Dual inhibition of PDK1 and Aurora Kinase A: an effective strategy to induce differentiation and apoptosis of human glioblastoma multiforme stem cells

The poor prognosis of Glioblastoma Multiforme (GBM) is mainly attributed to drug resistance mechanisms and to the existence of a subpopulation of glioma stem cells (GSCs). Multi-target compounds able to both affect different deregulated pathways and the GSC subpopulation could escape tumour resistance, and most importantly, eradicate the stem cell reservoir. In this respect, the simultaneous inhibition of Phosphoinositide-dependent kinase-1 (PDK1) and Aurora Kinase A (AurA), each one playing a pivotal role in cellular survival/migration/differentiation, could represent an innovative strategy to overcome GBM resistance and recurrence. Herein, the cross-talk between these pathways was investigated, using the single-target reference compounds MP7 (PDK1 inhibitor) and Alisertib (AurA inhibitor). Furthermore, a new ligand, SA16, was identified for its ability to inhibit the PDK1 and the AurA pathways at once, thus proving to be a useful tool for the simultaneous inhibition of the two kinases. SA16 blocked GBM cell proliferation, reduced tumour invasiveness, and triggered cellular apoptosis. Most importantly, the AurA/PDK1 blocker showed an increased efficacy against GSCs, inducing their differentiation and apoptosis. To the best of our knowledge, this is the first report on combined targeting of PDK1 and AurA. This drug represents an attractive multi-target lead scaffold for the development of new potential treatments for GBM and GSCs.