Extended Data Fig. 1: PDA favors the use of glutamine over arginine for polyamine synthesis.
From: Ornithine aminotransferase supports polyamine synthesis in pancreatic cancer
a, Schematic depicting all 3 pathways leading to synthesis of the polyamine precursor ornithine: De novo ornithine synthesis (DNS) via OAT in red, urea cycle via ARG2 in yellow and creatine synthesis via GATM in purple. ARG, arginase; ASL, argininosuccinate lyase; ASS1, argininosuccinate synthase 1; CPS1, carbamoyl-phosphate synthase 1; GAMT, guanidinoacetate N-methyltransferase; GATM, glycine amidinotransferase; GLS, glutaminase; GSA, glutamate-γ-semialdehyde; α-KG, α-ketoglutarate; NOS, nitric oxide synthase; OAA, oxaloacetate; OAT, ornithine aminotransferase; ODC1, ornithine decarboxylase 1; OTC, ornithine transcarbamoylase; P5C, pyrroline-5-carboxylate; P5CS, pyrroline-5-carboxylate synthase (product of ALDH18A1 gene or aldehyde dehydrogenase 18 family member A1); P5CDH, pyrroline-5-carboxylate dehydrogenase (product of ALDH4A1 gene or aldehyde dehydrogenase 4 family member A1); PRODH, proline dehydrogenase 1; PYCR, pyrroline-5-carboxylate reductase; SMS, spermine synthase; SRM, spermidine synthase. b, c, Schematics tracing the fates of 15N-(amine) of glutamine (b) or all 4 nitrogens of 15N4-arginine (c) into ornithine and polyamine synthesis (left), or the urea cycle (right). Circles in White: 12C; in Red (b) or Green (c): 15N; in Gray: 14N; in Black: 14N when the urea cycle is off, as in PDA cells in vitro, but 15N when the urea cycle is on, as in PDA tumors in vivo7. Thicker arrows indicate enhanced flux into DNS and polyamine synthesis (b) or into generation of argininosuccinate, urea, ornithine and polyamines (c). d, Percent 15N-labeled metabolites in AsPC-1 cells fed 15N-(amine)Gln for 24 h. n = 6 biological replicates. e, Percent 15N-labeled metabolites in AsPC-1 cells fed 15N4-Arg for 24 h. Consistent with urea cycle inactivity, only 15N4-Arg-derived citrulline (M+3), the result of nitrogen oxide synthase (NOS) activity, but not citrulline (M+2), product of ornithine transcarbamoylase (OTC) in the urea cycle, was detected (see schematic in c). Furthermore, arginine-derived 15N-argininosuccinate (As, M+4) but not (M+2) was detected, indicating reverse argininosuccinate lyase (ASL) reaction10, rather than transfer of 15N from citrulline via argininosuccinate synthetase (ASS1) in the urea cycle (see schematic in c). n = 4 biological replicates. f,g, Percent labeled 15N-ornithine (f) and 15N-putrescine (g) in 29 cancer cell lines representing 5 cancer types (PDA; BRCA: breast carcinoma; LUAD, COAD and PRAD: adenocarcinomas of the lung, colon and prostate, respectively) with tissue-matched normal cell lines, indicated by arrowheads, that were fed 15N4-Arg for 24 h. n = 4 biological replicates per cell line. h,i, Relative abundance of 15N-labeled ornithine (h) or 15N-labeled putrescine (i) normalized to 15N-labeled glutamate in cell lines fed 15N-(amine)Gln for 24 h, as described in Fig. 1b, c. n = 4 biological replicates. M+1 and M+2 indicate a mass shift of 1 or 2 nitrogens, respectively. Data represent the mean ± s.d. p-values were obtained by one-way ANOVA, followed by Tukey test. Stars indicate statistical significance between each cancer cell line and its tissue-matched normal cell line/s. Data are representative of six (d), three (e) or two (f–i) independent experiments.
