere formation and with expression of stemness markers in sphere-cultured GBM cells. Furthermore, we show that the molecular and biological characteristics of GBM cells with impaired ABL are reversible by restoring ABL levels, thus uncovering a remarkable plasticity of GBM cells to ABL threshold. A phospho-signalling screen revealed that loss of tumorigenic and self-renewal properties in GBM cells under permanent ABL inhibition coincide with drastic changes in the expression and/or phosphorylation levels of multiple signalling components. Our findings identify ABL as a crucial player for migration, invasion, proliferation, tumorigenic, and stem-cell like properties of GBM cells. Taken together, this work supports the notion that the oncogenic role of ABL in GBM cells is associated with its capability to coordinate a signalling setting that determines tumorigenic and stem-cell like properties.

Highlights

The non-receptor tyrosine kinase (RTK) ABL influences behaviour of cells by regulating migration, invasion, survival, and proliferation, according to the cellular context [1,2,3]
ABL inhibition leads to morphological and molecular changes in GBM cells The U87 GBM cell line has been extensively used to assess the effectiveness of several drugs targeting signalling components such as RTK inhibitors [45, 5154]
To achieve successful ABL targeting with the short hairpin RNA (shRNA) strategy, the efficiency of 3 different shRNA sequences to down-regulate ABL was tested in transfected cells after selection (Supplementary Table 1)

Summary

Introduction

The non-receptor tyrosine kinase (RTK) ABL influences behaviour of cells by regulating migration, invasion, survival, and proliferation, according to the cellular context [1,2,3]. ABL was shown to regulate cell membrane protrusions by modulating actin polymerization [4] and to control cell polarity by acting on polarized junctional dynamics in drosophila embryos [5, 6]. Through these mechanisms, ABL influences cell motility and directional collective cell migration, processes occurring during embryogenesis and cancer. Abl influences mouse female fertility during chemotherapy [13] and its alteration may impact neurodegenerative diseases and therapies [14]

Methods

Results

Discussion

Conclusion