Cells were transfected with 20 nM siRNA targeting RIOK3 (SI02223396; siRIOK3) or AllStars Negative control (1027281; siCon) using HiPerFect reagent (Qiagen, Manchester, UK). Custom siRNA oligonucleotides containing 3 sequences targeting HIF-1α (1 CAAGCAACTGTCATATATA, 2 TGCCACCACTGATGAATTA, 3 TGACTCAGCTATTCACCAA) or HIF-2α (1 TAACGACCTGAAGATTGAA, 2 CAAGCCACTGAGCGCAAAT, 3 TGAATTCTACCATGCGCTA) were purchased from Eurogentec (Southampton, UK). pGIPZ plasmids targeting RIOK3 (Clone ID V2LHS_16875; shRIOK3) or non-silencing control shRNAmir (RHS4743; shCon) were obtained from Thermo Scientific. Lentivirus packaging and titration was carried out as described.38 (link) Cells were transduced at MOI 1 and pools of transduced cells were selected with 1 μg/mL puromycin (Life Technologies) 48 h post-transduction.