Fig. 3: KRAS-driven UPP1 liberates ribose and is increased in PDA.

a, Western blot validation of UPP1-KO in human PDA cell lines. 1A and 1B denote UPP1-KO cells. WT, wild type. b,c, RMA from tetrazolium assay showing uridine-derived reducing potential (b) and CellTiter Glo showing ATP production (c) in UPP1-KO and wild-type PATU8988S and ASPC1 cells cultured with or without 1 mM uridine for 48 h. d, Relative intracellular uracil as determined by LC–MS in wild-type and UPP1-KO human PDA clones cultured with 1 mM uridine for 24 h (PATU8988S) or 6 h (ASPC1). e, Mass isotopologue distribution of 1 mM [¹³C₅]uridine-derived carbon in glycolysis and TCA cycle metabolites in wild-type or UPP1-KO ASPC1 cells after 6 h. α-KG, α-ketoglutarate; 1,3-BPG, 1,3-bisphosphoglycerate; DHAP, dihydroxyacetone phosphate; fructose-1,6-BP, fructose-1,6-bisphosphate. f, UPP1 mRNA expression in PDA tumours and non-tumoural pancreas tissues in microarray datasets. Liver met, liver metastasis; NT, non-tumour tissue. g,h, RNAscope showing representative UPP1 mRNA expression in tumour and adjacent normal tissue (adj) sections (g) and quantification from three patients (Pt 1–3) with PDA (h). Scale bars, 100 μm. i, Kaplan–Meier overall survival analysis (log-rank test) based on ranked UPP1 expression in the PDA dataset published previously⁴⁴. j, Comparison of UPP1 mRNA expression in human PDA tumours annotated as KRAS^G12D or with no alteration (No Alt) in KRAS from the TCGA dataset. k, qPCR data showing Upp1 expression in mouse cell lines (A9993 and 9805) with doxycycline-inducible oncogenic Kras (iKras*). l, Western blot validation of MAPK pathway induction as indicated by phosphorylated ERK (pERK) in the iKras* cell lines. m,n, qPCR for UPP1 mRNA (m) and western blot for pERK and UPP1 (n) in ASPC1 cells cultured with or without 5 mM glucose, 1 mM uridine and 1 μM trametinib for 48 h. o, MTT assay showing relative proliferation of PDA cell lines with 1.25 μM trametinib and 1 mM uridine in the absence of glucose. See Methods ‘Statistics and reproducibility’ section for additional information.