High-throughput screening uncovers miRNAs enhancing glioblastoma cell susceptibility to tyrosine kinase inhibitors.

Glioblastoma (GBM) is a deadly and therapy resistant malignant brain tumour, characterized by an aggressive and diffuse growth pattern, which prevents complete surgical resection. Despite advances in the identification of genomic and molecular alterations that fuel the tumour, average patient survival post-diagnosis remains very low (∼14.6-months). In addition to being highly heterogeneous, GBM tumour cells exhibit high adaptive capacity to targeted molecular therapies owing to an established network of signalling cascades with functional redundancy, which provides them with robust compensatory survival mechanisms. Here, we investigated whether a multimodal strategy combining multitargeted tyrosine kinase inhibitors (MTKIs) and microRNA (miRNA) modulation could overcome the signalling pathway redundancy in GBM and, hence, promote tumour cell death. By performing a high-throughput screening, we identified a myriad of miRNAs, including those belonging to the miR-302-3p/372-3p/373-3p/520-3p family, which coordinately act with the MTKI sunitinib to decrease GBM cell viability. Two members of this family, hsa-miRNA-302a-3p and hsa-miRNA-520 b, were found to modulate the expression of receptor tyrosine kinase mediators (including AKT1, PIK3CA and SOS1) in U87 and DBTRG human GBM cells. Importantly, administration of mimics of these miRNAs with sunitinib or axitinib resulted in decreased tumour cell proliferation and enhanced cell death, whereas no significant effect was observed when coupling miRNA modulation with temozolomide, the first-line drug for GBM therapy. Overall, our results provide evidence that combining the 'horizontal' inhibition of signalling pathways promoted by MTKIs with the 'vertical' inhibition of the downstream signalling cascade promoted by hsa-miR-302a-3p and hsa-miR-520 b constitutes a promising approach towards GBM treatment.