Ex vivo PDTX Drug Screening

The ex vivo drug treatment protocol was performed as previously described (Bruna et al, 2016 (link)). Briefly, frozen patient‐derived tumour xenografts (PDTXs) were thawed and dissociated into single cell suspensions by combining mechanical and enzymatic dissociation using the soft tumour dissociation protocol on a GentleMACS Dissociator and the human tumour dissociation kit (Miltenyi Biotec, Cat ID 130‐093‐235) according to the manufacturer instructions. Single cells were plated at ~40,000 cells/ml in 50 µl per well in 384 well plates and dosed 72 h after plating. The selected drugs were added to the wells after 24 h of seeding using Echo Liquid Handler 550 (Labcyte). Cell viability was assessed using CellTiterGlo 3D Cell Viability (Promega) 6–10 days after dosing following manufacturer specifications and normalised against blank wells and control wells treated by Dimethyl Sulfoxide (DMSO, Sigma). Plates were read on the Pherastar plate reader using the Luminescence module.