TIGAR and osteosarcoma: As expected, RNAi-mediated depletion of VPRBP markedly elevates the expression of p53 target genes (e.g., p21, TIGAR, PUMA, and Mdm2) in human osteosarcoma U2OS cells, but not in isogenic p53-null U2OS cells (Fig. 1a and Supplementary Fig. 3a).